D-bar Operators on Quantum Domains

We study the index problem for the d-bar operators subject to Atiyah- Patodi-Singer boundary conditions on noncommutative disk and annulus.     

Numerical modelling of Tb<Superscript>3+</Superscript> doped selenide-chalcogenide multimode fibre based spontaneous emission sources

A model is developed of a terbium (III) ion doped selenide chalcogenide glass fibre source that provides spontaneous emission within the mid-infrared (MIR) wavelength range. Three numerical algorithms are used to calculate the solution and compare their properties.     

Influence of cellulose polymorphs on the polypropylene crystallization

Results of the hitherto research work on alkalisation of lignocellulosic materials have been much divergent. In view of the above, the subject of this study is mercerization of cellulose from pine wood. This choice of the subject permitted observation of transformation of cellulose I to cellulose II with no participation of other components of lignocellulosic materials. According to X-ray results, during mercerization the isolated cellulose was easily (completely) transformed into cellulose II variety, while the pine wood was converted more slowly to cellulose II polymorphs. Therefore, it could be concluded that the presence of lignin and hemicelluloses in wood prevented the transformation from cellulose I to II. The main objective of this research was to establish the effect of cellulose varieties on the nucleation ability of different fillers by using differential scanning calorimetry (DSC) and polarizing microscopy. The nucleating effect of the fillers occurs only in the presence of cellulose I variety. In contrast, the presence of cellulose II variety seems to practically eliminate the nucleating effect of the fillers. Moreover, nucleation of the mercerized wood (mixture of cellulose I and II) can be also observed, but this effect is not strong. It should be emphasised that as yet no correlation has been reported between the quantitative composition of cellulose polymorphic forms (appearing not only in wood, but in cellulose isolated from wood as well) and the nucleation ability of lignocellulosic fillers.     

An efficient and convenient synthesis of unsymmetrical disulfides from thioacetates

We have developed convenient methods for the synthesis of functionalized unsymmetrical dialkyl disulfides under mild conditions in very good yields. The designed method is based on the reaction of (5,5-dimethyl-2-thioxo-1,3,2-dioxaphosphorinan-2-yl)-disulfanyl derivatives 1 with functionalized alkyl thiolate anions, generated in situ from thioacetates 2 and sodium methoxide or butylamine. The developed method allows the preparation of unsymmetrical disulfides bearing additional hydroxy, carboxy, amino, azido, biotin, or maleimide functionalities.     

Detection and quantitation of a pheomelanin component in melanin pigments using pyrolysis–gas chromatography/tandem mass spectrometry system with multiple reaction monitoring mode

Here, we describe the reliable method for the detection and quantitation of a pheomelanin component in melanin pigments. Synthetic melanins with various contents of pheomelanin‐type structural units were thermally degraded, and the multiple reaction monitoring mode was applied to detect the pheomelanin markers in the pyrolysates by GC/MS/MS. The method allowed the specific detection and quantitation of a pheomelanin component in melanin with the incorporation of pheomelanin‐type units as low as 0.05%. Considering highly universal character of the pheomelanin markers, the method could be applied for structural studies of natural melanin pigments being mixtures of eumelanin and pheomelanin. Copyright © 2012 John Wiley & Sons, Ltd.     

Electrochemical wiring of alpha, omega-alkanedithiol molecules into an electrical circuit

The intrinsic electrical conductivity of alpha, omega-alkanedithiol increases if both ends of the molecule are covalently bonded to metallic contacts.     

Synthesis of the Trans and Cis Higher Sugar Allylic Alcohols—Direct Precursors of Dodecoses

Abstract

Reaction of 6,7-dideoxy-l,2:3,4-di-O-isopropylidene-α-D-galacto-hept-6-ynopyranose (3) with 3-O-benzyl-l,2-O-sopropylidene-α-D-xylo-pentodiulose (4) afforded two diastereo-isomeric propargylic alcohols: 5a (n-glycero, R) and 5b (L-glycero, S) in 70% yield and in the 33:67 ratio. Hydrogenalion of 5a and 5b over Pd/BaSO₄ gave cis-allylic alcohols 6a and 6b. Semireduction of the triple bond in 3 with tri-n-butyltin hydride afforded trans-olefin 7 which reacted with 4 yielding two diastereoisomeric trans-allylic alcohols: 8a (D-glycero, R) and 8b (L-glycero, S) in a 74% yield and a 72:28 ratio.