Virginia Tech™home

Past Discussion Meetings

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Fall 2019

Organizer: Vinh Nguyen

These meetings occur on Fridays from 4:00pm to 5:00pm in Robeson 304.
Refreshments are served at 3:45pm (unless otherwise indicated)

August 2019
August 30

Friday 4:00pm
304 Robeson Hall
(poster)

Host:

September 2019
September 6

Friday 4:30pm
304 Robeson Hall
(poster)

Host:

September 13

Friday 4:00pm
304 Robeson Hall
(poster)

Host:

September 20

Friday 4:00pm
304 Robeson Hall
(poster)

.

Host:

September 27

Friday 4:00pm
304 Robeson Hall

(poster)

Host:

October 2019
October 4

Friday 4:00pm
304 Robeson Hall

(poster)

Host:

October 11

Friday 4:00pm
304 Robeson Hall

(poster)

Host:

October 18

Friday 4:00pm
304 Robeson Hall

(poster)

Ahmadreza Azizi (Physics, Virginia Tech)

"Critical Phenomena in Presence of Symmetric Absorbing States"

Phase transitions in non-equilibrium systems have been the subject of many studies in the area of statistical physics. In this talk, I will discuss standard steady-state and time-dependent quantities for models which exhibit a voter-like phase transition, a symmetry-breaking phase transition in absence of bulk noise, and an absorbing phase transition belonging to the Directed Percolation universality class. The Langevin description of systems with two symmetric absorbing states will be introduced and the resulting phase diagram with three different phases (disordered and active, ordered and active, absorbing) separated by critical lines belonging to three different universality classes (generalized voter, Ising, and directed percolation) will be discussed. I also present a proposed microscopic model with two symmetric absorbing states that possesses all the features of the Langevin description.

Advisor: Michel Pleimling

October 25

Friday 4:00pm
304 Robeson Hall

(poster)

Host:

November 2019
November 1

Friday 4:00pm
304 Robeson Hall

(poster)

Host:

November 8

Friday 4:00pm
304 Robeson Hall


(poster)

Host:

November 15

Friday 4:00pm
304 Robeson Hall

(poster)

"TBD"

Host:

November 22

Friday 4:00pm
304 Robeson Hall

(poster)

Host:

November 29

Friday 4:00pm
304 Robeson Hall

(poster)

Thanksgiving Holiday (No Classes)

Host:

December 2019
December 6

Friday 4:00pm
304 Robeson Hall
(poster)

Host:

December 13

Friday 4:00pm
304 Robeson Hall
(poster)

Exam Day (No Classes)

Host:

December 20

Friday 4:00pm
304 Robeson Hall
(poster)

University and Graduate Ceremonies (No Classes)

Host:
December 27

Friday 4:00pm
304 Robeson Hall
(poster)

Holiday (No Classes)

Host:
December 30

Friday 4:00pm
304 Robeson Hall
(poster)

Holiday (No Classes)

Host:
Back to Top
Center for Soft Matter and Biological Physics Friday Discussion Meetings

Summer 2019

Organizer: Vinh Nguyen

These meetings occur on Fridays from 1:30pm to 2:30pm in Robeson 304 (unless otherwise indicated)

May 2019
May 24

Friday 1:30pm
304 Robeson Hall
(poster)

"CSB Symposium Week"

"No Discussion Meeting"

May 31

Special Time: Friday 4:00pm
304 Robeson Hall
(poster)


Ruslan Mukhamadiarov and Shengfeng Deng (Physics, Virginia Tech)

"Central Concepts of Nonlinear Dynamics and Chaos"

In a series of Center summer meetings, Shengfeng Deng and I will explore the central concepts of nonlinear dynamics and chaos. We will demonstrate how these abstract ideas can be applied in physics and biology. The list of topics that we plan to cover includes one- and two-dimensional flows, bifurcations, Lorenz equations, one-dimensional maps, and fractals. This talk series is intended mainly for graduate students and will be held in the form of informal discussion meetings.

Host: Uwe Tauber

June 2019
June 7

Friday 1:30pm
304 Robeson Hall
(poster)

Tuo-Xian Tang (Biological Sciences, Virginia Tech)

"The Functional Basis of Phafin2 in Autophagy"

Autophagy is a highly conserved cellular pathway in the eukaryotic cells. A portion of the cytosol, which contains invading pathogens and long-lived proteins, is taken up by an autophagosome. This double-membrane organelle fuses with lysosomes, where the contents were digested by the lysosomal enzymes. Previous data showed that Phafin2 was involved in autophagy. After the induction of autophagy, Phafin2 and Akt accumulate on the lysosomal membranes through the interactions between Phafin2 and phosphatidylinositol 3-phosphate (PtdIns(3)P). Phafin2 has two domains, one N-terminal PH (Pleckstrin Homology) domain and one C-terminal FYVE (Fab 1, YOTB, Vac 1, and EEA 1) domain. In this study, the binding affinity between PtdIns(3)P and Phafin2 was studied by surface plasmon resonance. Results showed that Phafin2 binds PtdIns(3)P with high affinity, triggering minor conformational changes in the protein. We also demonstrated that Phafin2 FYVE domain is responsible for the binding of PtdIns(3)P. Another interesting finding is that Phafin2 can cause membrane curvature, which may be required for tethering of lysosomes to autophagosomes, and consequently initiating autophagy.

Host: Vinh Nguyen

June 14

Friday 1:30pm
304 Robeson Hall
(poster)

Shengfeng Deng (Physics, Virginia Tech)

"Phase Portraits of Two-Dimensional Flows"

Higher-dimensional phase spaces can display more intricate and interesting dynamics. Two dimensional phase space already shows fixed points with different kinds of stabilities, and winding trajectories etc. We first discuss linear systems in two dimensions and the classification of fixed points, which will play an important role in the classification for fixed points of nonlinear systems. The phase portraits then allows us to predict the long-term behaviors of many physical systems.

Host: Uwe Tauber

June 21

Friday 1:30pm
304 Robeson Hall
(poster)

James Stidham (Physics, Virginia Tech)

"Ordering in Magnetic Skyrmion Lattices"

Ordering in magnetic skyrmion lattices is an active area of research for skyrmion systems. In this talk, I will present recent results obtained using Langevin molecular dynamic simulations, based on a previously derived particle model of skyrmion. Using a Vornoi cell algorithm, we examined the effect of the Magnus force present in skyrmion systems and how it affects ordering when noise is both present and absent in the system. We observed power law behavior during late time ordering in these skyrmion systems. We also found power law behavior when looking at the difference in time of consecutive events as the system orders.

Host: Michel Pleimling

June 28

Friday 1:30pm
304 Robeson Hall
(poster)

Ruslan Mukhamadiarov (Physics, Virginia Tech)

"Nonlinear Dynamics and Chaos: Limit Cycles and 2-D Bifurcations"

Ubiquitous in nature, limit cycles are inherently nonlinear phenomena that can model systems with self-sustained oscillations. I am going to outline the existence conditions for the limit cycles, and I will show how the concept of limit cycles can be applied to study nonlinear oscillation problems. In the second part of the talk we will revisit the bifurcations and extend the concepts that we covered in the first meeting to the phase plane. I am also going to consider the other possible scenarios that arise in two dimensions, namely Hopf bifurcations and global bifurcations of cycles.

Host: Uwe Tauber

July 2019
July 5

Friday 1:30pm
304 Robeson Hall
(poster)

"Last day of Classes of Summer Session I"

No Discussion Meeting

July 12

Friday 1:30pm
210 Robeson Hall
(poster)

Prof. David Minh (Chemistry, Illinois Institute of Technology)

"New Computational Tools for Designing Compounds Active Against Biological Macromolecules"

Most pharmaceuticals are small organic molecules that work via noncovalent interactions with biological macromolecules. Although drugs have saved or improved countless lives, drug discovery remains an inexact science that involves much trial and error. The main focus of my research group is the development of computer modeling tools to quickly characterize noncovalent protein-ligand interactions. Most of our tools are based on implicit ligand theory, a theoretical framework that I derived to predict how tightly molecules bind and how they influence the population of conformations accessed by their targets. At this point, we have established that our methods are able to reproduce results of more computationally expensive approaches. We are working on making them more efficient and feasible to use with large libraries of chemical compounds. We have also advanced the theory of end-point binding free energy methods, in which binding affinity is predicted based on molecular simulations of the bound complex.

Host: Igor Tolokh

July 19

Friday 1:30pm
304 Robeson Hall
(poster)

Austin Warren
(Physics, Virginia Tech)

"Nonlinear Dynamics and Chaos: Lorenz System and 1-D Maps"

Despite being entirely predictable in principle, many deterministic systems display extremely complicated, apparently random long term behavior. This chaotic behavior appears in many practical everyday problems, from understanding how populations grow to predicting tomorrow's weather. In this talk, I'll be discussing what we mean when we talk about chaos and what it looks like in practice. In particular, we'll be looking at how chaos emerges from order in two well-known systems: the continuous Lorenz system and the discrete logistic map.

Host: Uwe Tauber

July 26

Friday 1:30pm
304 Robeson Hall
(poster)

Connor Mackert
(Physics, Virginia Tech)

"Gray Scott Model Parameter Adjustment Effects"

The Gray Scott Model has been subject of numerous investigations. Due to the nonlinear nature of the reaction-diffusion system many studies have used overly broad strokes. Through systematic parameter adjustment we are able to find novel system pattern formations that were previously overlooked.

Host: Michel Pleimling

August 2019
August 2

Friday 1:30pm
304 Robeson Hall
(poster)

Vinh Ho
(Physics, Virginia Tech)

“Broadband and High Responsivity Graphene-based Photodetectors at Room-temperature”

Ability to covert light of graphene occurs in an ultra-broadband spectral range from violet to mid-infrared region, making graphene as desirable photodetectors for various technology applications in imaging, sensing, spectroscopy and telecommunication. However, the low responsivity of graphene photodetectors about 10 mA/W, due to the ultra-fast recombination of photocarriers, limits their potential applications. Here, we have engineered the interface between graphene and dielectric films to introduce trapping centers. The interface layer efficiently convert the photon energy into a large electrical signal. Thus, our graphene-based photodetectors have showed a high sensitivity up to 2 × 10^5 A/W together with a fast response time in a broadband spectral at room temperature.

Host: Vinh Nguyen

August 9

Friday 1:30pm
304 Robeson Hall
(poster)

"TBD"

Host:

August 16

Friday 1:30pm
304 Robeson Hall
(poster)

"Exams Begins for Summer Session II

August 23

Friday 1:30pm
304 Robeson Hall
(poster)

Anri Karanovich (Physics, Virginia Tech)

“Nonlinear Dynamics and Chaos: Fractals and Strange Attractors”

The emergence of deterministic chaos in many nonlinear systems, including the Lorentz map and the logistic map, is closely related to the existence of strange attractors - nontrivial closed subsets of the phase space, fractal in nature, to which nearby trajectories are converging. In order to gain a deeper insight into the patterns of the system evolution and its chaotic behavior, we need to study the main properties and geometric characteristics of the strange attractors. In the first part of the talk, I will define and provide basic examples of fractals, and then discuss the notion of fractional dimensionality and the various ways to measure it. In the second part, we will consider the simple examples of strange attractors, their characteristic features, methods of analysis, and relation to the chaotic properties of the system.

Host: Vinh Nguyen

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Spring 2019

Organizer: Vinh Nguyen

These meetings occur on Fridays from 4:00pm to 5:00pm in Robeson 304 (unless otherwise indicated)

January 2019
January 4

Friday 4:00pm
304 Robeson Hall

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

January 11

Friday 4:00pm
304 Robeson Hall

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

January 18

Friday 4:00pm
304 Robeson Hall

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

January 25

Friday 4:00pm
304 Robeson Hall
(Flyer)

Center for Soft Matter and Biological Physics Workshop (Location Blacksburg Community Center)

"No Discussion Meeting"

Organizers: William Ducker & Katrina Loan

January 28

"Special Date and Time" Monday 5:30pm
304 Robeson Hall

Student discussion with Dr. Rui Zhang (University of Chicago)

Host: Shengfeng Cheng

February 2019
February 1

Friday 4:00pm
304 Robeson Hall

Student discussion with Dr. Ting Ge (Duke University)

Organizer: Shunsaku Horiuchi

February 8

Friday 4:00pm
304 Robeson Hall

Student discussion with Dr. Daniel Sussman (Syracuse University)

Organizer: Michel Pleimling

February 15

Friday 4:00pm
304 Robeson Hall

Student discussion with Dr. Antonia Statt (Princeton University)

Organizer: Uwe Tauber

February 18

"Special Date and Time" Monday 5:30pm
304 Robeson Hall


Student discussion with Dr. Cihan Nadir Kaplan (Harvard University)

Host: Rana Ashkar

February 22

Friday 4:00pm
304 Robeson Hall

"APS March Meeting Practice"

Organizer: Vinh Nguyen

February 25

"Special Date and Time" Monday 5:30pm
304 Robeson Hall


Student discussion with Dr. Trung Dac Nguyen (Northwestern University)

Host: Daniel Capelluto

March 2019
March 1

Friday 4:00pm
304 Robeson Hall

"Faculty Meeting"

Organizer: Vinh Nguyen

March 8

Friday 4:00pm
304 Robeson Hall

"APS March Meeting" (Boston)

"No discussion meeting scheduled"

Organizer: Vinh Nguyen

March 15

Friday 4:00pm
304 Robeson Hall

"Spring Break continuing ends March 17"

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

March 22

Friday 4:00pm
304 Robeson Hall
(poster)


Organizer: Vinh Nguyen

March 29

Friday 4:00pm
304 Robeson Hall
(poster)

"Faculty Meeting"

"No Discussion Meeting"

Organizer: Vinh Nguyen

April 2019
April 5

Friday 4:00pm
304 Robeson Hall
(poster)

"Faculty Meeting"

:No Discussion Meeting"

Organizer: Vinh Nguyen

April 12

Friday 4:00pm
304 Robeson Hall
(poster)

Nicole Abaid (Biomedical Engineering and Mechanics, Virginia Tech)

"Passive and active sensing in the Vicsek model

While many social animals move in groups using passive senses like vision, bats form very large colonies while using on sonar for navigation. Sonar is a so-called active sense, which relies on a self-generated signal (sound) rather than one already present in the environment (e.g., light for vision). From an engineering perspective, using active sensing in large groups poses many challenges centered around interference between signals produced by peers. However, experimental work with bats suggests that these animals may be capable of using their peers' signals for passive sonar, which may ameliorate some of these complications. Taking this system as inspiration, we explore the possibility of combining passive and active sensing in a well-studied model which shows collective behavior, the Vicsek model. The Vicsek model enforces a local alignment rule in groups of self-propelled particles perturbed by noise. Phase transition is observed in both the presence and absence of passive sensing, yet the range of parameters for which ordered and disordered group states exist dramatically changes when passive sensing is used. Notably, we find numerous cases of the model for which the implementation of passive sensing increases the robustness of the collective behavior to noise.

Organizer: Vinh Nguyen

April 19

Friday 4:00pm
304 Robeson Hall
(poster)

"Faculty Meeting"

"No Discussion Meeting"

Organizer: Vinh Nguyen

April 26

Friday 4:00pm
304 Robeson Hall
(poster)

Dr. Saptarshi Chakraborty (Physics, Virginia Tech)

"Polymer-Stabilized Colloidal Catalysts: Role of Polymers and Strategies for Recovery and Reuse"

Gold nanoparticles (AuNPs) have attracted enormous attention due to their unique catalytic activities. Colloidal AuNPs provides the benefit of selectivity, greater surface area per mass of catalyst compared to supported catalysts, catalyzes reactions under mild conditions and are very effective for chiral catalysis. On a per metal basis colloidal AuNPs demonstrate higher catalytic activity than their supported counterparts. Colloidal AuNPs however requires surface functionalization with ligands to prevent aggregation which causes surface passivation and significant reduction in catalytic activity. Colloidal AuNP catalytic activity is strongly dependent on ligand packing and conformation on the AuNP surface. Large polymeric ligands demonstrate increase in available surface area leading to increased catalytic activity, while small molecule ligands lead to complete AuNP surface passivation. A major drawback of colloidal AuNPs as catalysts is the catalyst recovery from the product stream. We have employed small pH sensitive ligands as AuNP stabilizers to show that AuNPs can be recovered from the product stream by altering the pH to selectively precipitate or phase transfer catalyst into organic solvents. However, due to the high small molecule packing density on AuNP surface, complete surface passivation was observed. Catalytic activity could be recovered by partially functionalizing the AuNP surface, however at the cost of recoverability. To maintain catalytic activity in recoverable catalysts, we have developed pH sensitive polymer ligands by synthesizing thiolated polymer ligands. AuNPs functionalized with thiolated polymer, demonstrate similar recoverability while retaining high catalytic activity. Application of colloidal AuNP as catalysts, thus entails fine tuning ligand MW, structure, catalytic activity and recoverability.

Organizer: Vinh Nguyen

May 2019
May 3

Friday 4:00pm
304 Robeson Hall
(poster)

Prof. Jonathan Boreyko (Mechanical Engineering, Virginia Tech)

"Fun with Water: Catching Fog, Building Trees, and Freezing Bubbles"

Nature displays incredible feats of fluid mechanics that have much to teach us. Here, we study and exploit four different kinds of nature-inspired fluid phenomena: two involving liquid-phase behavior and two involving freezing water. First, we’ll explain how coastal redwoods have inspired a “fog harp” that harvests several times more water than existing fog harvesters. Second, we demonstrate that synthetic trees are capable of passively pumping water against gravity on the same scale as natural trees. The beauty of freezing bubbles is explained by novel physical models. Finally, we show that simple scaling laws can rationalize the development of passive anti-frosting surfaces

Organizer: Vinh Nguyen

May 8

Wednesday 4:00pm
304 Robeson Hall
(poster)

Classes end


(No CSB Discussion Meeting)

Organizer: Vinh Nguyen

May 10

Friday 4:00pm
304 Robeson Hall
(poster)

Exams Begin


(No CSB Discussion Meeting)

Organizer: Vinh Nguyen

May 17

Friday 4:00pm
304 Robeson Hall
(poster)

University Commencement and College and Department Ceremonies


(No CSB Discussion Meeting)

Organizer: Vinh Nguyen

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Fall 2018

Organizer: Vinh Nguyen

These meetings occur on Fridays from 4:00pm to 5:00pm in Robeson 304 (unless otherwise indicated)

August 2018
August 24

Friday 4:00pm
304 Robeson Hall
(poster)

Faculty Meeting (No CSB Discussion Meeting)

Organizer: Vinh Nguyen

August 31

Friday 4:00pm
304 Robeson Hall
(poster)

Organizer: Vinh Nguyen

September 2018
September 7

Friday 4:00pm
304 Robeson Hall
(poster)

Organizer: Vinh Nguyen

September 14

Friday 4:00pm
304 Robeson Hall
(poster)

Organizer: Vinh Nguyen

September 21

Friday 4:00pm
304 Robeson Hall
(poster)

Deepali Shirsekar (Mechanical Engineering)

“Bidirectional Reflectance Measurement of Black Coating Z302 for use in Optical Instrument Design ”

The bidirectional reflectance distribution function (BRDF) plays a fundamental role in the optical characterization of a surface. The BRDF is a measure of the amount of light incident from one direction that is scattered by a surface in another direction. This talk introduces the concept of BRDF and presents the thesis research of graduate student, Deepali Shirsekar, to investigate the BRDF of black coating, Aeroglaze Z302. Work includes design and fabrication of a high-accuracy bidirectional reflectometer and its use to measure the bidirectional reflectance of a black absorber Aeroglaze Z302®. A BRDF model consisting of diffuse, glossy, and specular components is fitted to the experimental results. Finally, the Monte Carlo ray-trace (MCRT) method is used to simulate the performance of any optical instrument which has Z302 material coated on its active surfaces.

Organizer: Vinh Nguyen

September 28

Friday 4:00pm
304 Robeson Hall
(poster)

Faculty Meeting (No CSB Discussion Meeting)

Organizer: Vinh Nguyen

October 2018
October 5

Friday 4:00pm
304 Robeson Hall
(poster)

Nazia Munir (Mechanical Engineering)

"Investigation of the Gold-Black Absorption Mechanism"

The material called gold-black is an absorptive material frequently used in various thermo-detector. The advantages of gold-black that make it preferable over the other absorptive material is that it has the absorptivity almost one (α=1) in the visible and infrared range which means that it absorbs all the radiation incident on it and appears black in an observer’s eye. For this unique property gold-black has been used in thermal detector such as in micro-bolometer. The micro-bolometer converts the incident radiation to an electrical signal. Gold-black is used as a coating on the micro-bolometer to ensure a 100% absorption of the radiation. Micro-bolometer with gold-black coating has several applications specially in various program of Earth Radiation Budget where the global warming is closely monitored with satellite having micro-bolometer attached on it. The purpose of this effort is to establish a model of gold-black so that it can be used more efficiently in various detector. We seek a first-principle model for predicting the spectral absorptivity of gold-black. Gold-black has been widely used in various thermal and optical applications for more than a century. In most relevant contributions to the literature, gold-black is treated as a homogeneous layer whose behavior is governed by its bulk optical properties. However, on the microscopic level gold-black more closely resembles a fuzzy layer of moss or a miniature forest. This suggests that the optical behavior of gold-black can be better characterized by taking into account its actual morphology. We propose to model a layer of vacuum-deposited gold-black as a “fractal forest” where each branch of each tree is isolated and considered as an individual building block. In this treatment each individual branch acts as a dipole antenna with the forest as a whole behaving as a random-fractal antenna array. The approach of the current effort is to develop a model for the conversion of incident electromagnetic (EM) radiation to sensible heat by an individual branch behaving as a lossy antenna. The output of such a model would be the energy conversion efficiency (absorptivity), corresponding to a given wavelength, of a single branch having a specified length, diameter, and orientation with respect to incident EM radiation. The overall absorptivity of the forest at that wavelength would then be based on the statistical description of the spatial and angular distributions of branches of various length and diameter. The required statistical rules would be derived from microscopic study of actual gold-black layers.

Organizer: Vinh Nguyen

October 12

Friday 4:00pm
304 Robeson Hall
(poster)

Faculty Meeting (No CSB Discussion Meeting)

Organizer: Vinh Nguyen

October 19

Friday 4:00pm
304 Robeson Hall
(poster)

"Fall Break" (No CSB Discussion Meeting)

Organizer: Vinh Nguyen

October 26

Friday 4:00pm
304 Robeson Hall
(poster)

Harrison Wood (Biomedical Engineering and Mechanics)

“A study on the effects of in-plane swelling gradients on orthotropic plates”

In this study, we examine the effects of in-plane swelling gradients on resulting shapes of thin, orthotropic plates. Emphasis is placed on understanding how different swelling gradients and orthotropic material properties result in different shapes. This talk focuses on introducing the topic of incompatible elasticity applied to programming swelling functions and shapes in plates, and summarizes the current research of graduate student Harrison Wood on swelling and warping of engineered wood products. Several surface parameterizations are explored to explain warped shapes of orthotropic plates. An energy expression based on mid-plane strains and curvatures is minimized with respect to surface parameters, and competition between stretching and bending energy terms is studied to determine equilibrium shapes. Using some simple toy models of plate warp as inspiration, some scaling arguments are being developed to validate certain behaviors and shapes, such as the case where a specific in-plane swelling gradient results in a cylindrical-like shape at equilibrium for an orthotropic plate.

Organizer:Vinh Nguyen

November 2018
November 2

Friday 4:00pm
304 Robeson Hall
(poster)

Prof. Michael Flatte (University of Iowa)

Meeting with Students

Organizer: Giti Khodaparast

November 9

Friday 4:00pm
304 Robeson Hall
(poster)

Prof. William Ducker (Chemical Engineering)

"Absorption at Confined Interfaces"

Thin liquid films have different properties than bulk solutions because of the effects of the fields extending from the boundaries. These altered properties are important in determining the stability of colloid and nano-particle suspensions, wetting films, adsorption in confined spaces, and in the fabrication and application of nanoscale devices. Our interest is in adsorption, which affects many of these applications: there is a multitude of applications where surfactants, polymers, ions, etc. are adsorbed to effect changes in thin films, for exam-ple, to alter the stability of colloidal particles. We describe measurements of adsorption between two flat plates when the plates are separated by 0 – 65 nm and several results for several examples: depletion of a simple ion in dilute solution and adsorption in very concentrated salt solutions. These measurements have been made possible by our development of new tech-nique. Measurement of all separations is achieved simultaneously by measuring visible-light interference in a wedge-shaped crack created between an oxidized-silicon wafer and a glass wafer. The adsorbed amount is measured from the fluorescence emission of a dye, after accounting for the optical interference. The specific measurement is of the depletion of a divalent anion, fluorescein, in aqueous solution between two anionic solids. For dilute solutions at large separations between the flat plates, the dye is depleted rela-tive to the bulk concentration. At smaller separations, the depletion of the dye decreases. The range of the depletion and the magnitude of depletion decrease with shorter Debye-length. Both of these effects are con-sistent with a simple calculation using the Poisson-Boltzmann equation. For concentrated solutions, results do not agree with Poisson-Boltzmann theory. That theory predicts that the surface potential decays exponential-ly with a decay length (Debye-length) that decreases with increasing concentration. Results are consistent with an increase in decay length with increasing concentration. We make comparisons to results in ionic liq-uids and drawn conclusions for crystal growth through particle attachment. We

Organizer: Vinh Nguyen

November 16

Friday 4:00pm
304 Robeson Hall
(poster)

Faculty Meeting (No CSB Discussion Meeting)

Organizer: Vinh Nguyen

November 23

Friday 4:00pm
304 Robeson Hall
(poster)

Thanksgiving Break (No CSB Discussion Meeting)

Organizer: Vinh Nguyen

November 30

Friday 4:00pm
304 Robeson Hall
(poster)

Michael Kane (Mechanical Engineering)

"Topography and Mechanical Properties of Nanostructured PNIPAM Films"

PNIPAM is a thermo-responsive polymer that has wide applications in biological applications, including its use as a cell growth scaffold. In this talk, we will discuss some of the recent measurements that we have done on PNIPAM films on nanostructured substrates. Using Atomic Force Microscopy, we investigate the surface topography of the films at different temperatures as well as their mechanical properties in different parts of the sample.

Organizer: Rana Ashkar

December 2018
December 7

Friday 4:00pm
304 Robeson Hall
(poster)

First Day of Exams (No CSB Discussion Meetings)

Organizer: Vinh Nguyen

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Summer 2018

Organizer: Vinh Nguyen

These meetings occur on Fridays from 1:30pm to 2:30pm in Robeson 304 (unless otherwise indicated)

May 2018
May 25

Friday 1:30pm
304 Robeson Hall
(poster)


Organizer: Vinh Nguyen

June 2018
June 1

Friday 1:30pm
304 Robeson Hall
(poster)

Organizer: Vinh Nguyen

June 8

Friday 1:30pm
304 Robeson Hall
(poster)


Organizer: Vinh Nguyen

June 15

Friday 1:30pm
304 Robeson Hall
(poster)


Organizer: Vinh Nguyen

June 22

Friday 1:30pm
304 Robeson Hall
(poster)

Ruslan Mukhamadiarov (Physics, Virginia Tech)

"Transverse Temperature Interface in Katz-Lebowitz-Spohn Model"

Driven lattice gas with attractive nearest neighbor interactions and periodic boundaries demonstrate intriguing dynamics, when parts of lattice held at different temperatures. In two dimensions, this complex system experiences a jamming transition in the high temperature zone, and forms stripes in the low temperature regions. Density profiles are strikingly similar with those for Asymmetric Exclusion Process (ASEP) with open boundary conditions when injection and ejection rates are equal. In this talk, I will discuss the dynamics of two-temperature driven lattice gas system and characterize its density profile using analytical results and Monte Carlo simulations.


Organizer: Vinh Nguyen

June 29

Friday 1:30pm
304 Robeson Hall
(poster)

Prof. Uwe Tauber (Virginia Tech, Physics)

"Interactive Discussion: Manuscript writing"


Organizer: Vinh Nguyen

July 2018
July 6

Friday 1:30pm
304 Robeson Hall
(poster)

Shadi Esmaeili

"An Exploration of Characteristics of System of Kuramoto Oscillators"

Coupled oscillators and emergent synchronized patterns can be found in many phenomena in nature. Kuramoto model is the simplest model of coupled oscillators with an exact solution that can explain many such phenomena. By choosing a proper coupling constant and topology the system shows multi-stability. Also, by choosing non-homogeneous frequencies long period orbits emerge in the system. We study the effects of the change in different parameters of the system (e.g. coupling constant and width of frequency distribution) as well as the response of the system to external noise.


Organizer: Vinh Nguyen

July 13

Friday 1:30pm
304 Robeson Hall
(poster)

Ahmadreza Azizi (Physics, Virginia Tech)

"Microscopic description of Generalized Voter Model"

The Langevin equation of critical phenomena in the presence of two symmetric absorbing states is considered as a novel macroscopic description of generalized Voter model (GVM). Numerical integration of GVM in two dimensions shows that the direct transition from a disorder phase to either of the absorbing states is described by voter critical point. Also, indirect transitions to the ordered state can happen where the Voter critical point is split into Ising and Directed percolation (DP) critical points. Although the Langevin description of GVM is successful, there is no known microscopic version of GVM in two dimensions which clearly presents all three critical points together. We will study one of the possible ways to achieve a microscopic version of GVM with Voter, Ising and DP critical points.


Organizer: Vinh Nguyen

July 20

Friday 1:30pm
304 Robeson Hall
(poster)

Prof. John B. Phillips (Biological Sciences, Virginia Tech)

"Quantum Biology meets Behavioral Biology (and a Behavioral Biologist): a new sensory system and a new class of sensory receptors in the mammalian retina"

The ability of animals to detect the Earth’s magnetic field remains the least understood of the major senses. Many vertebrates have two functionally distinct magnetoreception mechanisms: a light-dependent, photoreceptor-based mechanism that provides directional (‘compass’) information and a non-light-dependent, magnetite-based mechanism that provides positional (‘map’) information. The light-dependent magnetic compass (LDMC) is mediated by a manifestly quantum process thought to involve a light-dependent radical pair reaction that forms long-lived, spin-coordinated radical pair intermediates (“radical pair mechanism” or RPM). The most compelling evidence for the RPM is the finding that magnetic compass orientation in a variety of animals can be altered or abolished by exposure to low-level radio frequency (RF) fields (> 1nT) that can alter the electron-spin dynamics of the radial pair. Interest in the RPM spans a wide range of disciplines, and has been a primary impetus for the emerging field of Quantum Biology. Studies of murine rodents (mice, rats, etc.) have played a central role in both basic and applied (i.e., biomedical) research on mammalian spatial behavior and cognition. A number of well-characterized spatial cells (e.g., head direction cells, place cells, grid cells, boundary vector cells, and velocity cells; see 2014 Nobel Prize in Medicine) underlie a path integration system that encodes the animal’s spatial position as it moves through the environment. However, the spatial circuitry characterized to date only provides accurate navigational information over distances of a few 10s of meters, falling well short of the 100s of meters routinely moved by even small rodents like deer mice (20g) under natural conditions. A magnetic compass sense can dramatically increase both the range and accuracy of a path integration system, as well as play important roles in many other aspects of spatial behavior and cognition. Nevertheless, the consensus of the literature is that murine rodents do not rely on magnetic cues, despite evidence that a magnetic compass is virtually ubiquitous in other animals, including some mammals (bats, mole rats, dolphins). Contrary to the prevailing view in the literature, we have found that mice and rats have a well-developed magnetic compass. However, consistent behavioral and neurophysiological responses to magnetic cues can only be elicited reliably when the testing apparatus is shielded to screen out low-level RF noise. We have also identified photoreceptors in animals as different as flies, frogs, and mice that appear specialized for detection of the geomagnetic field. In this talk, I’ll briefly discuss evidence: (1) that there are a specialized photoreceptors in which the response to light is dependent on the alignment of an earth-strength magnetic field, (2) that in animals where specialized photo-magnetoreceptors are located in the compound eye (flies) or retina (birds, mice), the magnetic field may be perceived as a 3-dimensional pattern of light intensity and/or color superimposed on the animal’s surroundings, (3) that both behavioral and neurophysiological responses to magnetic cues can be altered or abolished by low-level radio frequency noise at intensities commonly found in laboratory environments, and (4) that the magnetic field plays multiple, previously unrecognized, roles in the spatial behavioral and cognition of murine rodents over a variety of spatial scales.


Organizer: Vinh Nguyen

July 27

Friday 1:30pm
304 Robeson Hall
(poster)

Professor Michel Pleimling (Physics, Virginia Tech)

"Aging processes in systems far from equilibrium I: An overview of the phenomenology of physical aging"

Physical aging scaling is encountered in numerous systems with slow dynamics. In this talk I introduce the phenomenology of physical aging and show that many of the characteristic features of physical aging can be understood through the investigation of simple coarsening systems. Dynamical scaling of two-time quantities like the autoresponse and autocorrelation functions is discussed for systems with a single time-dependent length scale.


Organizer: Vinh Nguyen

August 2018
August 3

Friday 1:30pm
304 Robeson Hall
(poster)

Professor Uwe Tauber (Physics, Virginia Tech)

“Interactive Discussion on Applications”


Organizer: Vinh Nguyen

August 10

Friday 1:30pm
304 Robeson Hall
(poster)

Professor Michel Pleimling (Physics, Virginia Tech)

"Aging processes in systems far from equilibrium II: Systems with complex ordering processes"

In this talk I first discuss aging scaling properties of a many-species system undergoing coarsening with non-trivial in-domain dynamics. The second part of the talk is devoted to physical aging in interacting skyrmion matter. Two-time correlation functions are analyzed to study the non-linear stochastic relaxation dynamics in the aging regime.


Organizer: Vinh Nguyen

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Spring 2018

Organizer: Vinh Nguyen

These meetings occur on Fridays from 4:00pm to 5:00pm in Robeson 304 (unless otherwise indicated)

January 2018
January 5

Friday 4:00pm
304 Robeson Hall
(poster)

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

January 12

Friday 4:00pm
304 Robeson Hall
(poster)

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

January 19

Friday 4:00pm
304 Robeson Hall
(poster)

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

January 26

Friday 4:00pm
304 Robeson Hall
(poster)

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

February 2018
February 2

Friday 4:00pm
304 Robeson Hall
(poster)

"No CSB Discussion Meeting Scheduled"

Organizer: Vinh Nguyen

February 9

Friday 4:00pm
304 Robeson Hall
(poster)

Jacob Carroll (Department of Physics, Virginia Tech)

"Sparsely Encoding Convolutional Neural Networks II"

Neural networks are a family of models that range from the biologically inspired recurrent networks that serve as models of the brain, to the feed-forward, deep-learning networks that have been at the forefront of machine learning in recent years. This talk will continue to introduce a specific type of neural network that while biologically inspired, has been developed for the purpose of machine learning and computer science: the sparsely encoding convolutional neural network. This talk will explain how these systems are used for imaged denoising, and how finite size scaling was observed in these networks as they denoised images across many different values of sparsity. This finite size scaling implies that these systems undergo a continuous as sparsity is varied.

Organizer: Vinh Nguyen

February 16

Friday 4:00pm
304 Robeson Hall
(poster)

Priyanka (Department of Physics, Virginia Tech)

"Study of anomalous behavior in one-dimensional harmonic system"

I will start with some theoretical models which have been developed to understand the violation of Fourier's Law in the lower dimension. Anomalous transport, nonlinear temperature profile etc, are the key feature of these model. In detail, I will talk about one of these models (harmonic chain with volume exchange) and present some its analytical and numerical results. I will present exact expression of two-point function in a stationary state and also shows that the dynamics are governed by fractional Laplacian.

Organizer: Vinh Nguyen

February 23

Friday 4:00pm
304 Robeson Hall
(poster)

Weigang Liu (Department of Physics, Virginia Tech)

"A numerical study of the two-dimensional complex Ginzburg-Landau equation"

The complex Ginzburg-Landau equation with additive noise is a stochastic partial differential equation that describes a remarkably wide range of physical systems: coupled non-linear oscillators subject to external noise near a Hopf bifurcation instability; spontaneous structure formation in non-equilibrium systems, e.g., in cyclically competing populations; and driven-dissipative Bose-Einstein condensation, realized in open systems on the interface of quantum optics and many-body physics. We employ a finite-difference method to numerically solve the noisy complex Ginzburg-Landau equation on a two-dimensional domain with the goal to investigate the coarsening dynamics following a quench from a strongly fluctuating defect turbulence phase to a long-range ordered phase. We start from a simplified amplitude equation, solve it numerically, and then study the spatio-temporal behavior characterized by the spontaneous creation and annihilation of topological defects (spiral waves). We check our simulation results against the known dynamical phase diagram in this non-equilibrium system, tentatively analyze the coarsening kinetics following sudden quenches between different phases, and have begun to characterize the ensuing aging scaling behavior.

Organizer: Vinh Nguyen

March 2018
March 2

Friday 4:00pm
304 Robeson Hall
(poster)

Physics Faculty Meeting (No CSMB Discussion Meeting)

Organizer: Vinh Nguyen

March 9

Friday 4:00pm
304 Robeson Hall
(poster)

"Spring Break" (No CSB Discussion Meeting Scheduled)

Organizer: Vinh Nguyen

March 16

Friday 4:00pm
304 Robeson Hall
(poster)

CSB Faculty Meeting (No CSMB Discussion Meeting)

Organizer: Vinh Nguyen

March 23

Friday 4:00pm
304 Robeson Hall
(poster)

Ali Charkhesht (Department of Physics, Virginia Tech)

"Probing Collective Motions of Proteins and Hydration Dynamics by a Wide Range Dielectric Spectroscopy"

Studying dynamics of proteins in their biological milieu such as water is interesting because of their strong absorption in the terahertz range that contain information on their global and sub-global collective vibrational modes (conformational dynamics) and global dynamical correlations among solvent water molecules and proteins. In addition, water molecules dynamics within protein solvation layers play a major role in enzyme activity. However, due to the strong absorption of water in the gigahertz-to-terahertz frequencies, it is challenging to study properties of the solvent dynamics as well as conformational changes protein in water. In response, we have developed a highly sensitive megahertz-to-terahertz dielectric spectroscopy system to probe the hydration shells as well as large-scale dynamics of these biomolecules. . Thereby, we have deduced the conformation flexibility of proteins and compare the hydration dynamics around proteins to understand the effects of surface-mediated solvent dynamics, relationships among different measures of interfacial solvent dynamics, and protein-mediated solvent dynamics based on the complex dielectric response from 50 MHz up to 2 THz by using the system we developed. Comparing these assets of various proteins in different classes helps us shed light on the macromolecular dynamics in a biologically relevant water environment.

Organizer: Vinh Nguyen

March 30

Friday 4:00pm
304 Robeson Hall
(poster)

Physics Faculty Meeting (No CSMB Discussion Meeting)

Organizer: Vinh Nguyen

April 2018
April 6

Friday 4:00pm
304 Robeson Hall
(poster)

Physics Faculty Meeting (No CSMB Discussion Meeting)

Organizer: Vinh Nguyen

April 13

Friday 4:00pm
304 Robeson Hall
(poster)

Riya Nandi (Department of Physics, Virginia Tech)

"Short-Time Dynamics of Three-Dimensional Magnetic Systems with Heisenberg Interaction"

This project aims to explore the initial relaxation dynamics of Heisenberg ferro and anti-ferromagnets. It involves a new simulation technique of combining reversible mode coupling dynamics with the simple diffusive relaxation dynamics in order to obtain the correct dynamic exponent and identify the correct universality class. The system undergoes critical aging and relevant exponents identified. Finally, for a system with non-conserved order-parameter, i.e., the anti-ferromagnet, theory predicts non-universal initial slip exponent. This work aims to study its dependence on the width of the initial distribution of the conserved quantities. This is a work in progress, at best just beginning to show promising results.

Organizer: Vinh Nguyen

April 20

Friday 4:00pm
304 Robeson Hall
(poster)

Physics Faculty Meeting (No CSMB Discussion Meeting)

Organizer: Vinh Nguyen

April 27

Friday 4:00pm
304 Robeson Hall
(poster)

Physics Faculty Meeting (No CSMB Discussion Meeting)

Organizer: Vinh Nguyen

May 2018
May 4

Friday 4:00pm
304 Robeson Hall
(poster)

Exam Week (No CSMB Discussion Meeting)

Organizer: Vinh Nguyen

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Fall 2017

Organizer: Vinh Nguyen

These meetings occur on Fridays from 4:00pm to 5:00pm in Robeson 304 (unless otherwise indicated)

September 2017
September 1

Friday 4:00pm
304 Robeson Hall

Physics Department Faculty Meeting. No talk scheduled.

September 8

Friday 4:00pm
304 Robeson Hall

CSB Center Meeting. No talk scheduled.

September 15

Friday 4:00pm
304 Robeson Hall

Discussion with Prof. Nigel Goldenfeld (J. Mark Sowers Distinguished Speaker)

Organizer: Uwe Täuber

September 22

Friday 4:00pm
304 Robeson Hall

Physics Department Faculty Meeting. No talk scheduled.

September 29

Friday 4:00pm
304 Robeson Hall

No talk scheduled.

Organizer: Vinh Nguyen

October 2017
October 6

Friday 4:00pm
304 Robeson Hall

No talk scheduled

October 13

Friday 4:00pm
304 Robeson Hall

Fall Break. No talk scheduled.

October 20

Friday 4:00pm
304 Robeson Hall

Physics Department Faculty Meeting. No talk scheduled

Organizer: Vinh Nguyen

October 27

Friday 4:00pm
304 Robeson Hall

(poster)

Jacob Carroll  (Department of Physics, Virginia Tech)

Topic: Sparsely Encoding Convolutional Neural Networks I

Neural networks are a family of models that range from the biologically inspired recurrent networks that serve as models of the brain, to the feed-forward, deep-learning networks that have been at the forefront of machine learning in recent years. This talk will introduce a specific type of neural network, that while biologically inspired, has been developed for the purpose of machine learning and computer science: the sparsely encoding convolutional neural network. This talk will explain this model in detail, and will serve as the basis for a second talk in January that will explore observed finite-size scaling in these sparsely encoding convolutional neural networks.

Organizer: Vinh Nguyen

November 2017
November 3

Friday 4:00pm
304 Robeson Hall

(poster)

Yanfei Tang   (Department of Physics, Virginia Tech)

Topic: Young-Laplace Equation

Organizer: Vinh Nguyen

November 10

Friday 4:00pm
304 Robeson Hall

(poster)

Prof. Hildegard Meyer-Ortmanns (Jacob University Bremen, Germany)

Topic: ABOUT INTERESTING CYCLES IN OSCILLATORY SYSTEMS AND IN GAMES OF WINNERLESS COMPETITION

Upon identifying physical aging in oscillatory systems we discovered two interesting phenomena in a system of repulsively coupled Kuramoto oscillators, which have a rather rich attractor space. One is the emergence of long-period orbits, whose periods are orders of magnitude longer than the period of individual oscillators. The cycles here consist of repeating temporary patterns of phase-locked motion. The other phenomenon refers to the self-similarity of these cycles, when the strength of deviations from a uniform natural frequency distribution is appropriately tuned. In connection with winnerless games of competition we search for heteroclinic cycles that are supposed to be responsible for spiral pattern formation and even hierarchies of spirals, when these games are placed on a spatial grid. Here we indicate ongoing work.

Organizer: Vinh Nguyen

November 17

Friday 4:00pm
304 Robeson Hall

Physics Department Faculty Meeting. No talk scheduled

Organizer: Vinh Nguyen

November 24

Friday 4:00pm
304 Robeson Hall

Thanksgiving Holiday. No talk scheduled.

December 2017
December 1

Friday 4:00pm
304 Robeson Hall

Chengyuan Wen (Department of Physics, Virginia Tech)

Topic: Evaporation of Liquids

Organizer: Vinh Nguyen

December 8

Friday 4:00pm
304 Robeson Hall

(Department of Physics, Virginia Tech)

Talked Canceled and Rescheduled for Future

Organizer: Vinh Nguyen

   

Center for Soft Matter and Biological Physics Summer Discussion Meetings

Summer 2017

These meetings occur on Fridays from 1:30pm to 2:30pm in Robeson 304 (unless otherwise indicated)

< 2016 | May | June | July | August | 2018 >

May 2017
May 26

Friday 1:30pm
304 Robeson Hall
 

No talk scheduled.

June 2017
June 2

Friday 1:30pm
304 Robeson Hall

CSB Seminar
Prof. P. S. Krishnaprasad   (University of Maryland)

Topic: Subriemannian geometry and finite time thermodynamics

Subriemannian geometry has its roots in optimal control problems. The Caratheodory-Chow-Rashevskii theorem on accessibility also places the subject in contact with an axiomatic approach to macroscopic thermodynamics. Explicit integrability of optimal control problems in this context is of interest. As in the case for integrability questions in mechanics, here too symmetries and conservation laws have a key role. In this talk we discuss model problems and results pertaining to such questions in isolated systems and ensembles of interacting systems. Of special interest is the problem of determining thermodynamic cycles that draw useful work from fluctuations. This work is in collaboration with PhD student Yunlong Huang, and Dr. Eric Justh of the Naval Research Laboratory.

Organizers: Vinh Nguyen

June 9

Friday 1:30pm
304 Robeson Hall
Wen Xiong   (Dept. of Biological Sciences, Virginia Tech)

Topic: Structural and functional basis of alternative endosomal ESCRT-0 protein complexes

Early endosomes represent the first sorting station for vesicular ubiquitylated cargo. Cargo transport is mediated by the endosomal sorting complex required for transport (ESCRT) machinery. Similar to the structural organization of ESCRT-0 proteins, alternative ESCRT-0 (alt-ESCRT- 0) proteins, such as Tollip and Tom1, also present multiple ubiquitin-binding domains, including the C2 and CUE (Tollip) and VHS and GAT (Tom1) domains. Tollip localizes the Tollip-Tom1 complex at endosomal compartments by association with phosphatidylinositol 3-phosphate (PtdIns(3)P) through its central C2 domain. Tom1, through its GAT domain, is recruited to endosomes by binding to Tollip's Tom1-binding domain (TBD) through an unknown mechanism. Our NMR data revealed that Tollip TBD is a natively unfolded domain that partially folds at its N-terminus when bound to the first two helices of the Tom1 GAT domain through high affinity hydrophobic contacts. Furthermore, this association abrogates binding of Tollip to PtdIns(3)P by additionally targeting its C2 domain. Binding of the Tollip C2 domain is mediated by the third helix of the Tom1 GAT domain. We propose that association with Tom1 favors Tollip's release from endosomal membranes, allowing Tollip to commit to cargo trafficking. To directly test the ability of Tom1-Tollip complexes to bind ubiquitinated cargo within a lipid bilayer, a system was developed to measure the distribution of an ubiquitin-conjugated substrate at nanometer-scale resolution using AFM so as to clarify the formation mechanism of Tom1-Tollip complex in the absence and presence of monoubiquitin and polyubiquitin chains, and the modulatory role of PtdIns(3)P. Also, we identified a conserved central hydrophobic patch at the ubiquitin surface to be the binding site for the Tom1 VHS domain. The ubiquitin hydrophobic patch is also involved in Tom1 GAT domain binding, suggesting that Tom1 can bind ubiquitin molecules through two independent sites.

Organizers: Vinh Nguyen

June 16

Friday 1:30pm
1028 Pamplin Hall
Udaya Sree Datla and Sheng Chen   (Dept. of Physics, Virginia Tech)

Topic: The spatiotemporal network dynamics of acquired resistance in engineered microecological systems

Organizers: Vinh Nguyen

June 23

Friday 1:30pm
304 Robeson Hall
Chuanhui Chen   (Dept. of Physics, Virginia Tech)

Topic: Scanning probe Microscopy Study of Molecular Nanostructures on 2D Materials

Nanostructures self-assembled from molecules adsorbed on emerging two-dimensional (2D) materials confer physical and chemical properties desirable for potential applications in photovoltaics, electronics and quantum information. In this talk, I will present our scanning tunneling microscopy (STM) study of temperature evolution of quasi-one dimensional (1D) C60 nanostructures on rippled graphene. We demonstrated that C60 molecules can be arranged into a quasi-1D chain structure through careful control of the subtle balance between the linear periodic potential of rippled graphene and the C60 surface mobility, which can transition to a more compact hexagonal close packed stripe structure by annealing at a higher temperature. I will also present the formation of sub-monolayer C60 and perylenetetracarboxylic dianhydride (PTCDA) on graphene wrinkles. Beyond graphene, I will briefly discuss our STM investigation on few-layer molybdenum disulfide (MoS2) and liquid-cell atomic force microscopy (AFM) study of Toll interacting protein (Tollip) on a lipid membrane.

Organizers: Vinh Nguyen

June 30

Friday 1:30pm
304 Robeson Hall
Wei Song   (Dept. of Biological Sciences, Virginia Tech)

Topic: Design of a Disabled-2-derived peptide to impair platelet-mediated cancer cell extravasation

Disabled-2 (Dab2) targets membranes and triggers a wide range of biological events, including endocytosis and platelet aggregation. Dab2, through its phosphotyrosine-binding (PTB) domain, inhibits platelet aggregation by competing with fibrinogen for ?IIb?3 integrin receptor binding. We have shown that the N-terminal region, including the PTB domain (N-PTB), drives Dab2 to the platelet membrane surface by binding to sulfatides through two sulfatide-binding motifs (SBM), modulating the extent of platelet aggregation. SBM peptide contains two helices when embedded in dodecylphosphocholine micelles, reversibly binds to sulfatides with moderate affinity, lies parallel to the micelle surface, and when added to a platelet mixture, reduces the number and size of sulfatide-induced aggregates. Moreover, tumor cells are reported to have the ability of aggregating platelets, which occurs following tumor cell intravasation into the vasculature, thereby facilitating tumor cell migration, invasion and arrest within the vasculature. Contributions of platelets aggregation to tumor cell survival and spread suggest platelets as a new avenue for therapy. Overall, our findings identify and structurally characterize a minimal region in Dab2 that modulates platelet homotypic interactions, all of which provide the foundation for rational design of a new generation of anti-aggregatory peptide for therapeutic purposes of cancer.

Organizers: Vinh Nguyen

July 2017
July 7

Friday 1:30pm
304 Robeson Hall
Prof. Shengfeng Cheng   (Dept. of Physics, Virginia Tech)

Topic: Evaporation as a Phenomenon and a Tool

Organizers: Vinh Nguyen

July 14

Friday 1:30pm
304 Robeson Hall
Shadi Sadat Esmaeili   (Dept. of Physics, Virginia Tech)

Topic: Breaking of Time Translation Invariance in Kuramoto Dynamics

We identify the breaking of time-translation invariance in a deterministic system of repulsively coupled Kuramoto oscillators, which are exposed to a distribution of natural frequencies. We consider grid sizes with different characteristics of the attractor space, which is by construction quite rich. This may cause long transients until the deterministic trajectories find their stationary orbits. The stationary orbits are limit cycles with periods that extend over orders of magnitude. It is the long transient times that cause the breaking of time-translation invariance in autocorrelation functions of oscillator phases. This feature disappears close to the transition to the monostable phase, where the phase trajectories are just irregular and no stationary behavior can be identified.

Organizers: Vinh Nguyen

July 21

Friday 1:30pm
304 Robeson Hall
Harmeet Singh  (Dept. Engineering Mechanics, Virginia Tedh)

Geometric singularities in the mechanics of strings and rods

We will discuss propagating geometric discontinuities in one-dimensional bodies, particularly those mediated by partial contact with obstacles that may serve as singular sources of momentum and energy. Invariance arguments and basic assumptions about contact interactions reveal counterintuitive behavior during pick-up, lay-down, impact, peeling, and other processes. Related phenomena can be found in string instruments, mooring lines, and many other systems.

Organizers: Vinh Nguyen

July 28

Friday 1:30pm
304 Robeson Hall
 

No talk scheduled.

August 2017
August 4

Friday 1:30pm
304 Robeson Hall
 

No talk scheduled.

August 11

Friday 1:30pm
304 Robeson Hall
Laura Hanzly   (Dept. of Biological Systems Engineering, Virginia Tech)

Topic: Protein Nanoscale Self-Assembly and Nanofiller Applications

Proteins can easily be manipulated to suite a variety of applications. Proteins have the capability of forming macroscopic structures as well as the ability to assemble on the nanoscale. Here, the modification and nanoscale self-assembly of the protein wheat gluten will be discussed. Interesting effects on the kinetics of self-assembly are observed when wheat gluten is assembled in mediums other than pure water. Practical applications for wheat gluten as a nanofiller in materials such as synthetic rubber are currently being investigated.

Organizers: Vinh Nguyen

August 18

Friday 1:30pm
1028 Pamplin Hall

CSB Steering Committee Meeting. No talk scheduled.

August 25

Friday 1:30pm
304 Robeson Hall
Parviz Seifpanahi Shabane   (Dept. of Physics, Virginia Tech)

Topic: Intrinsically Disordered Proteins -- What do they look like?

Organizers: Vinh Nguyen

   
Back to Top

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Spring 2017

Organizer: Vinh Nguyen

These meetings occur on Fridays from 4:00pm to 5:00pm in Robeson 304 (unless otherwise indicated)

January 2017
January 20

Friday 4:00pm
304 Robeson Hall

Faculty search event. No talk scheduled.

January 27

Friday 4:00pm
304 Robeson Hall

Faculty search event. No talk scheduled.

February 2017
February 3

Friday 4:00pm
304 Robeson Hall

Faculty search event. No talk scheduled.

February 10

Friday 4:00pm
304 Robeson Hall

Faculty search event. No talk scheduled.

February 17

Friday 4:00pm
304 Robeson Hall

Faculty search event. No talk scheduled.

February 24

Friday 4:00pm
304 Robeson Hall

Faculty search event. No talk scheduled.

March 2017
March 3

Friday 4:00pm
304 Robeson Hall

Faculty meeting. No talk scheduled.

March 10

Friday 4:00pm
304 Robeson Hall

Spring Break. No talk scheduled.

March 17

Friday 4:00pm
304 Robeson Hall

APS March Meeting. No talk scheduled.

March 24

Friday 4:00pm
304 Robeson Hall
Sheng Chen (Dept. of Physics, Virginia Tech)

Topic: Computational study of biodiversity with evolution and natural selection

Organizers: Vinh Nguyen and Will Mather

March 31

Friday 4:00pm
304 Robeson Hall
Heather Deter (Dept. of Physics, Virginia Tech)

Topic: Big data analysis of differential production within toxi-antitoxin systems

Organizers: Vinh Nguyen and Will Mather

April 2017
April 7

Friday 4:00pm
304 Robeson Hall

Special talk in engineering. No CSB talk scheduled.

April 14

Friday 4:00pm
304 Robeson Hall
William Ducker (Dept. of Chemical Engineering, Virginia Tech)

Topic: Micrometer-sized spheres driven into crystalline array by simple simple rubbing

Organizers: Vinh Nguyen and Will Mather

April 21

Friday 4:00pm
304 Robeson Hall

No talk scheduled.

Organizers: Vinh Nguyen and Will Mather

April 28

Friday 4:00pm
304 Robeson Hall

Faculty Meeting, No CSB Talk Scheduled

May 2017
May 5

Friday 4:00pm
304 Robeson Hall

Exam week. No CSB talk scheduled.

   

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Fall 2016

Organizer: Vinh Nguyen

These meetings occur on Fridays from 4:00pm to 5:00pm in Robeson 304 (unless otherwise indicated)

August 2016
August 26

Friday 4:00pm
304 Robeson Hall

Physics Department Faculty Meeting. No talk scheduled.

September 2016
September 2

Friday 4:00pm
304 Robeson Hall

No talk scheduled.

September 9

Friday 4:00pm
304 Robeson Hall
Udaya Sree Datla (Virginia Tech)

Topic: Evolutionary dynamics in synthetic predator-prey ecologies

Organizers: Vinh Nguyen and Will Mather

September 16

Friday 4:00pm
304 Robeson Hall

Talk cancelled.

September 23

Friday 4:00pm
304 Robeson Hall
Prudvi Gaddam (Dept. of Chemical Engineering, Virginia Tech)

Topic: A liquid state thermal diode

Organizers: Vinh Nguyen and Will Mather

September 30

Friday 4:00pm
304 Robeson Hall
William Mather

Topic: Modeling Gene Networks

Organizers: Vinh Nguyen and Will Mather

October 2016
October 7

Friday 4:00pm
304 Robeson Hall

No talk scheduled.

October 14

Friday 4:00pm
304 Robeson Hall

Fall Break. No talk scheduled.

October 21

Friday 4:00pm
304 Robeson Hall

CSB Center Faculty Meeting. No talk scheduled.

October 28

Friday 4:00pm
304 Robeson Hall
Harshwardhan Chaturvedi   (Dept. of Physics, Virginia Tech)

Topic: Flux Lines in Superconductors: Planar Defects and Beyond

Organizers: Vinh Nguyen and Will Mather

November 2016
November 4

Friday 4:00pm
304 Robeson Hall
Chola Regmi   (Dept. of Physics, Virginia Tech)

Topic: Tubulin binding energies from all-atom molecular dynamics simulations

Organizers: Vinh Nguyen and Will Mather

November 11

Friday 4:00pm
304 Robeson Hall

83rd Annual Meeting of the APS Southeastern Section. No talk scheduled.

November 18

Friday 4:00pm
304 Robeson Hall

Physics Department Faculty Meeting. No talk scheduled.

November 25

Friday 4:00pm
304 Robeson Hall

Thanksgiving Holiday. No talk scheduled.

December 2016
December 2

Friday 4:00pm
304 Robeson Hall

(poster)

Bart Brown (Dept. Physics, Virginia Tech)

Topic: Noncyclic interactions: games within games

Cyclic predator prey games can create complex patterns in space and time such as domains and propagating spirals from simple microscopic rules. The coexistence of domains and spirals has been observed in a cyclic six species game where each species preys upon three others. This game is of particular interest as it exhibits the dynamical generation of multiple space and time scales. In this work we explore different interaction schemes to investigate the effects of these different scales on the patterns produced by the system and introduce a new non-cyclic game of nine species which produces spirals within spirals.

Organizers: Vinh Nguyen and Will Mather

   

Center for Soft Matter and Biological Physics Friday Discussion Meetings

Summer 2016

Organizer: Vinh Nguyen

These meetings occur on Fridays from 4:00pm to 5:00pm in Robeson 304 (unless otherwise indicated)

May 2016
May 23

Monday 1:30pm
304 Robeson Hall
Ali Charkhesht and Vinh Nguyen   (Dept. of Physics, Virginia Tech)

Topic: Protein hydration and dynamics

Organizers: Vinh Nguyen and Will Mather

May 30

Monday 1:30pm
304 Robeson Hall
 

Memorial Day. No meeting scheduled.

Organizers: Vinh Nguyen and Will Mather

June 2016
June 6

Monday 1:30pm
304 Robeson Hall
Steve Melville   (Dept. of Biological Sciences, Virginia Tech)

Topic: How do you pull a hydrophobic protein out of a membrane and put it in a fiber 1,000 times per second?

Organizers: Vinh Nguyen and Will Mather

June 13

Monday 1:30pm
304 Robeson Hall
Will Mather   (Dept. of Physics, Virginia Tech)

Topic: Whither noise? A discussion concerning the utility of stochastic modeling for cellular networks.

Biology is in the middle of a mathematical revolution, where quantitative models for complex biological systems are increasingly being used to detangle underlying molecular mechanisms. My presentation will first provide a general introduction for non-experts concerning the application of these mathematical models, and in short time, I will discuss the usefulness of stochastic (probabilistic) modeling for cellular systems. My claim is that nearly all single cell phenomena are noisy, but it is not immediately clear that the added workload required to pursue stochastic modeling ultimately pays off. I will provide supporting evidence (with caveats) in favor of this approach, which will serve as a launching pad for discussion.

Organizers: Vinh Nguyen and Will Mather

June 20

Monday 1:30pm
304 Robeson Hall
David Popham   (Dept. of Biological Sciences, Virginia Tech)

Topic: Water and solutes in bacterial spores: Effects on protein and lipid mobility

Organizers: Vinh Nguyen and Will Mather

June 27

Monday 1:30pm
304 Robeson Hall
Alexey Onufriev   (Dept. of Computer Science, Virginia Tech)

Topic: Existing water models for atomistic modeling: the bad and the ugly

Organizers: Vinh Nguyen and Will Mather

July 2016
July 4

Monday 1:30pm
304 Robeson Hall
 

Independence Day. No meeting scheduled.

Organizers: Vinh Nguyen and Will Mather

July 11

Monday 1:30pm
304 Robeson Hall
 

No meeting scheduled.

Organizers: Vinh Nguyen and Will Mather

July 18

Monday 1:30pm
304 Robeson Hall
 

No meeting scheduled.

Organizers: Vinh Nguyen and Will Mather

July 25

Monday 1:30pm
304 Robeson Hall
Justin Barone   (Dept. of Biological Systems Engineering, Virginia Tech)

Topic: Protein amyloid self-assembly

Organizers: Vinh Nguyen and Will Mather

August 2016
August 1

Monday 1:30pm
304 Robeson Hall
Shihoko Kojima   (Dept. of Biological Sciences, Virginia Tech)

Topic: Oscillators from nature - circadian clocks

Organizers: Vinh Nguyen and Will Mather

August 8

Monday 1:30pm
304 Robeson Hall
Will Mather   (Dept. of Physics, Virginia Tech)

Topic: Machine Learning, with Image Analysis in Fiji as an Example

Organizers: Vinh Nguyen and Will Mather