Evolution of the gas-puff Z-pinch column

The evolution of a neon implosion of low energy discharge (4 kJ, 40 kV, 150 kA, 1.1 μs) was studied using X-ray, schlieren, and high speed electrooptical visible gated quadro camera diagnostics. The geometry, an helical structure of pinched column, two steps of pinching, and X-ray emission have been studied. The hypothesis of an axial component of magnetic field generation, the helical shape of the magnetic and electric field lines, and the release of magnetic energy during the second pinching of the column are discussed     

New method for resolving the enantiomeric composition of 2-methyltetrols in atmospheric organic aerosols

In order to facilitate the determination of the primary and secondary origin of atmospheric organic aerosols, a novel method involving chiral capillary gas chromatography coupled with mass spectrometry has been developed and validated. The method was focused on the analysis of 2-methylerythritol and 2-methylthreitol, considered to be tracers of secondary organic aerosols from the oxidation of atmospheric isoprene. The method was validated by performing various tests using authentic standards, including pure enantiomeric standards. The result showed that the analytical method itself does not affect the enantiomeric composition of the samples analyzed. The method was applied on atmospheric aerosols from a boreal forest collected in Aspvreten, Sweden and on laboratory samples obtained from liquid phase oxidation of isoprene and smog chamber experiments. Aerosol samples contained one enantiomer of 2-methylerythritol in significantly larger quantities than the others. In contrast, the liquid-phase oxidation of isoprene and its gas-phase oxidation in the smog chamber produced all enantiomers in equal quantities. The results obtained where the enantiomer fraction, EF, is larger than 0.50 suggest that 2-methyltetrols in atmospheric aerosols may also have biological origin. Information about the differences between enantiomer fractions obtained using this method brings new insights in the area of atmospheric aerosols.     

Non-local temperature-dependent phase-field models for non-isothermal phase transitions

We propose a model for non-isothermal phase transitions withnon-con-served order parameter driven by a spatially non-localfree energy with respect to both the temperature and the orderparameter. The resulting system of equations is shown to bethermodynamically consistent and to admit a strong solution.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

Identification of the laminar-turbulent transition process in a plasma plume

This paper illustrates the complete dynamics of the laminar-turbulent transition process in a plasma plume using a simple measurement of the magnation-point heat flux correlated with acoustic, optical, and voltage drop fluctuations. In the laminar flow regime a steady jet is produced and the heat fluxes are accurately predicted hr laminar correlations. The initial stage of transition is characterized by the formation of axisymmetric structures and velocity fluctuations which increase the heat flux over laminar correlations. This is followed by a rapid decrease in heat flux as the vortex structures become more intense and rapidly entrain external air into the plume. The plume oscillations (acoustical and voltage drop) become most intense and are identical in frequency at the point of minimum heat flux. The transition is complete which the transition to small-scale turbulence in the exiting boundary layer which results in dec reased entrainment and increased heat flux.