Contact reduction

In this article I propose a new method for reducing co-oriented contact manifold equipped with an action of a Lie group by contact transformations. With a certain regularity and integrality assumption the contact quotient at is a naturally co-oriented contact orbifold which is independent of the contact form used to represent the given contact structure. Removing the regularity and integrality assumptions and replacing them with one concerning the existence of a slice, which is satisfied for compact symmetry groups, results in a contact stratified space; i.e., a stratified space equipped with a line bundle which, when restricted to each stratum, defines a co-oriented contact structure. This extends the previous work of the author and E. Lerman.

     

Sub-ppt detection limits for copper ions with Gly-Gly-His modified electrodes

An electrochemical metal ion sensor has been developed with a detection limit of less than 0.2 ppt by the covalent attachment of the tripeptide Gly-Gly-His as a recognition element to a 3-mercaptopropionic acid modified gold electrode.     

Anisotropic disorder in high-mobility 2D heterostructures and its correlation to electron transport

Surface morphology of high-mobility heterostructures is examined and correlated with dc transport. All samples examined show evidence of lines in the [11-0] direction with roughness ranging from small-amplitude features to severe anisotropic ridges. Transport in these samples is consistent with that in samples having artificially induced 1D charge modulations. The native surface properties reflect a prevalent, anisotropic disorder affecting 2D electron conduction. Importantly, the native lines are orthogonal to the stripes theoretically proposed to explain high Landau level transport anisotropies.     

Exchange coupling mediated by N-H···Cl hydrogen bonds: experimental and theoretical study of the frustrated magnetic system in bis(o-phenylenediamine)nickel(II) chloride

The title compound crystallizes in the monoclinic P2(1)/c space group with a = 11.2470(3) ?, b = 5.9034(2) ?, c = 12.0886(3) ?, β = 115.143(1)°, and V = 726.58(4) ?(3) and consists of discrete monomeric NiCl(2)(o-phenylendiamine)(2) molecules. Each o-phen ligand coordinates in a bidentate mode with the chloride ions occupying trans positions in the resulting tetragonally distorted octahedral coordination sphere. Two discrete sets of N-H···Cl hydrogen bonds link the octahedral molecules into a two-dimensional network, with type 1 interactions linking adjacent monomers along the c axis and type 2 interactions linking monomers along the diagonals in the bc plane. Analysis of the magnetic data reveals the existence of weak antiferromagnetic coupling within the layers via these hydrogen bonds, in addition to the presence of zero field splitting, with the best fit obtained for a 1d antiferromagnetic model with g = 2.0917(7), J/k = -2.11(4) K [J = -1.47(3) cm(-1)], and D = 1.05(3) cm(-1) [β = D/|J| = 0.72(6)] for the model with D > 0 and g = 2.0911(6), J/k = -2.26(1) K [J = -1.57(1) cm(-1)], and D = -0.86(1) cm(-1) [β = D/|J| = 0.55(6)] for the model with D < 0. Theoretical calculations of the exchange coupling confirm the experimental results, yielding values of J(1) = -1.39 cm(-1) for the type 1 hydrogen bonds and J(2)/k = -0.56 cm(-1) for the type 2 hydrogen bonds.