High-performance liquid chromatography of ternary nickel dithiocarbamate complexes derived from some sympathomimetic drugs

Summary Nickel dithiocarbamate complexes derived from some sympathomimetic drugs are examined on silica Radial-Pak columns using binary solvents containing a small percentage of an organic polar modifier. Both the type and concentration of this modifier was found to influence the separation of the ternary from the parent binary complexes. When the two ligands in a ternary complex are racemic to each other, separation of the ternary complex is only possible when certain structural requirements of the molecule are fulfilled. Ternary complexes which contain structurally similar, but nonracemic ligands, are shown to be readily separated from binary complexes. When two such complexes differ only in that one of the ligands in one is enantiomeric to a ligand in the second complex, then it can be shown that the ternary complex with the (+) enantiomer ligand elutes faster from the silica column than the one with the (–) enantiomer ligand. An example of the use of ternary complexes for the identification of optical and structurally related impurities in pharmaceutical products is also given.     

Mass spectrometry in structural and stereochemical problems. Part CLIII. Electron impact-promoted fragmentation of n-alkyl cyanides

In spite of previous extensive studies on the mass spectrometry of alkyl cyanides, no good mechanistic insight has as yet been gained into the behavior of straight chain alky1 cyanides. For this reason the possible origins for the principal ions in the mass spectrum of a typical alkyl cyanide (n-hexyl cyanide) have been determined using high resolution mass spectrometry anddeuterium labeling of every carbon atom. The results lead to the conclusion that most of the typical fragmentation processes of n-alkyl cyanides proceed through cyclic intermediates.     

Thermodynamics and phase transitions in the Overhauser model

We analyze the thermodynamics of the Overhauser model and demonstrate rigorously the existence of a phase transition. This is achieved by extending techniques previously developed to treat the BCS model in the quasi-spin formulation. Additionally, we compare the thermodynamics of the quasi-spin and full-trace BCS models. The results are identical up to a temperature rescaling.     

Classical and thermodynamic limits for generalised quantum spin systems

We prove that the rescaled upper and lower symbols for arbitrary generalised quantum spin systems converge in the classical limit. For a large class of models this enables us to derive the asyptotics of quantum free energies in the classical and in the thermodynamic limit.Research supported by a European Science Exchange Fellowship of the Royal Society, London     

Selbstduffusion von gasf?rmigem CO2 im kritischen Bereich

Ohne Zusammenfassung     

Electron-impact induced hydrogen scrambling in cyclohexanol and methylcyclohexanols

Exact mass measurements and the mass spectral behavior of O-deuterated cyclohexanols, coupled with a re-evaluation of previously published data^1,2, show that the hydrogen attached to oxygen undergoes partial scrambling with the 2, 3, 5 and 6 position ring hydrogens prior to or during the formation of the major primary fragment ions.     

Stability of Bose-Einstein condensation in Fröhlich's pumped phonon system

We show that the non-equilibrium stationary state of Fröhlich's pumped phonon system is stable in the sense that it is the terminal state of the system for all initial conditions.     

Control and recovery from rare congestion events in a large multi-server system

We develop deterministic fluid approximations to describe the recovery from rare congestion events in a large multi-server system in which customer holding times have a general distribution. There are two cases, depending on whether or not we exploit the age distribution (the distribution of elapsed holding times of customers in service). If we do not exploit the age distribution, then the rare congestion event is a large number of customers present. If we do exploit the age distribution, then the rare event is an unusual age distribution, possibly accompanied by a large number of customers present. As an approximation, we represent the large multi-server system as an M/G/∞ model. We prove that, under regularity conditions, the fluid approximations are asymptotically correct as the arrival rate increases. The fluid approximations show the impact upon the recovery time of the holding-time distribution beyond its mean. The recovery time may or not be affected by the holding-time distribution having a long tail, depending on the precise definition of recovery. The fluid approximations can be used to analyze various overload control schemes, such as reducing the arrival rate or interrupting services in progress. We also establish large deviations principles to show that the two kinds of rare events have the same exponentially small order. We give numerical examples showing the effect of the holding-time distribution and the age distribution, focusing especially on the consequences of long-tail distributions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Gas chromatographic mass-specific investigation of dextromoramide (Palfium) metabolism in the horse

Dextromoramide (Palfium) was given by intravenous injection to a Thoroughbred horse at a dosage of 20 mg and urine was collected 2, 4, 6 and 8 h after drug administration. Enzymatic hydrolysis of the urine followed by solvent extraction gave a residue which was back-extracted into 0.1 M sulphuric acid. After basification to pH 9 and solvent extraction, the resulting residue was submitted to gas chromatographic-mass spectrometric analysis. Both electron-impact and ammonia chemical-ionization mass spectra were recorded and, based on the observed fragmentation patterns, the principal metabolites in horse urine were shown to be 2,2-diphenyl-3-methyl-4-morpholinobutyramide (compound 2) and the product of hydroxylation of one phenyl ring in dextromoramide (compound 3), respectively. The electron-impact mass spectra of compounds 2 and 3, and of their derivatisation products from oncolumn methylation in the gas chromatograph, are reported.