In this note, we report the discovery of a novel pyridinium chlorochroamte-catalyzed process in which an α-bromomethyl-tetrahydrofuran bond was oxidatively cleaved to give a γ-lactone functionality. The title compound was synthesized from a C15 polybrominated acetogenin compound, isolated from the marine sponge Mycale rotalis, by benzoylation followed by pyridinium chlorochromate-catalyzed oxid...

The behaviour of the (I-V) characteristics is investigated in n+-i-n+ highly compensated Si resistors at temperatures 4.2-45K. The conduction mechanisms are discussed in detail here. The prebreakdown and breakdown regions of I-V characteristics were simulated by a one-dimensional model including the evidence of impurity high compensation and freeze out effects as well as the shallow-dopants imp...

Experimental results on partial photo-ionisation cross sections of helium are analysed in the light of recent advances in the semiclassical theory of two-electron atoms. Byun et al [1] predict that the total photo-ionisation cross section below the double-ionisation threshold can, semiclassically, be described in terms of contributions associated with classical orbits starting and ending in the...

Context . Detailed numerical models of the chromosphere and corona are required to understand heating solar atmosphere. An accurate treatment is complicated by effects arising from non-local thermodynamic equilibrium (NLTE) radiative transfer. A small number strong, highly scattering lines dominate cooling in chromosphere. Additionally, recombination times ionised hydrogen longer than dynamical...

A one-dimensional (1-D) steady state drift-diffusion device model that incorporates impact ionisation has been developed for the simulation of avalanche photodiodes. The model uses finite difference analysis to solve the time independent semiconductor equations across a user specified structure. The model includes DC illumination, allowing wavelength dependent effects to be modelled. The effect...

Phenolic compounds of purple loosestrife (Lythrum salicaria L.) were analysed by the use of liquid chromatography-mass spectrometry (LC/MS) equipped with atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI). The presence of vitexin and orientin as well as their isomers, isovitexin and isoorientin, were confirmed using ion trap multiple stage LC/MS3 analysis. Several...

The characteristics of an Elekta Precise treatment machine with a gating interface were investigated. Three detectors were used: a Farmer ionisation chamber; a MatriXX ionisation chamber array and an in-house, single pulse-measurement ionisation chamber (IVC). Measurements were made of dosimetric accuracy, flatness and symmetry characteristics and duty cycle for a range of beam-on times and gat...

A generic method to screen for new or unexpected contaminants at ppm levels in food has been developed. The method comprises an acidic acetonitrile extraction, detection with ultra-high-pressure liquid chromatography coupled to electrospray ionisation time-of-flight mass spectrometry and statistical evaluation using a metabolomics approach comparing suspected contaminated food with uncontaminat...

Electroluminescence is observed during porous etching of n-type GaP single crystals at strongly positive potential. The emission spectra, which include a supra-bandgap contribution, are markedly different from the spectra observed under optical excitation or minority carrier injection. The current density and electroluminescence intensity show a strong potential dependence and a similar hystere...

We calculate the ionisation fraction in protostellar disk models using a number of different chemical reaction networks, including gas–phase and gas–grain reaction schemes. The disk models we consider are conventional α–disks, which include viscous heating and radiative cooling. The primary source of ionisation is assumed to be X–ray irradiation from the central star. For most calculations we a...