Condensed Matter Theory

Abstract:

The applicability of a mesoscale modeling approach to the problem of contact line motion in one and two phase fluids was investigated. The thermodynamics boundary conditions were implemented, which allows to fix the static contact angle in the simulations. It was found that the contact line was overcome by evaporation or condensation near the contact line which was driven by the curvature of the diffuse interface. An analytic approximation was also derived for the angular position of a sheared interface.

Abstract:

We found that a novel optically-induced in-plane separation of plasmas of opposite charge is responsible for the large ring emission pattern around a laser excitation spot observed in modulation doped quantum well (QW) structures. The charge separation is a result of an interplay between the electrical field applied perpendicular to the QW and the diffusion of optically generated carriers in the QW plane. Excitonic emission at the sharp boundary between the positive and negative charges forms the ring. The initially hot carriers that are generated optically, cool as they diffuse and are therefore cold before they recombine at the ring. Such separation of charges was only observed when the excitation energy is above the barrier height of the QW. The effect of the lower energy excitation is found to be dramatically different, resulting in a shrinkage and even a total collapse of an existing ring pattern. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract:

We investigate the applicability of a mesoscale modeling approach, lattice Boltzmann simulations, to the problem of contact line motion in one- and two-component two phase fluids. In this, the second of two papers, we consider binary systems. We show that the contact line singularity is overcome by diffusion which is effective over a length scale L about the contact line and derive a scaling form for the dependence of L on system parameters.

Abstract:

We investigate the applicability of a mesoscale modeling approach, lattice Boltzmann simulations, to the problem of contact line motion in one and two component, two phase fluids. In this, the first of two papers, we consider liquid-gas systems. Careful implementation of the thermodynamic boundary condition allows us to fix the static contact angle in the simulations. We then consider the behavior of a sheared interface. We show that the contact line singularity is overcome by evaporation or condensation near the contact line which is driven by the curvature of the diffuse interface. An analytic approximation is derived for the angular position of a sheared interface.

Abstract:

In this perspective we address the question: why are proteins seemingly so hard to crystallize? We suggest that this is because of evolutionary negative design, i.e. proteins have evolved not to crystallize, because crystallization, as with any type of protein aggregation, compromises the viability of the cell. There is much evidence in the literature that supports this hypothesis, including the effect of mutations on the crystallizability of a protein, the correlations found in the properties of crystal contacts in bioinformatics databases, and the positive use of protein crystallization by bacteria and viruses.