Date & Time  Speaker  Event / Title  Type & Location 
Wednesday 11. Oct 2017 10:00

Manuel Laso Institute of Optoelectronics Systems and Microtechnology, Universidad Politecnica de Madrid, Spain 
Order, disorder and confinement in hardsphere polymers Show / Hide Abstractmissing

POLYPHYS Seminar HCI J 498 
Wednesday 5. Jul 2017 10:15

Aleksandar Donev Courant Institute of Mathematical Sciences, New York University, United States 
Brownian dynamics of colloids in quasi twodimensional confinement Show / Hide AbstractRecent theoretical work has lead to the discovery that diffusion of colloids confined to a twodimensional flat interface between two fluids is anomalous in a number of unusual ways (see, for example, Bleibel et al., Soft Matter 10(17):29452948, 2014). This is because the quasi twodimensional (q2D) fluid flow on the interface is not divergence free, even though the three dimensional fluid flow in the whole system is divergence free. In particular, this means that the divergence of the hydrodynamic mobility matrix M is not zero, even within the RotnePrager approximation, as it is for diffusion in three dimensions. Rather, the Ito stochastic drift term proportional to kT*div(M) looks like a longranged electrostatic repulsion between the colloids. This has a number of nontrivial consequences such as a shorttime collective diffusion coefficient that diverges as 1/k, where k is the wavenumber. I will describe an algorithm that can effectively perform Brownian Dynamics of as many as one million colloidal particles confined to diffuse on a planar interface. The algorithm, which is a q2D version of the fluctuating Force Coupling Method (FCM), uses fluctuating hydrodynamics to incorporate Brownian motion and uses twodimensional FFTs to achive a dramatic speedup over fully threedimensional simulations. I will present results obtained using this algorithm on diffusive mixing of a binary mixture of particles in q2D, including enhanced collective diffusion, as well as results on giant nonequilibrium fluctuations in q2D. I will discuss the differences with truly twodimensional systems, as well as particles confined near boundaries, and point to several interesting physical questions that arise from the unusual nature of diffusion in q2D.

POLYPHYS Seminar HCI D 8 
Wednesday 28. Jun 2017 10:15

Ioanna Tsimouri Department of Chemical Engineering, University of Patras, Greece 
A rheological model for blood from nonequilibrium thermodynamics Show / Hide AbstractMany deaths are the result of cardiovascular diseases associated with unusual blood rheological properties in the circulatory system [1]. Thus, understanding the rheological behavior of blood is paramount in providing insights on the causes of various diseases and the tailordesign of the transport of drug directly to the infected area [1]. Blood is mainly a suspension of elastic particulate cells, among which red blood cells (RBCs) dominate, in plasma, usually considered as a Newtonian fluid. The RBCs are deformable since they consist of an elastic membrane enclosing a hemoglobin solution (also considered a Newtonian fluid) [1,2]. It has been observed than under quiescent conditions, when the shear rate is not high enough (~ 15 s^{1}) RBCs aggregate, forming columnlike structures called rouleaux [1,2,3]. As the shear rate increases, rouleaux break and, after a critical shear rate, eventually only individual RBCs can be observed [1,3]. A constitutive model capable of predicting this dynamical behaviour is the one suggested by Owens and coworkers [4,5] in which each rouleaux is modeled by an elastic dumbbell and their time evolution is described using the Smoluchowski equation which does takes into account the forming and destruction of rouleaux [4]. In the present work, we derive Owens model within the framework of nonequilibrium thermodynamics, particularly using the generalized bracket formalism [6]. We appropriately consider the momentum density, m^{(i)} the number density, n_{i}, and the conformation tensor C^{(i)} for each rouleaux (including single RBCs) in the vector of state variables. We also suggest proper expressions for both the Poisson and Dissipation brackets and for the system Hamiltonian. Using the generalized bracket formalism, we are then able to reproduce Owens model and confirm its thermodynamic admissibility. Possible drawbacks of Owens model will be highlighted and propositions as to how they may be obviated will be presented. References [1] Yilmaz F., Gundogdu M. Y. (2008). Korea Australia Rheology Journal, Vol. 20, No. 4, 197211 [2] Pries A. R., Secomb T.W., Gaehtgens P. (1996). Cardiovascular Research, 32, 654667 [3] Fedosov D. A. (2011). PNAS, Vol. 108, No. 29, 11772–11777 [4] Owens R. G. (2006). J. NonNewtonian Fluid Mech. 140, 57–70 [5] MoyersGonzales M., Owens R. G., Fang J. (2008). J. Fluid Mech., 617, 327–354 [6] Beris A. N., Edwards B. J. ( 1994). Thermodynamics of Flowing Systems with Internal Microstructure, Oxford University Press: New York

POLYPHYS Seminar HCP F 43.4 
Tuesday 13. Jun 2017 17:00

Norman J. Wagner University of Delaware, United States 
The micromechanics of shear thickening fluids and their application as protective materials for medical professionals, first responders, football players, astronauts and spacecraft 
Talk HCI H 8.1 
Wednesday 7. Jun 2017 10:15

Bingyu Cui University of Tokyo, Japan 
Quantum field theory as a faithful image of nature Show / Hide AbstractQuantum field theory, which represents the marriage of quantum mechanics with special relativity and provides the mathematical framework in which to describe the interactions of elementary particles, is developed to formulate modern particle physics. It is a powerful tool in depicting all fundamental processes except for gravitation. Here, I am going to, on a conceptual level, briefly clarify the foundations of quantum field theory. After laying basic mathematical and physical elements required for dissipative quantum field theory that combines both rigor and relevance in its early development, I will elaborate formal renormalization procedure implied by the dissipative approach to fundamental particle physics by taking the most studied φ^{4} theory (scalar field theory) as an example. Also, another modern idea known as BRST quantization dealing with the issue of gauge degree will be illustrated along with quantum electrodynamics. [1] Hans Christian Öttinger, arXiv: 1509.09278 [2] Mark Srednicki, Cambridge University Press (2007)

POLYPHYS Seminar HCP F 43.4 
Wednesday 31. May 2017 10:15

Matteo Colangeli Universita degli Studi dell Aquila, Department of Information Engineering, Computer Science and Mathematics, Italy 
Particle models with self sustained current Show / Hide AbstractWe present some computer simulations run on a stochastic CA (cellular automaton). The CA simulates a gas of particles which are in a channel, the interval [1,L] in Z, but also in 'reservoirs' R1 and R2. The evolution in the channel simulates a lattice gas with Kawasaki dynamics with attractive Kac interactions; the temperature is chosen smaller than the mean field critical one. There are also exchanges of particles between the channel and the reservoirs and among reservoirs. When the rate of exchanges among reservoirs is in a suitable interval the CA reaches an apparently stationary state with a non zero current; for different choices of the initial condition the current changes sign. We have a quite satisfactory theory of the phenomenon but we miss a full mathematical proof.

POLYPHYS Seminar HCP F 43.4 
Wednesday 17. May 2017 10:15

Alberto Montefusco Polymer Physics, Department of Materials, ETH Zurich 
A generalisation of the fluctuationdissipation relation of the second kind through largedeviation theory Show / Hide AbstractProperly formulating stochastic models is a very important task of a thermodynamicist, for both theoretical developments and purposes of simulation. The present work deals with the mutual structural properties of a class of stochastic systems and their corresponding deterministic limit. Fluctuationdissipation relations are very general properties of many systems in statistical mechanics. A Fluctuationdissipation relation of the second kind (FDR2) establishes a relationship between the frictional properties of a system and the stochastic noise on a system, both resulting from the interaction with an environment. A FDR2 is generally formulated for Langevin dynamics, where it provides a onetoone relationship between the structures of the drift term and the diffusion matrix. We call this formulation a classical FDR2. The aim of this talk [work] is to lift a FDR2 to more general processes in the following way. Firstly, we see a classical FDR2 from the perspectives of largedeviation theory and gradient flows: the former concerns the properties of the stochastic system and the latter represents the structure of the corresponding deterministic limit. Next, we realise that this viewpoint provides a straightforward lift to any general sequence of reversible Markov processes satisfying a largedeviation principle. Finally, we provide an abstract formulation of a FDR2, which appears as a relationship between the largedeviation properties of a stochastic system and the (generalised) gradient structure of the corresponding deterministic limit. We provide an explicit example in the context of chemical reactions in a wellstirred volume, which is the typical benchmark for extension of nonequilibrium thermodynamic theories to the nonlinear regime.

POLYPHYS Seminar HCP F 43.4 
Wednesday 3. May 2017 10:15

Alexander Weyman Institute for Computational Physics, University of Stuttgart, Germany 
A coarsegrained model for polyionic liquids Show / Hide AbstractPolyionic liquids or polymerized ionic liquids (PILs) are a relatively new class of polyelectrolytes that combine both the advantages of polymeric materials and the unique properties of ionic liquids and therefore have become the focus of scientific interest in recent years. We show results from molecular dynamics (MD) simulation using a coarsegrained model for polyionic liquids in order to analyze structural features and transport properties. The polymer chains are described by a beadspring model where the single PIL monomers are represented by single beads that are interconnected via bond potentials. Following the observation of microphase separation in dense bulk systems of ionic liquids, dense systems of polyionic liquids are simulated, and partial structure factors are calculated for the quantitative analysis of the likewise occurring microphases. Using a classical density functional theory framework, a selection of partial structure factors is calculated and compared with MD simulations. Furthermore, we also find an enhancement of the conductivity, if the PILs are confined between two planeparallel interfaces, due to the occurrence of a larger conductivity near the interfaces which is in agreement with experimental findings that have speculated about the occurrence of conductivity channels.

POLYPHYS Seminar HCP F 43.4 
Wednesday 12. Apr 2017 10:15

Laura Stricker Max Planck Institute for Dynamics and SelfOrganization, Gottingen, Germany 
Numerical study of artificial microswimmers propelled by Marangoni flow Show / Hide AbstractIn order to understand the behaviour of biological microswimmers, such as bacteria and spermatozoa, it is important to know which aspects are governed merely by the physics of the system and which aspects are biologyrelated. In the present study we address the mechanisms of locomotion of nonbiological swimmers. In particular, we consider the behaviour of a single artificial microswimmer, namely an active droplet moving by Marangoni flow. We provide a numerical treatment for the main factors playing a role in real systems, such as advection, mass diffusion and the presence of several mutually interacting chemical species. The flow field inside and outside the droplet is modelled, to account for the twoway coupling between the motion of the swimmer and the surrounding fluid. We also consider the evolution of two concentration fields: the surfactant concentration in the liquid surrounding the droplet, and the surfactant concentration on the surface, related to the surface tension. We examine different interaction mechanisms between the concentration fields, such as the case of insoluble surfactants and the case of soluble surfactants with adsorption/desorption at the surface. The numerical results have been validated through comparison with analytical calculations. We show that our model can reproduce the typical pusher/puller behaviour presented by squirmers. It is also able to capture the selfpropulsion mechanism of droplets driven by BelousovZhabotinsky (BZ) reactions, as well as a typical chemotactic behaviour.

POLYPHYS Seminar HCP F 43.4 
Wednesday 5. Apr 2017 10:15

Susmita Roy Department of Theoretical Physics, Bayreuth, Germany 
Nonequilibrium molecular dynamics simulation technique for polymers Show / Hide AbstractBeyond equilibrium Molecular dynamics is a powerful simulation tool. Including living system processes, decription of any kind of ow in nature can be explained with beyond equilibrium molecular dynamics simulation technique. Beyond equlibrium thermodynamics and statistical mechanics are the basics behind this MD simulation. I will discuss the role of nonequilibrium thermodynamics based on GENERIC (general equation for the nonequilibrium reversibleirreversible coupling), for the description of Molecular dynamics simulation.

POLYPHYS Seminar HCP F 43.4 
Friday 3. Mar 2017 10:00

Maksym Osmanov Polymer Physics, Department of Materials, ETH Zurich 
Entropydriven dynamics of open quantum systems 
Talk HCI J 574 
Thursday 2. Mar 2017 10:15

Mathias Nagel Soft Materials, Department of Materials, ETH Zurich 
The role of hydrodynamic models for the probing of viscoelastic interfaces 
POLYPHYS Seminar HCP F 43.4 
Wednesday 1. Mar 2017 15:00

Ludwik Leibler École supérieure de physique et de chimie industrielles de la ville de Paris (ESPCI ParisTech) 
Principles of vitrimer chemistry 
Talk HCI G 7 
Wednesday 7. Dec 2016 13:00

Guanchen Li Virginia Tech, Blacksburg, United States 
Steepest entropy ascent in nonequilibrium thermodynamics Show / Hide AbstractThermodynamics has been very successful in explaining the properties of macroscopic systems in equilibrium and nearequilibrium states. Many thermodynamic concepts, including the canonical distribution and the Onsager relations, can be viewed as concise patterns in the collective behavior of individual particles at a more microscopic level. However, the application of these thermodynamic concepts as currently formulated requires assumptions of nearequilibrium or localequilibrium behavior. Thus, the study of phenomena in the farfromequilibrium or nonlocalequilibrium realm still generally relies on an investigation of the mechanical processes (e.g., collisions) of individual quantum states or particles, an approach, which necessarily entails a heavy computational burden. To address this drawback, recent research has pursued taking advantage of the use of thermodynamic patterns of collective particle behavior even in the nonequilibrium realm in order to simplify model requirements and hence the computational burden via the inclusion of thermodynamic information. One approach, whose reach has recently been extended to cover all spatial and temporal scales from a practical standpoint, is a novel firstprinciples nonequilibrium thermodynamicensemble framework called SteepestEntropyAscent Quantum Thermodynamics (SEAQT). Its equation of motion is able to predict irreversible state evolutions on the basis of a gradient dynamics in system state space (such as phase space or Hilbert or Fock space) without explicitly tracking the microscopic particle or quantum state mechanics. The advantage of this approach is not only computational but is one in which all of the laws of physics and thermodynamics are inherently satisfied. This talk demonstrates how many thermodynamic concepts (e.g., equilibrium state, intensive properties, the Gibbs relation, the Clausius inequality, and the Onsager relations) can be generalized fundamentally into the farfromequilibrium realm using the SEAQT framework applied to the relaxation of a local, isolated system in nonequilibrium. This is followed by illustrations of its application to modeling the transient behavior of reactive systems, nonquasiequilibrium thermodynamic cycles, local nonequilibrium transport at a solidstate interface, and biological systems.

POLYPHYS Seminar HCI J 2 
Monday 7. Nov 2016 10:15

Santosh Ansumali Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bangalore, India 
Molecular dice Show / Hide AbstractGood quality pseudorandom numbers are at the heart of many computer simulation methodologies in science and engineering. Starting from pseudorandom number generators, one often defines appropriate inversion schemes to generate desired distributions. As Gaussian statistics appears very often in physical processes, the inversion scheme for generating Gaussian statistics, BoxMuller method, plays an important role in scientific simulations. However, this method requires 1001000 floating point operations to generate a single Gaussian random number. Our ability to do large scale simulations can be greatly enhanced if an analog of pseudorandom number generators can be found for direct generation of Gaussian random sequence. We propose a new algorithm ``Molecular dice'' to directly generate Gaussian random number. This new algorithm is able to generate Gaussian sequence as fast as uniform number sequence itself. We explore possible O(N) extension of this algorithm for multivariate normal distribution. Finally, we comment on possibility of generating other statistics such as Poisson distribution using molecular dice idea.

POLYPHYS Seminar HCP F 43.4 
Tuesday 4. Oct 2016 11:00

S. Ramakrishnan Indian Institute of Science, Bangalore, India 
From Chain Folding to 2D Polymers Show / Hide AbstractControl of chain conformation in solution has several interesting ramifications – from mimicking the exquisite conformational control seen in biological macromolecules to understanding factors that govern the lamellar crystallite sizes in semicrystalline polymers. During the past decade we have examined several aspects dealing with control of chain conformation in solution; and we have also attempted to translate this control towards regulating the morphological characteristics of the bulk polymer. The lamellar morphology that is often realized in these attempts leads to the layering of different types of immiscible domains; a closer examination of these layered structures prompted us to begin exploring the similarity between these systems and 2D polymers. 2D polymers have begun to attract the attention of several groups worldwide; although many early efforts have examined polymerization at airwater interfaces and also within vesicles, these do not typically constitute robust structures that would withstand exfoliation. One of the prime drivers of this field is graphene, which could be viewed as the archetypical 2D polymer – a robust and reasonably stiff system that can be readily exfoliated to generate single atomthick carbon sheets. The remarkable properties of graphene amply justify the incredible attention that this class of materials has received during the past decade. As a polymer chemist one can ask – what are the possible design strategies to prepare 2dimensional polymers? Evidently, folding of polymer chains does constitute one way to generate 2D polymeric nanoobjects; the thickness of these sheets would be the height of a folded chain – something we have recently demonstrated. However, these are not robust structures that can be prepared in bulk and exfoliated. It is with this challenge that we have just begun to examine alternate approaches to prepare 2D polymers; broadly, our strategy is to preorganize multisegmented monomers bearing at least two polymerizable units at the segment junctions. The preorganization is designed to be driven by segment immiscibility and strengthened by the strong interactions, such as crystallization, within the domains; polymerization of the double bonds in the solid or semimolten state it was expected would lead to the formation of a crosslinked and reasonably stiff sheet that would represent a 2D polymer. By suitable choice of the outer segments, it was felt that exfoliation could be made feasible. In the talk, I shall describe our efforts beginning with chain folding and I shall end with our recent foray into 2D polymers.

Talk HCI J 498 
Tuesday 4. Oct 2016 10:15

Anna C. Balazs Department of Chemical Engineering Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA 
Pattern Recognition with Materials that Compute: Exploiting the Properties of Selfoscillating Polymer Gels Show / Hide AbstractDriven by advances in both materials and computer science, researchers are attempting to design systems where the computer and the material are one and the same entity. Using theoretical and computational modeling, we design a hybrid material system that can autonomously transduce chemical, mechanical and electrical energy to perform a computational task in a selforganized manner, without the need for external electrical power sources. Each unit in this system integrates a selfoscillating gel, which undergoes the BelousovZhabotinsky (BZ) reaction, with an overlaying piezoelectric (PZ) cantilever. The chemomechanical oscillations of the BZ gels deflect the piezoelectric layer, which consequently generates a voltage across the material. When these BZPZ units are connected in series by electrical wires, the oscillations of these units become synchronized across the network, with the mode of synchronization depending on the polarity of the piezoelectric. Taking advantage of this synchronization behavior, we show that the network of coupled BZPZ oscillators can perform pattern recognition tasks. We define the “stored” pattern as a set of polarities of the individual BZPZ units, and the input patterns are coded through the initial phase of the oscillations imposed on these units. The results of the computational modeling show that the input pattern closest to the stored pattern exhibits the fastest convergence time to the stable synchronization behavior. In this way, the networks of coupled BZPZ oscillators achieve pattern recognition. Further, we show that the convergence time to the stable synchronization provides a robust measure of the degree of match between the input and stored patterns. Through these studies, we establish experimentally realizable design rules for creating materials that compute.

Talk HCP E 47.2 
Thursday 29. Sep 2016 11:00

David R. Nelson Lyman Laboratory of Physics, Harvard University 
Thermalized sheets and shells: curvature matters Show / Hide AbstractUnderstanding deformations of macroscopic thin plates and shells has a long and rich history, culminating with the Foepplvon Karman equations in 1904, characterized by a dimensionless coupling constant (the ”Foeppl von Karman number”) that can easily reach vK = 107 in an ordinary sheet of writing paper. However, thermal fluctuations in thin elastic membranes fundamentally alter the long wavelength physics, as exemplified by exper iments from the McEuen group at Cornell that twist and bend individual atomicallythin freestanding graphene sheets (with vK = 1013). We review here the remarkable properties of thermalized sheets, where enhancements of the bending rigidity at T = 300 K by factors of ∼ 5000 have now been observed. We then move on to discuss thin amorphous spherical shells with a uniform nonzero curvature, accessible for example with soft matter experi ments on diblock copolymers. This curvature couples the inplane stretching modes with the outofplane undulation modes, giving rise to qualitative differences in the fluctuations of thermal spherical shells compared to flat membranes. Interesting effects arise because a shell can support a pressure difference between its interior and exterior. Thermal corrections to the pre dictions of classical shell theory for microscale shells diverge as the shell radius tends to infinity.

Talk HIT E 41.1 
Wednesday 14. Sep 2016 17:00

W. Hugh Woodin Department of Philosophy, Harvard University, United States 
Bernays Lecture: Unsolvable Problems in Mathematics and what to do about them 
Talk HG F 3 
Wednesday 6. Jul 2016 10:15

Mauricio Del Razo Sarmina Department of Applied Mathematics, University of Washington, Seattle, USA 
Twodimensional immersed interface method for moving interfaces Show / Hide AbstractImmersed interface problems usually arise when modeling the dynamics between two different materials, like water and oil, or the same material at different states, such as water and ice. The modeling and computational simulation of these problems have multiple applications ranging from phase transition to biological interfaces. The immersed interface method is a powerful secondorder accurate numerical method to model such problems. In the present talk, we will show how to implement the immersed interface method for 2D heat equations with fixed or moving immersed interfaces and a singular forcing term along the interface. Specifically, we solve the Stefan problem in two dimensions with an arbitrary interface.

POLYPHYS Seminar HCP F43.4 
Wednesday 22. Jun 2016 13:30

Jérôme Flakowski Polymer Physics, Department of Materials, ETH Zurich 
Thermodynamics of Mesoscopic Quantum Systems: from a single qubit to light harvesting complexes 
Talk HCI J 574 
Wednesday 6. Apr 2016 10:15

Markus Hütter Eindhoven University of Technology, Mechanical Engineering, Polymer Technology, The Netherlands 
Thermodynamic Modeling of Glasses: Identification of the Cauchy Stress, and the Effects of Physical Aging and Mechanical Rejuvenation Show / Hide AbstractPolymer glasses typically age and change their mechanical behaviour when kept for a certain waiting time at a temperature below their glass transition temperature before mechanical testing. Particularly, the yield stress increases with the waiting (=aging) time. On the other hand, the application of a high mechanical load tends to ‘rejuvenate’ the aged sample. In this paper, I am concerned with modelling the influence of physical aging on the viscoplasticity (yield and postyieldbehavior) of glassy materials. To that end, the concept of two distinct subsystems, kinetic and configurational, is combined with elastoviscoplasticity. In the literature, the configurational subsystem is described by a socalled configurational (a.k.a. fictive or effective) temperature, whereas in this presentation I use the corresponding entropy density instead. Using nonequilibrium thermodynamics, it is shown that the stress tensor is in general not simply related to the derivative of the thermodynamic potential with respect to deformation, but that there can be nonpotential contributions (akin to hypoelasticity) that vanish as the system tends to thermal equilibrium. This has ramifications for the driving forces for viscoplastic deformation and mechanical rejuvenation. Part of this thermodynamic modelling, namely the identification of the stress tensor, is related to the Poisson operator that must satisfy the Jacobi identity. Checking this identity is usually tedious, certainly in the current case. I present some lessons learned that help to drastically simplify the corresponding calculations. The main step is to use a Lagrangian formulation of the model for which the Jacobi identity can be checked readily, and subsequently reducing the Lagrangian Poisson bracket to the Eulerian setting.

POLYPHYS Seminar HCI J498 
Thursday 24. Mar 2016 10:15

Johannes Kemper Institute of Theoretical Physics, WWU Münster, Germany 
Thermodynamically consistent gradient dynamics models for interfacedominated evolution of thin films Show / Hide AbstractThe talk begins with an introduction of the two simplest types of gradient dynamics equations for single scalar order parameter fields that are often employed to describe interface evolution. Here we use the example of evolution equations for the profile of a thin liquid film without and with evaporation, respectively. For a conserved field it has the structure of the CahnHilliard equation while the nonconserved equation is of AllenCahn type [1,2]. The underlying free energy (or Lyapunov functional) includes geometric interfacial energy contributions as well as a filmsubstrate interaction potential that accounts for wettability. The gradient dynamics approach will then be extended towards the case of two order parameter fields and I will shortly discuss the Onsager character of the mobility matrix. Then I will show that these models are able to describe different systems involving simple and complex liquids. In particular, I focus on the description of films of mixtures and suspensions and present the underlying energies and mobilities [3,4]. In addition, the model even allows one to study the evolution in certain nonequilibrium settings like, for instance, drops sliding down an inclined surface. Based on my master thesis, I will further illustrate how a general viscoelastic description of a soft layer that incorporates an additional elastic energy contribution can be simplified by a local approximation [5]. A twolayer model can then be extended to include such a local elastic energy to describe a liquid film and drops on top of a viscoelastic material. References: [1] U. Thiele, J. Phys.Cond. Mat. 22, 084019 (2010). [2] U. Thiele, Eur. Phys. J. Special Topics, 197 213220 (2011). [3] U. Thiele, A. J. Archer and M. Plapp, Phys. Fluids 24, 102107 (2012). [4] U. Thiele, D. V. Todorova and H. Lopez, Phys. Rev. Lett. 111, 117801 (2013). [5] J. Kemper, “Modeling of viscous drops on soft substrates”, Masterthesis, WWU Münster (2015).

POLYPHYS Seminar HCP F43.4 
Wednesday 23. Mar 2016 10:15

Fernando Bresme Department of Chemistry, Imperial College London, UK 
Molecular Simulations of the Interfacial structure of soft interfaces Show / Hide AbstractSoft interfaces deform easily under the action of thermal fluctuations. These interfaces appear in many problems of scientific and technological interest; liquidvapour, liquidliquid, surfactant thin films, biological membranes, fluidnanomaterial interfaces or fluids in confined spaces. Experiments (Xray, neutron diffraction, neutron reflectivity and non linear spectroscopy) and computer simulations (classical and ab initio simulations) have advanced our ability to scrutinise the interfacial structure of these systems at the molecular level. However, the precise characterisation of the interface represents a considerable challenge since interfaces fluctuate permanently as a response to the thermal fluctuations, blurring the interfacial structure and making difficult the comparison of simulation and experimental data. I will discuss computational approaches to quantify the interfacial structure of soft interfaces by considering the thermal fluctuations. The application of these approaches to liquid interfaces (non polar  alkanes , polar water, molten salts, ionic solutions), and self assembled structures (surfactant monolayers, surfactant thin films and phospholipid bilayers) provide structural information at an exquisite level of detail, opening a route to tackle important questions in interfacial science, from hydrophobicity to ion adsorption at aqueous interfaces.

POLYPHYS Seminar HCI J498 
Wednesday 10. Feb 2016 10:15

Yitzhak Rabin Department of Physics and Institute for Nanotechnology and Advanced Materials, Bar−Ilan University, Israel 
A truly complex fluid: particles with random interactions Show / Hide AbstractWe use molecular dynamics simulations to study multicomponent systems in which all the particles are different (APD). The particles are assumed to interact via LennardJones (LJ) potentials, with identical size parameters but their pair interaction parameters are generated at random from some distribution We analyze both the global and the local properties of these systems at temperatures above and below the freezing transition and find that APD fluids relax into a nonrandom state characterized by clustering of particles according to the values of their pair interaction parameters (Neighborhood Identity Ordering  NIO). In order to separate NIO from the freezing transition we introduce the Random Bond Lattice model in which N(N1)/2 bond parameters between neighboring particles are generated at random (quenched realization of bonds). The particles are then placed on a hexagonal lattice and the system is studied using MC simulations with particle exchange. We find that similarly to spin glasses, there exists a temperature above which the statistical properties of the system can be calculated using annealed averaging over all possible realizations of the bond parameters. However, the presence of particle exchange leads to a new phenomenon: the annealed approximation becomes accurate at any temperature, if the size of the system is increased above a certain (temperaturedependent) value. We discuss the ramifications of this result for the statistical properties of NPhard problems.

POLYPHYS Seminar HCI J 574 
Friday 11. Dec 2015 11:00

Alberto FernandezNieves School of Physics. Georgia Institute of Technology 
Toroidal Physics Show / Hide AbstractThe torus is an interesting mathematical surface. Its topological and geometrical properties both affect a variety of phenomena. This talk will discuss some of our recent work with toroidal droplets. We will briefly cover their generation and hydrodynamic instability, both in the presence and absence of charge, and discuss how to effectively “freeze” the toroidal shape with the use of yieldstress materials. We will then focus on nematic liquid crystals, and show that these experience spontaneous reflection symmetry breaking when confined inside toroidal spaces. We will end by briefly presenting recent results with active nematics confined to the toroidal surface; these are the first realization of nematic order on a torus.

Talk HCI J 498 
Wednesday 9. Dec 2015 10:15

David A. Edwards School of Engineering and Applied Sciences, Harvard University, MA, US 
Redesigning Nutrition Delivery Show / Hide AbstractTechnological innovations, including food additives and plastics, critical to the 20th century food system feeding a growing human population with relatively low cost, accessible, reasonably nutritious and good tasting food, are today seen as obstacles to improving human health and environmental sustainability. Lowering these obstacles will require scientific advances and changing consumer behavior. This talk summarizes recent innovations from our lab, which since 2007 has been open to the public, joined by a futureoffood restaurant, to permit early public engagement in and shaping of new food delivery technologies aimed at improved health and environment, including edible food packaging, air food, and digitized scent.

POLYPHYS Seminar HCI G574 
Wednesday 2. Dec 2015 10:15

Sam Safran Department of Materials and Interfaces, Weizmann Institute of Science, Israel 
Line Active Lipids Promote Formation of Nanoscale Domains in Model Membranes Show / Hide AbstractFinitesized (10100 nm), longlived domains, are found in biological membranes where they are termed “lipid rafts” that selectively transport proteins and lipids. The existence of these domains has inspired studies of lipid phase separation in model, multicomponent membranes. A priori, one expects the size of phase separated domains to be on the order of the system size because the positive line tension of the interfaces between the domains of incompatible lipids drives domain coarsening. This expectation motivates the puzzle of the observed stability of nanometric domains in some model systems. In this talk on possible theoretical resolutions of this puzzle, we first review the physics of phase separation in mixtures and mention several scenarios in which finite sized domains (akin to modulated structures) can be stable in equilibrium. We then introduce the relevant experiments that focus on domain formation in mixed membranes. The theory explains how nanosized domains may be stabilized by line active, “hybrid” lipids (such as POPC) that can reside at the interfaces separating domains of saturated and unsaturated lipids; in the absence of these line active species, the domains are of the order of the system size. The line activity arises solely from the chain packing characteristics of the hybrid lipids near the saturatedunsaturated interface and not from hydrophobichydrophilic effects. In the higher temperature, mixed (single phase) regime, the theory predicts correlation lengths and correlation times that are, respectively, shorter and longer when hybrid lipids are added. Nanoscale fluctuation domains are more probable and have longer lifetimes than in twocomponent, saturated/unsaturated mixtures. In the lower temperature, phase separated (coexistence) regime, zero line tension between domains rich in saturated/unsaturated lipids may occur at physiologically relevant temperatures and large hybrid fractions. Under these conditions, the membrane can spontaneously form more interfaces and promote the formation of stable nanoscale domains. Collaborations: Benoit Palmieri, Tetsuya Yamomoto, Robert Brewster

POLYPHYS Seminar HCI J498 
Thursday 24. Sep 2015 11:15

Stefan Wenk Laboratory of Biosensors and Bioelectronics , Institute for Biomedical Engineering, ETH Zurich 
Simulating Magnetorelaxometry and Magnetic MultiCore Nanoparticles Show / Hide AbstractI will address the magnetization dynamics of magnetic single domain nanoparticles and cluster nanoparticles. I will talk about my approaches using Brownian dynamics and LandauLifshitzGilbert equation. In a second part I will explain a newly developed model that is able to describe so far unexplained high magnetic moments of some cluster nanoparticles, such as FeraSpin R.

POLYPHYS Seminar HCI J 574 
Wednesday 16. Sep 2015 10:15

Meisam Pourali Department of Physical Chemistry, University of Tehran, Iran 
Nonequilibrium Thermodynamics Approach to Interfacial Transport Phenomena Show / Hide AbstractThe dynamic properties of interfaces often play a crucial role in the macroscopic dynamics of multiphase soft condensed matter systems. These properties affect the dynamics of many phenomena such as emulsions, dispersions of vesicles, biological fluid, free surface flows, immiscible polymer blends, and dynamics of many other complex systems. In the description of transport through and along interfaces using nonequilibrium thermodynamics, one may use excess densities, fluxes, and also structural variables at the socalled dividing surface. But the precise choice of the location of this dividing surface within the interfacial region is not unique and density of conserved quantities change with the precise location of the dividing surface within the interfacial region. So balancing of corresponding extensive quantities at interfaces in terms of excess densities is ambiguous. Recently Ottinger and Venerus [HC Öttinger and DC Venerus, AIChE Journal 60 (4), 14241433 (2014) (and references therein)] proposed a method to handle such ambiguities for moving interfaces. In this seminar this method is presented. First we introduce the interfacial velocity and principle of gauge transformation to establish relationships between bulk phase thermodynamic quantities and to identify relevant thermodynamic quantities of the moving interface. Then we formulate jump balance for mass and momentum and evolution equations of entropy and energy. With local equilibrium assumption we obtain an expression for entropy production and then we are able to formulate forcefluxes relations, constitutive equations, for transport both within the interface and between the interface and bulk. Finally usefulness and generality of this approach is illustrated by several examples.

POLYPHYS Seminar HCI J 574 
Wednesday 24. Jun 2015 10:15

Horacio Andres Vargas Guzman Max Planck Institut für Polymerforschung (MPIP), Mainz 
A 2 scale approach to combine continuum simulations of dynamic AFM with soft materials dynamics Show / Hide AbstractDynamic atomic force microscopy techniques have been developed in the field of nanoscience. Their most significant milestones go from achieving true atomic resolution in inorganic surfaces to imaging biological system with unprecedented molecular resolutions. A relevant research avenue within those experimental techniques is devoted to the generation of molecular resolution images of soft materials in liquid environments and its mechanical characterization. Despite its impressive experimental development, the technique has some key limitations from the modeling point of view. The modeling framework of AFM dynamic techniques fail to reproduce soft materials phenomena existing in polymeric and biological systems, such as viscoelasticity and/or high deformation regimes. Analytical expressions to estimate the exerted force by an AFM cantilever tip will facilitate the interpretation and allow further development of dynamic AFM techniques, such as the envisioned applications in the medical and advanced materials fields. However there are several constraints while deducing analytical expressions for the exerted force, such as the nonlinear character of the cantilevertip system. We have deduced a closedform analytical expression to estimate the tipsample peak forces while imaging soft materials in liquid environment. Whereby we have combined a multivariate regression analysis with the use of the virialdissipation method and continuum contact mechanics models. The delivered expression enables to estimate the peak force based on dynamic AFM observables, probe characteristics and the material properties of the sample. Moreover, the accuracy of this expression has been verified but comparing it to numerical simulations of dynamics AFM. Another ongoing work is to couple the presented analytical expression for the forces to Coarse Grained (CG) simulations on the target soft material. This will allow us to understand the connection between the measured effective mechanical properties and the simulated dynamics of the targeted materials (e.g. IgM antibody in water), and thus complete the theoretical description of the sample's non invasive imaging regime with dynamic AFM.

POLYPHYS Seminar HCI J 574 
Wednesday 20. May 2015 10:15

Jay Schieber Illinois Institute of Technology 
Complex flow predictions of highly entangled polymers Show / Hide AbstractThe DoiEdwards tube model provides by far the most popular basis for a molecular model of entangled polymer dynamics. However, in order to provide reasonably quantitative agreement with observation, there have been many independent phenomenological additions to the model, such that there really is no single tube model, but rather different models for different kinds of flows, different chain architectures, or blends. Because of these limitations, we developed an alternative approach. We use a series of hypothesisdriven coarsegraining steps to create a hierarchy of integrated sliplink models. This procedure produces a mathematical model whose calculations are 3 million times faster than the mostdetailed level of description, and 20 billion times faster than atomisticlevel calculations. Using any single member of the hierarchy, we can then fit our single adjustable (friction) parameter to a dynamic equilibrium experiment of a single chain molecular weight and architecture, and make predictions of the nonlinear rheology of any chain architecture, molecular weight, blends of these and in any flow field. Predictions of experiment are quantitative. Porting of our code to GPUs gives an additional two orders of speedup, making most calculations possible on a desktop computer with a single graphics card. More important than computational speed up is the dramatic reduction in the number of dynamic variables necessary to describe the system, which suggests a deep understanding of the physics of entangled polymers, justifying the postulations made by Sam Edwards and PierreGilles de Gennes more than 40 years ago.

POLYPHYS Seminar HCI J 574 
Friday 8. May 2015 10:30

Ahmad Moghimi Kheirabadi School of Mechanical Engineering, Sharif University of Technology, Tehran 
Blockcopolymers at interfaces: results and perspectives Show / Hide AbstractFirstly, I will briefly discuss about projects which I have done in my career including nonequilibrium molecular dynamics simulation (NEMD), coarse graining molecular dynamics (CGMD), direct simulation Monte Carlo (DSMC) and CFD simulation in the field of condensed matter. In the second part of my talk, I will present a literature review on numerical modeling and experimental analysis of blockcopolymers. Brownian dynamics, dissipative particle dynamics and other methods for microscale modeling and CGMD and MC methods for molecular modeling of blockcopolymers will be reviewed. Also in this part, different methods of experimental analysis of polymers such as AFM, SEM, Xray and Neutron reflectivity will be discussed. Finally I will present my ideas about blockcopolymers at interfaces and both computational and experimental issues will be examined. We can use MDMC simulation in the molecular level to predict the amphiphilic blockcopolymer behaviors. Also we can use various types of microscopy and also reflectivity measurements to determine rheological properties and structures of blockcopolymers at interfaces.

POLYPHYS Seminar HCI J 574 
Wednesday 15. Apr 2015 10:40

Thierry Savin Department of Engineering, Cambridge University 
Phase diagram of 2D polymers in poor or good solvents Show / Hide AbstractI will briefly present preliminary results on a 2D model of polymer that can predict the configurations adopted by a chain in good or poor solvents. We model a polymer as a selfavoiding walk on square lattice, and introduce simple, trackable expressions for its bending energy and its interaction with the solvent. This model allows us to derive a phase diagram of polymer configurations as a function of the temperature, the chain’s persistence length and the quality of the solvent.

POLYPHYS Seminar HCI J 574 
Wednesday 15. Apr 2015 10:15

Thierry Savin Department of Engineering, Cambridge University 
Nonequilibrium thermodynamics of an interface Show / Hide AbstractInterfacial thermodynamics has deep ramifications in understanding the boundary conditions of transport theories. Gibbs' pioneer treatment of phase coexistence describes an interface as a separate and autonomous 2D “dividing surface,” whose temperature is unequivocally the one adopted uniformly by the entire equilibrium system. However, in nonequilibrium processes such as evaporation/condensation or heterogeneous catalysis, large variations of temperature across the interface are observed and therefore invalidate Gibbs' approach to describing these most common situations. I will present a formulation of the local equilibrium for interfaces that extends the thermodynamics of the dividing surface to nonequilibrium. By identifying the position of the interface with a gauge degree of freedom, we exploit gaugeinvariance requirements to consistently define the intensive variables for the interface. The model is verified under stringent conditions by employing highprecision nonequilibrium molecular dynamics simulations of a coexisting vaporliquid LennardJones fluid. We conclude that the interfacial temperature is determined using the surface tension as a “thermometer,” and can be significantly different from the temperatures of the adjacent phases. These findings lay new foundations for nonequilibrium interfacial thermodynamics.

POLYPHYS Seminar HCI J 574 
Wednesday 1. Apr 2015 14:00

Maksym Osmanov Polymer Physics, Department of Materials, ETH Zurich 
Entropic fluctuations of open quantum systems. Show / Hide AbstractWe discuss the entropic fluctuation relations for the recently developed thermodynamically consistent nonlinear master equation describing open quantum systems out of equilibrium. Such fluctuation theorem is already proven for a Lindblad master equation, based on a deformation of the dissipative generator. We suggest a new way of deforming the generator, which extends to the nonlinear case while still be supported by statistical mechanical arguments, and numerically compute the generating function of the mean entropy transport. We show that the obtained generating function yields fluctuation relations, boiling down to Onsager relations in linear response regime.

POLYPHYS Seminar HCI J 574 
Tuesday 31. Mar 2015 16:45

Daan Frenkel Department of Chemistry, University of Cambridge, UK 
Entropy and addressable selfassembly 
Talk HCI J 3 
Wednesday 25. Mar 2015 10:15

Jérôme Flakowski Polymer Physics, Department of Materials, ETH Zurich 
Beyond the strict weakcoupling limit: just do it but stay coherent Show / Hide AbstractCan we say something new about the quantum dissipative evolution of a simple twolevel quantum system? Its decay times? Thanks to a recently developed set of thermodynamically consistent nonlinear master equations we explore these questions in the linear response regime and have so far found a positive answer. Most importantly, we observed a temperaturedependent bifurcation phenomenon in the T2 over 2*T1 ratio reflected in the timeevolution by a biexponential decay of the polarisations. Relying on these renewed understandings, we briefly reinterpret some experimental results. Finally, based on these new insights we discuss future prospects ranging from nanoelectronics to lightharvesting complexes.

POLYPHYS Seminar HCI J 574 
Wednesday 18. Mar 2015 10:15

Ingo Füreder Polymer Physics, Department of Materials, ETH Zurich 
Towards a constitutive model for supercooled liquids Show / Hide AbstractVarious soft matter systems (foams, dense emulsions, colloids etc.) show rheological properties similar to those of supercooled liquids. In order to relate structural properties in these materials to dynamical behavior, it appears to be promising to focus on the local potential minima of the system (its inherent structure, IS). Extending previous work on the response of the IS on external perturbation, we identify regions in the system which rearrange in a cooperative manner and are the basis for the description of stress relaxation processes in the system. We will discuss a tentative draft of a simple constitutive model for supercooled liquids and compare it to reference data obtained from nonequilibrium molecular dynamics simulations.

POLYPHYS Seminar HCI J 574 
Wednesday 11. Mar 2015 16:00

Steven Shu Secretary of Energy of the United States of America, 2009  2013 
Energy, Climate Change and Sustainability Show / Hide Abstract

Talk HG F 30 
Wednesday 11. Mar 2015 10:15

Alan Luo Polymer Physics, Department of Materials, ETH Zurich 
Rheology in flatland: first steps Show / Hide Abstract present a rather general approach based on nonequilibrium thermodynamics for describing the interfacial rheology of particlestabilised interfaces. This approach bridges the gap between macroscopic constitutive equations and the underlying microscopic model and here, I illustrate it for a microscopic model of hard ellipsoids confined to lie inplane, which is intended to simply represent anisotropic particles adsorbed on a fluidfluid interface. Further directions this work could take (including into the third dimension!) will be discussed.

POLYPHYS Seminar HCI J 574 
Wednesday 4. Mar 2015 10:15

Carl Zinner Polymer Physics, Department of Materials, ETH Zurich 
Rarefied Gas Channel Flows Show / Hide AbstractWe discuss the numerical implementation of moment equations and their boundary conditions for rarefied gases in simple channel flows.

POLYPHYS Seminar HCI J 574 
Thursday 26. Feb 2015 10:15

Marco Schweizer Polymer Physics, Department of Materials, ETH Zurich 
Systematic coarsegraining in nucleation theory Show / Hide AbstractA vast zoo of models describing the initial stage of nucleation processes has been obtained since Becker and Doering gave the starting signal through their publication about the kinetic theory of nucleation (1935). However, coarsegrained attempts to obtain the key quantity  the nucleation rate  still fail to give accurate results by 34 orders of magnitude as compared to bruteforce molecular dynamics simulations, considered to be exact. In the talk it is intuitively explained that from a nonequilibrium thermodynamics perspective only one very specific class of nucleation equations can be admissible [1]. We show further evidence in this direction by presenting a connection of microscopic dynamics and the aforementioned coarsegrained structure of admissible equations via a systematic coarsegraining procedure. Finally, we claim that the coarsegraining procedure will not lack 34 order of magnitude in nucleation rate predictions. The latter being an artefact of describing nucleation through additional degrees of freedom rather than the amputated choice of a single degree of freedom.

POLYPHYS Seminar HCI G 574 
Wednesday 18. Feb 2015 10:15

Grégoire Julien Laboratoire Polymère et Matériaux Avancés, UMR 5268 CNRS/SolvayRhodia, France 
Dynamics in polymers blends close to and below the glass transition temperature: aging and rejuvenation. Show / Hide AbstractIn this work, we propose a model for describing the dynamics in polymer blends where at least one of the species corresponds to molecular weight below the entanglement threshold. The model incorporates the he terogeneous nature of dynamics close to Tg on a scale of dynamical heterogeneities of size ξ of order 35 nm. We assume that spatial distributions of relaxation times are the consequence of concentration fluctuations. A Gibbs free energy model (which is an extension of the FloryHuggins model) for compressible blends is proposed for calculating driving forces. The spatial dynamics follows then from an Onsager like description and the evolution of concentrations is calculated by Langevin equations on the scale of dynamical heteroge neities. The dynamics takes also into account a ”facilitation mechanism” which describes the relaxation of slow dynamic heterogeneities when surrounded by faster subunits as due to free volume diffusion or diffusion of different components. This model is applied to study phase separation close to and below Tg upon co oling, and rejuvenation upon heating. In the course of a phase separation, slow structures are observed to be forming in coexistence with faster ones. In the same time, the global dynamics of the system slows down and domains grow like the logarithm of the time. During rejuvenation, the temperature is increased again in a totally miscible range of temperatures far above Tg. In particular, we observe that glassy morphologies melt much faster the elapsed time required to build them during aging : there is a temporal asymmetry between the aging and the rejuvenation process. We also show that the facilitation mechanism is a key for describing the rejuvenation of such a material. Finally, this work can be used for designing longlived nanocomposite polymer materials with a desired shape of morphologies.

POLYPHYS Seminar HCI J 574 
Wednesday 26. Nov 2014 10:15

Pavlos S. Stephanou Department of Mathematics and Statistics, University of Cyprus 
Development of scalebridging methodologies for the reliable prediction of the viscoelastic properties of polymer melts Show / Hide Abstract Polymeric chains are characterized by a broad spectrum of length and time scales, which gives rise to properties that are totally different from those of the simple Newtonian liquids, especially under flow conditions. Our aim is to contribute to the understanding of the complex interplay between microscopic chain configurations or conformations and macroscopic behaviour, which is a central goal in polymer science and technology and a prerequisite for the design of improved polymers tailored for specific applications. Guided from the reptation theory of de Gennes and Doi/Edwards, we will first show how one can predict the linear viscoelastic properties of polymer melts by using atomistic trajectories from detailed MD simulations to calculate the primitive path (PP) segment survival probability function ψ(s,t) for entangled melts, both for mono and bidisperse polymers. This function is at the heart of the Doi/Edwards reptation theory but also of all tube models. Next, we will show how one can use modern formalisms of nonequilibrium thermodynamics to construct differential constitutive equations for polymer melts. Our emphasis here will be on the derivation of a set of dynamic equations describing in a unified way the microstructure, the linear and nonlinear rheology, and the phase behaviour of polymer melts filled with nanoparticles (also known as polymer nanocomposite melts).

POLYPHYS Seminar HCI J 574 
Thursday 13. Nov 2014 10:15

Mark Peletier Technische Universiteit Eindhoven, Netherlands 
Stochastic origins of gradient flows: a general connection Show / Hide AbstractAlthough it has been known for some time that certain gradientflow structures are related to the large deviations of a stochastic process, until recently we only understood this at the level of examples. In this lecture I will explain a general structure that gives rise to the following property: for every sequence of reversible stochastic processes with a largedeviations principle, the limiting equation is a generalized gradient flow that maps onetoone to the largedeviations rate function. Therefore the large class of reversible stochastic processes generates a correspondingly large class of generalized gradient flows. This is joint work with Michiel Renger and Alexander Mielke (both WIAS).

POLYPHYS Seminar HCI J 8 
Friday 3. Oct 2014 14:00

Constantino Creton Laboratoire de Sciences et Ingénierie de la Matière Molle, ESPCI ParisTech 
Sacrificial bonds for the toughening of soft elastic materials 
Talk HCI J 489 
Thursday 18. Sep 2014 16:30

Jerome Crassous Physical Chemistry, Chemical Center, Lund University 
Supracolloidal selfassembly of composite microgels 
Talk HCI H 507 
Wednesday 16. Jul 2014 10:15

Alberto Montefusco Politecnico di Milano 
TOWARDS GEOMETRIC THERMODYNAMICS: Comparison of the GENERIC and SEA formalisms with focus on the Boltzmann Equation Show / Hide AbstractThe talk will deal with the dynamical modelling of thermodynamic systems out of equilibrium and is articulated in three parts. The first is a brief review of the main interpretations attached to Thermodynamics and of some dynamic principles proposed during the twentieth century. The second aims at understanding similarities and differences between the Steepest Entropy Ascent (SEA) dynamical model proposed by Beretta and the GENERIC formalism developed, among others, by Grmela and Öttinger. In order to accomplish this task, a reformulation of SEA dynamics using Differential Geometry formalism has been considered necessary. In the third part, the realisation of both these dynamical models in Kinetic Theory is illustrated: the Boltzmann equation is interpreted differently using the building blocks of the two models. Moreover, as SEA aims at proposing new model equations for its resolution, numerical results of the application of SEA methods for the relaxation from nonequilibrium states are presented: good agreement with the ‘exact’ solution is shown for nearequilibrium situations, while poorer results are obtained farther from equilibrium. This means that improvements, with particular regard to the choice of the metric, are needed.

POLYPHYS Seminar HCI J 574 
Wednesday 11. Jun 2014 11:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Electromagnetically induced transparency and its description through quantum master equations including the nonlinear thermodynamic one Show / Hide AbstractWe will discuss the phenomenon of the electromagnetically induced transparency (EIT) and its description through quantum master equations. EIT is achievable only in atoms with specific energy structures: e.g., for a 3level system (to which the present study has focused), it requires two dipole allowed transitions (the 13 and the 23) and one forbidden (the 13). The phenomenon is observed when a strong laser (control laser) is tuned to the resonant frequency of the upper two levels. And then, as a weak probe laser is scanned in frequency across the other transition, the medium is observed to exhibit both: a) transparency at what was the maximal absorption in the absence of the coupling field, and b) large dispersion effects at the atomic resonance. We will present numerical and in some cases analytical results from three types of master equations: a) an empirically modified von Newmann allowing for decays from each energy state, b) a typical Lindblad with timedependent operators, and c) the recently proposed nonlinear thermodynamic quantum master equation. We will discuss advantages and disadvantages of the three methods, in particular in their capability to describe the temperature dependence of the phenomenon. In cases (2) and (3) we will also see how the friction coefficient (a measure of the coupling with the environment) affects the phenomenon.

POLYPHYS Seminar HCI J 574 
Thursday 22. May 2014 10:15

Aleksandar Donev Courant Institute of Mathematical Sciences, New York University 
A reversible mesoscopic model of diffusion in liquids: from giant fluctuations to Fick's law Show / Hide AbstractDiffusion is one of the most ubiquitous transport processes and is often thought to be one of the simplest dissipative mechanisms. Fick's law of diffusion is derived in most elementary textbooks, and relates diffusive fluxes to the gradient of chemical potentials via a diffusion coefficient that is typically thought of as an independent material property. In this talk we will discuss the miscroscopic and mesoscopic mechanism of diffusion in liquids, for both molecular diffusion and diffusion of colloidal particles. Through a combination of theory and simulations I will demonstrate that diffusion in liquids is, in fact, a rather subtle process due to the crucial contribution of hydrodynamic momentum fluctuations. Using multiscale analysis we derive a closed form stochastic diffusion equation that captures both Fick's law for the ensembleaveraged mean and also the longrange correlated giant fluctuations in individual realizations of the mixing process. These giant fluctuations, observed in experiments, are shown to be the result of the longranged hydrodynamic correlations among the diffusing particles. Through a combination of Eulerian and Lagrangian numerical experiments we demonstrate that mass transport in liquids can be modeled at all scales, from the microscopic to the macroscopic, not as irreversible Fickian diffusion, but rather, as reversible random advection by thermal velocity fluctuations. Our model gives effective dissipation with a diffusion coefficient that is not a material constant as its value depends on the scale of observation. Our work reveals somewhat unexpected connections between flows at small scales, dominated by thermal fluctuations, and flows at large scales, dominated by turbulent fluctuations.

POLYPHYS Seminar HCI J 574 
Wednesday 14. May 2014 10:15

David C. Venerus Department of Chemical and Biological Engineering Illinois Institute of Technology, Chicago, IL 60616 
Tears of wine: new insights on an old phenomenon Show / Hide AbstractAnyone who has enjoyed a glass of wine has undoubtedly noticed the regular pattern of liquid beads that fall along the inside of the glass commonly referred as ‘tears of wine.’ The fascinating feature of this phenomenon is that the tearing continues to take place even if the liquid within the glass is stationary, which is possible only if there is a flow against gravity in the liquid film on the inside of the glass. In 1855, J. Thomson identified the driving force for the upwards flow necessary for the continuous formation of tears as a gradient in interfacial tension. Some 15 years after Thomson, Marangoni described this phenomenon, which is commonly associated with his name. There has been considerable interest in understanding both the Marangoni flow within the liquid film and the instability leading to the formation of tears. It is generally accepted that the flow leading to wine tears is due to a composition gradient that results from the evaporation of ethanol, which in turn produces an interfacial tension gradient. Here, we revisit the tears of wine phenomenon using a simple hydrodynamic model and a novel experimental technique. Our results demonstrate that the Marangoni force responsible for wine tears is the result of both composition and temperature gradients whose relative contribution depends on the bulk ethanol concentration. The methods developed here can be used to obtain a deeper understanding of Marangoni flows induced by evaporation, which are ubiquitous in nature and modern technologies.

POLYPHYS Seminar HCI J 574 
Wednesday 7. May 2014 10:15

Oivind Wilhelmsen Department of Chemistry, Norwegian University of Science and Technology, Trondheim, Norway 
Heat and Mass Transfer through Interfaces of Nanosized Bubbles and Droplets Show / Hide AbstractBubbles and droplets are found everywhere, as precipitating rain or in your soda. They are all born at the nanoscale, where their sizes are comparable with the interfacial width. Consequently, their behavior in the initial growth phase depends strongly on the properties of the interface. An introduction is given to how curvature dependent interfacial resistances to heat and mass can be calculated for nanoscopic bubbles/droplets with density functional theory. First, we discuss how bubbles and droplets can be stabilized in closed systems, to properly examine their properties. Using the first approximation to density functional theory, the square gradient model, interface resistances are calculated for bubbles/droplets with radii down to 2 nm. We present interface resistances which vary continuously with curvature, from negative (bubbles) to zero (planar interface) to positive (droplet) values. The interface resistances of 2 nm radii bubbles/droplets are in some cases one order of magnitude different from those of the planar interface. Molecular dynamics simulations and experiments indicate that the thermal resistance of a droplet decreases with its size. We use local resistivity functions qualitatively consistent with nonequilibrium molecular dynamics simulations, where the peak in resistivity is closer to the vaporphase. Remarkably, density functional theory then predicts thermal interface resistance of droplets to decrease with droplet size, similar to experiments. Moreover, the framework also predicts curvature to have the opposite effect on interface resistances of bubbles. We believe that this explains why thermal conductivity is enhanced with decreasing particle size in nanoparticle suspensions, while the thermal conductance decreases with smaller pores in nanoporous materials. The importance of including the heats of transfer through the interface is emphasized, and we show that they depend much less on curvature than the interface resistances.

POLYPHYS Seminar HCI J 574 
Wednesday 30. Apr 2014 10:15

Henning Struchtrup Department of Mechanical Engineering, University of Victoria, Canada 
Model reduction in kinetic theory by order of magnitude of moments. Show / Hide AbstractProper scaling of the kinetic equations describing rarefied gas flows introduces the Knudsen number, which can be used to reduce the description based on the order of magnitude of the Knudsen number. The order of magnitude method considers the reduction not of the kinetic equation itself, but of an associated system of moment equations. In its core, it combines elements of the ChapmanEnskog and Grad methods such that the benefits of both methods are retained, but their shortcomings are removed. The method yields a hierarchy of increasingly complex moment systems that are relevant for increasing order of the Knudsen number. The talk will highlight recent results for hard sphere molecules and polyatomic molecules, for which the scaling leads to two different Knudsen numbers and thus an increased level of complexity.

POLYPHYS Seminar HCI J 574 
Thursday 10. Apr 2014 10:15

Masao Doi Beihang University, Beijing, China 
Onsager principle in dynamics of soft matter Show / Hide AbstractIn the celebrated paper on the reciprocal relation for the kinetic coefficients in irreversible processes, Onsager extended Rayleigh’s principle of the least energy dissipation to general irreversible processes. In this paper, I shall show that this principle gives us a very convenient framework for deriving many equations which describe the nonlinear and nonequilibrium phenomena in soft matter, such as (i) stressdiffusion coupling in solutions, (ii) gel dynamics (ii) molecular modeling for viscoelasticity and (iv) nematohydrodynamics etc. Onsager principle can therefore be regarded as a general ground for soft matter physics.

POLYPHYS Seminar HCI J 574 
Wednesday 2. Apr 2014 10:15

Dick Bedeaux Department of chemistry, Norwegian University of Science and Technology Trondheim, Norway 
Nonequilibrium thermodynamic description of the three phase contactline Show / Hide AbstractIn order to give a solid foundation of the description of the motion of the three phase contact line, we developed a nonequilibrium thermodynamic description of the contact line. It is postulated that during its motion the contact line features as a separate thermodynamic system. Conservation laws are given for the excess densities of the components, the momentum and the energy along the line. The Gibbs law is formulated for the contact line and using this law the excess entropy production density along the line is constructed. This identifies the conjugate thermodynamic forces and fluxes for the contact line. Linear laws relating these quantities can then be given. The special case considered by Shikmurzaev, who gave the first satisfactory description of the motion of the contact line, is considered in more detail. A new boundary condition is found, which was not used by Shikhmurzaev. The need for such an additional boundary condition for this case was discussed in recent work by Billingham.

POLYPHYS Seminar HCI J 574 
Wednesday 19. Mar 2014 10:15

Signe Kjelstrup Department of chemistry, Norwegian University of Science and Technology, Trondheim 
Entropy production minimisation Show / Hide AbstractThe lecture will discuss why it is important to determine the entropy production of industrial processes, and how this can be done in practice (S. Kjelstrup, D. Bedaux, E. Johannessen and J.Gross, Nonequilibrium thermodynamics for engineers, World Scientific, Singapore, 2010). As examples, some simple process units will be described. For these, it is possible to obtain an analytical solution to the problem of how to operate a process with minimum total entropy production. The solution is characterized by constant local entropy production in the unit. Numerical solutions will be given for energy efficient operation of chemical reactors, using the reformer as an example (Ø. Wilhelmsen, E. Johannesen and S. Kjelstrup, Energy efficient reactor design simplified by second law analysis, Int. J. Hydrogen Res., 35 (2010) 1321912231). The solution, which applies to cases which have highly nonlinear fluxforce relations, has a surprisingly constant entropy production, provided that the boundary conditions are not too strict. This then leads to the formulation of the socalled highway hypothesis for energy efficient design. It is speculated that such designs can be found in nature. The lecture is concluded with some rules of thumb for energy efficient design.

POLYPHYS Seminar HCI J 574 
Thursday 13. Mar 2014 15:15

Yitzhak Rabin Physics Departiment, BarIlan University, Israel 
Chromatin Hydrodynamics Show / Hide AbstractFollowing recent observations of large scale cooperative motion of chromatin inside the nuclei of live cells, we present a hydrodynamic theory in which the nucleoplasm is described as a twocomponent fluid consisting of chromatin plus the surrounding solvent subject to active scalar and vector events associated with chromatin remodeling. Scalar events drive the longitudinal viscoelastic modes (where chromatin moves relative to solvent) while vector events generate the transverse modes (where chromatin moves together with solvent). Using linear response methods, we derive explicit expressions for the response functions that connect the chromatin density and velocity correlation functions to the corresponding correlation functions of the active sources in terms of the complex viscoelastic moduli of the nucleoplasmic medium. We then derive general expressions for the flow spectral density (FSD) of the chromatin velocity field and compare them to experimental results obtained by one of the present authors and her coworkers. We find that while the time dependence of the experimental data for both native and ATPdepleted chromatin can be wellfitted using a simple viscoelastic model (i.e., the Maxwell model), the observed wavelength dependence appears to be more complex than that of the Maxwell model, suggesting that a more complete theory may have to incorporate a lengthscale dependent viscoelastic moduli and to account for spatial and temporal correlation between the active sources.

POLYPHYS Seminar HCI J 574 
Wednesday 5. Mar 2014 10:15

Ioannis G. Economou Texas A+M University at Qatar, Chemical Engineering Program, Doha, Qatar and National Center for Scientific Research “Demokritos”, Aghia Paraskevi, Greece 
Molecular Thermodynamics for Chemical Process and Product Design Show / Hide AbstractThe accurate knowledge of physical properties and phase equilibria of complex fluids is a critical factor towards the design and optimization of chemical processes and novel products. Experimental measurements are often limited by temperature and pressure conditions, toxicity, flammability or instability of one or more of the components, cost, etc. Thermodynamic models with strong physical basis provide the means to understand and quantify interactions and phenomena at the molecular and mesoscopic level and eventually predict macroscopic properties of interest. The unprecedented increase of computing power at relatively low price in recent decades has allowed the development of predictive methods that span the entire range of length and time scales, from subatomic quantum mechanical calculations up to macroscopic equations of state. In this presentation, we will discuss molecular simulation methods that are used widely for chemical process and product design. Molecular Dynamics (MD) allows the accurate study of a physical system as it evolves over time and the calculation of macroscopic properties as statistical averages. In this respect, one can calculate both equilibrium thermodynamic properties and timedependent transport and dynamic properties. We will discuss a few examples from our recent research, mainly associated with the oil & gas industry. In the first example, we use MD to predict the diffusivity of gases (carbon monoxide, hydrogen and water) in heavy nalkanes at elevated temperature and pressure. Predictions are subsequently used for the design of a FischerTropsch process known as GasToLiquid that allows formation of high value hydrocarbons from natural gas. The second example is driven by the need to develop efficient technologies for CO2 capture and sequestration, which are critical for the control of greenhouse gas concentration in the atmosphere. Here, we use MD simulations to predict the diffusivity of CO2 in H2O at various temperatures and pressures. In all cases, the use of a realistic and accurate forcefield for the calculation of intermolecular interactions plays a critical role. Finally, we will present recent work on the development of a statistical mechanicsbased equation of state for the prediction of complex mixture phase equilibria. Representative examples for the case of highly polar mixtures will be discussed. In all cases, comparison against experimental data will be presented.

POLYPHYS Seminar HCI J 574 
Wednesday 12. Feb 2014 10:15

Francesco Petruccione National Institute for Theoretical Physics, KwaZuluNatal (NIThePKZN), Durban, South Africa 
Open Quantum Walks Show / Hide AbstractA new model of quantum walks is described, that takes into account the behavior of open quantum systems [S. Attal et. al. J. Stat. Phys. 147, Issue 4, 832 (2012)]. Open Quantum Walks (OQWs) are the exact quantum analogues of classical Markov chains. OQWs have been shown to be useful for the implementation of quantum algorithms for dissipative quantum computing [I. Sinayskiy and F. Petruccione, QIP 11, 1301 (2012)] and to model quantum effects in biological systems [I. Sinayskiy and F. Petruccione, in preparation]. Recently, the connection between the rich dynamical behavior of OQWs and the corresponding microscopic systemenvironment models has been established. The microscopic derivation of an OQW as a reduced system [I. Sinayskiy, F. Petruccione, Open Syst. & Inf. Dyn. 20, 1340007 (2013)] allows to explain the dependance of the dynamical behavior of the OQW on the temperature and coupling to the environment. For thermal environments we observe Gaussian behaviour, whereas at zero temperature population trapping and solitonlike behaviour are possible. Physical realizations of OQWs in quantum optical setups will be discussed.

POLYPHYS Seminar HCI J 574 
Wednesday 11. Dec 2013 10:45

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Dynamics and topological constraints in ringlinear polymer melts from atomisticlevel simulations Show / Hide AbstractWe will present results for the conformational and dynamic properties of ring polymer melts and of ringlinear polymer blends obtained from molecular simulations. The simulations have been executed with a very accurate atomistic model for polyethylene oxide (PEO) and refer to PEO melts with molecular weight (MW) both below and below the corresponding entanglement MW of pure linear PEO (5,000 g/mol). Initially, we will review quickly the Rouse theory for rings. And then, we will present the simulation predictions for: 1) The scaling of the radiusofgyration of rings with their MW 2) The relaxation of normal modes and the diffusivity of the ring centersofmass; also how these properties are altered when the ring is contaminated by linear chains 3) The nature of topological interactions (ring threading by linear molecules) in ringlinear blends and how these affect the dynamics of the ring molecules. At the very end of the talk, we will briefly report some very recent data from nonequilibrium MD (NEMD) simulations for the shear rheology of PEO ring melts. In all cases, the simulation predictions will be compared with the Rouse theory, very recent experimental data, and other simulation results in the literature obtained with a coarsegrained (beadspring chain) model.

POLYPHYS Seminar HCI J 574 
Thursday 28. Nov 2013 10:00

Dimitris Vlassopoulos Polymer Physics, Department of Materials, ETH Zurich 
Tailoring metastable states in soft colloidal mixtures 
POLYPHYS Seminar HCI J 574 
Wednesday 20. Nov 2013 11:15

Dimitris Vlassopoulos Polymer Physics, Department of Materials, ETH Zurich 
Experimental study of the viscoelasticity of critically purified ring polymers Show / Hide AbstractSince free ends play an important role in the motion of entangled polymers (reptation, fluctuations), examining the behaviour of ring polymers is a challenge. In fact, the topic has attracted the attention of scientific community in the 1980s but no final conclusions could be drawn. The controversial results were attributed to the presence of impurities in the ring samples. To overcome this problem, and in particular the unlinked linear side products from their anionic synthesis, ring polymers were purified via liquid chromatography at the critical condition. Recently, it has been shown that this approach yields reasonably pure ring polystyrenes which at a molar mass corresponding to 12 entanglements do not exhibit a rubbery plateau, in contrast to their linear counterparts. This is suggestive of a (new) selfsimilar mechanism of stress relaxation of these macromolecules, which reflects the conformation they adopt in the entanglement state (lattice animal). We have extended this work in different directions: we have used different chemistries, polyisoprene, polystyrene and poly(ethylene oxide); molar masses extend from unentangled regime to about 15 entanglements. We have compared the assynthesized and purified ring polymers, and blended the latter with linear polymers of the same molar mass over a wide range of concentrations. Moreover, we have compared results against scaling predictions as well as recent molecular dynamics simulations. Results are critically discussed in view of the emerging picture of the dynamics of ring polymers, whereas open issues and new challenges are outlined. This work is part of a huge international effort involving the groups of Jülich (A. Bras, A. Wischnewski, W. PyckhoutHintzen, J. Allgaeir, D. Richter), Athens/KAUST (G. Sakellariou, N. Hadjichristidis), Pohang (Y. C. Yeong, T. Chang), North Carolina (M. Rubinstein) and Crete (R. Pasquino, D. Vlassopoulos). It is supported in part by the Greek General Secretariat for Research and Technology (ESPA ARISTEIARINGS).

POLYPHYS Seminar HCI J 574 
Wednesday 23. Oct 2013 11:15

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Electromagnetically induced transparency and its description through quantum master equations including the nonlinear thermodynamic one Show / Hide AbstractIn this seminar, our focus will be on the phenomenon of the electromagnetically induced transparency (EIT) and its description through quantum master equations. The EIT is achievable only in atoms with specific energy structures. For, example, for a three level system (to which the present study has focused), EIT requires two dipole allowed transitions (the 13 and the 23) and one forbidden (the 13). The phenomenon is observed when a strong laser (termed the control laser) is tuned to the resonant frequency of the upper two levels. Then, as a weak probe laser is scanned in frequency across the other transition, the medium is observed to exhibit both: a) transparency at what was the maximal absorption in the absence of the coupling field, and b) large dispersion effects at the atomic resonance. We will derive the Hamiltonian describing the phenomenon and we will present results from three types of master equations: a) an empirically modified von Newmann allowing for decays from each energy state, b) a typical Lindblad, and c) the recently proposed nonlinear thermodynamic quantum master equation. In cases (a) and (b), analytical results are possible under certain approximations, which have been confirmed through a direct solution of the full master equation. In case of the nonlinear (thermodynamic) quantum master equation, only numerical results have been possible. We will discuss these, especially in comparison with those of the modified von Newmann and the Lindblad ones.

POLYPHYS Seminar HCI J 574 
Wednesday 4. Sep 2013 10:15

Grigory Sarnitsky Moscow Institute of Physics and Technology 
Prospective application of GENERIC framework to turbulence modeling Show / Hide AbstractTurbulence is one of the classical examples of nonequilibrium phenomena and its full theoretical description is one of the big unsolved problems in physics. Though turbulent motion of classical fluids is a natural candidate to study within GENERIC framework, to my knowledge there is no published work on the matter. This talk discusses how GENERIC illuminates the problem of turbulence modeling within the approach of Reynoldsaveraged Navier–Stokes equations. Specifically, I show how it helps in determining the physical quantities that describe turbulent flow. Importance of algebraic treatment is emphasized and the action of Reynolds coarsegraining operator on GENERIC is considered. GENERIC framework offers physically founded method to determine the primary set of equations governing turbulent flow, with a closure however yet to be found. I argue that GENERIC is to bring a substantial advance to the study of turbulence.

POLYPHYS Seminar HCI J 574 
Wednesday 29. May 2013 10:15

Raphael Chetrite Université de Nice SophiaAntipolis, Nice, France 
Fluctuation Relations for Quantum Markovian Dynamical Systems Show / Hide AbstractAn open quantum system interacting with its environment can be modeled under suitable assumptions as a Markov process, described by a Lindblad master equation. In this seminar, i will show how we derive a general set of fluctuation relations for systems governed by a Lindblad equation. These identities provide quantum versions of JarzynskiHatanoSasa and Crooks relations.

POLYPHYS Seminar HCI J 574 
Wednesday 15. May 2013 10:15

Sofie Liljegren Imperial College London, UK 
Dynamic coarsegraining approach to quantum field theory Show / Hide AbstractIrreversible terms are included into quantum field theory, in line with the thermodynamic quantum master equation framework, to develop a thermodynamic approach to scalar quantum field theory with quartic interaction. In this case vacuum is represented by the thermodynamic equilibrium state rather than the ground state and regularization is provided by friction mechanism. Perturbation theory is used to handle interaction with first and secondorder propagators and fourpoint correlation being derived. The step to generalize this approach more complex fields, for example YangMills gauge fields, is further discussed. From work done by Hans Christian Öttinger.

POLYPHYS Seminar HCI J 574 
Wednesday 24. Apr 2013 10:15

Peter Sollich King's College, London, UK 
Uniﬁed study of glass and jamming rheology in soft particle systems Show / Hide AbstractWe explore numerically the shear rheology of soft repulsive particles at large volume fraction. The interplay between viscous dissipation and thermal motion results in multiple rheological regimes encompassing Newtonian, shearthinning and yield stress regimes near the ‘colloidal’ glass transition when thermal ﬂuctuations are important, crossing over to qualitatively similar regimes near the ‘jamming’ transition when dissipation dominates. In the crossover regime, glass and jamming sectors coexist and give complex ﬂow curves. Although glass and jamming limits are characterized by similar macroscopic ﬂow curves, we show that they occur over distinct time and stress scales and correspond to distinct microscopic dynamics. We propose a simple rheological model describing the glass to jamming crossover in the ﬂow curves, and discuss the experimental implications of our results. Time permitting a systematic comparison of the model to data for a number of paradigmatic experimental systems will be described.

POLYPHYS Seminar HCI J 574 
Wednesday 17. Apr 2013 10:15

Yitzhak Rabin BarIlan University, Israel 
The Nuclear Pore Complex: Geometry, Hydrophobicity, Charge, Sequence Show / Hide AbstractThe molecular structure of the Nuclear Pore Complex (NPC) and the translocation of model particles have been studied with a molecular theory that accounts for the geometry of the pore and the amino acid sequence and anchoring position of the unfolded domains of the nucleoporin proteins (the FGNups), which control selective transport through the pore. The theory explicitly models the electrostatic, hydrophobic, steric, conformational and acidbase properties of the FGNups. The electrostatic potential within the pore, which arises from the specific charge distribution of the FG‑Nups, is predicted to be negative close to pore walls and positive along pore axis. The positive electrostatic potential facilitates the translocation of negatively charged particles and the free energy barrier for translocation decreases for increasing particle hydrophobicity. The above results agree with the experimental observation that transport receptors which form complexes with hydrophilic/neutral or positively charged proteins to transport them through the NPC, are both hydrophobic and strongly negatively charged. The combination of electrostatic and hydrophobic interactions gives rise to complex potential of mean force, displaying a combination of wells and barriers, in contrast to the simple barrier potential observed for a hydrophilic/neutral translocating particle. This work demonstrates the importance of explicitly considering the amino acid sequence and hydrophobic, electrostatic and steric interactions in understanding the translocation through the NPC.

POLYPHYS Seminar HCI J 574 
Wednesday 10. Apr 2013 10:15

Olivier Buisson Institut Néel, CNRS Grenoble, France 
A superconducting artificial atom with two internal degrees of freedom Show / Hide AbstractThe richness of the energy level structure and the diversity of the associated transitions are at the heart of atomic and quantum optics experiments. They are provided by the multiples degrees of freedom existing in these systems. In our recent work, by adding a large inductance in a dcSQUID phase qubit loop, we create a superconducting artificial atom with two internal degrees of freedom. This device can be described by two anharmonic oscillators labelled s (symmetric) and a (antisymmetric) because the current oscillations at each junction can be either inphase or in phaseopposition, respectively [1]. Spectroscopic measurements show an anticrossing of two levels which demonstrates a nonlinear coupling between the two modes “s” and “a”. We also demonstrate a time resolved up and down frequency conversion in the microwave domain [2]. Finally such artificial atom with two degrees of freedom can provide substantial benefits with regard to non destructive qubit readout. We present a theoretical study of a quantum nondemolition (QND) readout scheme based on a diamond shaped artificial atom coupled to a microwave resonator in a circuit quantum electrodynamics (CQED) architecture [3]. [1] Nonlinear coupling between the two oscillation modes of a dcSQUID, F. Lecocq, et al, Phys. Rev. Lett. 107, 197002 (2011). [2] Coherent Frequency Conversion in a Superconducting Artificial Atom with Two Internal Degrees of Freedom, F. Lecocq, et al, Phys. Rev. Lett. 108, 107001 (2012). [3] Ultrafast QND measurements based on diamondshape artificial atom. I. Diniz, et al, Phys. Rev. A 87, 033837 (2013).

POLYPHYS Seminar HCI J 574 
Wednesday 13. Feb 2013 10:15

Robert Alicki Gdańsk University, Institute of Theoretical Physics and Astrophysics, Poland 
Models of quantum engines and refrigerators Show / Hide AbstractThe recently developed technique combining the weak coupling limit with the Floquet formalism for quantum open systems is outlined and the obtained Markovian master equations are shown to be consistent with thermodynamics. The theory is illustrated by examples of quantum heat engines and refrigerators, in particular by a model of twolevel atom driven by a strong laser field and weakly coupled to heat baths. The case of two thermal reservoirs: an electromagnetic one at finite temperature and the second dephasing one, which can be realized as a phononic or buffer gas reservoir is studied in details. This system can work in two regimes depending on the detuning sign: a heat pump transporting heat from the dephasing reservoir to an electromagnetic bath or can heat both, always at the expense of work supplied by the laser field.

POLYPHYS Seminar HCI J 574 
Friday 8. Feb 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Cooperative (manybody) effects in the nonlinear response 
POLYPHYS Seminar HCI H 539 
Thursday 7. Feb 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: The local field approximation in the nonlinear response of molecular assemblies 
POLYPHYS Seminar HCI H 539 
Wednesday 6. Feb 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Birefringence and Dichroism 
POLYPHYS Seminar HCI H 539 
Monday 4. Feb 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Resonant Grating, PumpProbe and HoleBurning spectroscopy 
POLYPHYS Seminar HCI H 539 
Friday 1. Feb 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Photon Echo Techniques 
POLYPHYS Seminar HCI H 539 
Wednesday 30. Jan 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Coherent Raman Spectroscopy 
POLYPHYS Seminar HCI H 539 
Monday 28. Jan 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Fluorescence and Spontaneous Raman spectroscopy 
POLYPHYS Seminar HCI H 539 
Friday 25. Jan 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Cumulant expansion. Spectral density and its symmetries. The multimode Brownian Oscillator model 
POLYPHYS Seminar HCI H 539 
Thursday 24. Jan 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Nonlinear response functions 
POLYPHYS Seminar HCI H 539 
Wednesday 23. Jan 2013 9:00

Vlasis Mavrantzas Dept. of Chemical Engineering, Patras, Greece 
Principles of nonlinear optical spectroscopy: Optical Measurements and Polarization. Linear Response and Kubo formula, KramersKronig relations 
POLYPHYS Seminar HIL D 60.1 
Wednesday 12. Dec 2012 9:30

Jérome Flakowski Polymer Physics, Department of Materials, ETH Zurich 
My latest adventures in the fascinating world of quantum dissipative systems 
POLYPHYS Seminar HCI F 8 
Wednesday 28. Nov 2012 10:15

Roland Winkler Polymer Physics, Department of Materials, ETH Zurich 
Mesoscale Hydrodynamic Simulation of Polymers in Flow Fields Show / Hide AbstractExperimental studies of individual DNA molecules in steady shear flow by fluorescence microscopy have provided a wealth of information on single polymer dynamics. In particular, these experiments reveal remarkably large conformational changes due to tumbling motion; i.e., a polymer stretches and recoils in the coarse of time. Since shear flows are omnipresent in biological systems and technical applications, e.g., microfluidics, the understanding of the dynamics of semiflexible polymersuch as DNAis of great practical interest. The microscopic conformational properties affect the macroscopic rheological behavior of the polymer solution, and hence a detailed theoretical description of the microscopic dynamics is desirable. The dynamic behavior of a macromolecule in shear flow is governed by various parameters; aside from the shear rate, the finite chain extensibility is of major importance. The the talk, the significance of hydrodynamic interactions on the dynamics of dsDNA molecules in solution will be discussed based on an analytical model for semiflexible polymers. In addition, the dynamics of semiflexible polymers under the influence of shear flow is studied. Power laws are derived for various conformational and dynamical quantities which are in agreement with experimental findings. In particular, the tumbling motion is analyzed. The calculations explain the similarities in the behavior of flexible and semiflexible polymers as well as freedraining and nondraining systems.

POLYPHYS Seminar HCI J 574 
Thursday 30. Aug 2012 10:15

Yoshitaka Tanimura Department of Chemistry, Graduate School of Science, Kyoto University 
Reduced Hierarchy Equations of Motion Approach to a Quantum Dissipative System Show / Hide AbstractIn this talk, I explore and describe the roles of different physical phenomena that arise from the peculiarities of the systemenvironment coupling in multidimensional spectra. For this purpose, I employ a Brownian oscillator model with the nonlinear systembath interaction. The quantum reduces hierarchy equations of motion is then reduced in a Wigner space representation that can deal with a strongsystem bath coupling as well as a nonMarkovian noise. The reduced hierarchy equations of motion for system with discrete energy levels will also be derived using a coherent state representation for the path integrals. Various applications of the hierarchy equation of motion approach, including linear and nonlinear spectroscopies, electron transfer, photo dissociation, chemical reactions, quantum tunneling, and quantum information problems will also be discussed. The distributed source code, nonMarkovian2009, will be demonstrated and examined.

POLYPHYS Seminar HCI J 574 
Friday 20. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Thursday 19. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Wednesday 18. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Tuesday 17. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Monday 16. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Friday 13. Jul 2012 8:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Thursday 12. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Wednesday 11. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Monday 9. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Friday 6. Jul 2012 8:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Thursday 5. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Wednesday 4. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Monday 2. Jul 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Friday 29. Jun 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Thursday 28. Jun 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Wednesday 27. Jun 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI D 8 
Monday 25. Jun 2012 9:00

Vlasis Mavrantzas Polymer Physics, Department of Materials, ETH Zurich 
Theory of Open Quantum Systems 
POLYPHYS Seminar HCI J 574 
Wednesday 13. Jun 2012 10:15

Leonard Sagis Wageningen University, NL & ETH Zürich, CH 
Dynamics of complex fluidfluid interfaces Show / Hide AbstractSurface rheological properties often play an important role in the stability and stressdeformation behavior of emulsions, foam, biological fluids, or immiscible blends [1]. This is particularly true when the interfaces in these systems have a complex microstructure, for example, when the surface active components stabilizing the interface form a 2d gel phase, a 2d glass phase, or 2d (liquid) crystalline phase. Applied deformations induce changes in the microstructure of the interface, and the resulting changes in the surface rheological properties (such as surface shear thinning and thixotropic behavior) affect the behavior of the multiphase system on a macroscopic scale. Most currently available constitutive models for the surface extra stress tensor either do not account for the strain (rate) dependence of surface rheological properties, or are appropriate only for infinitesimally small rates, where departures from linear behavior are very small [1]. In this paper we will discuss recent advances in the development of nonlinear constitutive equations for the stressdeformation behavior of fluidfluid interfaces in the framework of nonequilibrium thermodynamics (NET). Using the classical irreversible thermodynamics (CIT) framework, and the generalequationforthenonequilibriumreversibleirreversiblecoupling (GENERIC) framework, we construct models that describe the effect of microstructural changes on the nonlinear response of an interface to a deformation through a dependence of the surface stress tensor on a set of scalar and a tensorial structural variables. We present the time evolution equations for these structural variables, and evaluate the ability of these types of models to describe shear thinning behavior of an interface stabilized by anisotropic colloidal particles in both simple and oscillatory shear. We find that both frameworks allow us to construct nonlinear expressions for the surface extra stress tensor capable of describing the shear thinning behavior observed experimentally for this type of interface, but the CIT model gives realistic predictions only for small departures from equilibrium, whereas the GENERIC framework allows us to create models valid also far from equilibrium. These results show that microstructural models developed using NET provide a valuable tool for the analysis of the highly nonlinear dynamics of multiphase systems with complex liquidliquid interfaces. [1] L.M.C. Sagis, Rev. Mod. Phys. 83 (2011) 1367.

POLYPHYS Seminar HCI J 574 
Monday 11. Jun 2012 10:00

Michael Shirts Laboratorium für Physikalische Chemie, ETH Zurich 
Putting the Statistics Back in Statistical Mechanics 
Talk HCI J 3 
Wednesday 30. May 2012 15:45

Joseph Brader Universität Freiburg 
Colloidal dispersions in external flow fields Show / Hide AbstractColloidal dispersions are commonly encountered in everyday life (e.g. ink, milk or mayonnaise) and represent an important class of complex fluid. Of particular significance for many commercial products and industrial processes is the ability to control and manipulate the macroscopic flow response of a dispersion by tuning the microscopic interactions between the constituents. An important step towards attaining this goal is the development of robust theoretical methods for predicting from firstprinciples the rheology and nonequilibrium microstructure of well defined model systems subject to external flow. In this talk I will outline, using a series of examples, recent theoretical approaches for predicting the response of colloidal dispersions to external flow fields.

Talk HCI G 7 
Wednesday 23. May 2012 15:45

Eran Bouchbinder Weizmann Institute 
How Things Break? – A Failure Story Show / Hide AbstractCracks are the major vehicle for material failure and often exhibit complex dynamics. In spite of the fact that the laws that govern their motion have been intensively investigated for nearly a century, several fundamental issues in dynamic fracture remain poorly understood. A major stumbling block in making progress in this problem is that it involves the coupling between widely separated scales; fast fracture, which is ultimately driven by the release of (linear) elastic energy slowly stored on large scales, is affected by the rapid, nonlinear and dissipative processes taking place in the very small scales near the front of a moving crack. In this talk, I will describe some of the major challenges in this field and review recent experimental and theoretical advances, highlighting basic properties of the recently developed “Weakly Nonlinear Theory of Dynamic Fracture” and its success in explaining various experimental observations, including a highspeed crack instability.

Talk HCI G 7 
Wednesday 16. May 2012 9:30

Thierry Savin Polymer Physics, Department of Materials, ETH Zurich 
Local equilibrium of the Gibbs interface in twophase systems Show / Hide AbstractThe classical approach to equilibrium interfacial thermodynamics in phase coexistence describes the interface as a separate two dimensional thermodynamic system characterized by excess densities. Gibbs' original formulation relies on the uniformity of intensive variables throughout the system. Therefore, it cannot be directly applied to nonequilibrium situations such as evaporation/condensation processes or heterogeneous catalysis, where jumps in temperature and chemical potential across the interface can occur. We present a conceptually clear formulation of local equilibrium for interfaces. In particular, we gain new insights by formulating, in terms of gauge transformations, the ambiguity in locating the interface. This notably allows us to generalize the Clapeyron relationships to nonequilibrium situations. We support our theoretical predictions by performing stringent tests with nonequilibrium molecular dynamics simulations.

POLYPHYS Seminar HCI J 574 
Tuesday 15. May 2012 10:15

PierLuca Maffettone University of Naples, Italy 
Single line particle focusing induced by viscoelasticity of the suspending liquid: theory, experiments and simulations to design a micropipe flowfocuser 
Talk LFO C13 
Wednesday 2. May 2012 10:15

David Taj Politecnico di Torino 
Microscopic theory of relaxation and decoherence for weakly coupled quantum open systems Show / Hide AbstractWe shall revisit the conventional adiabatic or Markov approximation, which —contrary to the semiclassical case— does not preserve the positivedefinite character of the corresponding density matrix, thus leading to highly nonphysical results. To overcome this serious limitation, originally addressed by Davies and coworkers almost three decades ago [1], we shall propose an alternative more general adiabatic procedure, which (i) is physically justified under the same validity restrictions of the conventional Markov approach, (ii) in the semiclassical limit reduces to the standard Fermi’s golden rule, and (iii) describes a genuine Lindblad evolution, thus providing a reliable/robust treatment of energydissipation and dephasing processes in electronic quantum devices [2, 3, 4]. Unlike standard masterequation formulations, our procedure guarantees a positive evolution for a variety of choices for the subsystem (that include the common partial trace reduction), and quantum scattering rates are well defined even in case the subsystem is infinitely extended/has continuous spectrum. We shall compare the proposed Markov dissipation model with the conventional one also through basic simulations of energyrelaxation versus decoherence channels in prototypical semiconductor nanodevices, and show how the new approach could be used to model quantum transport for a toy model spatially resolved device. [1] E.B. Davies, “Markovian Master Equations,” Commun. math. Phys., vol. 39, p. 91–110 (1974). [2] D.TajandF.Rossi,“CompletelypositiveMarkovianquantumdynamicsintheweakcouplinglimit,”Phys. Rev. A, vol. 78, 052113 (2008). [3] D. Taj, R.C. Iotti and F. Rossi, “Dissipation and decoherence in nanodevices: a generalized Fermi’s golden rule,” Semiconductor Science and Technology, pp. 6, Vol. 24. (2009) [4] D. Taj, ”Van Hove Limit for Infinite Systems, Ann. Henri Poincar, 11, 1303 (2010)

POLYPHYS Seminar HCI J 574 
Wednesday 18. Apr 2012 15:45

Matthias Fuchs Universität Konstanz 
Mode coupling theory of the history dependent deformation of colloidal glass Show / Hide AbstractI will present and discuss recent results on the history dependence of rheological experiments in dense colloidal dispersions obtained from a first principles approach to the nonlinear rheology. Assuming homogeneous flow and neglecting hydrodynamic interactions, a theoretical description of the stresses, microstructure, and particle motion close to a colloidal glass transition are developed. Results for large amplitude oscillatory shearing, stepstrains, and other timedependent transient deformation protocols provide a unifying description of the dispersion properties under general strains. Shearthinning, plastic deformation and anelastic behavior are observed. Adding Brownian dynamics simulations, the shearinduced particle motion provides information on the microscopic transport mechanisms in the dense dispersions close to the colloidal glass transition.

Talk HCI G 7 
Monday 2. Apr 2012 14:30

Wilson Poon School of Physics & Astronomy, University of Edinburgh 
Colloids and defects: new routes to soft solids 
Talk HIF E19 
Wednesday 21. Mar 2012 10:15

Raymond Kapral University of Toronto 
Nonadiabatic Dynamics of Open QuantumClassical Systems Show / Hide AbstractMixed quantumclassical methods, where a quantum subsystem is coupled to a classical environment, provide a means to study the dynamics of complex open quantum systems that cannot be studied easily by other means. The talk will focus on descriptions based on the quantumclassical Liouville equation for the evolution of such systems. The roles of quantum coherence and decoherence in the subsystem as a result of coupling to both deterministic and dissipative environments will be discussed. Simulations of the dynamics based on the evolution of ensembles of trajectories using various representations of the quantum subsystem states will also be described. The results will be illustrated by computations on a variety of model systems.

POLYPHYS Seminar HCI J 574 
Wednesday 14. Mar 2012 10:15

Andrea Cavagna Institute for Complex system, Roma, Italy 
Looking for a growing correlation length in glassforming liquids Show / Hide AbstractFrom the theory of critical phenomena we learn that divergences in the space domain and in the time domain go together: whenever a relaxation time explodes, a correlation length does too. Yet, one of the more frustrating aspects in the phenomenology of glassforming liquids is the the fact that the spectacular increase of the relaxation time is apparently unaccompanied by the growth of any obvious correlation length. Bluntly put, the static structure of a deeply supercooled liquid in its highly viscous phase, is virtually impossible to distinguish from that of a high temperature, very fluid liquid. In fact, this is true as long as we use standard structural correlation functions. Recent developments in the theory of the glass transition, though, have shown that this dilemma may be solved if we introduce some nonstandard means to detect the growth of structural order in glassformers. What is intriguing in this line of research is that we have to unveil growing order in an intrinsically disordered material (glass), so to make any interpretation of the sentence growing order exotic, to say the least. In this talk, I will examine one of the new methods (there are several), based on the (actually quite old) idea that in the presence of large correlations, boundary conditions rule entirely the thermodynamic state of the system.

POLYPHYS Seminar HCI J 574 
Wednesday 22. Feb 2012 10:15

Orit Peleg Polymer Physics, Department of Materials, ETH Zurich 
Minimalistic Design Principles of a MechanoResponsive Fiber: Lessons to be learned from Fibronectin 
POLYPHYS Seminar HCI J 574 
Wednesday 15. Feb 2012 10:15

Alan Luo Imperial College London 
Nonequilibrium molecular dynamics applied to the simplest complex fluid: water Show / Hide AbstractMolecular dynamics is an established simulation technique to solve for the time evolution of a manybody system at the atomic level. Here we will outline the general methodology and apply it to the simplest complex fluid: water. Using the single point charge  extended model we attempt to understand the anomalous behaviour of water in both liquid and solid phases. Finally, coarse graining will be introduced, once again using water as an example.

POLYPHYS Seminar HCI J 574 
Wednesday 25. Jan 2012 10:15

Andrei Gusev Polymer Physics, Department of Materials, ETH Zurich 
Theory of spacetime elasticity Show / Hide AbstractWe present the theory of spacetime elasticity and demonstrate that it involves traditional thermoelasticity. Assuming linearelastic constitutive behavior and using spacetime transverselyisotropic elastic constants, we derive all principal thermodynamic relations of classical thermoelasticity. We introduce the spacetime principle of virtual work, and use it to derive the equations of motion for both reversible and dissipative thermoelastic dynamics. We show that spacetime elasticity directly implies the Fourier and the MaxwellCattaneo laws of heat conduction. However, spacetime elasticity is richer than classical thermoelasticity, and it advocates its own equations of motion for coupled thermoelasticity, complemented by the spectrum of boundary and interface conditions. We argue that the presented framework of spacetime elasticity should prove adequate for describing the thermoelastic phenomena occurring at low temperatures, for interpreting the results of molecular simulations of heat conduction in solids, and also for the optimal heat and stress management in the microelectronic components and the thermoelectric devices.

POLYPHYS Seminar HCI J 574 
Wednesday 14. Dec 2011 10:15

HeinzPeter Breuer Theoretical Condensed Matter Physics and Quantum Statistics, AlbertLudwigsUniversitaet Freiburg 
Quantification and control of nonMarkovian dynamics in open quantum systems Show / Hide AbstractRealistic quantum mechanical systems are always exposed to an external environment. The presence of the environment often gives rise to a Markovian process in which the system irretrievably loses information to its surroundings. However, many quantum systems exhibit a pronounced nonMarkovian behavior which is characterized by a flow of information from the environment back to the open system. This backflow of information implies the presence of memory effects and represents the key feature of nonMarkovian quantum dynamics. We introduce a general measure for the degree of nonMarkovian behavior in open quantum systems and discuss recent experiments which allow to control the information flow between system and environment, to monitor the transition from the Markovian to the nonMarkovian regime, and to directly determine the measure for nonMarkovianity by measurements on the open system.

POLYPHYS Seminar HCI J 574 
Wednesday 7. Dec 2011 11:15

Sofia Kantorovich Institute for Computational Physics, Universität Stuttgart 
Theory and Simulations of Dipolar Systems Show / Hide AbstractWe study the influence of dipoledipole interaction on the microstructure of magnetic soft matter. Various theoretical and combined theorysimulation methods are employed to elucidate the relationship between microscopical properties and macroscopical behaviour of dipolar systems. In particular, we focus on magnetic fluids, capped colloids, and magnetic gels. Analytical methods we use allow to broaden the understanding of dipolar soft matter, in particular, to see the general trends inherent to any of those systems independently from the scale and the nature of dipoles.

POLYPHYS Seminar HCI J 574 
Wednesday 7. Dec 2011 10:30

Fabio Mavelli University A. Moro of Bari  Italy 
Stochastic simulations of minimal cell model systems 
POLYPHYS Seminar HCI J 574 
Wednesday 30. Nov 2011 10:15

Sabine Klapp Institut für Theoretische Physik, T.U. Berlin 
Dynamics of ferrofluids in external fields Show / Hide AbstractWe present computer simulation and theoretical results for the dynamical behavior of simple model ferrofluids under the influence of spatially homogeneous magnetic fields. In the first part we focus on the translational diffusion in static fields. Using Molecular Dynamics and Brownian Dynamics [1] we demonstrate that the anisotropic, yet normal diffusive behavior seen in weakly coupled systems and finite fields becomes anomalous both parallel and perpendicular to the field at sufficiently high dipolar coupling and field strength. After the initial ballistic regime, chain formation along the field first yields cagelike motion in all directions. At later time we observe transient, mixed diffusivesuperdiffusive behavior resulting from cooperative motion of the chains. We also report on simulation results for the actual chain aggregation in (static) magnetic fields and compare these to experimental results [2]. The second part focusses on the impact of rotating fields. We construct a full nonequilibrium phase diagram as function of the driving frequency and field strength. This diagram contains both synchronized states, where the individual particles follow the field with (on average) constant phase difference, and asynchronous states. The synchronization is accompanied by layer formation, i.e. by spatial symmetrybreaking, similar to systems of induced dipoles in rotating fields. In the permanentdipole case, however, too large frequencies yield a breakdown of layering, supplemented by complex changes of the singleparticle rotational dynamics from synchronous to asynchronous behavior. We show that the limit frequencies ωc can be well described as a bifurcation in the nonlinear equation of motion of a single particle rotating in a viscous medium. Finally, we present a simple density functional theory, which describes the emergence of layers in perfectly synchronized states as an equilibrium phase transition [3]. 1. J. Jordanovic, S. Jäger, and S. H. L. Klapp, Phys. Rev. Lett. 106, 038301 (2011). 2. D. Heinrich, A. R. Goni, A. Smessaert, S. H. L. Klapp, L. M. C. Cerioni, T. M. Osan, D. J. Pusiol, and C. Thomsen, Phys. Rev. Lett. 106, 208301 (2011). 3. S. Jäger and S. H. L. Klapp, Soft Matter 7, 6606 (2011).

POLYPHYS Seminar HCI J 574 
Wednesday 23. Nov 2011 10:15

Andrea Cavagna Institute for Complex system, Roma, Italy 
Talk has been cancelled Show / Hide AbstractFrom the theory of critical phenomena we learn that divergences in the space domain and in the time domain go together: whenever a relaxation time explodes, a correlation length does too. Yet, one of the more frustrating aspects in the phenomenology of glassforming liquids is the the fact that the spectacular increase of the relaxation time is apparently unaccompanied by the growth of any obvious correlation length. Bluntly put, the static structure of a deeply supercooled liquid in its highly viscous phase, is virtually impossible to distinguish from that of a high temperature, very fluid liquid. In fact, this is true as long as we use standard structural correlation functions. Recent developments in the theory of the glass transition, though, have shown that this dilemma may be solved if we introduce some nonstandard means to detect the growth of structural order in glassformers. What is intriguing in this line of research is that we have to unveil growing

POLYPHYS Seminar HCI J 574 
Wednesday 16. Nov 2011 11:00

Patrick Doyle Chemical Engineering, MIT, USA 
DNA Polymer Dynamics in Nanoconfinement and Electric Fields Show / Hide AbstractThe development of fluorescence microscopy of singlemolecule DNA in the last decade has fostered a bold jump in the understanding of polymer physics. With the recent advance of nanotechnology, devices with welldefined dimensions that are smaller than typical DNA molecules can be readily manufactured. The combination of these techniques has provided an unprecedented opportunity for researchers to examine confined polymer behavior, a topic far less understood than its unconfined counterpart. We have used a nanofluidic crossslot device to investigate the influence of slitlike confinement on the coilstretch transition of single DNA molecules in a 2D homogeneous extensional electric field. In contrast to microchannels, DNA molecules in the nanochannels exhibit highly modified coilstretch processes. Specifically, the onset of DNA stretching starts earlier, the transition progresses more gradually, and most importantly, we identify two distinct critical strain rates in the transition. We have constructed a Brownian dumbbell model that is able to provide qualitative predictions of the coilstretch transition of DNA in confinement. We will also discuss some recent experiments in which we see an unexpected compression of DNA in DC electric fields, and what we believe are selfentangled polymer states.

POLYPHYS Seminar HCI J 574 
Wednesday 16. Nov 2011 15:45

Ludovic Berthier Laboratoire Charles Coulomb, Universite de Montpellier 
From dynamic heterogeneity to static correlations in glassforming materials Show / Hide AbstractAmorphous solids are mechanically rigid while possessing a disordered structure similar to that of dense liquids. I will briefly review recent research indicating that dynamical heterogeneity, spatiotemporal fluctuations in local dynamical behavior, might help understanding the statistical mechanics of glassy states. The observation of dynamic heterogeneity also suggests that the physics of glassforming materials near the glass transition might be controlled by the emergence of a form of amorphous static order . This idea is currently under intense scrutiny, in particular through the characterization and measurement of pointtoset correlation functions. I will explain both the goals and the current status of this very recent line of investigations.

Talk HCI D2 
Wednesday 2. Nov 2011 10:15

Maksym Osmanov Polymer Physics, Department of Materials, ETH Zurich 
Open quantum systems coupled to classical environment with memory Show / Hide AbstractAny realistic quantum systems unavoidably interact with its surrounding environment, which leads to decoherance. Understanding decoherance has fundamental reasons (the measurement problem, the quantumclassical crossover etc.) as well as practical applications (quantum computers, quantum optics, quantum state manipulations). Usually, environment is described as a set of quantum harmonic oscillators and characterizes by its spectral function [1]. There is another point of view, decoherance caused by coupling of quantum systems to classical environment [2]. In this case, evolution of quantum system can be described by nonlinear thermodynamic master equation [3]. Markovian approximation can be done considering quantum system coupled to heat bath, characterized by it entropy and energy. In this talk we will discuss more complex environment with additional classical variables. It will be shown how these changes in environment affect evolution of quantum system. 1. H. P. Breuer and F. Petruccione: The theory of open quantum systems, Clarendon press, Oxford, 2010 2. Öttinger, H.C.: The geometry and thermodynamics of dissipative quantum systems. Europhys. Lett. 94, 10006 (2011) 3. Öttinger, H.C.: Nonlinear thermodynamic quantum master equation: Properties and examples. Phys. Rev. A 82, 052119 (2010)

POLYPHYS Seminar HCI J 574 
Wednesday 26. Oct 2011 10:15

Eric VandenEijnden Courant Institute, New York University 
A general strategy for the design of seamless multiscale methods Show / Hide AbstractI will present a new general framework for designing multiscale methods. Compared with previous work such as Brandt’s systematic upscaling, the heterogeneous multiscale method and the “equationfree” approach, this new framework has the distinct feature that it does not require reinitializing the microscale model at each macro time step or each macro iteration step. In the new strategy, the macro and micromodels evolve simultaneously using diﬀerent time steps (and therefore diﬀerent clocks), and they exchange data at every step. The micromodel uses its own appropriate time step. The macromodel runs at a slower pace than required by accuracy and stability considerations for the macroscale dynamics, in order for the micromodel to relax. I will discuss applications of the new seamless approach to a toy system used in climatic studies, to the modeling of complex fluids, and to free energy calculations in molecular dynamics. This is joint work with Weinan E and Weiqing Ren with applications performed in collaboration with Ibrahim Fatkullin and Luca Maragliano.

POLYPHYS Seminar HCI J 574 
Wednesday 19. Oct 2011 10:15

Eleni Panagiotou Department of Mathematics, National Technical University, Athens, Greece, and Polymer Physics, Department of Materials, ETH Zurich 
A study of the entanglement in polymer melts Show / Hide AbstractPolymer melts are dense systems of macromolecules. In such dense systems the conformational freedom and motion of a chain is significantly affected by entanglement with other chains which generates obstacles of topological origin to its movement. In this talk we will discuss methods by which one may quantify and extract entanglement information from a polymer melt configuration using tools from knot theory. A classical measure of entanglement is the Gauss linking integral which is an integer topological invariant in the case of pairs of disjoint oriented closed chains in 3space. For pairs of open chains, we will see that the Gauss linking integral can be applied to calculate an average linking number. In order to measure the entanglement between two oriented closed or open chains in a system with threedimensional periodic boundary conditions (PBC) we use the Gauss linking number to define the periodic linking number. Using this measure of linking to assess the extend of entanglement in a polymer melt we study the effect of CReTA (Contour Reduction Topological Analysis) algorithm on the entanglement of polyethylene chains. Our results show that the new linking measure is consistent for the original and reduced systems.

POLYPHYS Seminar HCI J 574 
Thursday 22. Sep 2011 11:00

Srikanth Sastry Jawaharlal Nehru Center for Advanced Scientific Research 
Structural Relaxation and Correlation Length Scales in Glass Forming Liquids Show / Hide AbstractThe rapid rise of structural relaxation times in supercooled liquids upon decreasing temperature, and their transformation to an amorphous solid state (the glass transition), display many puzzles which have eluded a satisfactory explanation despite decades of experimental and theoretical investigation. A key mystery is the role of structural or other lengthscales in determining dynamical slow down. The conventional view holds that lengthscales associated with structural ordering do not grow appreciably as the glass transition is approached. Nevertheless, the role of growing static and dynamical length scales in determining relaxation times in glass forming liquids has received increasing attention in recent years. New insights into spatial correlations in structure and dynamics, and their relationship with the rapid rise of relaxation times in glass forming liquids, obtained via computer simulations of model liquids, will be described. Specific issues addressed will be the relationship of the short and long time relaxation and corresponding length scales, the validity of the AdamGibbs relation and the breakdown of the StokesEinstein relation in different spatial dimensions.

POLYPHYS Seminar HIF E 19 
Wednesday 21. Sep 2011 10:15

Amin Moosaie Technische Universität München 
Direct Numerical Simulation of Turbulent Drag Reduction by Rigid Fiber Additives Show / Hide AbstractA twoway coupled simulation technique for a dilute suspension of rigid fibers in turbulent flows is developed. It is based on an Eulerian direct numerical simulation of the incompressible NavierStokes equations and a Lagrangian direct MonteCarlo simulation of the fiber conformation. The developed simulation tool is employed to study the turbulent drag reduction by rigid fibers in a channel flow. In particular, the modification in turbulence intensities due to the action of fibers is studied using the pressurestrain correlation. It turns out that the reduction in pressure fluctuations (partly) and the reduction in strain fluctuations (mainly) are responsible for the reduction in the pressurestrain correlation

POLYPHYS Seminar HCI J 574 
Wednesday 7. Sep 2011 10:15

Wim Briels University of Twente, the Netherlands 
Memory in Brownian dynamics simulations of soft matter 
POLYPHYS Seminar HCI J 574 
Friday 5. Aug 2011 10:15

Todd Squires Department of Chemical Engineering, UCSB, Santa Barbara, CA 931065080, USA 
Nonlinear, interfacial, and nonlinear interfacial microrheology 
Talk LFO C13 
Wednesday 3. Aug 2011 10:15

Yitzhak Rabin Department of Physics, BarIlan University 
Hairy Nanopores Show / Hide AbstractI will present a study of nanopores in solid membranes, with polymer chains grafted over the inner surface. We examine the effects of various length scales such as pore length and diameter and polymer length, as well as the effect of solvent, on the morphology of the hairy pore. We also consider electrostatic phenomena in nanopores with grafted polyelectrolytes, under the action of potential gradients.

POLYPHYS Seminar HCI J 574 
Wednesday 3. Aug 2011 14:00

Orit Peleg Polymer Physics, Department of Materials, ETH Zurich 
Hairy Nanopores: Application to the Nuclear Pore Complex 
POLYPHYS Seminar HCI J 574 
Wednesday 13. Jul 2011 9:00

Majid Mosayebi Polymer Physics, Department of Materials, ETH Zurich 
Nonaffine displacement of inherent structures in supercooled liquids 
POLYPHYS Seminar HCI J 574 
Wednesday 6. Jul 2011 10:15

Sebastian Matera Fritz Haber Institut der Max Planck Gesellschaft, Berlin 
An Introduction to Quantum Dissipation Show / Hide AbstractIn this talk I will give an overview on the modeling of open quantum systems. I will start with the linear quantum master equation and motivate the Lindblad form for weak systembath couplings. I will then explain how the corresponding Markov process in Hilbert space can be simulated. Finally nonmarkovian processes and some related numerical aspects will be discussed.

POLYPHYS Seminar HCI J 574 
Thursday 30. Jun 2011 16:15

Anthony Beris Department of Chemical Engineering, University of Delaware, Newark DE 19716, USA 
Nonequilibrium Thermodynamics Applications to Rheologically Complex Systems 
Talk CAB G 61 
Wednesday 29. Jun 2011 10:15

Ingo Füreder Harvard University, United States 
Methods for free energy/entropy calculations for coarse grained polymeric systems 
POLYPHYS Seminar HCI J 574 
Wednesday 15. Jun 2011 10:15

Lydéric Bocquet Université Lyon 1, France 
Fluid transport at the nanoscales Show / Hide Abstract« There is plenty of room at the bottom ». This visionary foresight of R. Feynman, introduced during a lecture at Caltech in 1959, was at the root of numerous scientific and technological developments, taking benefit of the strange phenomena occuring at the smallest scales. There remains however a lot to explore, in particular in the context of fluids at the nanoscales and their specific transport properties. The great efficiency of biological nanopores, such as aquaporins, in terms of permeability or selectivity is definitely a great motivation to foster research in this direction. How to reach such efficiency in artificial nanosystems, and build new devices taking benefit of the strange transport behavior of fluids at nanoscales is still an open question. In this talk, I will discuss some theoretical and experimental results obtained in our group on the fluid transport at small scales. I will in particular focus on the strange transport behavior of water in carbon nanotubes. Reference: « Nanofluidics, from bulk to interfaces», L. Bocquet , E. Charlaix, Chemical Society Reviews 39, 1073 (2010) « Molecular origin of fast water transport in carbon nanotube membranes», K. Falk, F. Sedlmeier, L. Joly, R. R. Netz and L. Bocquet NanoLetters 10 4067 (2010)

POLYPHYS Seminar HCI J 574 
Wednesday 1. Jun 2011 9:15

Monirosadat Sadati Polymer Physics, Department of Materials, ETH Zurich 
Influence of long chain branches on the flow kinematics and stress field in a crossslot channel 
POLYPHYS Seminar HCI J 574 
Wednesday 18. May 2011 10:15

Rafael DelgadoBuscalioni Universidad Autonoma de Madrid 
Particle hydrodynamics based on hybrid methods Show / Hide AbstractThis talk presents two types of multiscale methods to solve particle and fluid dynamics which combine different techniques in a concurrent way. Novel generalizations of typeB methods shall be presented. Type A: Domain decomposition hybrids [1] can be designed to solve a certain domain of interest at fine detail molecular dynamics (MD) and connect it with a hydrodynamic description of the surrounding flow field. This approach is particularly suited for nontrivial or complex boundary conditions, which might contain singularities, interfaces or even macromolecules. At the interfase between coarse and fine models, the coupling might be based on fluxes or variable exchange. An unified framework is proposed. Type B: Particle hydrodynamics involved in colloidal or polymeric suspensions or dispersions of larger particles are frequently solved using hybrid EulerianLagrangian approaches whereby fluid flow is solved in an Eulerian mesh and particle motion is solved in the continuum space [2]. At low Reynolds number (typical of microdevices) the Stokes drag is a good approximation to the fluidparticle force [2]. However, the Stokes limit is not valid in highly unsteady scenarios such as those encountered when manipulating micronsize particles using ultrasound. We present a generalisation inspired on a modification of the Immersed Boundary method [3] which obtains such force upon the imposition of noslip at the particle center. The method [4] is simple to implement and it properly describes ultrasound forces, particle inertia and lubrication. Moreover, there is no dissipative channel related to particle friction (thus neither a “particle noise term” [2]); instead particle kinetic temperature is uniquely determined by transfer of fluid momentum fluctuations to the particle. [1] G. De Fabritiis, R. DelgadoBuscalioni and P. Coveney, Phys. Rev. Lett 97, 134,501 (2006); R .DelgadoBuscalioni and G. De Fabritiis, Phys. Rev. E 76, 036709 (2007); R. DelgadoBuscalioni, K. Kremer and M. Praprotnik, J. Chem. Phys. 131, 244107 (2009) [2] Tri T. Pham, et al. J. Chem. Phys. 131, 164114 (2009). [3] Uhlmann, Phys. Fluids 20, 053305 (2008) [4] F. Balboa Usabiaga and R. DelgadoBuscalioni, in preparation.

POLYPHYS Seminar HCI J 574 
Thursday 12. May 2011 10:00

Igal Szleifer Northwestern University, Evanston, United States 
How to combine chemical reaction equilibrium and physical interactions for biological activity: a biophysicist approach to targeted drug delivery to cancer cells 
POLYPHYS Seminar HCI J 574 
Wednesday 11. May 2011 10:15

Mohan Sarovar Sandia National Laboratories, Livermore, CA, USA 
Quantum coherent properties of natural and biomimetic light harvesting antennas Show / Hide AbstractRecent demonstrations of quantum coherent behavior during energy transfer in photosynthetic light harvesting antennas (LHAs) have spurred much activity aimed at understanding the extent and role of quantum coherence in these biomolecular systems. I will present an overview of our current state of understanding of the prevalence and importance of quantum coherence in Nature's extremely efficient energy transfer machinery. This will include a discussion of the quantum entanglement present in LHAs during energy transfer. In the second half of the talk I will review a new direction of research that aims to apply the lessons learned from analyzing natural LHAs to construct artificial organic photovoltaics with engineered quantum properties that enhance photon capture and energy transfer efficiency. Part of the work presented was done in collaboration with: K. Birgitta Whaley, Akihito Ishizaki, Graham Fleming, Dan Finley, and Matthew Francis, all of the University of California, Berkeley.

POLYPHYS Seminar HCI J 574 
Thursday 5. May 2011 10:30

Asaph WidmerCooper School of Chemistry, University of Sydney 
Assembly of anisotropic nanoparticles for plasmonic and solar energy applications Show / Hide AbstractNanoparticles can now be made in an incredible array of materials, sizes, shapes, and patterns, often with unusual and tunable optical and electronic properties. However, organizing such particles into extended structures that could revolutionize technology remains a challenge. I will discuss two projects that I have worked on in this area. The first concerns the selfassembly of silver nanopolyhedra into mmsized plasmonic supercrystals, where we have recently discovered and explained the formation of a new packing of octahedra with complex helical motifs (see image); and the second involves directing the assembly of semiconducting nanorods into nanocarpets that can be used for printing solar cells or, when combined with catalysts and embedded in a polymer membrane, for splitting water into hydrogen and oxygen. A key element of this work has been close interaction between experiment and theory in order to understand the interactions that exist between nanoparticles, and between nanoparticles and various interfaces, as well as their phase behavior and nonequilibrium dynamics, and to thereby gain better control over the assembly process.

POLYPHYS Seminar HCI J 574 
Wednesday 4. May 2011 10:15

Anne Tanguy Laboratoire de Physique de la Matière Condensée et Nanostructures, Université Claude Bernard, Lyon 
An atomistic Study of the Mechanical Response of Amorphous Materials Show / Hide AbstractDisordered Materials like usual glasses have very specific thermodynamical and mechanical properties. They are obtained by an appropriate mixing of species, or by a rapid quench from the liquid state. They are characterized by a very high Heat capacity at low temperature, a low thermal conductivity and a very high hardness in comparison with crystals of the same composition. The plastic flow localizes along shear bands. We have performed Molecular Dynamics study of the elastoplastic response of Model amorphous materials (LennardJones glasses, StillingerWeber glasses  a model for aSi , and BKS glasses  a model for aSiO2). We will show the analogies and the differences in the mechanical response of these materials, when submitted to different mechanical loads (Shear, Hydrostatic compression..). We will show evidence of finitesize effects in the global stressstrain behaviour of the different samples, and relate the global behaviour to specific atomistic motions. This will allow us to discuss local plastic criteria at different scales, as a function of different materials characteristics, like bond directionality or local order.

POLYPHYS Seminar HCI J 574 
Wednesday 20. Apr 2011 10:15

Carl Zinner Polymer Physics, Department of Materials, ETH Zurich 
Rarefied Gas Dynamics: prototype applications and moment equations 
POLYPHYS Seminar HCI J 574 
Thursday 14. Apr 2011 11:00

Matthieu Wyart Department of Physics  New York University, USA 
Elasticity, transport and flow near the jamming threshold Show / Hide AbstractThe elasticity, the transport properties and the rheology of amorphous materials such as grains, colloids or molecular glasses is complicated by the presence of disorder. In recent years it has been realized that for simple systems, such as frictionless particles, the length scale at which disorder has strong effects becomes much larger than the particle size, and in fact diverges near the jamming transition delimiting the liquid and the solid phase. This has led to new concepts to describe amorphous materials and sphere packings that will be reviewed, together with open questions.

POLYPHYS Seminar HCI J 574 
Wednesday 6. Apr 2011 10:15

Timothée Martiel ESPCI, Paris, France 
Brownian dynamics simulations: numerical strategies for stochastics processes Show / Hide AbstractBrownian motion is a universal phenomenon in physics. After a summary of the mathematical tools used to describe and manipulate Brownian motion, we will discuss some usual stochastic differential equations. Numerical resolution is often needed for these equations. Different approaches will be discussed, such as Euler and RungeKutta methods. Our recent diploma work on Brownian motion in soft spheres suspensions will be exposed as an illustration of Euler method. Beyond simple resolution, we will see how we can take advantage of Brownian motion in Monte Carlo methods.

POLYPHYS Seminar HCI J 574 
Wednesday 30. Mar 2011 10:15

Evangelos Siminos Département de Physique Théorique et Appliquée, CEA  France 
Linear stability of nonlinear waves in rarefied plasmas Show / Hide AbstractKinetic effects in rarefied plasmas can be modeled by Boltzmann's equation coupled to macroscopic electromagnetic fields described by Maxwell's equations. In many situations of interest, including space and fusion plasmas, one may focus on longrange interactions and ignore collisional effects in the Boltzmann equation, which leads to the socalled VlasovMaxwell system. Despite the effort put in the theoretical understanding and numerical simulation of the VlasovMaxwell system, many fundamental issues remain unresolved. An outstanding issue of crucial importance to current inertial confinement fusion efforts is that of stability of nonlinear waves. Here we restrict attention to spatially periodic, nonlinear electrostatic waves in one spatial dimension (governed by the Vlasov equation and Poisson's law). We study the stability problem as an eigenproblem in a FourierHermite basis (in the space and velocity variables, respectively) of finite dimension. The Hermite expansion can be thought of as a formal moment expansion with no imposed closure. However, projection onto a finite dimensional system faces fundamental difficulties due to the Hamiltonian structure, longrange interactions, extreme range of scales and continuous linear spectrum in the VlasovPoisson system. These difficulties were resolved in our study using an operatortheoretic technique (spectral deformation), which establishes a formal connection to dissipative systems and suppresses nonessential scales. This formulation allows the determination of the unstable eigenmodes of a Vlasov equilibrium and illuminates the physical mechanism underlying the instability. As an example application, I will present a vortexfusion instability scenario, of importance to the saturation of nonlinear processes in laserplasma interaction.

POLYPHYS Seminar HCI J 574 
Wednesday 9. Mar 2011 10:15

Dick Bedeaux Department of Chemistry, Norwegian University of Science and Technology, Norway 
Thermodynamics of a small system in a mu,T reservoir Show / Hide AbstractDue to advances in experimental techniques operating at the nanoscale, it is possible to compute properties from density fluctuations by studying ``snapshots'' of particle configurations. Thermodynamics on a small scale is different from thermodynamics in bulk systems. We show how the molar enthalpy and the inverse thermodynamic correction factor depend on system size and how these properties can be computed from fluctuations at the nanoscale. We find a one over size (1/L) effect for all thermodynamic quantities for a small system in contact with a &mu,T reservoir, where L is the length of the system in a single dimension.

POLYPHYS Seminar HCI J 574 
Wednesday 23. Feb 2011 10:15

Kokou Dadzie Department of Mechanical Engineering, University of Strathclyde, UK 
Corrections to the NavierStokesFourier model to account for nonlocalequilibrium Show / Hide AbstractMost engineering flow problems are solved using the NavierStokesFourier continuum mechanical model. But this model fails to account properly for nonequilibrium flow and heat transfer effects in rarefied gases. Various attempts to improve the capability of the continuum model have been made, e.g. the application of velocity slip and temperature jump corrections at solid bounding surfaces. This talk will start with a brief survey of some of these methods to improve the NavierStokesFourier capabilities, and then discuss and present results based on an unconventional mass/volumediffusion correction that has been hypothesized recently as a route to account for strong nonequilibrium gas flow effects. Sound wave propagation, shock wave structures, and flowrates in microchannels are among the theoretical results discussed and compared with experimental data.

POLYPHYS Seminar HCI J 574 
Wednesday 26. Jan 2011 10:15

David C. Venerus Chemical Engineering, Illinois Institute of Technology 
Two Interesting Problems in Fluid Mechanics Show / Hide AbstractIn this seminar, two problems in fluid mechanics are investigated. The commonality between the two problems lies in the fact that they are both interesting and accessible to the presenter, who is an experimentalist. The first problem concerns the effects of transducer compliance on transient stress measurements in torsional flows of a viscoelastic fluid, which play an important role in the experimental rheology of complex fluids. The second problem is laminar flow of compressible Newtonian fluids in capillaries and channels, which is relevant to flows in microfluidic devices. Both problems are solved using a simple perturbation method. In the torsional flow problem, we find a new criteria for avoiding transducer compliance, and a possible connection to instabilities in rheometric flows that have been a subject of great interest in recent years. For the compressible flow problem, we find that a commonly used method for analyzing microchannel flow experiments obscures a rather simple dependence of pressure drop on the same parameter used in the perturbation method.

POLYPHYS Seminar HCI J 574 
Wednesday 19. Jan 2011 10:15

John H. Maddocks EPFL 
Statistical Mechanics of SequenceDependent Coarse Grain Models of DNA Show / Hide AbstractDNA is a rather stiff polymer, where it is believed that nonuniformity due to the specific sequence along the molecule is biologically important. I will describe ongoing work in my group on extracting constitutive relations for coarse grain models of DNA from fully atomistic Molecular Dynamics simulations, along with the analysis necessary to model in vitro experimental data to assess the accuracy of the constitutive relations.

POLYPHYS Seminar HCI J 574 
Wednesday 15. Dec 2010 10:15

Sabrina Maniscalco Department of Physics and Astronomy, University of Turku, Finland 
Sudden transition between classical and quantum decoherence Show / Hide AbstractThe interaction between a quantum system and its environment causes the rapid destruction of all quantum properties, such as the existence of quantum superpositions and of quantum correlations in composite systems. Decoherence and dissipation caused by the environment are responsible for the extreme fragility of quantum states and explain why quantum phenomena appear so weird to our eyes and our mind, used to deal with everyday classical objects. Moreover, decoherence is the major enemy of quantum technologies such as quantum computers and quantum communication devices. Is there any environmentresistant quantum property? Is there any physical system in which quantum correlations can survive, completely unaffected by the environment? After reviewing the main results on the quantum to classical transition, I will present the first evidence of the existence of a positive answer to these questions. The discovery of environmentresistant quantum correlations unveils a new feature of one of the most fundamental and fascinating aspects of quantum theory and may be a key breakthrough on quantum technologies.

POLYPHYS Seminar HCI J 574 
Wednesday 8. Dec 2010 10:15

Michael Wübbenhorst Department of Physics and Astronomy, K.U.Leuven, Belgium 
Ups and downs in the glass transition temperature of ultrathin polymer films – new insights from dielectric relaxation spectroscopy Show / Hide AbstractDespite 15 years of extensive research, the glass transition of ultrathin polymer films (L < 100 nm) is still a subject of deep controversy. While a vast majority of studies has revealed substantial changes in the glass transition temperature (Tg) of e.g. polystyrene (PS), there are a few research groups claiming that there is basically no “confinement” effect in ultrathin polymer films down to a few nm in thickness. This presentation discusses various mechanisms that might affect the glass transition dynamics in ultrathin polymer films. Starting from early concepts such as endgroup segregation, free volume arguments or De Gennes sliding mode, we will try to identify relevant types of “confinement induced” perturbations and their implication for the segmental dynamics. Based on dielectric relaxation spectroscopy (DRS) and capacitive dilatometry, being our principal experimental techniques, we will address the following issues: Mobility profiles of the segmental dynamics across the film thickness as deduced from the thickness dependences of the dielectric strengths and the mean relaxation time. The role of conformation perturbations (transgauche ratio) on Tg in relation to (non)equilibrium states during film preparation and subsequent thermal treatment. The specific role of surface induced polymer configurations at the solidpolymer interface (adsorbed layer) and a free polymer surface. Here, particular attention will be paid to the evolution and impact of an irreversible adsorbed polymer “monolayer”, a phenomenon recently studied in our group by analyzing the dielectric response of labeled and unlabeled PS. Summarizing the particular findings we will present a new physical picture of ultrathin polymer films taking into account both features of the polymer solution history (casting and drying process) and the evolution of a density and mobility profile driven by polymer adsorption and reorganization at the solidliquid interface.

POLYPHYS Seminar HCI J 574 
Wednesday 1. Dec 2010 10:15

Elisabetta Paladino Dipartimento di Fisica e Astronomia  Universita' di Catania, Italy 
Quantum control of superconducting networks in the presence of solid state noise Show / Hide AbstractIntense research on solid state nanodevices during the last 10 years has established their potentiality to combine quantum coherent behavior with the existing integratedcircuit fabrication technology. Highfidelity single qubit gates based both on semi and superconducting technologies are nowadays available and twoqubit logic gates have been demostrated. Limitations in the performances arise from noise due to material and device dependent sources. Contrary to the quantum optics realm, solid state noise has broadband character being often strong at lowfrequencies. Optimizing the tradeoff between efficient addressing and noise is a central issue for the achievement of advanced quantum control comparable to atomic systems. Effects due to non Gaussian and non Markovian noise, as 1/f noise or noise due to strongly coupled impurities are well known in single qubits. In larger logical systems they may limit seriously the performance of advanced protocols, since controlled degrees of freedom may exhibit small energy splittings and enhanced sensitivity to noise. Because of this, constrains on device design to observe phenomena as coherent population transfer via adiabatic passage emerge. Another key example is the implementation of qubit couplings, where also the presence of several noise sources, correlated to a different extent, may play an important role. Controlled generation of entangled states and preservation of quantum correlations represent critical issues towards the achievement of the high performances required to overcome classical processors. Implications are implementation of universal twoqubit gates, the possibility to store entangled states in solidstate memories and entanglement preservation during local operations in quantum algorithms. Identification of strategies to counteract physical processes detrimental to quantum coherent behavior is a fundamental step towards this goal. Here we present a general route to reduce inhomogeneous broadening in nanodevices due to 1/f noise. We apply this method to a universal twoqubit gate and demonstrate that for selected optimal couplings, a highefficient gate can be implemented even in the presence of 1/f noise. Entanglement degradation due to interplay of 1/f and quantum noise is quantified via the concurrence. A chargephase sqrt(iSWAP) gate for spectra extrapolated from single qubit experiments is analyzed. Beside the interest for quantum gates engineering, on a more fundamental level our analysis is relevant for optimizing faulttolerant architectures, showing that the influence of 1/f fluctuations in the solid state can be limited by exploiting the band structure of coupled nanodevices. In addition, motivated by the fact that disentanglement may markedly differ from the single qubit decoherence, we study entanglement degradation of two noninteracting qubits subject to independent baths with broadband spectra. We obtain the analytic form of the concurrence in the presence of adiabatic noise for classes of entangled initial states presently achievable in experiments. We find that adiabatic (low frequency) noise affects entanglement reduction analogously to pure dephasing noise. Due to quantum (high frequency) noise, entanglement is totally lost in a statedependent finite time. The possibility to implement onchip both local and entangling operations is briefly discussed.

POLYPHYS Seminar HCI J 574 
Wednesday 17. Nov 2010 10:15

Evelyne van Ruymbeke Chimie et Physique des hauts polymères  Université catholique de Louvain, Belgium 
Modeling the rheology of complex polymer melts and supramolecular polymeric assemblies Show / Hide AbstractWe present a general coarsegrained model for predicting the linear viscoelasic properties of branched polymers from the knowledge of their molecular structure and three viscoelastic parameters, i.e. the Rouse time of an entanglement segment, the plateau modulus and the entanglement molecular weight. The model uses the ingredients of the tubebased theories of McLeish and coworkers, and its implementation is based on a timemarching algorithm. With proper account of polydispersity and use of macromolecular coordinates for the diffusion of the branching points, successful description of a wide range of rheological data of H, pompom, treelike or comb polymers is obtained. We are now extending this approach in order to predict the nonlinear rheology of polymer melts. Then, using the same framework, we investigate the linear viscoelastic response of transient networks obtained by supramolecular interactions between linear and star polyisoprenes (of varying molar mass above the entanglement limit). This requires accounting for the association status of the chains via the dipolar interactions at each time step. A good agreement of the predictions with two adjustable parameters (the average times when two dipolar pair remain associated or free, respectively) is obtained, which suggests design criteria for choosing supramolecular assemblies.

POLYPHYS Seminar HCI J 574 
Wednesday 10. Nov 2010 10:15

Peter Van Puyvelde Applied Rheology and Polymer Processing  K.U. Leuven, Belgium 
Flowinduced crystallization at processing speeds 
POLYPHYS Seminar HCI J 574 
Wednesday 3. Nov 2010 10:15

Karsten Kruse Theoretische Physik  Universität des Saarlandes, Saarbrücken 
Selforganization of active polar gels and cell motility Show / Hide AbstractMany movements of eukaryotic cells are driven by the cytoskeleton. This cellular structure plays essential roles in various vital processes like cell division, cell locomotion, or the internal organization of subcellular components. From a physical point of view it is an active polar gel that consists of filamentous proteins, notably microtubules and actin filaments, which are structurally polar. Activity in the system results from processes driven by the hydrolysis of ATP, like filament assembly and disassembly or the action of motor proteins. While a lot is now known about the biochemistry of individual cytoskeletal proteins, we still lack a thorough understanding of how these components are organized on a cellular scale. In this talk, physical descriptions of cytoskeletal dynamics will be discussed. The central finding is that collective effects emerging from interactions between a few key cytoskeletal components can lead to spatiotemporal structures similar to those observed in cells. Specifically, I will first discuss the cytoskeletondependent organization of pigments in cells that allow fish to change color. Secondly, I will address the role played by selforganized polymerization waves for orchestrating cytoskeletal constituents in crawling neutrophils and amoeba.

POLYPHYS Seminar HCI J 574 
Wednesday 27. Oct 2010 10:15

Maksym Osmanov National Technical University of Ukraine, Kiev 
Solitons (Classical and Quantum Theory) Show / Hide AbstractA soliton is a selfreinforcing solitary wave that maintains its shape while it travels at constant velocity. Solitons arise as the solutions of a widespread class of nonlinear partial differential equations describing physical systems (hydrodynamics, Langmuir films, optical solitons in fibers, polymeric chain, nonlinear magnetization dynamics in ferromagnets with the easyaxis type anisotropy, transmissions lines made out of arrays of Josephson junctions of superconductors, proteins and DNA etc.). In this talk I will discuss the classical and quantum solitons theory. From the classical theory following issues will be represented: Hamiltonian structure of solitons equations [1], method of inverse scattering (Lax representation [2] and zero curvature representation [3]), Hirotaís method [4, 5]. From the quantum theory: soliton quantization (WKB method and path integral) [6], number state method [7] and quantum inverse scattering [8]. To illustrate the theory, following equations will be solved: Kortevegde Vries, sineGordon equation, Nonlinear Schrodinger equation, KadomtsevPetviashvili equation, AblowitzLadik equation, Heisenberg ferromagnet etc. 1. L. A. Dickey. Soliton Equations and Hamiltonian Systems, 2003, 420 p. 2. S. Novikov, S. V. Manakov, L. P. Pitaevslij, V. E. Zakharov. Theory of Solitons: The Inverse Scattering Method, 1984, 292 p. 3. L. D. Faddeev, L. A. Takhtajan. Hamiltonian Methods in the Theory of Solitons, 1987, 592 p. 4. R. Hirota, A. Nagai, J. Nimmo, C. Gilson. The Direct Method in Soliton Theory, 2004, 212 p. 5. T. Miwa, M. Jimbo, E. Date. M. Reid. Solitons: Differential equations, symmetries and infinite dimensional algebras, 2000, 118 p. 6. R. Rajaraman. An Introduction to Solitons and Instantons in Quantum Field Theory, 1987, 418 p. 7. A. Scott. Nonlinear Science: Emergence and Dynamics of Coherent Structures. 2003, 504 p. 8. V. E. Korepin, Bogoliubov N. M, Izergin A. G. Quantum Inverse Scattering Method and Correlation Functions, 1997, 576.

POLYPHYS Seminar HCI J 574 
Monday 25. Oct 2010 12:30

Carl Zinner Polymer Physics, Department of Materials, ETH Zurich 
Boundary Conditions in Extended Hydrodynamics 
POLYPHYS Seminar HCI J 574 
Wednesday 13. Oct 2010 10:15

Rut Besseling School of Physics and Astronomy, The University of Edinburgh, UK 
New phenomena in the flow of concentrated colloids Show / Hide AbstractConcentrated hard sphere colloids are among the simplest of soft matter systems and a popular model system to study the dynamics of the glass transition. Yet the flow behaviour of ‘glassy’ suspensions, especially their nonlinear rheology is poorly understood. In this talk I will discuss both shear banding as well as shear melting behaviour on the particle level, which we have studied via fast confocal microscopy and simultaneous rheology. For volume fractions above ~60%, we observe a type of shear banding so far unobserved in soft glasses, with velocity profiles which become increasingly nonlinear below a characteristic rate and strongly localized near yielding. I will discuss a new theory which attributes this behaviour to small concentration gradients arising from a fundamental flow instability due to flowconcentration coupling. The model accounts for all aspects of the observed phenomenology and may have strong implications for nonuniform flow in other glassy materials [1]. On the particle level, we have studied the shear induced speeding up of structural relaxation in the system, which shows a nontrivial powerlaw dependence on the flow rate [2]. This behaviour is inconsistent with flow induced relaxation expected for an ‘ideal’ glass, and instead provides support for a recently proposed Eyringtype model. [1] R. Besseling, et al. condmat. arXiv:1009.1579 [2] R. Besseling, et al. Phys. Rev. Lett. 99, 028301 (2007).

POLYPHYS Seminar HCI J 574 
Wednesday 6. Oct 2010 10:15

Alexei E. Likhtman Department of Mathematics, University of Reading  UK 
Hierarchy of models for entangled polymers Show / Hide AbstractI will briefly review multiscale approach to modelling of entangled polymers, which includes molecular dynamics (MD), single chain stochastic models (slipsprings) and the tube model. After that I will concentrate on the link between many chain (MD) and single chain models. I will report results from molecular dynamics simulations on stress relaxation and show the detailed comparison with slipspring model. In the second part of the talk I will turn to the issue of microscopic definition of entanglement in molecular dynamics. We propose to define entanglement as a longlived contact between mean paths of the two chains. Using this definition, we present empirical evidence and statistical properties of such entanglements, and discuss the implications for the tube theory and the slipspring model.

POLYPHYS Seminar HCI J 574 
Wednesday 29. Sep 2010 10:15

Thierry Savin Polymer Physics, Department of Materials, ETH Zurich 
The mechanism of gut loops morphogenesis Show / Hide AbstractThe small intestine has a remarkably complex morphology. It exhibits a distinguished coiled shape, with a succession of loops and twists. The latter allow for the long transit times required for digestion and nutrients absorption that characterize its function. Given this peculiar configuration, understanding development and morphogenesis of the gut appears to be a challenging, yet important task. I will show how we explain the formation and shape of gut loops by using a simple mechanical model, based on the differential growth between the gut tube and the mesentery (the membrane tissue that holds the intestine in place).

POLYPHYS Seminar HCI J 574 
Wednesday 15. Sep 2010 10:15

Jérôme Flakowski Polymer Physics, Department of Materials, ETH Zurich 
Unraveling nonlinear quantum master equation : a stochastic simulation  Part II 
POLYPHYS Seminar HCI J 574 
Wednesday 8. Sep 2010 9:00

Jérôme Flakowski Polymer Physics, Department of Materials, ETH Zurich 
Unraveling nonlinear quantum master equation : a stochastic simulation Show / Hide AbstractWhen considering open quantum systems, the most popular approach is to exploit linear quantum master equation of the Lindblad form[1]. The main drawback of this method is that it invokes an incorrect quantumregression hypothesis [2] and is often not applicable at low temperatures[3]. In this talk, we will outline an alternative approach including nonlinearities to overcome the problem. The nonlinear quantum master equation investigated here was obtained by an extension of the geometric formulation of nonequilibrium thermodynamic from classical to quantum system[4,5] and was previously derived by timedependent projection operator techniques[2]. Here a numerical solution of this equation is explored in the case of a damped harmonic oscillator in contact with a heat bath[6]. It is based on stochastic simulation methods with a general class of piecewise deterministic Markovian jump[7]. The talk will be conducted in a work in progress style : it will start with a short survey of the formalism, followed by the presentation of the simulation techniques, and end with a discussion on the possible applications of the developed methodology. [1] Lindblad, G., On the generators of quantum dynamical semigroups, Comm. Math. Phys., Volume 48, Number 2 (1976); [2] Grabert, H., Nonlinear relaxation and fluctuations of damped quantum systems, Z. Physik B 49, (1982); [3] Weiss, U. , Quantum Dissipative Systems, 3rd Edition Series in Modern Condensed Matter Physics, World Scientific, Singapore, (2008); [4] Öttinger, H.C., The geometry and thermodynamics of dissipative quantum systems, Phys. Rev. Lett., (2010) submitted and arXiv:1002.2938;
[5] Öttinger, H.C., The nonlinear thermodynamic quantum master equation, Phys. Rev. A, (2010) submitted and arXiv:1002.5023;
[6] Öttinger, H.C., Nonlinear thermodynamic quantum master equation for the damped harmonic oscillator, Phys. Rev. A, (2010) submitted and arXiv:1004.0652;
[7] Öttinger, H.C., Stochastic process behind nonlinear thermodynamic quantum master equation, EPL, (2010) submitted and arXiv:1005.1190.

POLYPHYS Seminar HCI J 574 
Wednesday 25. Aug 2010 10:15

AndreiValentin Plamadă Department of Physics, Alexandru Ioan Cuza University, 700506 Iasi, Romania 
A micromagnetic study on magnetization behavior of two interacting magnetic particles Show / Hide AbstractThe twoparticle system (2PS) can be solved with high accuracy and may therefore serve as a benchmark for more complicated particle arrays. An example of 2PS is the synthetic antiferromagnet (SAF) structure. The SAF structure is a system of two ferromagnetic layers antiferromagnetically coupled through a nonmagnetic metallic spacer layer. SAF structures received great interest due to their application in magnetoresistance sensors, spin electronics, highdensity recording technology, as active parts of toggle magnetic random access memory. Using the single domain assumption the exact expressions for the switching fields were derived and the switching behavior was analyzed [15]. When the field is applied along the easy axis the energy barriers are obtained analytically only on certain intervals of applied field, and numerical calculations are needed to fully characterize the system [1]. In Refs. [2, 5] the analyses are based on the hysteresis loops without debating neither the possible jumps nor the energy barriers. Mainly, to understand the magnetic response of a 2PS one must analyze the free energy landscape with its local minima, and how the configuration of minima is altered as the field changes. To estimate the influence of thermal fluctuations on the system, the activation energies for all the energy barriers are necessary. So it is essentially to have a clear idea about the system minima, as well as about the corresponding saddle points and which minima make them available. The energy barriers are defined as the energy differences between the local minimum where the system is currently in and all the saddle points which can link the local minimum with another distinct equilibrium state. The activation energy is the lowest energy barrier. The equilibrium state solutions are found from the minima of the system’s free energy. Both minima and saddle points of free energy are particular cases of critical points. The second derivative test is used to distinguish between them. In this work we use a decoupling method to convert the critical points problem into an algebraic equation, and for the particular case of a field applied along the easy axis we show that the two particle system is completely analytically solvable [6, 7]. For this case, the switching diagram as a function of coupling parameters is presented. We present an elegant way to understand the key elements  the hysteresis loops and energy barriers by introducing a simple method, representing the energy as a function of magnetic field. We have derived the exact expressions for the energy's critical points, energy barriers, and we have identified all the possible hysteresis loops. We have also identified all the possible jumps as consequence of thermal fluctuations, these results being useful in the rate equation formalism. References [1] D. C. Worledge, Applied Physics Letters 84 (2004) 4559. [2] D. C. Worledge, Applied Physics Letters 84 (2004) 2847. [3] S.Y. Wang and H. Fujiwara, Journal of Magnetism and Magnetic Materials 286 (2005) 27. [4] H. Rohrer and H. Thomas, Journal of Applied Physics 40 (1969) 1025. [5] D. M. Forrester, E. K. Karl, and F. V. Kusmartsev, Physical Review B (Condensed Matter and Materials Physics) 76 (2007) 134404. [6] A. V. Plamada and A. Stancu, Magnetics, IEEE Transactions on 45 (2009) 3796. [7] A.V. Plamada, D. Cimpoesu, and A. Stancu, Applied Physics Letters 96 (2010) 122505.

POLYPHYS Seminar HCI J 574 
Monday 12. Jul 2010 10:15

Shiwani Singh Polymer Physics, Department of Materials, ETH Zurich 
Entropic Lattice Boltzmann Method for Dilute Polymer Solution Show / Hide AbstractIn the last two decades, Lattice Boltzmann Method emerges as an important tool to simulate hydrodynamics of Newtonian fluids. However, this success story is yet to be repeated in the case of nonNewtonian fluids. In this talk, we will outline how lattice Boltzmann approach for simulation of nonNewtonian fluids can be formulated. In particular, we will demonstrate how analogy between inertial dynamic of FENE dumbbell and Boltzmann FokkerPlanck equation can be used to create fast lattice Boltzmann type solver for FENE dumbbell. Finally, we will discuss how such a polymer solver can be coupled with hydrodynamic solvers.

POLYPHYS Seminar HCI J 574 
Wednesday 30. Jun 2010 10:15

Henning Struchtrup Department of Mechanical Engineering, University of Victoria 
How to (not) teach the second law Show / Hide AbstractWhen introducing the second law, most (engineering) textbooks follow the historical development and base the arguments on Carnot cycles. Obviously, this path requires discussion of property relations and processes, all based solely on the 1st law, before the 2nd law can be tackled. Two main problems arise from this: (a) Entropy and 2nd law are introduced relatively late, so that in an introductory course students have little time to get familiar with these important concepts. (b) After one has the 2nd law, one has to go back and discuss all processes again, this time with entropy included. In this talk I present an alternative introduction of entropy and the 2nd law for teaching purposes, which can be done early in a course. With this the 2nd law and entropy are available early on, and can be used for the discussion of cycles and processes from the beginning. The 2nd law is introduced based on the following observations/postulates for closed systems: (i) An isolated system will, after a while, assume a stable and unique equilibrium state. (ii) Energy can be transferred only by heat and work (the 1st law). (iii) The state of a closed system can be changed only through exchange of heat and work. (iv) Heat goes from hot to cold by itself, but not vice versa. (v) There is no direction restriction for work transfer (one can use gears and levers).

POLYPHYS Seminar HCI J 574 
Tuesday 29. Jun 2010 14:00

Roland Netz Physik Department, TU Munich, Germany 
Biopolymer adsorption and dynamics: theoretical approaches at different scales Show / Hide AbstractBiopolymer dynamics combines the fields of solvation chemistry, elasticity theory and hydrodynamics. Theoretical approaches span different length scales and rely on simulations, continuum modeling and scaling approaches.  Many biopolymers readily adsorb on both hydrophobic and hydrophilic surfaces. Single molecule AFM studies yield adsorption energies and point to an extremely high mobility on hydrophobic surfaces.[1] The dominant hydrophobic attraction can be quantitatively explained with classical MD simulations including explicit water. Both water structural effects and dispersion interactions contribute to this solvation attraction. The friction coefficient of bound polymers is very low on hydrophobic substrates, which is traced back to the presence of a vacuum layer between substrate and water, which forms a lubricating cushion on which a polymer can glide. Conversely, friction forces on hydrophilic substrates are large.[2]  The local dynamics of DNA is scale dependent and exhibits elastic effects, entropic effects and centerofmass dynamics as one goes from smaller to larger scales, in accordance with recent fluorescencecorrelation spectroscopy data.[3] [1] Peptide adsorption on a hydrophobic surface results from an interplay of solvation, surface and intrapeptide forces, D. Horinek, A. Serr, M. Geisler, T. Pirzer, U. Slotta, S. Q. Lud, J. A. Garrido, T. Scheibel, T. Hugel, R. R. Netz, PNAS 105, 2842 (2008) [2] Polypeptide friction and adhesion on hydrophobic and hydrophilic surfaces: A molecular dynamics case study, A. Serr, D. Horinek and R.R. Netz, JACS 130, 12408 (2008) [3] Global crossover dynamics of single semiflexible polymers, M. Hinczewski, and R.R. Netz, EPL 88 18001 (2009)

POLYPHYS Seminar HCI J 498 
Thursday 10. Jun 2010 10:15

Raffaele Mezzenga DAGRL ETHZ 
Protein Fibers.....Polymer Physics: Encounter at the Nanoscale (but do we understand everything ?) 
POLYPHYS Seminar HCI J 574 
Wednesday 9. Jun 2010 10:15

Maryam Naderian University of Konstanz 
Soft Glassy Materials Show / Hide AbstractWe encounter directly or indirectly ’soft glassy materials’ in our life in the form of complex fluids, foams, pastes, or creams. The common aspect of these everyday materials is that they are made of building blocks at the mesoscopic length scale. The investigation of their dynamic properties, especially in rheological aspects can give a significant insight into a broad range of important questions in material science. In this talk I will introduce the soft glassy rheology approach (SGR) [Sollich 1997] based on Bouchaud’s trap model. This model attributes the similarities in the rheology of soft glassy materials to their common properties, namely structural disorder and metastability. It conceptually subdivides the system into mesoscopic elements and captures interactions by a mean field noise temperature, x and an energy landscape. Glass transition occurs at x ~ 1 (in proper units). I will present the prediction of SGR for linear rheology and flow curves of systems which were observed in many experimental results.

POLYPHYS Seminar HCI J 574 
Wednesday 26. May 2010 10:15

Julian Engel Polymer Physics, Department of Materials, ETH Zurich 
Introduction to CUDA  How To Accelerate MD Simulations 
POLYPHYS Seminar HCI J 574 
Wednesday 21. Apr 2010 10:15

Gustav Schiefler Polymer Physics, Department of Materials, ETH Zurich 
Granular materials 
POLYPHYS Seminar HCI J 574 
Wednesday 14. Apr 2010 10:15

Jerome Zemp Department of Materials, ETH Zurich 
GENERIC treatment of viscoplastic deformation in metallic glass 
POLYPHYS Seminar HCI J 574 
Wednesday 31. Mar 2010 10:15

Dina Obeid Brown University 
Thermodynamics of nonequilibrium steady states Show / Hide AbstractFrom investigating the motion of a Brownian particle under the influence of a nonconservative force, an attempt is made to construct a thermodynamic theory of nonequilibrium steady states as a formal extension of equilibrium theory. In looking for a phenomenological theory that describes the interplay between heat and mechanical work that takes place during operations in which a system transitions between nonequilibrium steady states one finds that there is no systematic way within a phenomenological formulation to determine the work done by the system during such operations. The above work shows that the attempt to build a thermodynamics theory of nonequilibrium steady states in analogy to the equilibrium theory has limited prospect of success and that the pursuit of such as theory should be directed elsewhere.

POLYPHYS Seminar HCI J 574 
Wednesday 24. Mar 2010 10:15

Majid Mosayebi Polymer Physics, Department of Materials, ETH Zurich 
Structural signature of the glass transition 
POLYPHYS Seminar HCI J 574 
Tuesday 23. Mar 2010 10:15

Ignacio Romero Technical University of Madrid 
Structure preserving discretizations for GENERIC evolution problems Show / Hide AbstractThe development of numerical methods which preserve the mathematical structure of the equations whose solution they are meant to approximate has guided a large part of the efforts of numerical analysts during the last two decades. In Mechanics, most of the advances have taken place in the numerical solution of Hamiltonian problems, whose wellknown mathematical structure has guided the algorithmic design. In contrast, fewer results have been obtained for general evolution equations since no formalism exists that can encompass all of them. In those cases where a structure preserving discretization has been proposed, for example, for a dissipative problem, the methods were applicable only to those specific equations of evolution and thus have limited impact. The GENERIC formalism for nonequilibrium thermodynamics offers a fairly general framework which allows the unified description of many problems of evolution with applications to physics, chemistry, and engineering. This generality makes it a perfect candidate for guiding the design of structure preserving algorithms, and we have recently proposed discretizations that strictly preserve the most fundamental ingredients of GENERIC: the separation of flows derived from the reversible and irreversible phenomena and the satisfaction of the two laws of thermodynamics. In addition, the methods we have tested are extremely stable. In the talk, I would review structure preserving methods for Hamiltonian problems, describe the new GENERIC preserving algorithms, and show numerical examples for nontrivial infinite dimensional evolution problems.

POLYPHYS Seminar HCI J 498 
Wednesday 10. Mar 2010 10:15

Monirosadat Sadati Polymer Physics, Department of Materials, ETH Zurich 
Reconstruction of smooth velocity and velocity gradient fields from scattered velocity data in a complex flow situation. 
POLYPHYS Seminar HCI J 574 
Wednesday 10. Mar 2010 15:45

Andreas Bausch TU München 
Cytoskeletal mechanics: Structure and Dynamics Show / Hide AbstractThe actin cytoskeleton, a dynamic network of semiflexible filaments and associated regulatory proteins, is responsible for the extraordinary viscoelastic properties of cells. Especially in processes such as cell division, intracellular transport or cellular motility the controlled self assembly to well defined structures, which sill allow a dynamic reorganization on different time scales are of outstanding importance. One important and promising strategy to identify the underlying governing principles is to quantify the physical process in model systems mimicking the functional units of living cells. I will discuss the physical mechanisms which are exploited by cells to control their structural and mechanical integrity.

Talk HCI G7 
Friday 5. Mar 2010 10:15

Jay Schieber Illinois Institute of Technology 
What is measured in microbead rheology? Show / Hide AbstractThe dynamic modulus G* of a viscoelastic medium is often measured by following the trajectory of a small bead subject to Brownian motion in a method called ``passive microbead rheology

POLYPHYS Seminar HCI J 574 
Wednesday 24. Feb 2010 10:15

Martin Kröger Polymer Physics, Department of Materials, ETH Zurich 
Brief overview of 'our' recent research activities 
POLYPHYS Seminar HCI J 574 
Wednesday 10. Feb 2010 10:15

David C. Venerus Department of Chemical & Biological Engineering, Illinois Institute of Technology 
Equibiaxial Elongational Flows of Polymer Melts using Continuous Lubricated Squeezing Flow Show / Hide AbstractEquibiaxial elongation flow, where a fluid element is stretched equally in two directions while it contracts in the third direction, occurs in numerous situations that include the processing of synthetic polymers and foodstuffs. Despite its technological significance, the rheological behavior of complex fluids in equibiaxial elongational flow is largely unexplored. The simple reason for this is that methods for generating equibiaxial elongational deformations are either very complicated or generate nonhomogeneous deformations. The most reliable method for generating rheologically controlled, equibiaxial elongational deformations is the rotating clamp method, or MultiAxiale Dehnung (MAD), developed by Meissner and coworkers at the ETH in Zürich. However, the extremely complicated nature of the MAD rheometer has resulted in a relatively limited set of experimental data. A promising method that has been used with some success is known as Lubricated Squeezing Flow (LSF), where a polymer melt is squeezed between lubricated solid surfaces. Unfortunately, uncontrolled lubricant thinning limits the LSF technique to Hencky strains of roughly onehalf, or barely outside the linear viscoelastic limit. For the past 10 years, we have been developing a modified LSF technique that involves the continuous injection of lubricant through porous metal plates, which we refer to as Continuous LSF (CLSF). This development has involved a combination of experimental tests and modeling to significantly improve the CLSF setup and methods. This novel technique has been validated through comparisons with data collected using the MAD rheometer on a linear polystyrene melt and a branched polyethylene melt. New results obtained using the CLSF technique on a series of Metallocenecatalysed polyethylenes will be presented showing the effect of chain branching on rheological behavior in equibiaxial elongational flows.

POLYPHYS Seminar HCI J 574 
Wednesday 3. Feb 2010 10:15

Yang Liu Department of Physics, The Chinese University of Hong Kong 
Phase transitions from the perspective of statistical mechanics 
Talk HCI J 574 
Wednesday 6. Jan 2010 10:15

Peter D. Olmsted University of Leeds, UK 
Do entangled polymer shear band? Show / Hide AbstractEntangled polymer solutions relax their stress by the reptation mechanism, in which polymers slither or ``reptate” along their length. The original theory for this, due to Doi and Edwards (DE), has successfully captured many features of polymer dynamics. For applied shear rates much faster than the reptation time, the original DE theory predicts an instability due to the alignment of the ``tubes” that constrain the polymer. This instability could lead to shear banding, in which the fluid can break into regions flow at different shear rates. For decades this had not been observed in entangled polymers, and DE theory has been modified to incorporate crucial missing physics, which could eliminate the original instability. Recent experiments by a number of groups on polymer solutions show macroscopic flow inhomogeneities consistent with the original DE instability and shear banding, but have been interpreted in other ways. I will discuss the predictions of the DE and related theories for flow inhomogeneities under strong flow conditions, and show that many, but not all, of the recent experiments can be explained with no more new physics than is contained within DE theory. Note that most verifications and fittings of data to constitutive models (such as the DE model) assume homogeneous flow conditions: an important conclusion of this work is that one must study fully inhomogeneous flow to accurately validate these models.

POLYPHYS Seminar HCI J 574 
Thursday 3. Dec 2009 11:00

Sauro Succi Rome, Italy 
Mesoscopic Lattice Boltzmann Modeling of Flowing Soft Systems Show / Hide AbstractA multicomponent lattice Boltzmann model with shortrange repulsion between different species and short(mid)range attractive (repulsive) interactions between like molecules is discussed. The interplay between these composite interactions gives rise to many features of disordered liquid dispersions (microemulsions) and softglassy materials, such as longtime relaxation, caging effects, anomalous viscosity, ageing under moderate shear and flow above a critical shear rate. The new model shows excellent performance on GPU machines, and shows promises to offer a new angle of attack to the numerical simulation of complex flowing softmatter systems.

POLYPHYS Seminar HCI J 574 
Wednesday 2. Dec 2009 10:15

Ding Yi Polymer Physics, Department of Materials, ETH Zurich 
Verifying Interface Local Equilibrium by Direct Simulation 
POLYPHYS Seminar HCI J 574 
Wednesday 25. Nov 2009 10:15

Markus Hütter Polymer Physics, Department of Materials, ETH Zurich 
Free energy for a dislocation system 
POLYPHYS Seminar HCI J 574 
Thursday 19. Nov 2009 10:15

Erwin Frey University of München 
Biopolymer Conformations and Dynamics  traditional concepts and new ideas  Show / Hide AbstractBiopolymers as individual filaments or assembled into solutions and networks are highly versatile materials with a large variety of different mechanical properties. At the same time they are interesting model systems that allow for the test of fundamental concepts of statistical mechanics and soft matter physics. The challenge is to understand how macroscopic material properties emerge from the intriguing interplay between entropy, filament elasticity and topological constrains on a molecular scale. In this talk we review recent progress in our understanding of the conformations and dynamics of single filaments from the single filament level up to complex mutli component networks. We critically review standard theories like the tube model and the reptation idea and show how new concepts like “floppy modes” emerge for stiff biopolymer systems. In addition to their physical relevance these concepts also contribute to our understanding of the functional principles of the cytoskeleton.

POLYPHYS Seminar HCI J 498 
Wednesday 28. Oct 2009 10:15

Tanniemola Liverpool University of Bristol 
Soft active matter  from microscopics to hydrodynamics Show / Hide AbstractThe cytoskeleton provides eukaryotic cells with mechanical support and helps them perform their biological functions. It is a network of semiflexible polar protein filaments and many accessory proteins that bind to these filaments, regulate their assembly, link them to organelles and continuously remodel the network. We review recent theoretical work that aims to describe the cytoskeleton as a polar continuum driven out of equilibrium by internal chemical reactions. We show how this leads to the formulation of a general framework for the description of the structure and rheology of active suspension of polar filaments.

POLYPHYS Seminar HCI J 574 
Wednesday 14. Oct 2009 15:45

Patricia Basserau Institut Curie, Paris 
Physical Approaches to Intracellular Trafficking Show / Hide AbstractEndocytosis, exocytosis, membrane transport between intracellular compartments, virus or toxin entry or exit out of the cell are cellular events implying membrane deformation. Membrane deformation mechanisms of cell membranes by proteins are currently actively studied. Giant Unilamellar vesicles (GUV) are interesting model membrane systems because they are composed of a very limited number of components compared to cellular membranes. The deformations induced by the interaction with a specific protein, a virus or any other additional components to the system, can then be directly monitored and the deformation mechanism eventually understood. In this talk, I will present a few examples related to membrane trafficking where in vitro systems have contributed to a better understanding and modelling. I will show that toxins (Shiga and Cholera) interacting with GUV containing their lipid receptor, can form tubular structures in absence of any other cellular machinery which are essential for the entry of these toxins in cells. Comparison with nanoparticles functionalized with these toxins will be presented. Membrane nanotubes with controlled diameter can be pulled from GUV, allowing for quantitative measurements of the effects of membrane curvature. Indeed, fluorescence and force measurements can be obtained with an original setup combining confocal microscopy and optical tweezers. In a second part, I will present recent experiments showing the effect of membrane curvature on sorting of the above toxins and of lipids.

Talk HCI D2 
Wednesday 7. Oct 2009 10:15

Marjia Plodinec University of Basel 
The nanomechanical signature of tumorigenic transformation Show / Hide AbstractCells within tissues continuously encounter dynamic mechanical challenges to which they respond by remodeling their cytoskeleton. In cancer, these encounters are often altered thereby causing a change in the cellular response. Here we have been employing atomic force microscopy (AFM) which allows for measuring changes in the nanomechanical properties associated with tumorigenic transformation under nearphysiological conditions. For example, the local stiffness of a specimen may be determined at high spatial resolution by indenting the specimen surface with the AFM tip and monitoring its deformation. On a nanoscopic level, AFM has been recently used in a clinical setting to probe with high sensitivity cell and cartilage mechanics. To date, AFM has not yet been applied to threedimensional (3D) cell culture models or intact cancer tissues, which more appropriately represent the in vivo characteristics of the disease. Towards this goal, we have grown normal (wt) Rat2 fibroblasts and a tumorigenic derivative (Rat2sm9) in a 3D tissue culture system to yield spheroids. Structural changes in the cytoskeleton of these cells cultured on a flat support or as 3D spheroids were correlated with differences in their nanomechanical properties. In tumor spheroids we measured a gradual softening from their periphery to the core, whereas wt spheroids exhibited a homogeneous stiffness distribution. Structural and biochemical analyses indicated that the gradual, centripetal softening in tumor spheroids was caused by increasing hypoxia (lack of oxygen) towards the core. Nanomechanical testing of mammary tumors from transgenic mice corroborated these findings. To verify the clinical relevance for human breast carcinomas, we obtained breast biopsies from 25 patients of different age groups and measured their nanomechanical properties under nearphysiological conditions. In malignant tumors the stiffness decreased up to 15fold from the biopsy's periphery to its core, whereas in benign lesions the stiffness appeared similar in all regions. The nanomechanical signature of the different breast carcinomas correlated well with the pathologist's immunohistological findings. Our longterm goal is to establish nanomechanical properties as a diagnostic marker for mammary carcinomas.

POLYPHYS Seminar HCI J 574 
Wednesday 30. Sep 2009 10:15

Markus Grinschgl

The solid mechanics of polymeric materials: How is it affected by the microstructure? 
POLYPHYS Seminar HCI J 574 
Wednesday 23. Sep 2009 10:15

Giuseppe Foffi EPFL 
Extreme coarse grainings: from colloids to biomolecules. Show / Hide AbstractIn this seminar I will review some of the activities of my group. I will briefly describe the “brute” coarse grained (CG) approach of a colloidal physicist with its success and its pitfalls. I will then move to describe three biorelated systems that we are investigating presently: A)Mixtures of eyelens proteins. I will introduce these mixtures explaining their medical relevance with respect to cataract disease and I will show why they are good candidate to be treated as colloidal systems. I will introduce the model and its validation with experimental results. I will discuss how a fine balance of the interactions controls the stability of the system. Indeed thermodynamic stability is a general phenomena and the same observation that holds here for the eyelens proteins could be extended to other systems that could be of potential interest for food science as well as material science B)Diffusionlimited absorption in crowded media: Crowding is a crucial factor for reactions occurring in vivo. Nevertheless, biological reactions are usually discussed in the ideal Smoluchowski framework of noninteracting agents. We generalize the classic Smoluchowski problem to arbitrary crowding conditions by means of a novel computational scheme that treats the diffusing particles as hard spheres and allows to efficiently explore the effects of increasing packing on the encounter dynamics. In this way, we show and rationalize the emergence of an optimal packing fraction where the encounter rate hits a maximum. Remarkably, optimality is attained far below the dynamical arrest, at concentrations typical of cellular environments. C)A CG model for human immunoglobulin (IgG): Immunoglobulins are the soldiers of the immune system. They bind to what they recognize as dangerous for the body facilitating the immune response. We have developed a model for IgG that is based on very simple geometrical assumptions but that reproduces its main feature, namely the presence of highly flexible hinge. The model agrees well with the available experiments. With this model we conducted insilico binding experiments and we studied the effect of modifying the interactions on the binding process. We show clearly that the flexibility of these macromolecules is indeed fundamental to perform their task.

POLYPHYS Seminar HCI J 574 
Wednesday 1. Jul 2009 10:15

Thierry Savin Harvard 
Singlecell scale mechanical studies of scaffolding and flowing biomaterials Show / Hide AbstractCells such as fibroblasts can be assembled and organized into connective tissues. But other cells can present a high mobility in the body, as it is in the case of flowing blood cells. For these two types of scenario, I will present mechanical studies on corresponding bench models at the singlecell scale. First, a new system of selfassembling peptides forming a polymeric network, and thus mimicking the extracellular matrix that bonds cells into tissue, has been studied using particle tracking microrheology. Second, a unique microﬂow device has been used to track the pressuredriven motion of a single red blood cell in a capillary tube, hence describing blood flow in the microcirculation. I will present semiquantitative models and I will show how, in both cases, the cellscale results can be assessed from nanoscale events.

POLYPHYS Seminar HCI J 574 
Wednesday 10. Jun 2009 10:15

Oivind Wilhelmsen Polymer Physics, Department of Materials, ETH Zurich 
Self consistent mean field theory of polymers 
POLYPHYS Seminar HCI J 574 
Wednesday 27. May 2009 15:45

Fred Mackintosh Vrije Universiteit, Amsterdam 
Nonequilibrium fluctuations and mechanics of active gels and living cells Show / Hide AbstractMuch like the bones in our bodies, the cytoskeleton consisting of filamentous proteins largely determines the mechanical response and stability of cells. Such important cellular processes as locomotion, cell division, and mechanosensing are largely governed by complex networks of cytoskeletal biopolymers and the associated proteins that crosslink these and/or generate forces within the network. In addition to their important role in cell mechanics, cytoskeletal biopolymers have also provided new insights and challenges for polymer physics and rheology. Biopolymer networks, for instance, exhibit strongly nonlinear rheology—in many cases stiffening by orders of magnitude when subject to shear strains of less than unity. In the cell, these polymer networks or gels are far from equilibrium in a way unique to biology: they are subject to active, nonthermal internal forces generated by molecular motors. We describe recent theoretical and experimental results on active networks in vitro that demonstrate significant nonequilibrium fluctuations due to motor activity [1,2]. Furthermore, such gels hold out the promise of active materials, whose stiffness can be controlled by enzymatic activity. We also show how fluctuations and dynamics of individual cytoskeletal filaments can be used to probe both mechanical properties and nonequilibrium activity in living cells [3,4]. 1. D Mizuno, C Tardin, CF Schmidt, FC MacKintosh, Science, 315:370 (2007). 2. FC MacKintosh and AJ Levine, Phys Rev Lett, 100:018104 (2008). 3. CP Brangwynne, FC MacKintosh, DA Weitz, PNAS, 104:16128 (2007). 4. CP Brangwynne, GH Koenderink, FC MacKintosh, DA Weitz, J Cell Biology, 183: 583587 (2008).

Talk HCO G 7 
Wednesday 20. May 2009 15:45

Frank Jülicher MaxPlanckInstitute for the Physics of Complex Systems, Dresden 
Active Processes in Living Matter Show / Hide AbstractBiological cells and tissues represent an extraordinarily complex form of soft matter. This matter is inherently dynamic and far from a thermodynamic equilibrium. A prototype system for the study of dynamics and active processes in cells is the cytoskeleton, a complex gellike filament network which governs the material properties of cells. Dynamic phenomena in cells such as cell division and cell locomotion are driven by active processes on the molecular scale in the cytoskeleton, for example the action of motor molecules. On the cellular scale, this activity can result in emergent collective modes and spontaneous movements and flows. Furthermore, active processes generate novel material properties in fluids and gels such as contractile stresses and active responses that do not obey a fluctuation dissipation relation. Active processes also play a role in the organization of cells in tissues which exhibit properties of active fluids. In twodimensional sheets of cells, called epithelia, cell division and cell death drive local rearrangements of cells which determine the geometry of cell packings as well as the size and shape of growing tissues.

Talk HCI G 7 
Wednesday 13. May 2009 10:15

Daniel Bonn University of Amsterdam 
Density of states of colloidal glasses Show / Hide AbstractThe glass transition is perhaps the greatest unsolved problem in condensed matter physics: the main question is how to reconcile the liquidlike structure with solidlike mechanical properties. In solids, structure and mechanics are related directly through the vibrational density of states of the material. We obtain for the first time the density of states of colloidal glasses and supercooled liquids from a normalmode analysis of particle displacements measured using confocal microscopy. We find that the vibrational spectrum has many ’soft’, lowfrequency modes, more abundant and very different in nature from the usual acoustic vibrations of ordinary solids. This results in an anomalous lowfrequency peak in the density of states which approaches zero frequency as one goes deeper into the glass. The observed soft modes are due to collective “swirling” particle motions, that extend over surprisingly long length scales.

POLYPHYS Seminar HCI J 574 
Wednesday 6. May 2009 9:00

Pierre Sens ESPCI Paris 
OutofEquilibrium phase separation in Biological Membrane Show / Hide AbstractSpatial heterogeneity is often crucial to the proper function of biological membranes. Phase separation of lipids and membrane protein is for instance thought to be needed for biochemical signaling across the plasma membrane, or for the formation of proteincoated vesicles involved in cellular transport. Experimental evidences suggest that these dynamical processes are regulated, possibly by flux of membrane material, or through the activity of energyconsuming proteins. I will present theoretical investigations of situations where phase separation is maintained outofequilibirum by active processes. I will discuss the formation of membrane domains under continuous recycling of membrane material, and the formation of coated vesicles when the lifetime of the coat components at the membrane is controlled by the activity of a GTPase. In both situations, the stationary state of the membrane is shown to be tightly controlled by the dynamics of recycling, giving rise to nonlinear phenomena (dynamical switches) possibly relevant to the biological function of the membrane.

POLYPHYS Seminar HCI J 574 
Wednesday 10. Dec 2008 10:15

Pep Espanol Dpto. de Física Fundamental, Facultad de Ciencias (U.N.E.D.), Univ. Madrid 
Making Zwanzig projection operator theory a useful tool for coarsegrained simulations 
POLYPHYS Seminar HCI J 574 
Wednesday 12. Nov 2008 10:30

Roberto Piazza Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta”, Politecnico di Milano. 
Further insights in Soft Matter Show / Hide AbstractI shall discuss some topics which are of current interest in our lab, lingering in particular over the opportunity that these investigations yield to scrutinize basic aspects of equilibrium and non equilibrium statistical physics. More specifically:  A) I shall show that the analysis of the equilibrium and kinetic sedimentation profiles induced by gravity settling is an efficient route to obtain the equation of state of a colloidal suspension, to inspect fine details of its phase diagram, to provide information on the elastic properties of metastable phases, and to extract relevant information on hydrodynamic forces. In particular, I shall present some recent results on sedimentation of “sticky” hardspheres, where attractive (“depletion”) forces are induced by the presence of nonionic or charged surfactants. Eventually, sedimentation experiments may yield crucial information on the physical origin and nature of gel and glassy phases.  B) I shall discuss thermophoresis, a particularly puzzling non equilibrium transport phenomenon, which basically consists in particle drift induced by a thermal gradient. Thermophoresis can be profitably exploited in separation and fractionation methods, in particular using microfluidic devices: yet, the microscopic mechanisms underlying this effect are still partly understood. Here I shall review the experimental evidences on colloid thermophoresis collected by our group on a large class of colloid and macromolecular systems, ranging from micellar solutions to polymers, microemulsions, proteins, latex particles. These results have allowed us to extract basic ideas about the origins of thermallydriven particle transport, and to build up a tentative general hydrodynamic model of thermophoresis.

POLYPHYS Seminar HCI J 574 
Wednesday 5. Nov 2008 10:15

Majid Mosayebi Polymer Physics, Department of Materials, ETH Zurich 
Thermodynamically guided simulations of glassy systems: Research Plan 
POLYPHYS Seminar HCI J 574 
Wednesday 22. Oct 2008 10:15

Yitzhak Rabin Department of Physics, BarIlan University, RamatGan 52900, Israel 
Protonated DNA Monolayers 
POLYPHYS Seminar HCI J 574 
Wednesday 24. Sep 2008 16:45

Cédric Villani ENS, Lyon, France 
Entropy: The Mathematical Heritage of Ludwig Boltzmann Show / Hide Abstract

Talk HPV G4 
Wednesday 9. Jul 2008 14:15

Matteo Colangeli Polymer Physics, Department of Materials, ETH Zurich 
Eigenclosures and existence of invariant hydrodynamic manifolds 
POLYPHYS Seminar HCI J 574 
Wednesday 2. Jul 2008 10:15

Anthony N. Beris Department of Chemical Engineering, University of Delaware 
On the Hamiltonian and Dissipative Structure of Some LowOrder Models in Fluid Dynamics and Turbulence Show / Hide AbstractRecently various loworder models have been developed in fluid dynamics and turbulence [1,2]. The basis of those models is coupled threemode systems known as Volterra gyrostats (possibly coupled) plus terms describing forcing and friction. This structure has been postulated as enabling the preservation of certain important physics in the approximate models from the original fluid dynamical equations. In particular, in turbulence, it is shown that such a model exhibits Kolmogorov spectral behavior [1]. We discuss those systems here and draw analogies to GENERIC and Bracket formulations. [1] A. Gluhovsky and C. Tong, The structure of energy conserving loworder models, Physics of Fluids, 11:334343 (1999). [2] C. Tong and A. Gluhovsky, Energyconserving loworder models forthreedimensional RayleighBenard convection, Physical Review E, 65:046306(2002).

POLYPHYS Seminar HCI J 574 
Friday 27. Jun 2008 11:00

Sadati Monirosadat Polymer Physics, Department of Materials, ETH Zurich 
The CrossSlot Channel Project: Current State and Possible Improvements 
POLYPHYS Seminar HCI J 574 
Friday 27. Jun 2008 10:15

Majid Mosayebi Polymer Physics, Department of Materials, ETH Zurich 
Modeling mechanical properties of semicrystalline polymers 
POLYPHYS Seminar HCI J 574 
Wednesday 18. Jun 2008 10:15

Beat Lüthi Institut f.Umweltingenieurwissenschaften, ETH Zurich 
Particle tracking  Image based flow field measurements 
POLYPHYS Seminar HCI J 574 
Friday 13. Jun 2008 10:15

Brian J. Edwards Department of Chemical & Biomolecular Engineering, University of Tennessee 
Applying Nonequilibrium Thermodynamics Principles to NEMD Simulations 
POLYPHYS Seminar HCI J 574 
Wednesday 11. Jun 2008 10:15

Dave Venerus Center of Excellence in Polymer Science and Engineering, Illinois Institute of Technology, Chicago 
Thermal Transport in Colloidal Suspensions 
POLYPHYS Seminar HCI J 574 
Wednesday 4. Jun 2008 10:15

Asja Jelic Polymer Physics, Department of Materials, ETH Zurich 
From CahnHilliard to DoiOhta level: Overview. The friction matrix. 
POLYPHYS Seminar HCI J 574 
Wednesday 28. May 2008 10:15

Leonard M.C. Sagis Wageningen University, The Netherlands 
Interfacial transport phenomena formalism Show / Hide Abstract

POLYPHYS Seminar HCI J 574 
Wednesday 21. May 2008 10:15

Andre Bardow TU Delft, The Netherlands 
Free LatticeBoltzmann! Show / Hide AbstractThe Lattice Boltzmann (LB) method is a highly promising approach to the simulation of complex flows. However, the intrinsic coupling of momentum and space discretization restricts the applicability of the traditional Lattice Boltzmann method to uniform, regular lattices which is often disadvantageous in practice. In particular, the choice of a specific velocity model determines simultaneously the velocity, space and time discretization of the Boltzmann equation. In offlattice Boltzmann methods, these discretizations are independent. Offlattice Boltzmann methods therefore could offer the opportunity to independently discretize velocity, space and time for problemadapted simulations. Much research has been done on offlattice Boltzmann methods to enhance the geometrical flexibility of the LB method. In contrast, the additional freedom gained in velocity space seems to not have been systematically exploited. Both aspects are discussed in this presentation. The general characteristicbased algorithm for offlattice Boltzmann simulations proposed by the authors [1] preserves all appealing properties of the standard Lattice Boltzmann method while extending the method to unstructured grids. With respect to velocity discretization, we realize the recently proposed multispeed Lattice Boltzmann models [2] by exploiting the flexibility offered by offlattice Boltzmann methods. We show that the use of multispeed models indeed gives rise to major improvements in accuracy and that the Hermite model hierarchy provides the sound systematic framework [3]. References: [1] A. Bardow, I. V. Karlin, A. A. Gusev, General characteristicbased algorithm for offlattice Boltzmann simulations, Europhys. Lett., 75:434440, 2006; [2] S. S. Chikatamarla, S. Ansumali, I. V. Karlin, Entropic lattice Boltzmann models for hydrodynamics in three dimensions, Phys. Rev. Lett., 97: 010201, 2006. [3] A. Bardow, I. V. Karlin, A. A. Gusev, Multispeed models in offlattice Boltzmann simulations, Phys. Rev. E 77(2): 025701(R), 2008.

POLYPHYS Seminar HCI J 574 
Wednesday 30. Apr 2008 10:15

Yitzhak Rabin Department of Physics, BarIlan University, Israel 
Cooperativity and Elasticity in DNAProtein Interactions 
POLYPHYS Seminar HCI J 574 
Monday 28. Apr 2008 16:00

Emanuela Del Gado Polymer Physics, Department of Materials, ETH Zurich 
Nonaffine deformations of inherent structure as signature of cooperativity in supercooled liquids Show / Hide Abstracthttp://www.metphys.mat.ethz.ch/education/seminars

Talk HCI J 492 
Wednesday 16. Apr 2008 10:15

Alessio Zaccone Institute for Chemical and Bioengineering Department of Chemistry and Applied Biosciences, ETH Zurich 
HardMode Elasticity of Dense Colloidal Aggregates and Its Application to Problems in the Rheology of Colloidal Dispersions Show / Hide AbstractAggregates of small (colloidal) particles in fluids are relevant to many industrial problems (e.g., solidliquid processing) as well as to environmental systems (e.g., mudstone accretion in sedimentary geology, dynamics of sol particles in the atmosphere etc.). The timeevolution of these systems is controlled by the kinetics of aggregation and breakage which are function of different physical and chemical parameters such as the surface properties, the morphology and the mutual interactions of the particles as well as the properties of the flow. I will focus on the hitherto unsolved problem of breakage of aggregates of colloidal particles in shear and turbulent flows. Varying the shearrate of the flow, more than 20 years ago it has been observed for the first time that the steadystate size of the aggregates scales with shearrate as a powerlaw with exponent about 0.5. Despite theoretical and experimental efforts to explain this observation (that has been confirmed by many experiments and simulations), no satisfactory physical explanation for this scaling is available. In the case of turbulent flow, combining the most accurate theory of turbulence in terms of its multifractal spectrum within a breakageequation model with a CauchyBorn (freeenergy expansion), hardmode model for the elasticity of the disordered sheargenerated aggregates (and accounting for their dense glassylike structure in a statistical mechanical fashion), we obtained an approximate theory which predicts very accurately the scaling between the steadystate size of the aggregates and the shearrate.

POLYPHYS Seminar HCI J 574 
Wednesday 19. Mar 2008 10:15

Sergey Lurie Institute of Applied Mechanics of Russian Academy of Sciences, Moscow, Russia 
Variational formalism for the description of nonholonomic media models Show / Hide AbstractThe variational formalism for description of the nonholonomic media models is offered. Formal generalization of continued mechanics models on the fourdimensional space of events with a fourdimensional vector of the generalized displacements is used. Time of process is included in the generalized fourdimensional system of coordinates and considered as one of independent coordinates. As kinematic connections it is proposed to use generalized Cauchy relations for the generalized deformations, which correspond to a fourdimensional vector of the generalized displacement media. The general form of the constitutive equations for nonholonomic media is given. Common properties of the symmetry for the tensor of the physical properties are established. Variational equation for the nonholonomic linearmedium model is obtained and the appropriate initial  boundary problem is formulated. It is shown that irreversible processes proceed with positive dissipation, and the second law of thermodynamics takes place. The possible types of the channels of dissipation are established for considered media model. Within the framework of specific model the generalized equation of heat conductivity is received. The relations between heat flow, temperature and different thermodynamic parameters are established which generalize the Fourier equation (for heat flow) and DuamelNeumann equation. As a special case the combined model of the creep and relaxation is received.

POLYPHYS Seminar HCI J 574 
Wednesday 12. Mar 2008 10:15

Patrick Ilg Polymer Physics, Department of Materials, ETH Zurich 
Beyondequilibrium molecular dynamics of unentangled polymer melts: status report 
POLYPHYS Seminar HCI J 574 
Wednesday 5. Mar 2008 10:15

Asaph WidmerCooper School of Chemistry, University of Sydney, Australia 
Exploring structuredynamics correlations in supercooled liquids with the isoconfigurational ensemble Show / Hide AbstractGlasses  formed via a continuous transition from the liquid to the solid state  are ubiquitous in nature and play an important role in many technological applications, yet we still lack a clear picture of the relationship between structure and dynamics in such materials. For example, the role of structure in the appearance of slowly relaxing domains whose dimensions and lifetimes increase with supercooling. In this talk, I will present the isoconfigurational ensemble as a useful general tool for exploring the relationship between structure and dynamics when order is illdefined and transient. In particular, I will show that as supercooling increases, a given configuration increasingly contrains the propensity of particles to subsequently exhibit large displacements. This dynamic propensity allows one to test various hypotheses about the causal relationship between structure and dynamics at a microscopic level, and to ultimately arrive at a measure of structure that correlates with the spatial variation in propensity. Some other questions that can be addressed using the isoconfigurational ensemble will also be discussed.

POLYPHYS Seminar HCI J 574 
Thursday 28. Feb 2008 12:00

Torsten Granzow Darmstadt University of Technology, Germany 
From the atomic to the component scale: Factors influencing ferroelectric domain dynamics 
Talk HPM D 7.1 
Thursday 28. Feb 2008 9:00


MiniSymposium Functional Ceramic Materials  Day 2 
Talk HPM D 7.1 
Wednesday 20. Feb 2008 10:15

Yi Ding Polymer Physics and Chemistry, Department of Materials, ETH Zurich 
Modeling Dendronized Polymers 
POLYPHYS Seminar HCI J 574 
Friday 8. Feb 2008 9:40

H.M. Wyss Harvard University, Cambridge, MA, United States 
Soft Particles make Strong Glasses: On the Dynamics and Mechanics of Glass Formation 
Talk HIL E 8 
Friday 8. Feb 2008 9:00


MiniSymposium Functional Ceramic Materials  Day 1 
Talk HIL E 8 
Wednesday 30. Jan 2008 10:30

Manuel Torrilhon Seminar of Applied Mathematics SAM, ETH Zurich 
Continuum modeling of Gas MicroFlows 
Talk HIF E 19 
Wednesday 30. Jan 2008 10:15

Chunggi Baig and Vlasis Mavrantzas Dept. of Chemical Engineering, University of Patras, Greece 
Thermodynamicallyguided nonequilibrium Monte Carlo methodology for simulating polymer melts under flow 
POLYPHYS Seminar HCI J 574 
Monday 28. Jan 2008 9:00

Suzi Jarvis University College, Dublin 
Nanoscale Characterization of Protein Aggregates and Nanofibers Show / Hide AbstractAmyloid fibrils are quaternary protein structures formed from the nonspecific folding and subsequent aggregation of proteins into supramolecular crossed bsheet assemblies. Such structures are commonly regarded as ‘mistakes’ formed from ‘misfolded’ proteins due to their pathogenic association with neurodegenerative diseases such as Alzheimer’s and Parkinson’s. However, in recent years there has been increasing evidence to suggest that the amyloid structure is a generic form into which any polypeptide can fold, particularly in vitro under slightly denaturing conditions. We have recently discovered amyloid in various permanent and temporary natural adhesives. Using an atomic force microscope (AFM) we have been able to delicately pull apart amyloid fibrils in order to characterize their mechanical properties and thus provide an explanation for their mechanical strength based on ‘hidden length’ and ‘sacrificial bonds’ within the amyloid structure. We are now applying AFM to the mechanical and surface structural characterization of a range of pathogenic and physiological amyloid fibrils in order to identify the parameters that trigger the formation and influence subsequent structure and mechanical function, or indeed the pathogenic nature of the fibrils. In this way we hope to evaluate the feasibility of using amyloid fibrils as new biocompatible materials.

Talk HCI J 498 
Monday 28. Jan 2008 10:30

Jens Feder Department of Physics, University of Oslo 
SelfAffine Dynamics of StickSlip Friction Show / Hide AbstractI will discuss the historical background, and Coulomb's work on failure and on friction. I describe recent experiments on stickslip friction, and show that they are accurately described by a selfaffine joint distribution for magnitude and duration, and show that the measured exponents lead to the conclusion that this stickslip process is a scalefree selforganized critical (SOC) process. We discuss normal earthquakes and show that they are not SOC. However, recently discovered slow earthquakes have scaling exponents that are in the universality class as our experiments, and therefore SOC. For more information (e.g. pdf of the abstract) see http://www.ifb.ethz.ch/comphys/events

Talk HIF E 19 
Wednesday 19. Dec 2007 10:15

Markus Hütter Polymer Physics, Department of Materials, ETH Zürich 
Crystal plasticity: a kinetic toy model, and some ideas about possible extensions (Part 2) 
POLYPHYS Seminar HCI J 574 
Wednesday 12. Dec 2007 10:00

Avi Halperin CNRS, CEA Grenoble, France 
PEG brushes and their interactions with proteins: A simple theory 
POLYPHYS Seminar HCI J 498 
Wednesday 12. Dec 2007 11:15

Andreas Bick Scienomics 
Atomistic and Mesoscale Modeling with MAP Show / Hide AbstractThis presentation will illustrate how to use MAPS as an integrated modeling environment to do atomistic and mesoscale simulations on a variety of systems. Atomistic simulations will be presented using the LAMMPS and FHMixing plugins, and results from these calculations are then used as input parameters for Dissipative Particle Dynamics simulations. The systems presented will include Phospholipids, Nafion membranes, Carbon Natotube / polymer mixtures and a mixture of inorganic compounds. Phase behavior, surface tension, diffusion of particles and density profiles of the components will be discussed and a demonstration of MAPS will follow the presentation. There will also be time for informal discussions with individuals after the meeting by appointment.

POLYPHYS Seminar HCI J 498 
Wednesday 5. Dec 2007 10:15

Manuela R. Duxenneuer Laboratory of Food Process Engineering, Department of Agricultural and Food Science, ETH Zürich 
Flow Visualization of Polymer/Water/Surfactant Droplets in Oil using Coflow and FlowFocusing Channels with microPIV Technique Show / Hide AbstractIn this study, we have investigated the drop formation and breakup (dripping mode) in coflow and flowfocusing microchannels, producing pure water, Tween20surfactant/water (0.1cmc to 100cmc), and surfactant/polymer/water (0.1wt% to 0.2wt% hydroxypropylether guar gum) droplets (Ddrop=0.010 to 0.3mm) in sunflower oil. The flow fields with the surrounding continuous and disperse phase were analysed. Fluorescent particles with diameters ranging from 0.300 to 1mm were seeded into both the oil and water phases allowing the flow inside and outside of different sized droplets during formation and breakup to be visualized and analysed simultaneously. Droplet and continuous phase velocity distributions were quantified during droplet formation, pinchoff, and drop convection along the length of the channel. The velocity profiles show that fluid recirculation occurs inside the drop only when the drop is in contact with the wall and is blocking the continuous phase passing by. The recirculation can be attributed to wall slip and shearing at the leading edge and backside of the droplet. This is consistent with previous twophase studies utilizing confocal ?PIV or ordinary ?PIV for water/glycerol droplets in silicon oil. However, this phenomenon was not observed when the droplet creation event was very fast, resulting in the droplet size being much smaller than the channel depth (Dcell=0.5mm, Hcell=0.1 to 0.2mm, Lcell=34cm). The effect of elasticity on drop formation and breakup has also been explored by using various solutions as the disperse phase (water, surfactant [0.1100cmc], surfactant/polymer [0.10.2wt]). At constant flow rate, it was found that with increasing polymer concentration, the elasticity of the fluid increases and therefore the pinchoff distance of the droplet increases. The elongated neck of the drop also in the production results in small satellite droplets.

POLYPHYS Seminar HCI J 574 
Wednesday 21. Nov 2007 10:15

Markus Hütter Polymer Physics, Department of Materials, ETH Zürich 
Crystal plasticity: a kinetic toy model, and some ideas about possible extensions 
POLYPHYS Seminar HCI J 574 
Wednesday 14. Nov 2007 10:15

Dietmar Göritz Institute of Experimental and Applied Physics, University of Regensburg, Germany 
Energetic contributions to the deformation behaviour of polymer networks 
POLYPHYS Seminar HCI J 574 
Wednesday 31. Oct 2007 10:30

Emanuela Del Gado Polymer Physics, Department of Materials, ETH Zürich 
Colloidal gels and networks 
POLYPHYS Seminar HIF 419 
Friday 12. Oct 2007 9:45

Efthimios Kaxiras Department of Physics, Harvard University, Cambridge (MA), USA 
Multiscale methods in modeling complex materials 
POLYPHYS Seminar HCI J 574 
Wednesday 19. Sep 2007 10:15

Michael Junk Department of Mathematics, University of Konstanz, Germany 
Maximum entropy moment closures Show / Hide AbstractThe numerical solution of kinetic equations generally suffers from the high dimension of the phase space. Moment methods are therefore derived from the kinetic equations to reduce the problem to a system of equations defined on a lower dimensional space. If the required closure is based on a maximum entropy argument, the moment systems seem to possess interesting mathematical properties. But sometimes appearances are deceiving ... In the talk, the maximum entropy closure is introduced and its advantages and disadvantages are discussed.

POLYPHYS Seminar HCI J 574 
Wednesday 12. Sep 2007 10:15

Suzanne M. Fielding School of Mathematics, University of Manchester, UK 
Shear banding in complex fluids Show / Hide AbstractComplex fluids commonly undergo flow instabilities and flowinduced transitions that result in spatially heterogeneous shear banded states. Often, these banded states display oscillatory or chaotic dynamics, measured in the bulk rheological signals and in the motion of the interface between the bands. Until recently, however, theory predicted a steady state comprising stationary bands separated by a flat interface. I will discuss recent theoretical progress in capturing complex dynamics of the banded state: first in a model in which the interface (or interfaces) remains flat but moves in a chaotic way; second in a model that explicitly allows for undulations along the interface. I will also discuss the formation of vorticity structuring, as a secondary instability to ordinary shear bands. Time permitting, I will finally discuss some recent results on temperatureinduced fluidfluid demixing, subject to an applied shear flow.

POLYPHYS Seminar HCI J 574 
Monday 20. Aug 2007 10:15

Thomas Schweizer Polymer Physics, Department of Materials, ETH Zürich 
Flow reversal experiments with monodisperse polymer melts 
POLYPHYS Seminar HCI J 574 
Wednesday 8. Aug 2007 10:15

Miroslav Grmela Ecole Polytechnique, Montreal, Canada 
Multilevel view of reptation 
POLYPHYS Seminar HCI H 543 
Wednesday 18. Jul 2007 10:15

Pieter J. In' t Veld Sandia National Laboratories, USA 
Pathways for linking molecular properties and macroscopic observables Show / Hide AbstractI will present an exposition of my current and previous work as an illustration of how to integrate different length scales. In general I give an overview of different scaling techniques and approaches to connect molecular length scales to continuum models and will illustrate the concepts by examples. The first example describes thermal and mechanical properties of the interlamellar phase of semicrystalline polyethylene. In turn, these properties can be used in two and threephase finite element models, thus creating a macroscopic connection to either mechanical deformation or crystallization problems. The second example describes the development and application of a coarsegrained model for colloidal suspensions. I will show the efficacy and versatility of this model by discussing the phase behavior of pure colloidal systems, the response of bulk colloidal suspensions to external shear, and the liquid/vapor phase behavior of these suspensions. The third example introduces a coarsegrained model of collagen, combined with atomistic simulations, to analyze mechanical response as a function of an externally applied deformation. The applied simulation techniques encompass both molecular dynamics and Monte Carlo simulations.

POLYPHYS Seminar HCI J 574 
Wednesday 4. Jul 2007 10:15

Joachim Meissner Polymer Physics, Department of Materials, ETH Zürich 
Polymer melt recovery 
POLYPHYS Seminar HCI J 574 
Monday 25. Jun 2007 13:30

Several speakers ETH Zurich 
High Performance Computing 
Talk HCI J 574 
Wednesday 20. Jun 2007 15:45

Martin Kröger Polymer Physics, Department of Materials, ETH Zürich 
Insight into Computational Polymer Physics at DMATL 
Talk HCI G7 
Wednesday 20. Jun 2007 10:15

Manuel Torrilhon Department of Mathematics, ETH Zürich 
Boundary Conditions for Moment Equations in Kinetic Gas Theory Show / Hide AbstractBoundary conditions are the major obstacle in simulations based on advanced continuum models of rarefied and microflows. This talk presents a theory how to combine the nonlinear regularized 13momentequations derived from Boltzmann's equation with boundary conditions obtained from Maxwell's accommodation model. The regularized 13momentequations form a stable and highly accurate continuum model obtained from a hybrid combination of Grad's moment method and ChapmanEnskogexpansion. For the boundary, our hypothesis is that the equations have to be adapted to the boundary conditions in a way that the number of boundary conditions required does not depend on the process. To achieve this continuity condition, the equations need to be properly transformed while keeping their asymptotic accuracy with respect to Boltzmann's equation. After finding a suitable set of boundary conditions and equations, a numerical method for generic shear flow problems is formulated. Several test simulations for channel flow demonstrate the stable and oscillationfree performance of the new approach.

POLYPHYS Seminar HCI J 574 
Wednesday 13. Jun 2007 10:15

Asja Jelic Polymer Physics, Department of Materials, ETH Zürich 
Bridging scales in a phase separating binary fluid: From CahnHilliard to DoiOhta model 
POLYPHYS Seminar HCI J 574 
Thursday 7. Jun 2007 10:15

Rahmi Ozisik Rensselaer Polytechnic Institute, Materials Science and Engineering, Troy, NY 12180 
Crystallization of isotactic polypropylene and effect of stereotacticity defects on the formation of order Show / Hide AbstractBecause of recent developments in metallocene catalysts, a finetuning of material properties becomes possible by controlling the tacticity of polypropylene chain so that polypropylenes with properties ranging from semicrystalline thermoplastic to thermoplastic elastic can be achieved. As a result, the effect of defects on the properties of polypropylene, especially on its crystallization behavior, has received an increasing interest. The properties of these new polypropylenes depend significantly on the concentration and distribution of defects along the polymer chain. In general, the isotactic segments can afford a high degree of crystallinity if they are long enough so that the material would display the behavior of tough thermoplastics. However, the introduction of stereodefects would reduce the isotacticity and lead to some extent of elastic behavior. Coarsegrained, onlattice Monte Carlo simulations are performed to investigate the role of stereotacticity defects along an isotactic polypropylene chain on the formation of helices, which form the basic crystalline order within the chain. For this reason, systems with various stereodefect configurations are studied and are compared to neat isotactic polypropylene. All systems are equilibrated above the melting temperature and are cooled to lower temperatures in a stepwise manner, making sure each system is equilibrated at every temperature. Results indicate that chain ends have the lowest probability of being in helices. Addition of a single stereoerror (mrm) decreases the probability of five repeat units’ participation in helices (the repeat unit that contains the stereodefect and two nearest repeat units on both sides). The probability profile becomes more complicated when the number of stereodefects increases, however, the results indicate that the effects of many stereodefects can be explained by a simple addition of the effect of each stereodefect considered individually. The results also indicate that the presence of even a single stereodefect eliminates (within the temperature range studied) the transition to longer, more stable helices observed in neat isotactic polypropylene.

POLYPHYS Seminar HCI J 574 
Wednesday 6. Jun 2007 10:15

Brian Gettelfinger Materials Research Science and Engineering Center on Nanostructured Interfaces, University of WisconsinMadison, USA 
Liquid crystal relaxation in three dimensions: The effect of hydrodynamic interactions 
POLYPHYS Seminar HCI J 574 
Wednesday 30. May 2007 10:15

Lamberto Rondoni Department of Mathematics, Politecnico di Torino, Italy 
Transient and steady state fluctuation relations for nonequilibrium systems Show / Hide AbstractIn the past decade a number of authors have proposed relations describing the behaviour of nonequilibrium systems, with the common charactersitic of referring to the fluctuations of certain observables. Some of these relations concern states evolving out of equilibrium states, when certain external drivings have been switched on; other relations concern the fluctuations around nonequilibrium steady states. The framework within which these relations have been most investigated is that of nonequilibrium molecular dynamics (NEMD). Various experimental tests of these relations have been performed on nanoscale devices. These works indicate possible research avenues for a unifying picture of nonequilibrium phenomena. In this talk, some of the relevant NEMD models and the relevant fluctuation relations are illustrated.

POLYPHYS Seminar HCI J 574 
Wednesday 23. May 2007 15:45

Andreas Herrmann MaxPlanckInstitute for Polymer Research, Mainz, Germany 
Putting life into polymers 
Talk HCI G 7 
Wednesday 16. May 2007 10:15

Thomas Schweizer Polymer Physics, Department of Materials, ETH Zürich 
Shear banding in polymer melts 
POLYPHYS Seminar HCI J 574 
Wednesday 16. May 2007 15:45

Markus Niederberger Multifunctional Materials, Department of Materials, ETH Zurich 
Metal Oxide Nanoparticles: Synthesis, Assembly and Applications (1st MRC Colloquium) 
Talk HCI J 574 
Thursday 10. May 2007 10:15

Dick Bedeaux Institute of Physical Chemistry, Norwegian University of Science and Technology, Trondheim, Norway 
Heat and mass transfer into and through interfaces Show / Hide AbstractExperiments done in the last ten years have found temperature differences across the liquidvapour interface of up to 8 degrees Celsius during evaporation. These temperature differences are much larger than expected on the basis of kinetic theory. The challenge is to describe these results in a clear macroscopic context, on the one hand, and to understand them on a microscopic level, on the other hand. We will show that nonequilibrium thermodynamics provides the needed macroscopic description. Questions like: how do we describe the surface and is the surface in local equilibrium, need to be answered. The description chosen uses, as Gibbs did for equilibrium interfaces, excess densities. This implies that the surface is a separate thermodynamic system. When the system is not in equilibrium the surface will even have a temperature different from the temperatures of the adjacent phases. Away from equilibrium we extend Gibbs’ analysis by the introduction of excess fluxes along the interface. Using balance equations and the Gibbs relation we obtain the excess entropy production and are thereby able to give forceflux relations and boundary conditions for the surface. In order to elucidate all these questions we simulated such transports using molecular dynamics. On the basis of these simulations we were then able to verify that the description using nonequilibrium thermodynamics is correct and that the surface is in local equilibrium during evaporation and condensation. Results from molecular dynamics simulations of heat and mass transport through the surface during condensation will be presented and compared with the results from experiments and kinetic theory.

POLYPHYS Seminar HCI J 574 
Wednesday 9. May 2007 14:15

Monirosadat Sadati http://sadatpolymer.persianblog.com/ 
Experimental methods for measuring velocity fields in complex flow situations 
POLYPHYS Seminar HCI J 574 
Wednesday 9. May 2007 10:15

Jjun Wang MPI for Polymer research in Mainz 
Confined polymers: Forces between solid surfaces across polymer melts 
Talk HCI J 498 
Wednesday 2. May 2007 10:15

Greg Forest Department of Mathematics, Institute for Advanced Materials, Nanoscience and Technology, University of North Carolina at Chapel Hill, USA 
Rigidrod macromolecular dispersions: 30 years after the Hess 1976 classic Show / Hide AbstractIn 1976, Professor Siegfried Hess derived the Smoluchowski equation governing orientational distributions of a dispersion of rigidrod macromolecules in a prescribed flow field. The Hess kinetic equation generalizes several classical works: of Jeffery on a single rod in Stokes flow; of Onsager on the isotropicnematic phase transition of hardrod ensembles; and, of Leslie & Ericksen on the director theory of smallmolecule liquid crystals. This is not your garden variety kinetic equation; it is an infinitedimensional nonlinear diffusion equation on the sphere in which a Brownian rod senses its local environment of rods while accepting a deterministic flow torque. The secondmoment of the distribution function can be modeled by a finitemode spherical harmonic projection of the Hess model with an ad hoc closure, which recovers the LandaudeGennes class of models. Around 1981, Doi rederived the Hess equation. Since 1976, a remarkable history has unfolded, punctuated by several major physical predictions, rigorous and formal mathematical analyses, and computational phenomena. This lecture will reflect one person’s historical view of the past 30 years downstream of this landmark paper, ending with remaining open questions and challenges regarding nanorod and nanoclay composites, for which the HessDoi model remains the foundation!

POLYPHYS Seminar HCI J 574 
Thursday 26. Apr 2007 10:15

Majid Mosayebi Physics Department, Sharif University of Technology, Tehran, Iran 
Monte Carlo Methods in Statistical Physics (Multi Histogram and Parallel Tempering) 
POLYPHYS Seminar HCI J 574 
Wednesday 25. Apr 2007 10:15

Peter Van Department of Chemical Physics, Budapest University of Technology and Economics, Budapest, Hungary 
Weakly nonlocal nonequilibrium thermodynamics  fluids and beyond Show / Hide AbstractI show a general and rigorous methodology to exploit the Second Law in case weakly nonlocal constitutive state spaces (gradient dependent constitutive functions). Two examples are shown. First the GinzburgLandau equation is derived from the Second Law, without variational principles. The same method applied to one component fluids result in a general class of constitutive functions leading to the SchrödingerMadelung equation of quantum mechanics. Finally, two component phase separated fluids and weakly nonlocal statistical entropies are mentioned.

POLYPHYS Seminar HCI J 574 
Wednesday 28. Mar 2007 10:15

Patrick Charbonneau FOMAmolf, Amsterdam, The Netherlands 
Dynamical arrest in model colloidal systems Show / Hide AbstractWe compare measures of dynamical heterogeneity in repulsive and nearly attractive glass formers. Slow growing heterogeneities are observed near the attractive glass regime, which also shows a smaller dynamical lengthscale and a greater susceptibility to shortdistance processes than in the repulsive glass forming regime. This is consistent with the results from a spinglass model that shows similar dynamical arrest phenomenology.

POLYPHYS Seminar HCI J 574 
Monday 19. Mar 2007 10:45

Christian Sailer Polymer Physics, Department of Materials, ETH Zürich 
Melt flow properties of reactively compatibilized blends of polyamide 6 and styreneacrylonitrile: Linear viscoelasticity, melt elongation, and morphology Show / Hide AbstractReactive compatibilization of immiscible polymer blends has become a state of the art technology and is widely applied for various commercial blends. For example, the reactive coupling of polyamide 6 and styrenic polymers by reactive agents containing maleic anhydride is currently intensively investigated. In this work, the influence of reactive compatibilization on the melt rheology and morphology of polyamide 6/styreneacrylonitrile (PA 6/SAN) blends was studied. We investigated the rheological behaviour in linear viscoelastic oscillatory shear flow, simple elongation and recovery after simple elongation. Furthermore, the blend morphology and the flowinduced changes of the morphology were examined by atomic force microscopy and quantified. Before blending the reactive agent, a styreneacrylonitrilemaleic anhydride terpolymer (SANMA), was added to the SAN phase. Then three PA 6/SAN blends with different composition ratios (70/30, 50/50, 30/70) were prepared. Reactive compatibilization strongly influences the linear viscoelastic behaviour of all blends. In order to describe the linear viscoelastic data phenomenologically, the fractional Zener model was applied. The experimental data of the PA 6/SAN 30/70 blend gave strong evidence that an elastic network between neighbouring PA 6 domains was formed. In simple elongation, the transient elongational viscosity of this blend exceeded the linear viscoelastic prediction and showed strain hardening. On the contrary, for the PA 6/SAN 70/30 blend the theoretical prediction of the elongational viscosity agreed well with the experimental data. The morphological analysis revealed that during elongation the phase domains of all blends were considerably deformed. During recovery, the stretched phase domains retracted back to an isotropic shape. In addition, all blends showed a significantly larger recovered stretch compared to the blend components. The differences in the rheological behaviour between the PA 6/SAN 30/70 blend and the PA 6/SAN 70/30 blend were explained by the asymmetric properties of the compatibilized interface which stems from the asymmetric molecular architecture of the insitu generated SANMA multigrafted PA 6 chains.

POLYPHYS Seminar HCI J 574 
Wednesday 14. Feb 2007 10:15

Sebastian Heidenreich Institute of Theoretical Physics, Technical University Berlin, Germany 
Boundary conditions for fluid flow: Apparent slip associated with the molecular alignment Show / Hide AbstractIn nano and microfluidics the length scales of devices are comparable to the molecular lengths and fluidwall interactions become significant for the flow behavior. In continuum mechanical descriptions fluidwall interactions can be taken into account by special boundary conditions. Here the relaxation equation [1], an amended Landaude Gennes potential [2] is used to model the spatially inhomogeneous orientational dynamics of the fluid and the momentum balance equation to couple the velocity on the orientational dynamics. In order to model fluidwall interactions we use conditions on the alignment tensor as well as conditions on the alignment flux tensor (consequences of irreversible thermodynamics [3]). We show analytically that for stationary flows in the isotropic phase for special geometries (plane Couette, plane Poiseuille, cylindrical Couette and a flow down an inclined plane) boundary conditions on the alignment flux tensor lead to an apparent velocity slip and to a decrease of the effective viscosity. Furthermore the interplay between the flow velocity and the orientational dynamics in the nonNewtonian flow regime and in the nematic phase is considered. Preliminary results are presented. [1] S. Hess, Z. Naturforsch. 30a, 728, 1224 (1975) [2] S. Heidenreich, P.Ilg and S. Hess, Phys. Rev. E 73, 061710 (2006) [3] L. Waldmann, Z. f. Naturf. 22a, 1269 (1967); L. Waldmann and H. Vestner, Physica 99A, 1 (1979); S. Hess and H. M. Koo, J. NonEquilibrium Thermodyn. 14, 159 (1989); H. Vestner, Z. f. Naturforsch. 28a, 869, (1973).

POLYPHYS Seminar HCI J 574 
Wednesday 7. Feb 2007 10:15

Matteo Colangeli Polymer Physics, Department of Materials, ETH Zürich 
About hyperbolicity and stability of Chapman Enskog expansion 
POLYPHYS Seminar HCI J 574 
Monday 29. Jan 2007 9:45

Ralph Spolenak Department of Materials, ETH Zürich 
ETH Materials Day 2007: Do we understand Gecko Adhesion? On Single Spatulae and Biomimetic Nanostructures 
Talk HCI G7 
Monday 29. Jan 2007 11:45

Hans Christian Öttinger Polymer Physics, Department of Materials, ETH Zürich 
ETH Materials Day 2007: Thermodynamics of Wall Slip 
Talk HCI G7 
Wednesday 24. Jan 2007 10:15

Henning Struchtrup Department of Mechanical Engineering, University of Victoria, Canada 
Brenner's equations revisited 
POLYPHYS Seminar HCI J 574 