Biologically Inspired Cognitive Architectures (BICA) for Young Scientists

Abstract

A density functional theory is presented for the distribution of chargedhard spheres (model for salt) around an infinite, rigid, and impenetrablecharged cylinder (model for DNA or tobacco mosaic virus). The theoryis based on a weighted density approach where the hard-sphere contributionto the one-particle correlation function is evaluated nonperturbativelyusing a position dependent effective density, and the ionic partis obtained through a second-order functional Taylor expansion arounda uniform fluid. The theory is in good agreement with Monte Carlosimulations for the density distribution of monovalent, divalent,and mixed salts. For axial charge densities corresponding to DNA,the hypernetted chain integral equation theory is not as accurateas the density functional theory, but both liquid state approachesare superior to the Poisson-Boltzmann theory. For higher axial chargedensities the density functional theory predicts interesting chargeinversion effects that are absent in the nonlinear Poisson-Boltzmanntheory.