The Set of Measures Given by Bounded Solutions of the Complex Monge-Ampere Equation on Compact Kahler Manifolds

Consider the image of the Monge–Ampère operatoracting on bounded functions, defined on a compact Kählermanifold, whose sum with the local Kähler potential isplurisubharmonic. It is shown that a nonnegative Borel measurebelongs to this image if and only if it belongs to the imagelocally. In particular, those measures form a convex set.     

The smooth cohomology ofN=2 supersymmetric Landau-Ginzburg field theories

We compute the smooth cohomology (both unrestricted and compactly supported) of the supercharge of an ultraviolet cutoffN=2 supersymmetric Landau-Ginzburg field theory.Supported in part by the National Science Foundation under grant DMS-9206936.Supported in part by the Department of Energy under grant DE-FG02-88ER25065.     

Formation and stabilization of persistent free radicals

We demonstrate that stable and relatively unreactive “environmentally persistent free radicals (PFRs)” can be readily formed in the post-flame and cool-zone regions of combustion systems and other thermal processes. These resonance-stabilized radicals, including semiquinones, phenoxyls, and cyclopentadienyls, can be formed by the thermal decomposition of molecular precursors including catechols, hydroquinones and phenols. Association with the surfaces of fine particles imparts additional stabilization to these radicals such that they can persist almost indefinitely in the environment. A mechanism of chemisorption and electron transfer from the molecular adsorbate to a redox-active transition metal or other receptor is shown through experiment, and supported by molecular orbital calculations, to result in PFR formation. Both oxygen-centered and carbon-centered PFRs are possible that can significantly affect their environmental and biological reactivity.     

Hypersonic surface waves in 2D titanium nanostructure on silicon

The non‐destructive method of Brillouin spectroscopy was applied to investigate the vibrations of 2D titanium nanoislands. Simulations realized by the Finite Element Method permitted determination of the dispersion relations of the surface waves propagating in the island structure and silicon substrate as well as the width of the frequency gap for the system studied. 3D maps of unit cell deformation for the structure with nanoislands for individual modes were obtained. The Brillouin experiment is shown as an excellent tool for direct experimental determination of the presence of eigenvibrations and the frequency gap in phononic structures in the GHz range.

     

Continuous flow hydride generation for the preconcentration and determination of arsenic and antimony by GFAAS

A method has been developed for the determination of arsenic and antimony at sub-ppb level using hydride preconcentration inside the graphite furnace. The influence of the quality of the graphite surface, of its modification with palladium coating and of the ways of introducing hydride into the furnace on the analytical signal is discussed. After optimization of system parameters, detection limits of 25 and 36 pg were obtained for arsenic and antimony. Characteristic masses (for arsenic and antimony, respectively) were 31 and 33 pg/0.0044 A·s for direct injection GFAAS and 69 and 57 pg/0.0044 A·s for hydride in situ preconcentration and atomization in the palladium coated graphite tube. Therefore the overall efficiency of the hydride generation and trapping was estimated to be 45 and 58% for arsenic and antimony, respectively.     

A route to Prelog-Djerassi lactone from methyl α,D-glucopyranoside

The enone $\text{1}$ obtained from methyl α,D-glucopyranoside is converted into the corresponding diene $\text{5}$ which is hydrogenated to give predominantly the diequatorial dimethyl hexopyranoside $\text{3}$. C6 of the latter is converted stepwise to the methyl ketone from which Prelog-Djerassi Lactone $\text{8}$ and its 2-epimer $\text{9}$ are prepared in 3:2 ration.