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dc and ac voltage effects on a mixture of cholesteric liquid crystals are studied. The wavelength of the scattering light shifts to the longer wavelength-side with the application of ac voltage at a frequency higher than 20 Hz, while it shifts to the shorter wavelength-side with the increase in dc voltage. Moreover, it is demonstrated experimentally that the modulation of the light can be observed with ac voltage at a frequency lower than 20 Hz. The modulation frequency of the light changes from f to 2f at 0.1 Hz with decreasing the applied frequency f. The phenomena such as the modulation factor and the phase lag are observed strongly dependent upon the frequency.

The technical requirements of a twelve-channel ultra-short-wave multiplex system are discussed and the means of meeting them are described. The intermodulation between channels in equipment based on this design has been reduced to the point where it is possible to use twelve-channel radio systems in the toll plant. By employing a sufficient amount of envelope feedback, the transmitter can be operated with a high modulation factor without the use of spread sidebands.

The paper investigates the diffusion equation with drift term, ∂C/∂t = div (D grad C + + μ C grad U), in particular the question of its separability in three dimensions. (D is the diffusion coefficient, μ the mobility, both assumed to be constant scalar quantities; U denotes the potential giving rise to the drift.) The transformation to a new dependent variable f = C exp (μ U/2 D) transforms the equation into a Schrodinger equation. Using this it is shown that, for appropriate choices of the potentials U, the diffusion-drift equation is separable with modulation factor in the ellipsoidal coordinates (and its degenerate special cases) but in no other coordinate systems. The conditions to which U has to be subjected in order to lead to separability are stated and shown to have a close relationship to the factorization of the solutions of the original equation. Die Arbeit befast sich mit der Frage der Separierbarkeit der Diffusionsgleichung mit Driftterm, ∂C/∂t = div (D grad C + μ C grad U), in drei Dimensionen. (D bezeichnet den Diffusionskoeffizienten, μ die Beweglichkeit, beide als konstante Skalare betrachtet; U ist das Potential, das zur Drift Anlas gibt.) Die Transformation auf eine neue abhangige Variable f = C exp (μ U/2 D) fuhrt auf eine Schrodinger-Gleichung. Mit Hilfe dieses Ergebnisses wird gezeigt, das die Diffusions-Drift-Gleichung fur geeignete Potentiale in den Koordinaten des dreiachsigen Ellipsoids (und seinen Ausartungen) mit einem Modulationsfaktor separierbar ist, jedoch nicht in anderen Koordinatensystemen. Die Bedingungen, denen U genugen mus, um die Diffusions-Drift-Gleichung separierbar zu machen, werden angegeben. Sie stehen in einem engen Zusammenhang mit der Faktorisierung der Losungen der ursprunglichen Gleichung.

It is shown, that the wall current of the striated positive column in a neon low pressure glow discharge is modulated with the frequency of the moving striations. There is a phase shift between wall currents of electrons and ions (∼π/2–3/4π), A mass-spectrometric analysis of the ion currents shows Ne+ and Ne2+ ions, both currents are modulated. The modulation factor of the electron and ion current reaches values near 100% and 50%, repectively. The behaviour of the modulated wall currents may by explained by the potential oscillations in the Langmuir sheath near the wall.

Besides the classical method of ion current modulation there are other modes applied to the BAG with modulator. In the new method (proposed by Groszkowski) the cage modulator is operated without electron current, while reasonable high modulation factor is obtained. The behavior of this gauge is presented in a wide range of pressures for both noble and active gases. The comparison of the classical method with the new one is also given. The new method allows elimination of adsorption and desorption processes from the modulator as a main disadvantage of the classical method.

When a modulated Bayard-Alpert gauge is used in the Redhead 1 mode three phenomena occur which may introduce errors into a pressure measurement: (i) the modulation factor may vary with gas and emission ; (ii) pressure changes may occur in the system ; (iii) the residual current may be modulated. Experimental results are presented on the magnitude of effects (i) and (ii). A new method of using a modulated Bayard-Alpert gauge is suggested which reduces the magnitude of the previously listed effects while maintaining the advantage of a high modulation factor.

The experimental sequence of the values of the modulation factor in a modulated Bayard-Alpert gauge for He, Ne, At, and Kr is explained on ground of the differences in shape of the corresponding ionization cross-section curves. A short discussion concerning the dependence of the modulation factor on electron current and filament-grid spacing is also given.