Spatial variation of the linewidth of Kr atomic lines as observed on optogalvanic signals in cathode fall region of hollow cathode discharge

An abrupt change in the spectral width of optogalvanic (OG) signals of Kr atomic lines has been observed at a distance from the cathode wall where the signal itself changes its sign, by using a hollow cathode lamp whose cathode has its both ends open. The width is broader near the cathode wall with its magnitude varying by discharge current while the narrower width which is obtained on passing the laser beam in the central region of cathode cylinder is independent of the current. It is suggested that a well-defined region, where the particles of larger cross section of collisions with Kr atom are confined, is present in front of the cathode wall.     

Pyrolysis of azidopyrazines

2,3-Dichloro- and 2,5-dichloropyrazines were treated with sodium azide. The former gave diazidopyrazines and the latter, monoazidomonochloropyrazines. Pyrolysis of 2,3-diazidopyrazines resulted the production of 1,2-dicyanoiminoethanes and that of 2-azido-5-chloropyrazines, chloroimidazoles.     

Electronic structures of the LaBO3 (B = Co, Fe, Al) perovskite oxides related to their catalysis

The discrete-variational (DV) X α molecular orbital method has been applied to investigate the bulk and surface electronic structures of perovskite oxides such as LaCoO₃, LaFeO₃ and LaAlO₃. The calculated XPS spectra for these oxides are in good agreement with the experimental ones and only the LaCoO₂ exhibited a rather high electron density of states near the Fermi level (E_F). The catalytic behavior of these oxides is discussed on the basis of their electronic structures; the marked catalysis by LaCoO₃ is associated with electron occupation of crystal field d states near E_F and with the buildup of surface charge so as to enhance the electron transfer between a surface cation and an interacting molecule.     

An investigation of non-newtonian flow past a sphere

Any experimental work on the flow of a polymer solution or any theoretical analysis on the basis of a visoelastic constitutive equation does not always bring out viscoelastic effects but may be showing a non-Newtonian viscosity effect. Therefore, in order to obtain a clear understanding about viscoelastic effects, it is desirable to have a sufficient knowledge of the non-Newtonian viscosity effect. To facilitate this, finite-difference numerical solutions of non-Newtonian flow were carried out using a non-Newtonian viscous model for the Reynolds numbers of 0.1, 1.0, 20 and 60.Drag force measurements and flow visualization experiments were also performed over a wide range of experimental conditions using polymer solutions. The present work appears to support the following idea: When compared with the Newtonian case on the basis of DV_∞P/η₀, where η₀ is the zero shear viscosity, it is on account of the non-Newtonian viscosity that the friction and pressure drags decrease, that the separating vortices behind the sphere become larger, and that no shift occurs in the streamlines. On the other hand, it is due to viscoelasticity that the normal force drag increases, that the separating vortices behind the sphere become smaller, and that an upstream shift occurs in the streamlines.     

Effect of the content of divinylbenzene in ion-exchange resins on the chromatographic separation of alpha-cyclodextrin and glucose

In the chromatographic separation of alpha-cyclodextrin and glucose, the parameters relating to the adsorption equilibria and rate processes of the solutes were evaluated for the sodium forms of cation-exchange resins with contents of divinylbenzene (DVB) of 2, 4, 6 and 8%. By using these parameters, the chromatograms of the solutes were then calculated. It is concluded that the resin with 6% DVB is most suitable for the chromatographic separation of the solutes on a preparative scale.     

Free coating of viscoelastic and viscoplastic fluids onto a vertical surface

A modified four-constant Oldroyd model is used to predict the film thickness in free coating. The parameters are evaluated from previous steady shear data. The flow is assumed to be one of combined steady shearing and elongation. Despite the use of an integral momentum balance approach the agreement between theory and experiment is not good. However, the results seem to indicate that a more adequate characterisation of the coating fluid might produce better agreement.     

Brillouin scattering by pure-transverse phonons in GaSe and GaS

Brillouin scattering experiments in the layer-type semiconductors GaSe and GaS by the pure-transverse phonon domains have been carried out at room temperature. Weak resonant enhancement and cancellation have been found for both materials in the region of transparency. The non-diagonal elastic constants C₁₂ have also been determined to be 3.77 × 10¹¹ dyn cm^?2 (GaSe) and 5.35 × 10¹¹ dyn cm^?2 (GaS) by measuring the sound velocities of the phonon domains.