2 research outputs found
Mixed Mechanism of Lubrication by Lipid Bilayer Stacks
Although the key role of lipid bilayer
stacks in biological lubrication
is generally accepted, the mechanisms underlying their extreme efficiency
remain elusive. In this article, we report molecular dynamics simulations
of lipid bilayer stacks undergoing load and shear. When the hydration
level is reduced, the velocity accommodation mechanism changes from
viscous shear in hydration water to interlayer sliding in the bilayers.
This enables stacks of hydrated lipid bilayers to act as efficient
boundary lubricants for various hydration conditions, structures,
and mechanical loads. We also propose an estimation for the friction
coefficient; thanks to the strong hydration forces between lipid bilayers,
the high local viscosity is not in contradiction with low friction
coefficients
Molecular Simulations of Supercritical Fluid Permeation through Disordered Microporous Carbons
Fluid
transport through microporous carbon-based materials is inherent
in numerous applications, ranging from gas separation by carbon molecular
sieves to natural gas production from coal seams and gas shales. The
present study investigates the steady-state permeation of supercritical
methane in response to a constant cross-membrane pressure drop. We
performed dual control volume grand canonical molecular dynamics (DCV-GCMD)
simulations to mimic the conditions of actual permeation experiments.
To overcome arbitrary assumptions regarding the investigated porous
structures, the membranes were modeled after the CS1000a and CS1000
molecular models, which are representative of real microporous carbon
materials. When adsorption-induced molecular trapping (AIMT) mechanisms
are negligible, we show that the permeability of the microporous material,
although not significantly sensitive to the pressure gradient, monotonically
decreases with temperature and reservoir pressures, consistent with
diffusion theory. However, when AIMT occurs, the permeability increases
with temperature in agreement with experimental data found in the
literature