Experimental study of electron density distribution in crystals of antimony(V) dicarboxylate complexes

Structural Chemistry - The molecular structure and charge density distribution in the crystals of triphenylantimony bis[(2E)-3-phenylprop-2-enoate] [Ph3Sb(O2CCH=CHPh)2] and triphenylantimony...     

Dispersion Estimates for Spherical Schrödinger Equations

We derive a dispersion estimate for one-dimensional perturbed radial Schrödinger operators. We also derive several new estimates for solutions of the underlying differential equation and investigate the behavior of the Jost function near the edge of the continuous spectrum.     

The effect of temperature on the viscoelastic behavior of linear low-density polyethylene

Summary Observations are reported on linear low-density polyethylene in isothermal torsional oscillation and relaxation tests at various temperatures ranging from room temperature to 110 C. Constitutive equations are derived for the viscoelastic response of a semicrystalline polymer at small strains. The polymer is treated as an equivalent network of strands bridged by junctions (entanglements, physical cross-links on the surfaces of crystallites and lamellar blocks). The network is thought of as an ensemble of meso-regions with various potential energies for rearrangement of strands. Two types of meso-domains are introduced: active, where strands separate from temporary junctions as they are excited by thermal fluctuations, and passive, where detachment of strands is prevented by the surrounding macromolecules. The time-dependent behavior of the ensemble reflects separation of active strands from their junctions and merging of dangling strands with the network. Stress–strain relations are developed by using the laws of thermodynamics. The governing equations involve six material constants that are found by fitting the experimental data. The study focuses on the effects of (i) temperature, (ii) the deformation mode (torsion versus bending), and (iii) the loading program (oscillations versus relaxation) on the adjustable parameters.This work was partially supported by the West Virginia Research Challenge Grant Program     

Mirror symmetry for closed,open, and unoriented Gromov–Witten invariants

In the first part of this paper, we obtain mirror formulas for twisted genus 0 two-point Gromov–Witten (GW) invariants of projective spaces and for the genus 0 two-point GW-invariants of Fano and Calabi–Yau complete intersections. This extends previous results for projective hypersurfaces, following the same approach, but we also completely describe the structure coefficients in both cases and obtain relations between these coefficients that are vital to the applications to mirror symmetry in the rest of this paper. In the second and third parts of this paper, we confirm Walcher's mirror symmetry conjectures for the annulus and Klein bottle GW-invariants of Calabi–Yau complete intersection threefolds; these applications are the main results of this paper. In a separate paper, the genus 0 two-point formulas are used to obtain mirror formulas for the genus 1 GW-invariants of all Calabi–Yau complete intersections.     

Temperature effects in carbon monoxide and methanol electrooxidation on platinum–ruthenium: influence of grain boundaries

The temperature dependence of methanol and CO monolayer oxidation is studied on carbon-supported PtRu (1:1 atomic ratio) electrodes with different metal percentages (5, 30, and 60 wt.%) in an aqueous H₂SO₄ electrolyte. High-resolution transmission microscopy confirms that at high (30 or 60 wt.%) metal percentage PtRu nanostructures with a high concentration of intercrystalline boundaries are formed. These nanostructures comprise multiple-twinned particles, particles with intersecting randomly oriented intergrain boundaries, or particles with parallel intergrain boundaries. Formation of such nanostructures leads to a decrease of the apparent activation energy of the methanol and CO monolayer oxidation, while the Tafel slope and the reaction order in methanol show minor dependence on the type of nanostructure. Materials with a high concentration of grain boundary regions may be of interest for practical applications in direct methanol or proton exchange fuel cells fed with reformate.     

The effect of substrate material on the properties of tantalum oxide films

The effect of substrate material on the electrical characteristics of Ta _x O _y films produced by high-frequency magnetron sputtering of a tantalum oxide target is studied. The effect of oxygen plasma on leakage currents, dielectric permittivity, and dielectric dissipation factor of thin (300–400 nm) Ta _x O _y layers is found. It is proposed to process tantalum oxide films in oxygen plasma to control their electrical and dielectric properties.     

Orbifold equivalence and the sign problem at finite baryon density

We point out that SO(2N(c)) gauge theory with N(f) fundamental Dirac fermions does not have a sign problem at finite baryon number chemical potential μ(B). One can thus use lattice Monte Carlo simulations to study this theory at finite density. The absence of a sign problem in the SO(2N(c)) theory is particularly interesting because a wide class of observables in the SO(2N(c)) theory coincide with observables in QCD in the large N(c) limit, as we show using the technique of large N(c) orbifold equivalence. We argue that the orbifold equivalence between the two theories continues to hold at finite μ(B) provided one adds appropriate deformation terms to the SO(2N(c)) theory. This opens up the prospect of learning about QCD at finite μ(B) using lattice studies of the SO(2N(c)) theory.