Statistical mechanics of Arakawa’s discretizations

The results of statistical analysis of simulation data obtained from long time integrations of geophysical fluid models greatly depend on the conservation properties of the numerical discretization used. This is illustrated for quasi-geostrophic flow with topographic forcing, for which a well established statistical mechanics exists. Statistical mechanical theories are constructed for the discrete dynamical systems arising from three discretizations due to Arakawa [Arakawa, Computational design for long-term numerical integration of the equations of fluid motion: two-dimensional incompressible flow. Part I. J. Comput. Phys. 1 (1966) 119–143] which conserve energy, enstrophy or both. Numerical experiments with conservative and projected time integrators show that the statistical theories accurately explain the differences observed in statistics derived from the discretizations.     

Electrochemical nucleation of gold nanoparticles in a polymer film at a liquid-liquid interface

Simultaneous nucleation of gold nanoparticles and polymerization of tyramine has been carried out at an immiscible electrolyte interface. By transferring the gold ion of tetraoctylammoniumtetracloroaurate (TOAAuCl(4)) from the organic to the aqueous phase, a fast homogeneous electron transfer from the tyramine monomer reduces the gold ion. Electropolymerization then proceeds, and gold nanoparticles form. The newly formed nanoparticles act as nucleation sites for the deposition of the oligomers/polymer (and possibly vice versa). This results in gold nanoparticles stabilized in a polytyramine matrix. The size of the nanoparticles is controlled by the concentration of oligomers/polymer in solution. The polymer nanoparticle composite film was analyzed with TEM, XPS, and AFM.     

Target identification for a promising anti-lupus drug

Target identification is one of the more difficult aspects of modern chemical genetics. In this issue of Chemistry & Biology, Johnson et al. provide a compelling case for going through the trouble. As a byproduct of their identification of the cellular target of an anti-lupus compound, they have uncovered a powerful tool for the characterization of a fascinating molecular machine, the F1F0-ATP synthase.     

Remarkably improved complexation of a bisparaquat by formation of a pseudocryptand-based [3]pseudorotaxane

Significant improvement of complexation of a bisparaquat guest was achieved by the formation of a pseudocryptand-based [3]pseudorotaxane.     

Fluorescence studies of the intra-cellular distribution of zinc bis(thiosemicarbazone) complexes in human cancer cells

The uptake of zinc bis(thiosemicarbazone) complexes in human cancer cells has been studied by fluorescence microscopy and the cellular distribution established, including the degree of uptake in the nucleus.     

Photochromism of a spirooxazine in the single crystalline phase

The single crystals of a closed form spirooxazine spiro[azahomoadamantane-isoquinolinoxazine] were found for the first time to undergo photocoloration processes consistent with photochromism in the single crystalline phase.