p-Benzoquinone-2,3-dicarboxylic anhydride as highly reactive and versatile electron-accepting dienophile

Pericyclic reactions of p-benzoquinone-2,3-dicarboxylic anhydride(PBA) with homo-dienne and conjugated medium-ring polyenes have been examined. The high peri- and stereospecificity observed with dienes is explained using the frontier orbital model where the diene HOMO-PBA LUMO interaction predominates.     

Complex formation of univalent cations in acetonitrile with other solvents. Study of potassium ion complex formation with a cation-sensitive glass electrode

The formation constants of the complexes formed between potassium ion and other solvents in acetonitrile have been obtained potentiometrically by using a univalent cation-sensitive glass electrode. The formation constants of the mono-complexed potassium ions were 1.5 with dimethylformamide, 2.0 with dimethylacetamide, 2.4 with N-methylpyrrolidone, 2.8 with N-methylformamide, 2.9 with dimethyl sulfoxide, and 6.9 with hexamethylphosphoramide. Within the concentration ranges of the solvents studied (0.35–0.7 M for different solvents), only up to 1:2 K⁺: solvent species were detected, in contrast to the results for other univalent cations. Rubidium ion could not be studied effectively because of unsatisfactory response of the glass electrode. The complex formation constants of various univalent cations in acetonitrile with other solvents are summarized and discussed in detail.     

A dynamic model of the purchase of gasoline

Government regulators and gasoline retailers can manipulate certain inputs to the gasoline purchase process: station hours, inventory allocations, odd-even plans, etc. If one could model the purchasing dynamics, these inputs could be timed and otherwise planned to minimize inconvenience to the consumer. In this paper, we recognize that the refilling of gasoline tanks is a renewal process. The simplest model, is then, a first-order partial differential equation of continuity plus an integral boundary condition. Many properties of this model are derived here including an important mathematical link with the theory of queues (yielding estimates of daily average line lengths, for instance). The paper concludes with several simulations which demonstrate the significance of the dynamic effects (over-shoot, resonance) and the important effect of the retailers management rules on the length of gas lines.     

Magnetohydrodynamic flow in a rectangular channel at high Hartmann number

Résumé Dans cette communication, nous considérons le flux permanent d'un fluide visqueux et conducteur le long d'un canal, en présence d'un champ magnétique qui est uniforme et transverse. Le canal est rectangulaire et a des parois non-conductrices. Les formules asymptotiques, applicables aux valeurs élevées du nombre de Hartmann, sont obtenues pour la vitesse et le champ magnétique. Elles coïncident avec les résultats deSherciff, qui a fait usage de la théorie de la couche limite. La vitesse moyenne et le frottement de peau sont trouvés.     

Die Entflammbarkeit von mit Indigo-Farbstoffen gef?rbten Baumwoll-Geweben

Ohne Zusammenfassung     

Influence of chemical impurities on the performance of a flashlamp-pumped dye laser

The presence of ? 5% chemical impurities in Rhodamine 6G [Cl-] is shown to decrease the fluorescence quantum efficiency, increase the self-absorption cross-section, reduce lasing efficiency and shorten the usable lifetime of the lasing solution.     

Optical activity in chiral olefins : UV and CD spectra of some triterpenoid hydrocarbons

The UV and CD spectra of several related mono unsaturated steroidal and triterpenoid hydrocarbons have been measured. The electronic assignments are discussed and it is found that the Scott-Wrixon Rules can be successful in correlating the sign of the circular dichroism with molecular structure.