Soft Condensed Matter
Osmotic pressure of compressed lattice knots (1902.04490v1)
EJ Janse van Rensburg
2019-02-12
A numerical simulation shows that the osmotic pressure of compressed lattice knots is a function of knot type, and so of entanglements. The osmotic pressure for the unknot goes through a negative minimum at low concentrations, but in the case of non-trivial knot types
and
it is negative for low concentrations. At high concentrations the osmotic pressure is divergent, as predicted by Flory-Huggins theory. These results suggest that the physical and chemical properties of biopolymers in confined spaces will be a function of entanglements.
Multi-phase, non-isothermal transfer of water in a simple geometry (1902.04468v1)
Pierre Lidon, Etienne Perrot, Abraham D Stroock
2019-02-12
It has long been acknowledged that heat and water transport of in soils and plants are intimately coupled. Pioneering work by Philip and de Vries proposed the physical basis and governing equations to describe these processes; their theory has since been refined many times. However, the lack of appropriate sensors for in situ monitoring of water status has impeded clear interpretation of field experiments and no general consensus has emerged on a precise description of water transport in non-isothermal porous media. In this paper, we use a new microfluidic tool called the microtensiometer that measures water potential to study a simple model situation: we measure the evolution of water potential in a vapor gap across which a controlled temperature gradient is applied and report a decrease of water potential with temperature difference by
, in agreement with previous experiments using other techniques. Based on a thermodynamic analysis of our system, we derive a theoretical prediction for this effect. Our model differs from Philip and de Vries equations by an additional water flux, negligible in our experiment but which should become significant in the case of unsaturated, nanoporous media. Both predictions by our model and by Philip and de Vries are close to the experimental value but with a discrepancy significant when compared with experimental uncertainties.
Local versus global stretched mechanical response in a supercooled liquid near the glass transition (1812.04527v2)
Baoshuang Shang, Jörg Rottler, Pengfei Guan, Jean-Louis Barrat
2018-12-11
Amorphous materials have a rich relaxation spectrum, which is usually described in terms of a hierarchy of relaxation mechanisms. In this work, we investigate the local dynamic modulus spectra in a model glass just above the glass transition temperature by performing a mechanical spectroscopy analysis with molecular dynamics simulations. We find that the spectra, at the local as well as on the global scale, can be well described by the Cole-Davidson formula in the frequency range explored with simulations. Surprisingly, the Cole-Davidson stretching exponent does not change with the size of the local region that is probed. The local relaxation time displays a broad distribution, as expected based on dynamic heterogeneity concepts, but the stretching is obtained independently of this distribution. We find that the size dependence of the local relaxation time and moduli can be well explained by the elastic shoving model.
Non-equilibrium steady states, coexistence and criticality in driven quasi-two-dimensional granular matter (1811.05350v2)
Thomas Schindler, Sebastian C. Kapfer
2018-11-13
Nonequilibrium steady states of vibrated inelastic frictionless spheres are investigated in quasi-two-dimensional confinement via molecular dynamics simulations. The phase diagram in the density-amplitude plane exhibits a fluidlike disordered and an ordered phase with threefold symmetry, as well as phase coexistence between the two. A dynamical mechanism exists that brings about metastable traveling clusters and at the same time stable clusters with anisotropic shapes at low vibration amplitude. Moreover, there is a square bilayer state which is connected to the fluid by BKTHNY-type two-step melting with an intermediate tetratic phase. The critical behavior of the two continuous transitions is studied in detail. For the fluid-tetratic transition, critical exponents of
,
, and
are obtained.
Shear jamming and fragility in dense suspensions (1902.04361v1)
Ryohei Seto, Abhinendra Singh, Bulbul Chakraborty, Morton M. Denn, Jeffrey F. Morris
2019-02-12
The phenomenon of shear-induced jamming is a factor in the complex rheological behavior of dense suspensions. Such shear-jammed states are fragile, i.e., they are not stable against applied stresses that are incompatible with the stress imposed to create them. This peculiar flow-history dependence of the stress response is due to flow-induced microstructures. To examine jammed states realized under constant shear stress, we perform dynamic simulations of non-Brownian particles with frictional contact forces and hydrodynamic lubrication forces. We find clear signatures that distinguish these fragile states from the more conventional isotropic jammed states.
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