Weak-anchoring effects on a Freedericksz transition in an annulus

This paper investigates the effect of weak anchoring on static orientation patterns in a sample of nematic liquid crystal confined to a cylindrical annular geometry, in the presence of a magnetic field. The particular arrangement considered in detail is that in which a magnetic field is applied in the azimuthal direction to a sample of liquid crystal that is initially uniformly aligned parallel to the cylindrical axis and is weakly anchored at the inner cylinder, but strongly anchored at the outer cylinder. A static solution of the non-linear continuum equations is presented which suggests a possible experiment for evaluating the surface elastic coefficient k₂₄. In addition, a linear stability analysis based on the dynamic theory yields results for critical phenomena in agreement with those derived from the non-linear solution.     

Towards a total synthesis of the manadomanzamine alkaloids: the first asymmetric construction of the pentacyclic indole core

We report a highly diastereoselective approach for the synthesis of the pentacyclic indole core of the manadomanzamine alkaloid skeleton, with complete control over the relative and absolute stereochemistries at the three contiguous stereocentres at ring positions 1, 10, and 24, from a readily available chiral template.     

Optimisation of solvent desorption conditions for chemical warfare agent and simulant compounds from Porapak Q using experimental design. I. Methyl salicylate and di(propylene glycol) monomethyl ether

Factorial design (FD) was applied in order to develop an optimised method for the detection of chemical warfare (CW) agent simulant compounds on Porapak Q. Application of FD allowed study of the adsorption/desorption mechanism of analytes. Di(propylene glycol) monomethyl ether (DPM) and methyl salicylate (MS) were selected for study as both compounds are employed in agent simulation trials but are currently analysed by different methods. An analytical method for simultaneous determination of both compounds was developed using solvent desorption. The optimised method identified non-polar interactions as the primary adsorption/desorption mechanism. Steel tubes were shown to be more suited for sampling of simulants, due to lower variability in recovery compared to glass tubes. Atmospheric detection limits for both simulants were estimated to be 0.2 mg m(-3) allowing the trace analysis of these compounds by gas chromatography with flame ionisation detection (GC-FID).     

Amide–quinoxaline copolymers

A series of new amide–quinoxaline ordered copolymers derived from phthaloyl, isophthaloyl, and terephthaloyl chlorides have been synthesized and characterized. The isophthaloyl and terephthaloyl polymers had decomposition temperatures between 445–495°C and were soluble in a variety of solvents. These high molecular weight polymers were prepared by reacting aromatic bis-o-diamines with bis(benzilyl)amides. Phthaloyl chloride yielded low molecular weight polymers due to competing side reactions.     

Synthesis, structure, and reactivity of unexpectedly stable spiroepoxy-beta-lactones obtained by epoxidation of 4-alkylidene-2-oxetanones

We describe the first synthesis of spiroepoxy-beta-lactones obtained via epoxidation of ketene dimers. These compounds display unexpected stability that may be due to a double anomeric effect garnered from analysis of bond lengths by X-ray crystallography of one spirocycle in comparison to calculated bond lengths of related structures. These new strained intermediates display interesting reactivity leading to a butenolide, an alpha-hydroxyketone, a triol, an alpha-chloroketone, and an alpha-azidoketone.     

Modular synthesis of isoxazolopyridones and pyrazolopyridones

Herein we described the preparation of two novel heterocyclic nuclei isoxazolopyridone and pyrazolopyridone. The syntheses are modular in nature and fast to execute. The title compounds were obtained pure without intervention of chromatography.     

Interlaboratory Evaluation of Ultraviolet Radiation Emissions from Compact Fluorescent Lamps

There have been many recent reports regarding the potential risks of UV emissions from compact fluorescent lamps (CFLs). In some of these reports, the robustness of the measurements was difficult to discern. We conducted round‐robin measurements, involving three lamp manufacturers and two government research laboratories to gather reliable data on the UV emissions from commercially available CFLs. The initial sample of lamps consisted of 71 spiral‐shaped CFLs purchased from local retailers. From the initial sample, 14 “high UV emitting” CFLs were chosen for further evaluation. We compared the UV emissions at a distance of 20 cm with the UV exposure limits (ELs) published by the International Commission on Non‐ionizing Radiation Protection (ICNIRP). We found that the allowable exposure time for measured lamps ranged from 21 to 415 h. This indicates that the emissions would not exceed the short‐term ELs that have been established by the ICNIRP for healthy individuals. We also evaluated the potential long‐term risk and found it to be insignificant. There was a large variation in the UV emissions found, even for lamps from a single package, indicating that it is impossible to predict the UV output of a CFL based on its physical appearance and model designation.     

Modular syntheses of isoxazoloazepinones and pyrazoloazepinones

Herein we described an optimised synthesis of isoxazoloazepinone and novel heterocycle pyrazoloazepinone. These syntheses are modular in nature and fast to execute. The title compounds were obtained pure without the intervention of chromatography.     

Confirmatory analysis of malachite green, leucomalachite green, crystal violet and leucocrystal violet in salmon by liquid chromatography-tandem mass spectrometry

A method has been developed to analyse for malachite green (MG), leucomalachite green (LMG), crystal violet (CV) and leucocrystal violet (LCV) residues in salmon. Salmon samples were extracted with acetonitrile:McIIIvain pH 3 buffer (90:10 v/v), sample extracts were purified on a Bakerbond strong cation exchange solid phase extraction cartridge. Aliquots of the extracts were analysed by LC-MS/MS. The method was validated in salmon, according to the criteria defined in Commission Decision 2002/657/EC. The decision limit (CCalpha) was 0.17, 0.15, 0.35 and 0.17 microg kg(-1), respectively, for MG, LMG, CV and LCV and for the detection capability (CCbeta) values of 0.30, 0.35, 0.80 and 0.32 microg kg(-1), respectively, were obtained. Fortifying salmon samples (n=6) in three separate assays, show the accuracy to be between 77 and 113% for MG, LMG, LCV and CV. The precision of the method, expressed as RSD values for the within-laboratory reproducibility, for MG, LMG and LCV at the three levels of fortification (1, 1.5 and 2.0 microg kg(-1)), was less than 13%. For CV a more variable precision was obtained, with RSD values ranging between 20 and 25%.