317 research outputs found
A Bubble Model for the Gating of Kv Channels
Voltage-gated Kv channels play fundamental roles in many biological
processes, such as the generation of the action potential. The gating mechanism
of Kv channels is characterized experimentally by single-channel recordings and
ensemble properties of the channel currents. In this work, we propose a bubble
model coupled with a Poisson-Nernst-Planck (PNP) system to capture the key
characteristics, particularly the delay in the opening of channels. The coupled
PNP system is solved numerically by a finite-difference method and the solution
is compared with an analytical approximation. We hypothesize that the
stochastic behaviour of the gating phenomenon is due to randomness of the
bubble and channel sizes. The predicted ensemble average of the currents under
various applied voltages across the channels is consistent with experimental
observations, and the Cole-Moore delay is captured by varying the holding
potential
Micro-Macro Modeling of Polymeric Fluids and Shear-Induced Microscopic Behaviors
This article delves into the micro-macro modeling of polymeric fluids,
considering various microscopic potential energies, including the classical
Hookean potential, as well as newly proposed modified Morse and Elastic-plastic
potentials. These proposed potentials encompass microscopic-scale bond-breaking
processes. The development of a thermodynamically consistent micro-macro model
is revisited, employing the energy variational method. To validate the model's
predictions, we conduct numerical simulations utilizing a deterministic
particle-FEM method. Our numerical findings shed light on the distinct
behaviors exhibited by polymer chains at the micro-scale in comparison to the
macro-scale velocity and induced shear stresses of fluids under shear flow.
Notably, we observe that polymer elongation, rotation, and bond breaking
contribute to the zero polymer-induced stress in the micro-macro model when
employing Morse and Elastic-plastic potentials. Furthermore, at high shear
rates, polymer rotation is found to induce shear-thinning behavior in the model
employing the classical Hookean potential
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