Abstracts of Recent Scientific Publications by the Staff of N.v. Philips' Gloeilampenfabrieken

S OF RECENT SCIENTIFIC PUBLICATIONS BY THE STAFF OF N.V. PHILIPS' GLOEILAMPENFABRIEKEN Reprints of most of these publications may be obtained from the ,Philips Research Laboratories, Kastanjelaan 24, Eindhoven, Netherlands. For items marked with an asterisk no reprints are available. 2441: B. D. H. Tellegen: La recherche pour une série complète d'éléments de circuit idéaux non-linéaires (Rendiconti del seminario matematico e fisico di Milano 25, 134-144, 1953/54.) , The five ordinary circuit elements (resistance, inductance, capacitance, transformer, gyrator) can be considered, by definition, to represent the simplest linear constant passive systems. From a physical point of view, linear constant active systems, linear variable systems, and non-linear systems all belong to the class of non-linear constant passive systems. The search for the simplest non-linear constant passive systems leads to ideal non-linear network elements. For order zero these are the ideal rectifier, the elements called voltage sink and current sink, and four ideal amplifiers. 2442: H. G. van Bueren: Dislocaties in niet-metalen (Ned. T. Natuurk. 22, 394-402, 1956). (Dislocations in non-metals; in Dutch.) Dislocations have much more influence on the physical properties of alkali-halides and semiconducting elements than on those of metals. They can act as sources of vacancies, and therefore of colour centres, in ionic crystals, which explains the enhanced colouring by X-ray irradiation of previously cold-worked crystals, and the equally enhanced conductivity. 2443: J. Bloem, A. J. van der Houven van Oordt and F. A. Kröger: A new luminescence emission in CU20 (Physica 22, 1254-1256, 1956). CUBOis known to show luininescence in the infra red near 1 IL. In the present investigation it is shown that at 20 "K this emission consists of two sub-bands at 0·91 and 1·01 IL. Samples prepared at 960°C under oxygen pressures of 10-1 to 10-3 mm Hg show in addition two luminescence peaks at shorter wavelengths, viz. 0·72 IL and 0·82 IL. The former bands are attributed to copper vacancies, the latter to oxygen vacancies. 2444: J. A. Kok and M. M. G. Corbey: Breakdown of liquid insulating and dielectric material (Appl. sci. Res. B6, 197-206, 1956). . . One of the possible causes of long-time breakdown of low-frequency impregnated paper capacitors and cables is known to be the long-time formation of a conducting bridge between the electrodes, followed by a short-time thermal breakdown. Such a bridge may consist of polarizable particles, ions or colloidal contaminants of high dielectric constant, particularly conducting material. These particles flow towards a place of maximum stress because of the action of transverse quadratic gradient forces in a non-uniform field, thus forming a conducting path for the short-time development of gas and the subsequent breakdown by ionization. From a long-time breakdown strength of 50 kV/mm there follows a particle diameter of about 30 A. 2445: J. A. Kok: Theory and probe measurements of Gabor's gas-filled triode (Appl. sci. Res. B6, 207-221, 1956). . By means of a number of probe measurements in Gabor's gas-filled triode with a spread dark discharge in the cathode chamber, the form of the characteristic IaVa curves was established and several relations between various quantities derived. With these results it was possible to calculate a relation between Gabor's and Fetz's criteria of the transition of the spread discharge into a constricted one. 2446: J. Ugelstad and J. de Jonge: The alkaline hydrolysis of alkoxymethyl ureas (Acta chemica scandinavica 10, 1475-1487, 1956). ' Alkoxymethyl ureas, surprisingly enough, were found to be quite readily hydrolysed in moderately alkaline solution at room temperature, giving urea formaldehyde and an alcohol asend products. The decomposition ofdifferent alkoxymethyl ureas was investigated kinetically. The hydrolysis was found to be proportional to the OH-ion concentration. Based on kinetic investigations in strongly alkaline solution, a choice is made between two possible reaction paths for the reaction. It may be concluded that the reaction involves the breaking of another bond, i.e. that methylol urea and alcolhol are the first decomposition products. The reaction is specific for ethers of methylol urea, of methylol compounds of carboxylic acid amides being comparatively very stable in alkaline solution. The reaction mechanism is discussed. 2447: H. Zijlstra : Maximum energy product of crystal-oriented polycrystalline Ticonal G (Alnico 5) magnet steel (J. appl. Phys. 27, 1249-1250, 1956). Measurements and calculations relating to the effect of crystal orientation on the magnetic properties of Ticonal G.