Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F06: Active MaterialsLive
|
Hide Abstracts |
Sponsoring Units: DSOFT Chair: Mario Sandoval-Espinoza, University of California, San Diego Room: 06 |
Tuesday, March 16, 2021 11:30AM - 11:42AM Live |
F06.00001: Equilibrium to off-equilibrium crossover in homogeneous active matter Andrea Cavagna, Luca Di Carlo, Irene Giardina, Tomas Grigera, Giulia Pisegna We study the crossover between equilibrium and off-equilibrium dynamical universality classes in the Vicsek model near its ordering transition. Starting from the incompressible hydrodynamic theory of Chen et al*, we show that increasing the activity leads to a renormalization group (RG) crossover between the equilibrium ferromagnetic fixed point, with dynamical critical exponent z=2, and the off-equilibrium active fixed point, with z=1.7 (in d=3). We run simulations of the classic Vicsek model in the near-ordering regime and find that critical slowing down indeed changes with activity, displaying two exponents that are in remarkable agreement with the RG prediction. The value of the speed of the particles is the key ingredient to explore the crossover at a numerical level. I am going to focus on the explanation of how it is possible to tune the right microscopic parameter in order to find complete agreement between simulations and predictions of the mesoscopic theory. |
Tuesday, March 16, 2021 11:42AM - 11:54AM Live |
F06.00002: ’Maxwell-Boltzmann’ velocity distribution for noninteracting active matter Mario Sandoval We theoretically and computationally find a Maxwell-Boltzmann-like velocity distribution for noninteracting active matter (NAM). To achieve this, mass and moment of inertia are incorporated into the corresponding noninteracting active Fokker-Planck equation, thus solving for the first time, the underdamped scenario of NAM following a Fokker-Planck formalism. This time, the distribution results in a bimodal symmetric expression that contains the effect of inertia on transport properties of NAM. The analytical distribution is further compared to experiments dealing with vibrobots. This work is an important step toward characterising active matter using an equivalent non-equilibrium statistical mechanics. |
Tuesday, March 16, 2021 11:54AM - 12:06PM Live |
F06.00003: Controlling flows of an intra-droplet active fluid across droplet interface Brock Jolicoeur, Yen-Chen (Anderson) Chen, Chih-Che C Chueh, Kun-Ta Wu Fluid dynamics of conventional passive fluid are known to be affected by boundary condition. For example, flow rates in a pipe depend on slipperiness of pipe surface. Similarly, active fluid, which consumes fuels locally to flow spontaneously, was reported to self-flow along a meter-long tubing with the flow rate depending on tubing geometry. However, how boundary condition influences fluid dynamics in an active fluid system remains poorly understood. Here, we investigated how a fluid boundary influenced self-organization of confined active fluid by establishing a 3D COMSOL-based nemato-hydrodynamic simulation platform where active fluid was confined in a compressed cylindrical water-in-oil droplet. Since the droplet interface was fluid, the fluid dynamics within and outside the droplet were coupled. Our simulation demonstrated that flow behaviors of intra-droplet active fluid were influenced by the amount of oil that surrounded the droplet: Without altering the droplet geometry, expanding the volume of oil could induce a circulatory flow within the droplet, which resembled our experimental observation. Our work suggested the feasibility of controlling the fluid dynamics of a confined active fluid system across a fluid interface. |
Tuesday, March 16, 2021 12:06PM - 12:18PM Live |
F06.00004: Existence of the B-Form DNA helix in nanoDNA liquid crystals and its variation due to aggregate assembly Gregory Smith, Tommaso Fraccia, Mikhail Zhernenkov, Noel Anthony Clark We show using diffraction of a synchrotron X-ray microbeam that liquid crystalline aggregates of 12mer nanoDNA, such as the Drew-Dickerson Dodecamer (DD), demonstrate a marked B-form DNA double-helix with only marginally less order than seen in longer DNA, such as the calf-thymus DNA used by Rosalind Franklin to produce the historic Photo 51. This finding is significant because it shows that B-form helical order persists in liquid crystals of DD even though the backbone of the column contains a double-strand break at every twelfth position and the DD segments are not held rigidly in place as part of a crystal. The coherence of the B-form helix is influenced by the mode of aggregate self-assembly, where aggregates assembled by a base-paired sticky-end produce much longer helical correlation lengths than those formed by hydrophobic blunt-ends. Finally, we found that aggregates of blunt-end 4mer oligomers shorter than half of a single B-form helical turn no longer display the B-form helical diffraction pattern but order with a different structure. This study gives fundamental insight into the extent to which the classical DNA helix is affected by discontinuity in the polymer backbone. |
Tuesday, March 16, 2021 12:18PM - 12:30PM Live |
F06.00005: How to use fitting functions to estimate the diffusion coefficient of molecules in diffusion-controlled drug release systems Gary Slater, Maxime Ignacio We propose a unified approach to describe the solutions of the diffusion equation for spherically symmetric diffusion-controlled drug release systems. Using this unified description, we investigate how we can extract useful results from data fitting. The method we propose exploits the fact that most fitting functions (even those that appear to give poor results) provide good estimates of the surface area under the curve, τ*, when the normalized release function M*(t) is plotted as a function of time t. In particular, we demonstrate that we can obtain a good estimate of the molecular diffusion coefficient D from the value of τ*. As an example, we compare the results obtained using both the Weibull function and our recent theory-based Semi-Empirical fitting function. Finally, we test the accuracy of the estimated value of D when these fitting functions are used with various types of noisy synthetic data. |
Tuesday, March 16, 2021 12:30PM - 12:42PM Live |
F06.00006: First-principles study of C & Mo sites vacancy defects in water
adsorbed (HS) Graphene/MoS 2 materials hari neupane, Narayan Prasad Adhikari We studied structure, electronic & magnetic properties C & Mo sites vacancy defects in |
Tuesday, March 16, 2021 12:42PM - 12:54PM Live |
F06.00007: Hydrodynamic Instabilities in Confined 3D Active Fluids Minu Varghese, Michael F Hagan, Aparna Baskaran Through stability analysis of a 3D active fluid, I will elucidate the origins of three of the most spectacular phenomena seen in experimental systems- spontaneous coherent flows, growth of finite wavelength bend deformations, and nucleation of topologically neutral disclination loops. |
Tuesday, March 16, 2021 12:54PM - 1:06PM Live |
F06.00008: A Low-Cost Platform for Studying Low-dimensional Active Matter Khamla Thavone, Skanda Vivek, Sairam Tangirala While it’s known that simple interactions between active constituents reproduces collective phenomena such as flocking and schooling, there is a lack of comprehensive understanding of emergent collective behaviors in active matter. Here, we built a model system for studying emergent collective behaviors from customizable, low-cost bristle-bots. Our model system is a quasi-one-dimensional system of bristle-bots confined to a circular track, interacting only with the bot in front or behind. Examples of low dimensional active systems include ants moving in a line, motor proteins walking on microtubule filaments, and traffic jams. We find that bristle-bots form cooperative dynamic clusters, despite their innate heterogeneities. Our results demonstrate how quasi-one-dimensional interactions between heterogeneous active constituents can give rise to emergent collective behaviors. |
Tuesday, March 16, 2021 1:06PM - 1:18PM Live |
F06.00009: Structural features and dynamical predictions in dense active packings Julia Giannini, Ethan Stanifer, M Lisa Manning Amorphous solids and dense active materials are characterized by structural disorder, nontrivial mechanical properties, and interesting dynamics. In existing work that focuses on athermal disordered solids under shear, metrics derived from linear response theory forecast structural instabilities and plastic rearrangement using information from a single snapshot of a configuration. However, no such formulation of these metrics exists for systems with active forces or structural gradients. In the context of dense crowd dynamics, the linear response of active particulate systems has been approximated using positional fluctuations. While seminal, these methods have serious limitations in predictivity, as they require large amounts of time-resolved data. To address these shortcomings, we developed a novel theoretical and computational framework to study a class of packings formed by persistent self-propelled particles. Using a mapping between self-propulsion and an external potential, we test predictions of structural metrics in distinct regions of the system. Applications of this work could be instrumental in preventing dangerous emergent phenomena in dense human crowds and studying the stability of materials with structural gradients. |
Tuesday, March 16, 2021 1:18PM - 1:30PM Live |
F06.00010: Time-dependent propulsion of noninteracting inertial active stochastic particles Luis L. Gutierrez-Martinez, Mario Sandoval In most of the works reported so far on active matter, inertia is neglected and its self-propulsion speed is assumed constant. In this work, we propose a model in which active particles have non-negligible inertia (mass and moment of inertia) and a time-dependent periodic propulsion speed. We study the most general propulsion using Fourier series and address some particular cases such as a square wave signal for the propulsion speed. The effect of inertia and time-dependent propulsion on the system’s mean-square displacement, is found theoretically following a Langevin formalism. Langevin dynamics simulations are also employed to corroborate our theoretical findings. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700