The vorticity jump across a stationary magnetogasdynamic discontinuity

Résumé La condition du saut de vorticité est obtenue à travers une discontinuité magnéto-dynamique dans un gaz. On montre que la conclusion de Hayes pour la dérivation du saut de vorticité à travers une discontinuité dynamique dans un gaz n'est pas valable à travers une discontinuité magnéto-dynamique dans un gaz. On montre aussi que les résultats obtenus ne sont pas limités aux ondes de choc, mais valent également pour les ondes de la détonation et de la condensation. Les résultats concernant quelques cas particuliers intéressants ont aussi été déduits et discutés.     

Refractive Indexes of Binary Mixtures of Tetrahydrofuran with 1-Alkanols at 25°C and Temperature Dependence of n and ρ for the Pure Liquids

Refractive indexes at 25°C were measured for binary mixtures of tetrahydrofuran with 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol. Densities, from which excess molar volumes were derived, were measured at the same temperature for the system tetrahydrofuran + 1-decanol. Refractive indexes and densities for the pure compounds were determined at 11 temperatures between 20 and 30°C. The thermal expansion coefficients and the temperature derivatives of the refractive index for these liquids were calculated at 25°C. The temperature dependence of the molar refraction was also examined. The contribution to the molar refraction of a CH₂ group was calculated as was the difference between contributions from CH₃ and CH₂OH groups. The change of molar refraction on mixing is d iscussed in terms of molecular interactions and alkyl chain length.     

Generalized Bethe-Faddeev wave functions

Bethe-Faddeev wave functions are generalized toN-body clusters. A comparison made between the Bethe approximation and the Day approximation in the three body cluster indicates that the two approximations should be competitive for the higher body clusters.     

Anisotropic propagation of weak discontinuities in flows of thermally conducting and dissociating gases

The object of the present investigation is to study the anisotropic propagation of weak discontinuities in flows of thermally conducting and dissociating gases. The velocity of propagation of the wave frcnt is determined. A set of differential equations governing the growth and decay of weak discontinuities are obtained and solved. It is found that if the sonic wave is a compressive wave of order 1, then it terminates into a shock wave after a critical timet _c which has been determined. It is also observed that the effects of heat conduction and dissociation are to decrease the duration of time by which a weak discontinuity will generate into a shock wave.     

Near infrared and visible tunability from a diode pumped Nd3+ activated strontium barium niobate laser crystal

Tunable laser action from a diode pumped Nd³⁺ activated Sr_xBa_1-x(NbO₃)₂ crystal has been obtained. A wide continuous tuning range of 43 nm in the near infrared region (1050–1093 nm) has been demonstrated due to the broad ⁴F_3/2→⁴I_11/2 emission band present in this system. Simultaneously, 20 nm of tunability in the green region (525–545 nm), as well as 7 nm in the blue one (455–462 nm) have been achieved by tunable self-frequency conversion processes using the quasiphase matching technique, without any angle or thermal tuning of the laser crystal. The results evidence that the system is a reliable candidate for compact tunable coherent devices based on diode pumped Nd³⁺ active ions, which are of interest in many technological and scientific applications. PACS 77.84.Dy; 42.79.Nv; 42.60.Fc; 42.55. Xi     

Non-hazardous synthesis of isocephosphorin intermediates via α-vinylamino-β-lactams

The reaction of a Schiff Base derived from veratrylamine and cinnamaldehyde with (α-methyl-β-alkoxycarbonyl)-vinylamino acetic acid (from glycine and an acetoacetate ester) in presence of a chloroformate ester and triethylamine constitutes a safe synthesis of α-vinylamino β-lactams that can be converted by literature methods to known intermediates for the synthesis of isocephalosporins and analogs.