Molecular dynamics study of the sonic horizon of microscopic Laval nozzles.

A Laval nozzle can accelerate expanding gas above supersonic velocities, while cooling the gas in the process. This work investigates this process for microscopic Laval nozzles by means of nonequilibrium molecular dynamics simulations of stationary flow, using grand-canonical Monte Carlo particle reservoirs. We study the steady-state expansion of a simple fluid, a monoatomic gas interacting via a Lennard-Jones potential, through an idealized nozzle with atomically smooth walls.

The quest for energy traps in the CP43 antenna of photosystem II.

To identify energy traps in CP43, a subcomplex of the photosystem II antenna system, site energies and excitonic couplings of the QY transitions of chlorophyll (Chl) a pigments bound to CP43 are computed using electrostatic models of pigment-protein and pigment-pigment interactions. The computations are based on recent crystal structures of the photosystem II core complex with resolutions of 1.9 and 2.