Anne Marie Sapse

Theory of unsymmetric polymer–polymer interfaces

Solutions have been obtained to equations which described the interface between two immiscible polymers and are more general than the equations first introduced by Helfand and Tagami. Gaussian random−walk statistics are assumed for the macromolecules. As a consequence of the present work, limitations of the earlier theory are removed, particularly the assumption that the properties of the two polymers when pure are identical. Calculations are performed for a variety of polymers and comparison with experiment is made.

A Reevaluation of Side Chain Oscillator Effects in the Polyene Superconductor Model

Abstract The values calculated for the side chain oscillator interaction energy for the polyene superconductor model have been revised. The use of parallel and perpendicular transitions gives a value for the naphthalene oscillator of 2.1 eV, well within the postulated range for a possibly operable effective interaction. The macromolecular superconductor concept proposed by Little [1] has been considered from a variety of theoretical points of view. Most of the objections [2-10] which have been suggested seem to be answerable [1, 11] in an acceptable manner. Thus, it does not seem to be essential to require one-dimensionality [4], and the unscreened model [6] gives interaction differentials much too high (above the ionization potential). Also, the thermodynamics of the situation are difficult, if not impossible, to evaluate if the transition occurs at high temperatures. The basic concept, that of electron-electron interaction, appears to present a theoretically valid alternative to the phonon-electron mode...

An ab initio study of an oxidative mechanism that forms nitric oxide from theN-hydroxyguanidinium ion

The free-radical nitric oxide is now considered to play an important role in mammalian physiology and pathology. Enzymatic studies have shown that nitric oxide biosynthesis is initiated by an NADPH-dependentN-hydroxlation ofl-arginine, formingNω-hydroxy-l-arginine as an intermediate. However, the subsequent enzymatic steps that generate nitric oxide fromNω-hydroxy-l-arginine are unknown. We have used ab initio quantum chemical calculations to investigate a mechanism that forms nitric oxide fromN-hydroxyguanidine, used as a model forNω-hydroxy-l-arginine. Our calculations indicate that mechanisms of nitric oxide formation involving nucleophilic attack by hydroperoxy anion at theN-hydroxyguanidine carbon are energetically feasible.