Some remarks on subdynamics for systems interacting with reservoirs

It is shown that collision operators defined by the projector of Argyres and Kelley may provide useful examples for study of the subdynamics of the Brussels group. An application of this formalism to the optical pumping model of Barrat and Cohen-Tannoudji is discussed.     

Selective phosphatidylethanolamine translocation across vesicle membranes using synthetic translocases

Two sulfonamide derivatives of tris(aminoethyl)amine selectively facilitate the translocation of a fluorescent phospholipid probe containing the phosphoethanolamine head-group across vesicle membranes.     

Conformational analysis by solid-state NMR and its application to restrained structure determination from powder diffraction data

Solid-state NMR is used to dramatically improve the efficiency and reliability of molecular crystal structure determination from X-ray powder diffraction data.     

Solutions of higher dimensional Gauss–Bonnet FRW cosmology

We examine the effect on cosmological evolution of adding a Gauss–Bonnet term to the standard Einstein–Hilbert action for a (1 + 3) + d dimensional Friedman–Robertson–Walker (FRW) metric. By assuming that the additional dimensions compactify as a power law as the usual 3 spatial dimensions expand, we solve the resulting dynamical equations and find that the solution may be of either de Sitter or Kasner form depending upon whether the Gauss–Bonnet term or the Einstein term dominates.     

REDOR NMR on a hydrophobic peptide in oriented membranes

A method is presented for the calculation of REDOR dephasing for specifically labeled membrane-spanning peptides in uniformly aligned lipid bilayers under magic angle oriented sample spinning (MAOSS) conditions. Numerical simulations are performed for dephasing of (13)C signal by (15)N when the labels are placed in an alpha-helical peptide at the carbonyl of residue (i) and amide nitrogen of residue (i + 2) to show the dependency of REDOR echo intensity on the peptide tilt angle relative to the membrane normal. The approach was applied to the labeled transmembrane domain of phospholamban ([(15)N-Leu(37), (13)C-Leu(39)]PLBTM) incorporated into dimyristoylphosphatidylcholine bilayers. The dephasing observed for a random membrane dispersion showed that the peptide was alpha-helical in the region including the two labels, and dephasing in oriented membranes showed that the peptide helix was tilted by 25 degrees +/- 7 degrees relative to the bilayer normal. These results agree with those obtained by other spectroscopic methods.     

Irrational mode locking in quasiperiodic systems

A model for ac-driven systems, based on the Tang-Wiesenfeld-Bak-Coppersmith-Littlewood automaton for an elastic medium, exhibits mode-locked steps with frequencies that are irrational multiples of the drive frequency, when the pinning is spatially quasiperiodic. Detailed numerical evidence is presented for the large-system-size convergence of such a mode-locked step. The irrational mode locking is stable to small thermal noise and weak disorder. Continuous-time models with irrational mode locking and possible experimental realizations are discussed.     

Measuring functional renormalization group fixed-point functions for pinned manifolds

Exact numerical minimization of interface energies is used to test the functional renormalization group analysis for interfaces pinned by quenched disorder. The fixed-point function R(u) (the correlator of the coarse-grained disorder) is computed. In dimensions D=d+1, a linear cusp in R'(u) is confirmed for random bond (d=1, 2, 3), random field (d=0, 2, 3), and periodic (d=2, 3) disorders. The functional shocks that lead to this cusp are seen. Small, but significant, deviations from the 1-loop calculation are compared to 2-loop corrections and chaos is measured.