# Scholarly Works, Center for Soft Matter and Biological Physics

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Research articles, presentations, and other scholarship

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### Browsing Scholarly Works, Center for Soft Matter and Biological Physics by Content Type "Article"

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- Aging phenomena in the two-dimensional complex Ginzburg-Landau equationLiu, Weigang; Täuber, Uwe C. (2019-11)
Show more The complex Ginzburg-Landau equation with additive noise is a stochastic partial differential equation that describes a remarkably wide range of physical systems which include coupled non-linear oscillators subject to external noise near a Hopf bifurcation instability and spontaneous structure formation in non-equilibrium systems, e.g., in cyclically competing populations or oscillatory chemical reactions. 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 its non-equilibrium dynamics when the system is quenched into the "defocusing spiral quadrant". We observe slow coarsening dynamics as oppositely charged topological defects annihilate each other, and characterize the ensuing aging scaling behavior. We conclude that the physical aging features in this system are governed by non-universal aging scaling exponents. We also investigate systems with control parameters residing in the "focusing quadrant", and identify slow aging kinetics in that regime as well. We provide heuristic criteria for the existence of slow coarsening dynamics and physical aging behavior in the complex Ginzburg-Landau equation.Show more - Chain conformations and phase separation in polymer solutions with varying solvent qualityHuang, Yisheng; Cheng, Shengfeng (Wiley, 2021-10-02)
Show more Molecular dynamics simulations are used to investigate the conformations of a single polymer chain, represented by the Kremer-Grest bead-spring model, in a solution with a Lennard-Jones liquid as the solvent when the interaction strength between the polymer and solvent is varied. Results show that when the polymer-solvent interaction is unfavorable, the chain collapses as one would expect in a poor solvent. For more attractive polymer-solvent interactions, the solvent quality improves and the chain is increasingly solvated and exhibits ideal and then swollen conformations. However, as the polymer-solvent interaction strength is increased further to be more than about twice the strength of the polymer-polymer and solvent-solvent interactions, the chain exhibits an unexpected collapsing behavior. Correspondingly, for strong polymer-solvent attractions, phase separation is observed in the solutions of multiple chains. These results indicate that the solvent becomes effectively poor again at very attractive polymer-solvent interactions. Nonetheless, the mechanism of chain collapsing and phase separation in this limit differs from the case with a poor solvent rendered by unfavorable polymer-solvent interactions. In the latter, the solvent is excluded from the domain of the collapsed chains while in the former, the solvent is still present in the pervaded volume of a collapsed chain or in the polymer-rich domain that phase separates from the pure solvent. In the limit of strong polymer-solvent attractions, the solvent behaves as a glue to stick monomers together, causing a single chain to collapse and multiple chains to aggregate and phase separate.Show more - Critical Scaling and Aging near the Flux Line Depinning TransitionChaturvedi, Harshwardhan; Dobramysl, Ulrich; Pleimling, Michel J.; Täuber, Uwe C. (2019-12-03)
Show more We utilize Langevin molecular dynamics simulations to study dynamical critical behavior of magnetic flux lines near the depinning transition in type-II superconductors subject to randomly distributed attractive point defects. We employ a coarse-grained elastic line Hamiltonian for the mutually repulsive vortices and purely relaxational kinetics. In order to infer the stationary-state critical exponents for the continuous non-equilibrium depinning transition at zero temperature T = 0 and at the critical driving current density j_c, we explore two-parameter scaling laws for the flux lines' gyration radius and mean velocity as functions of the two relevant scaling fields T and j - j_c. We also investigate critical aging scaling for the two-time height auto-correlation function in the early-time non-equilibrium relaxation regime to independently measure critical exponents. We provide numerical exponent values for the distinct universality classes of non-interacting and repulsive vortices.Show more - Editorial: Signaling Proteins for Endosomal and Lysosomal FunctionCapelluto, Daniel G. S.; Conde, Cecilia B.; Tumbarello, David A.; van den Bogaart, Geert (Frontiers, 2021-12-16)
Show more - Feedback control of surface roughness in a one-dimensional KPZ growth processPriyanka; Täuber, Uwe C.; Pleimling, Michel J. (2019-12-11)
Show more Control of generically scale-invariant systems, i.e., targeting specific cooperative features in non-linear stochastic interacting systems with many degrees of freedom subject to strong fluctuations and correlations that are characterized by power laws, remains an important open problem. We study the control of surface roughness during a growth process described by the Kardar--Parisi--Zhang (KPZ) equation in $(1+1)$ dimensions. We achieve the saturation of the mean surface roughness to a prescribed value using non-linear feedback control. Numerical integration is performed by means of the pseudospectral method, and the results are used to investigate the coupling effects of controlled (linear) and uncontrolled (non-linear) KPZ dynamics during the control process. While the intermediate time kinetics is governed by KPZ scaling, at later times a linear regime prevails, namely the relaxation towards the desired surface roughness. The temporal crossover region between these two distinct regimes displays intriguing scaling behavior that is characterized by non-trivial exponents and involves the number of controlled Fourier modes. Due to the control, the height probability distribution becomes negatively skewed, which affects the value of the saturation width.Show more - Mechanically cycling gelatin bilayersHanzly, Laura E.; Chauhan, Natasha; Barone, Justin R. (2022-01-11)
Show more There is a growing interest in making stimuli-responsive polymer systems, particularly ones that are bio-inspired/biomimetic and could perform mechanical work. Here, a biological device made from gelatin is described that can mechanically cycle back and forth in response to solution pH or ionic strength changes. The gelatin bilayer has one layer of Type A gelatin and the other of Type B gelatin, which have 2 different isoelectric points and therefore ionization states at a given solution pH. The bilayer mechanically cycles back and forth when one layer swells more than the other layer, which occurs because of solution pH or ionic strength change. Maximum bilayer bending occurs at pH 10, when the Type B gelatin layer swells significantly more than the Type A layer. The results show the ability to use the unique properties of different sources of gelatin to design a simple biological machine.Show more - Non-universal critical aging scaling in three-dimensional Heisenberg antiferromagnetsNandi, Riya; Täuber, Uwe C. (2018-09-20)
Show more We numerically investigate the stationary and non-equilibrium critical dynamics in three-dimensional isotropic Heisenberg antiferromagnets. Since the non-conserved staggered magnetization couples dynamically to the conserved magnetization density, we employ a hybrid simulation algorithm that combines reversible spin precession with relaxational Kawasaki spin exchange processes. We measure the dynamic critical exponent and identify a suitable intermediate time window to obtain the aging scaling exponents. Our results support an earlier renormalization group prediction: While the critical aging collapse exponent assumes a universal value, the associated temporal decay exponent in the two-time spin autocorrelation function depends on the initial distribution of the conserved fields; here, specifically on the width of the initial spin orientation distribution.Show more - Parallel Temperature Interfaces in the Katz-Lebowitz-Spohn Driven Lattice GasMukhamadiarov, Ruslan I.; Priyanka; Täuber, Uwe C. (2020-10-08)
Show more We explore a variant of the Katz-Lebowitz-Spohn (KLS) driven lattice gas in two dimensions, where the lattice is split into two regions that are coupled to heat baths with distinct temperatures. The temperature boundaries are oriented parallel to the external particle drive. If the hopping rates at the interfaces satisfy particle-hole symmetry, the current difference across them generates a vector flow diagram akin to a vortex sheet. We have studied the finite-size scaling of the particle density fluctuations in both temperature regions, and observed that it is controlled by the respective temperature values. If the colder subsystem is maintained at the KLS critical temperature, while the hotter subsystem's temperature is set much higher, the interface current greatly suppresses particle exchange between the two regions. As a result of the ensuing effective subsystem decoupling, strong fluctuations persist in the critical region, whence the particle density fluctuations scale with the KLS critical exponents. However, if both temperatures are set well above the critical temperature, the particle density fluctuations scale according to the totally asymmetric exclusion process (TASEP). We have also measured the entropy production rate in both subsystems; it displays intriguing algebraic decay in the critical region, while it saturates quickly at a small but non-zero level in the hotter region. We have also considered another possible choice of the hopping rates across the temperature interfaces that explicitly breaks particle-hole symmetry. In that case the boundary rates induce a net particle flux across the interfaces that displays power-law behavior, until ultimately the particle exclusion constraints generate a clogging transition to an inert state.Show more - Requirements for the containment of COVID-19 disease outbreaks through periodic testing, isolation, and quarantineSerrao, Shannon R.; Deng, Shengfeng; Priyanka; Mukhamadiarov, Ruslan I.; Childs, Lauren M.; Täuber, Uwe C. (Virginia Tech, 2020-10-25)
Show more We employ individual-based Monte Carlo computer simulations of a stochastic SEIR model variant on a two-dimensional Newman{Watts small-world network to investigate the control of epidemic outbreaks through periodic testing and isolation of infectious individuals, and subsequent quarantine of their immediate contacts. Using disease parameters informed by the COVID-19 pandemic, we investigate the effects of various crucial mitigation features on the epidemic spreading: fraction of the infectious population that is identifiable through the tests; testing frequency; time delay between testing and isolation of positively tested individuals; and the further time delay until quarantining their contacts as well as the quarantine duration. We thus determine the required ranges for these intervention parameters to yield effective control of the disease through both considerable delaying the epidemic peak and massively reducing the total number of sustained infections.Show more - The viability of SARS-CoV-2 on solid surfacesHosseini, Mohsen; Behzadinasab, Saeed; Benmamoun, Zachary; Ducker, William A. (Elsevier, 2021-10-01)
Show more The COVID-19 pandemic had a major impact on life in 2020 and 2021. One method of transmission occurs when the causative virus, SARS-CoV-2, contaminates solids. Understanding and controlling the interaction with solids is thus potentially important for limiting the spread of the disease. We review work that describes the prevalence of the virus on common objects, the longevity of the virus on solids, and surface coatings that are designed to inactivate the virus. Engineered coatings have already succeeded in producing a large reduction in viral infectivity from surfaces. We also review work describing inactivation on facemasks and clothing and discuss probable mechanisms of inactivation of the virus at surfaces.Show more