Boundary layer growth on a magnetised circular cylinder

Résumé Dans le problème considéré, un cylindre parfaitement conducteur et magnetisé est mis en mouvement par impulsion dans un fluide visqueux incompressible et non-conducteur. On suppose de même qu'il y a un champ uniforme et magnétique imposé sur tout le champ d'écoulement. On demontre que la force du champ uniforme et magnétique et l'amplitude du champ normal initial à la surface solide jouent un rôle important dans la croissance de la couche limite sur le cylindre.     

Bulk and surface core level binding energies in the Pt80Fe20(111) alloy

Core level photoemission spectroscopy of the Pt 4f_7/2 level is used to investigate the surface and bulk Pt environments in the ordered catalytic alloy Pt₈₀Fe₂₀. The results obtained support a LEED model of Pt segregation to the surface. This implies the presence of two Pt surface sites.     

Thermodynamic study of a liquid crystal as a liquid phase in gas-liquid chromatography. II. A cholesteric liquid crystal.

Gas-liquid chromatography is utilized for the determination of thermodynamic solution parameters for various organic solutes at infinite dilution in the meso- and isotropic phases of cholesteryl palmitate. The thermodynamic data and trends in values of the activity coefficients for the solutes are discussed in relation to their structure and to the orientations of the liquid crystal.     

The preparation and reactions of 1-lithio-alkylamino-1-lithio-oxy-allene derivatives

The reaction of secondary α-keto-amide 2,4,6-tri-iso-propylbenzenesulphonylhydrazones with n-butyl-lithium generated, via a modified Shapiro reaction, the title carbanions (RCH=CC(O^-)N?R¹]. These reacted at carbon with deuterium oxide, aldehydes, and ketones and are therefore most useful for the introduction of acrylate functionality.     

The two-pion-exchange three-nucleon potential and nuclear matter

We derive the complete three-nucleon potential of the two-pion-exchange type, suitable for nuclear structure calculations, by extending away from the forward direction the subthreshold off-pion-mass-shell πN scattering amplitude of Coon, Scadron and Barrett. The off-mass-shell extrapolation, subject to current algebra and PCAC constraints, yields approximately model independent amplitudes (in that they depend primarily on πN data) in the complete potential. The subtraction of the forward propagating nucleon term from the amplitudes is done in greater generality than before. The contribution of this three-nucleon potential to the binding energy of symmetric nuclear matter is estimated using the perturbative formalism of McKellar and Rajaraman. In our treatment of correlations in nuclear matter, the dominant three-nucleon potential has strong components from both s-wave and p-wave πN scattering. A three-body potential based on the p-wave Δ isobar can be considered a special case of the derived potential. Therefore, we are able to trace most of the discrepancies in previously reported binding energy contributions back to the assumed energy denominator in second order. We find the contribution of the three nucleon potential to the energy of symmetric nuclear matter to be ? 1.90 ± 0.2 MeV.     

Quantitative determination of alkylated quaternary amines and their n-hydroxylated metabolites in an enzyme incubation matrix by liquid chromatography electrospray ionization mass spectrometry

A simple, rapid and sensitive reversed-phase liquid chromatography method coupled to electrospray ionization mass spectrometry has been developed for studying the in vitro metabolism of the long-chain quaternary ammonium compounds dodecyltrimethylamine, tetradecyltrimethylamine and hexadecyltrimethylamine. Samples were prepared from the biological matrix by a simple protein precipitation stage. The separation was performed using a BDS Hypersil C8 3 microm particle size (100 x 3 mm i.d.) column with a fast gradient separation (60% B to 100% B) using a mobile phase of 10 mm aqueous ammonium acetate (pH 4.0, with 0.06% triethylamine; (A)-acetonitrile (B) at 0.7 mL min(-1). To minimize contamination of the MS source a switching value was used to divert the solvent front to waste. Decylammonium bromide was used as the internal standard and analytes were identified and quantified by positive ion electrospray selected ion monitoring of their intact molecular cations. The assay had a limit of quantitation of 0.25 microm (6.25 pmol on column) and was linear over the range 0.25--100 microm assay concentration for this series of long-chain quaternary amines. The precision of intra- and inter-day assays was better than 19% and the accuracy was between 93 and 109%. The method was used to assess the in vitro metabolism of the quaternary amines by wild-type cytochrome P450 enzyme CYP 4 A 1 and mutants in an artifical membrane system.     

Practical synthesis and guest-guest communication in multi-hemicarceplexes

Single molecule hosts carrying three separately encapsulated guests are prepared in a seven step sequence in high overall yields.