Article
Chemistry, Physical
S. A. Khrapak, A. G. Khrapak
Summary: Recent data from the TIP4P/Ice water model demonstrate that self-diffusion and shear viscosity follow the microscopic version of the Stokes-Einstein relation without considering the hydrodynamic diameter.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Physics, Fluids & Plasmas
Chun-Lei Song, Ye Tao, Wei-Yu Liu, Yi-Cheng Chen, Rui Xue, Tian-Yi Jiang, Biao Li, Hong-Yuan Jiang, Yu-Kun Ren
Summary: We report a unique phenomenon in which liquid metal droplets can pump fluid under a pure ac electric field. Unlike the directional pumping that occurs upon reversing the electric field polarity under a dc signal, this phenomenon allows the direction of fluid motion to be switched by simply shifting the position of the liquid metal droplets. The physical mechanism behind this phenomenon is termed Marangoni flow, caused by nonlinear electrocapillary stress. We developed a physical description by treating the oxide layer as a distributed capacitance with variable thickness and connected with the electric double layer, which showed excellent consistency with simulation results.
Article
Chemistry, Physical
Stepan Timr, Simone Melchionna, Philippe Derreumaux, Fabio Sterpone
Summary: Macromolecular crowding affects protein mobility and intracellular processes. Molecular models are needed to describe crowded environments. OPEPv7 is a force field for rigid-body simulations of crowded protein solutions. It successfully reproduces diffusion slowdown and allows the study of protein assembly dynamics and computational rheology of protein solutions.
JOURNAL OF PHYSICAL CHEMISTRY B
(2023)
Article
Physics, Fluids & Plasmas
Tongli Wei, Xiansheng Cao, Decheng Ma, Yaojin Li, Chenglong Jia
Summary: This work analyzes the mean collision force of a small classical particle moving through rarefied gases by directly calculating the decrease of particle's velocity due to elastic collisions. The study provides a self-consistent solution for the mean collision force in Maxwell gas and compares it with the Stokes force. It is found that the friction force in rarefied gases exhibits a quadratic speed dependence at high speeds, unlike the linear speed dependence of the Stokes force.
Article
Materials Science, Multidisciplinary
Chiho Watanabe, Tomohiro Furuki, Yuki Kanakubo, Fumiya Kanie, Keisuke Koyanagi, Jun Takeshita, Miho Yanagisawa
Summary: Biomolecular condensates driven by liquid-liquid phase separation (LLPS) have been investigated as novel activity regulators of living organisms. However, whether membrane wetting can regulate LLPS has remained unexplored. In this study, the researchers demonstrate that membrane wetting can indeed regulate LLPS in cell-sized spaces and alter the equilibrium state. They also explain the space-size-dependent LLPS from the higher wettability of certain biomolecules. These findings suggest that LLPS can be regulated by cell-sized confinement and competition for membrane wettability, making it a feasible principle in living cells.
ACS MATERIALS LETTERS
(2022)
Article
Chemistry, Physical
Song-Nam Hong, Jun-Hyok Ri, So -Yon Mun, Chol-Jun Yu
Summary: This study investigates the viscosity and diffusivity of aqueous solutions containing nanobubbles through molecular dynamics simulations. The results reveal that increasing the porosity and temperature significantly reduces the viscosity and increases the self-diffusion coefficient of the nanobubble solutions.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Mechanics
F. Aitken, F. Volino
Summary: The aim of this paper is to calculate the time dependence of the mean position (and orientation) of a fluid particle under mechanical action in a thermodynamic equilibrium. Through the introduction of a mechanical energy functional and the use of inertial modes and action temperature, the model predicts a dynamic phase transition where the rheological behavior of the medium changes from solid-like to liquid-like with increased mechanical action. This model is applied to analyze recent liquid water viscoelastic data, indicating prevalent elastic behavior in confined geometry. The model provides a coherent and unified explanation for these data along with transport properties. It concludes that any finite volume of fluid at rest possesses static shear elasticity and should be considered as a solid-like medium.
Article
Chemistry, Physical
S. A. Khrapak, A. G. Khrapak
Summary: It is demonstrated that the freezing density scaling of transport coefficients in fluids, similar to the freezing temperature scaling, can be explained by the quasi-universal excess entropy scaling approach proposed by Rosenfeld. This scaling approach for freezing density has a considerably wider applicability on the phase diagram of Lennard-Jones and related systems. The excellent accuracy of this approach in reproducing the shear viscosity coefficients of saturated liquid argon, krypton, xenon, and methane further showcases its predictive power.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Analytical
Wolf Hiller, Bastian Grabe
Summary: This article discusses a universal calibration method for the determination of polymer molar mass dependence using diffusion-ordered spectroscopy (DOSY) and compares it to size exclusion chromatography (SEC) and other DOSY methods. By implementing the Mark-Houwink approach, a single mathematical function is derived that describes both structure- and solvent-independent calibrations for DOSY. Through extensive testing on different polymers and solvents, it is shown that this method can accurately determine molar masses and new Mark-Houwink parameters.
ANALYTICAL CHEMISTRY
(2023)
Article
Chemistry, Physical
Devin O. O. Klapatiuk, Shawn L. L. Waugh, Abdulrahman A. A. Mukadam, Allan L. L. East
Summary: New electrostatic equations are proposed to predict the degree of ion pairing and other associations in anhydrous amine/carboxylic acid mixtures. These equations were obtained by fitting constant-dielectric quantum chemistry data and showed excellent agreement with experimental results, indicating their predictive power.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Mechanics
Andrew Y. K. Hong, Michael A. Gallis
Summary: Recently, collision-specific parameters proposed for direct simulation Monte Carlo simulations were tested for binary mixtures of nitrogen, oxygen, and argon. The traditional collision-averaged parameters were found to be highly accurate under near ambient conditions, while the collision-specific parameters were not. However, simulating transport using the collision-averaged parameters for helium mixtures was inaccurate. Therefore, a novel method combining the Chapman-Enskog theory with empirical mixing rules and experimental data was proposed to determine molecular parameters. The optimized parameters greatly improved the accuracy of the simulated transport for binary mixtures of nitrogen, oxygen, and argon, as well as for helium mixtures.
Article
Physics, Fluids & Plasmas
Yuto Hosaka, Shigeyuki Komura, David Andelman
Summary: We discuss the linear hydrodynamic response of a two-dimensional active chiral compressible fluid with odd viscosity, resulting in the odd viscosity-dependent mobility tensor. Furthermore, we demonstrate that a finite-size disk moving laterally in the 2D fluid experiences a nondissipative lift force in addition to the dissipative drag force.
Article
Crystallography
Hiroaki Tanaka, Rei Utata, Keiko Tsuganezawa, Sachiko Takahashi, Akiko Tanaka
Summary: This study reports on experimental results and simulation studies of protein crystals using viscous polyethylene glycol (PEG) solvents. Through fluorescence correlation spectroscopy, the diffusion rates of proteins, peptides, and small molecules in viscous PEG solvents were investigated, and equations were developed to predict diffusion coefficients. A numerical model was also created to describe diffusion processes during crystallization.
Article
Physics, Fluids & Plasmas
S. A. Khrapak, A. G. Khrapak
Summary: The study shows that the reduced transport coefficients of Lennard-Jones fluids along isotherms exhibit quasi-universal scaling on the density divided by its value at the freezing point. This scaling is closely related to the density scaling of transport coefficients of hard-sphere fluids. Additionally, the Stokes-Einstein relation without the hydrodynamic diameter is valid in the dense fluid regime, with the lower density boundary of its validity serving as a practical demarcation line between gaslike and liquidlike regimes.
Article
Chemistry, Physical
Seung Jae Lee, Saurabh Talele, John T. King
Summary: In this study, the microsecond chemical reaction in the chromophore pocket of eGFP was investigated using single molecule techniques, revealing coupling of the reaction to solvent viscosity but with deviation from Kramers' behavior. This deviation was attributed to internal friction of the protein weakening protein-solvent coupling at high viscosity and intermediate time scales.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
