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Seminars - Winter term 2016/2017

Seminar “Special problems in colloidal physics”

Location: HHU Düsseldorf, Seminarroom 25.32.O2.51
Program:
DateSpeakerTopicTime
Thu 17.11.2016   E. Allahyarov  Smectic phase of hard spherocylinders on spherical surfaces with and without external fields  14:30 s.t.
Mon 12.12.2016   S. Canova  Active brownian particles near walls  14:30 s.t.
Thu 15.12.2016   P. Cremer  DFT for a one-dimensional model for ferrogels  14:30 s.t.
Wed 25.01.2017   E. Allahyarov  Energy storage in composite dielectrics: the role of nanoparticle clustering in host matrix  14:30 s.t.
Mon 30.01.2017   F. Smallenburg  Event-driven simulation of active hard particles  14:30 s.t.
Mon 30.01.2017   C. Hoell  DDFT of Microswimmers  15:30 s.t.
Wed 01.02.2017   S. Jahanshahi  The Brazil nut effect; and the speckle pattern  14:30 s.t.
Mon 06.02.2017   S. Babel  Pattern formation in feed-back driven colloidal suspensions  14:30 s.t.
Wed 08.02.2017   C. Sitta  DFT calculations of rectangles on a manifold  14:30 s.t.
Fri 10.02.2017   M. Puljiz  Particle-matrix interactions in linearly elastic media  14:30 s.t.
Prof. Dr. H. Löwen

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Seminar “Special problems in computer simulation of soft matter”

Location: HHU Düsseldorf, Seminarroom 25.32.O2.51
Program:
DateSpeakerTopicTime
Thu 17.11.2016   E. Allahyarov  Smectic phase of hard spherocylinders on spherical surfaces with and without external fields  14:30 s.t.
Mon 12.12.2016   S. Canova  Active brownian particles near walls  14:30 s.t.
Wed 14.12.2016   G.P. Shrivastav  Thermal glasses under oscillatory shear  14:30 s.t.
Mon 16.01.2017   N. Siboni  Magnetotransport in Classical Lorentz Gas  14:30 s.t.
Wed 18.01.2017   M. Eshraghi  Yukawa fluids near hard walls: Interfacial free energies via thermodynamic integration  14:30 s.t.
Wed 25.01.2017   E. Allahyarov  Energy storage in composite dielectrics: the role of nanoparticle clustering in host matrix  14:30 s.t.
Mon 30.01.2017   F. Smallenburg  Event-driven simulation of active hard particles  14:30 s.t.
Mon 06.02.2017   S. Babel  Pattern formation in feed-back driven colloidal suspensions  14:30 s.t.
Prof. Dr. J. Horbach

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Seminar “Soft Matter”

Location: HHU Düsseldorf, Seminarroom 25.32.O2.51
Program:
DateSpeakerAffiliationTime
Thu 09.02.2017   Wei Li  Iniversität Bochum  14:30 s.t.
Wei Li: „Cooperative Control of Multi-Agents On Non-Euclidean Manifolds”
Iniversität Bochum - Seminar@HHUD: 9.2.17 14:30 s.t., Seminarroom 25.32 O2.51

References

  • Wei Li (), "Collective motion of swarming agents evolving on a sphere manifold: A fundamental framework and characterization," Scientific Reports, vol. 5, Article ID: 13603, 2015. DOI:10.1038/srep13603
  • Wei Li, Mark W. Spong, "Unified cooperative control of multiple agents on a sphere for different spherical patterns," IEEE Transactions on Automatic Control, vol. 59, no. 5, pp. 1283-1289, May 2014
Cooperative Control of Multi-Agents On Non-Euclidean Manifolds
Mon 06.02.2017   Ben Guy  School of Physics and Astronomy, The University of Edinburgh, Edinburgh, United Kingdom  10:30 s.t.
Ben Guy: „The rheology of suspensions of intermediate-sized particles”
School of Physics and Astronomy, The University of Edinburgh, Edinburgh, United Kingdom - Seminar@HHUD: 6.2.2017 10:30 s.t., Seminarroom 25.32 O2.51

The flow of concentrated particulate suspensions plays a central role in many industrial sectors, ranging from the drilling of oil to the manufacture of confectionery. In spite of its ubiquity, concentrated suspension flow is poorly understood, even for model systems with well-controlled particle interactions. In the last two decades, considerable progress has been made in understanding the flow of granular suspensions (diameter d>50 micron), for which contact forces and inter-particle friction play a controlling role, and of colloidal suspensions (d<1 micron), for which entropic interactions dominate. A physical understanding of the intermediate size regime (1 micron<d<50 micron) remains elusive, however, even though many industrial dispersions inhabit precisely this regime. By performing experiments on well-characterised model systems, we have established a generic framework for the rheology of suspensions of intermediate-sized particles. In each system, one can identify two viscosity "branches" diverging at different concentrations, corresponding to the jamming volume fractions for lubricated and frictional particle-particle contacts [1]. If finite-range repulsion is present, the system undergoes a stress-dependent transition between the branches that manifests as shear thickening [2], supporting a recent theory of thickening by Wyart and Cates [3]. We discuss methods for controlling the two divergences, e.g., by introducing surface modifiers or size polydispersity, paving the way for a predictive description of concentrated suspension rheology.

References

  1. B. M. Guy, M. Hermes and W. C. K. Poon, Phys. Rev. Lett. 115, 088304 (2015)
  2. N. Y. C. Lin et. al., Phys. Rev. Lett. 115, 228304 (2015)
  3. M. Wyart and M. E. Cates, Phys. Rev. Lett. 112, 098302 (2014)
The rheology of suspensions of intermediate-sized particles
Thu 15.12.2016   Abdallah Daddi-Moussa-Ider  Universität Bayreuth  15:30 s.t.
Diffusion nearby elastic cell membranes
Thu 15.12.2016   Alan Denton  North Dakota State University, USA  11:30 s.t.
Soft Colloidal Particles in Crowded Environments
Fri 02.12.2016   Edan Lerner  University of Amsterdam, The Netherlands  14:30 s.t.
Edan Lerner: „Nonlinear plastic modes”
University of Amsterdam, The Netherlands - Seminar@HHUD: 2.12.16 14:30 s.t., Seminarroom 25.32 O2.51

Understanding the yielding transition observed upon deforming a glass beyond its elastic limit requires the proper identification of the micro-mechanical objects, akin to dislocations in crystals, that carry plastic flow. In my talk I will introduce a theoretical framework within which a robust, micro-mechanical definition of precursors to plastic instabilities in glassy solids naturally emerges. I will demonstrate how these precursors, coined nonlinear plastic modes, can be calculated without resorting to conventional harmonic eigenmode analyses, but instead by properly accounting for nonlinearities of the potential energy landscape. I will explain how nonlinear plastic modes are coupled to external deformations, and will argue that the a-priori detection of the soft-spots field in model glasses can be effectively carried out by a nonlinear plastic modes analysis.

Nonlinear plastic modes
Thu 24.11.2016   René Wittmann  University of Fribourg, Switzerland  14:30 s.t.
René Wittmann: „Effective interactions of active particles: interfacial phase behavior and mechanical properties”
University of Fribourg, Switzerland - Seminar@HHUD: 24.11.16 14:30 s.t., Seminarroom 25.32 O2.51

We employ classical density functional theory to study the self-organization in active systems.

We use a first-principles approach to map the self-propulsion onto an effective pair interaction potential, which has been shown [1] to account for the motility-induced phase separation (MIPS) observed for active Brownian particles.

n this talk we introduce an effective external potential and investigate inhomogeneous situations. Solely as a result of their activity, we predict [2] that active (Brownian) particles undergo a variety of interfacial phase transitions, e.g., wetting and capillary condensation in purely repulsive systems or drying and capillary evaporation of attractive colloids.

Finally, we explain why the effective thermodynamic pressure and interfacial tension do not represent the proper results one would measure mechanically and demonstrate how these can be recovered within a more general framework.

References

  1. T.F.F. Farage, P. Krinninger and J.M. Brader, Phys. Rev. E 91, 042310 (2015)
  2. R. Wittmann and J.M. Brader, EPL 114, 68004 (2016)
Effective interactions of active particles: interfacial phase behavior and mechanical properties
Mon 21.11.2016   Joachim Dzubiella  Helmholtz-Zentrum Berlin und Humboldt-Universität Berlin  14:30 s.t.
Joachim Dzubiella: „Rational design of stimuli-responsive nanoreactors”
Helmholtz-Zentrum Berlin und Humboldt-Universität Berlin - Seminar@HHUD: 21.11.16 14:30 s.t., Seminarroom 25.32 O2.51

The catalysis by metal nanoparticles is one of the fastest growing fields in nanoscience. However, the optimal control of catalytic activity and selectivity in nanoparticle catalysis remains a grand scientific challenge. Here, we describe our ongoing efforts how to theoretically derive design rules for the optimization of nanoparticle catalysis (in the fluid phase) by means of thermosensitive yolk-shell and core-shell carrier systems. In the latter, nanoparticles are stabilized in solution by an encapsulating, thermosensitive hydrogel shell. The latter contains and shelters the reaction. The physicochemical properties of this polymeric 'nanogate' react to stimuli in the environment and thus permit the reactant fluxes and with that the catalytic reaction to be switched and tuned, e.g., by the temperature, salt concentration, or solvent composition. Hence, the novel hybrid character of these emerging 'nanoreactors' opens up unprecedented ways for the control of nanocatalysis due to new designable degrees of freedom, if theoretical understanding and rational design principles are available.

Rational design of stimuli-responsive nanoreactors
Wed 02.11.2016   Christian Scholz  Friedrich-Alexander-Universität Erlangen-Nürnberg  14:30 s.t.
Christian Scholz: „Dancing to the Vibes - Demixing of active granular rotors”
Friedrich-Alexander-Universität Erlangen-Nürnberg - Seminar@HHUD: 2.11.16 14:30 s.t., Seminarroom 25.32 O2.51

The majority of animal life performs active motion, i.e. organisms store energy within internal degrees of freedom and later release it in terms of directed motion. While in biological organisms this topic itself has been studied extensively, from swimming bacteria to flocks of animals, interest grew also in physical systems of inanimate objects that perform active motion. Most noticeable artificial microswimmers, but also active granular walkers.

We create a system of 3D-printed active rotors, driven by vertical vibrations. Weobserve a phase separated stationary state, where rotors demix into domains of likewise rotation. The temporal evolution of the patterns from the mixed initial state can be quantified from the size of the clusters in analogy to spinodal decomposition. The particle motion can be mapped onto a Langevin equation, which via molecular dynamics simulations allows a direct comparison between experiment and simulation.

Dancing to the Vibes - Demixing of active granular rotors
Tue 11.10.2016   Vishwas V. Vasisht  Georgetown University, USA  11:00 s.t.
Evolution of dense amorphous systems under shear and vibration
Fri 23.09.2016   M. Medina Noyola  Universidad Autónoma de San Luis Potosí, Mexico and Universidad de Guanajuato, Campus León, Mexico  14:00 s.t.
M. Medina Noyola: „Cooling a liquid: first-principles statistical thermodynamic theory of amorphous solids (glasses, gels, sponge-like glasses, ...)”
Universidad Autónoma de San Luis Potosí, Mexico and Universidad de Guanajuato, Campus León, Mexico - Seminar@HHUD: 23.9.2016 14:00 s.t., Seminarroom 25.32 O2.51

The amorphous solidification of glass- and gel-forming liquids is an ubiquitous non-equilibrium process of enormous fundamental and practical relevance. In contrast with equilibrium crystalline solids, whose properties have no history dependence, non-equilibrium amorphous solids may exhibit aging and their properties do depend on their preparation protocol [1]. Predicting the main universal signatures of these phenomena, as well as their specific features reflecting the particular molecular interactions, is a long-standing statistical physics challenge. The recently-proposed non-equilibrium self-consistent generalized Langevin equation (NE-SCGLE) theory of irreversible processes in liquids [2], however, was recently shown to provide a simple and intuitive first-principles description [3] of the non-stationary and non-equilibrium structural relaxation of model liquids with purely repulsive interparticle interactions near their high-density transition to repulsive, hard-sphere like glasses. In this work we explain how the same non-equilibrium theory also predicts for model liquids with repulsive plus attractive interactions a far richer and more complex scenario, which includes the formation of sponge-like gels and porous glasses at low densities and temperatures by arrested spinodal decomposition [4]. We also discuss the possibility of formation of disordered non-equilibrium solids involving fibers and bundles when non-radially symmetric interactions are present [5].

References

  1. Angell C. A., Ngai K. L., McKenna G. B., McMillan P. F. and Martin S. F., J. Appl. Phys.88, 3113 (2000)
  2. P. E. Ramírez-González and M. Medina-Noyola, Phys. Rev. E 82, 061503 (2010)
  3. L. E. Sánchez-Díaz, P. E. Ramírez-González, and M. Medina-Noyola, Phys. Rev. E 87, 052306 (2013)
  4. J. M. Olais-Govea, L. López-Flores, and M. Medina-Noyola, J. Chem Phys. 143, 174505 (2015)
  5. E. C.Cortés-Morales, L.F. Elizondo-Aguilera, and M.Medina-Noyola, J. Phys. Chem B 120, 7975 (2016)
Cooling a liquid: first-principles statistical thermodynamic theory of amorphous solids (glasses, gels, sponge-like glasses, ...)
Fri 16.09.2016   Vili Heinonen  Aalto University, Helsinki, Finland  14:15 s.t.
Vili Heinonen: „Consistent hydrodynamics for phase field crystals”
Aalto University, Helsinki, Finland - Seminar@HHUD: 16.9.2016 14:15 s.t., Seminarroom 25.32 O2.51

Phase-field-crystal (PFC) models have been used succesfully for modeling properties of materials with a periodic, crystalline structure at diffusive time scales. In this talk I will give a short introduction to the amplitude expansion framework of the PFC model and briefly explain some limitations of overdamped dynamics. In order to try to overcome these limitations I will reformulate the dynamics for the model by coupling the system with a hydrodynamic velocity field. In the end I will try to convince the audience that the hydrodynamic approach is reasonable by showing some analytical and numerical results.

Consistent hydrodynamics for phase field crystals
Fri 19.08.2016   Manis Chaudhuri  Heinrich-Heine-Universität Düsseldorf  15:00 s.t.
Manis Chaudhuri: „Exploring triple point at the triple junction in a charged colloidal films”
Heinrich-Heine-Universität Düsseldorf - Seminar@HHUD: 19.8.2016 15:00 s.t., Seminarroom 25.32 O3.51

The triple point associated with face-centered-cubic (fcc) crystal, body-centered-cubic (bcc) crystal and liquid phases for repulsive Yukawa (screened Coulomb) systems has been explored experimentally at the single particle level using charge stabilized PMMA colloidal suspension in a nonpolar solvent. The triple point represents the triple junction which develops under mechanical equilibrium due to the intersection of solid-liquid interface and bcc-fcc grain boundary. The grain boundary energy has been estimated close to the triple point.

Exploring triple point at the triple junction in a charged colloidal films
Wed 03.08.2016   Simon Kaspar Schnyder  Department of Chemical Engineering, Kyoto University, Japan  14:30 s.t.
Collective motion of cells crawling on a substrate: roles of cell shape and contact inhibition
Fri 29.07.2016   Arjun Yodh  University of Pennsylvania, USA  14:00 s.t.
Coffe Stains
Prof. Dr. Egelhaaf, Prof. Dr. Horbach, Prof. Dr. Löwen

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poroSys-Talks

File: poroSys Talkslist

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Colloquia

Location: HHU Düsseldorf, Lecture Hall 5J (Building 25.31 Level 00)
Program:
DateSpeakerAffiliationTime
Thu 26.01.2017   Prof. Karsten Flensberg  Niels Bohr Institute, University of Copenhagen, Denmark  16:30 s.t.
Towards Majorana-based topological qubits?
Thu 19.01.2017   Prof. Michael Eikerling  Simon Fraser University, Vancouver, Canada  16:30 s.t.
The Physics of Electrochemical Energy Conversion
Thu 08.12.2016   PD Dr. Antonio Di Piazza  Max-Planck-Institut für Kernphysik, Heidelberg  16:30 s.t.
Tests of classical and quantum electrodynamics in intense laser beams
Thu 24.11.2016   Prof. Dr. Susana Huelga  Universität Ulm  16:30 s.t.
Vibrations, Quanta and Biology
Thu 27.10.2016   Prof. Joseph Indekeu  Theoretical Physics, KU Leuven, Belgium  16:30 s.t.
Short-range wetting in two dimensions: is it always second-order?
Thu 21.07.2016   Dr. Götz Lehmann  Heinrich-Heine-Universität Düsseldorf  16:30 s.t.
Habilitationsvortrag: Advanced plasma optics for high power lasers: Plasma-based pulse amplification and manipulation
Thu 14.07.2016   Dr. Florian Platten  Heinrich-Heine-Universität Düsseldorf  16:30 s.t.
Habilitationsvortrag: Soft matter perspective on protein self-assembly
Thu 30.06.2016   Prof. Thomas Hellweg  Universität Bielefeld  16:30 s.t.
Smart Microgels: Synthesis, Properties and Applications
Thu 16.06.2016   Prof. Herbert Spohn  TU München  16:30 s.t.
Random matrix theory and the dynamics of nonequilibrium interfaces
Thu 09.06.2016   Prof. Yoichi Ando  Universität Köln  16:30 s.t.
Topological Insulators and Superconductors
Thu 02.06.2016   Dr. Mirella Cerchez  Heinrich-Heine-Universität Düsseldorf  16:30 s.t.
Habilitationsvortrag: Interaction of relativistic pulses with solid matter
Thu 12.05.2016   Prof. Frank Schreiber  Universität Tübingen  16:30 s.t.
Do we understand crystallization and growth?
Thu 21.04.2016   Prof. Chiara Macchiavello  Universitá Pavia, Italy  16:30 s.t.
Entanglement, complementarity and correlations
WE Physik, Heinrich-Heine-Universität Düsseldorf

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Seminar about Bachelor, Master and other Theses from the Institut for Theoretical Physics II

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Link: Physics Colloquium
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