ABSTRACTS OF TECHNICAL ARTICLES 207 



methods involving conductivity and Hull effect. These new experiments and 

 their related theories may furnish a foundation for a new engineering science of 

 transistor electronics. 



Domain Patterns on Nickel * H. J. Williams^ and J. G. Walker^ 

 Phys. Rev., 83, pp. 634-636, Aug. 1, 1951. 



Domain patterns have been observed on two single crystals of nickel cut in 

 the form of hollow parallelograms. The length of the sides were parallel to the 

 (111) directions in one specimen and to the (110) directions in the other. The 

 crystals show domain structures with the three types of domain boundaries 

 which are to be expected from a material having the directions of easy magneti- 

 zation along the (111) directions. Domain boundary movement under the influ- 

 ence of an applied magnetic field was observed. 



Polymorphism in Potassium Niobate, Sodium Niohate, and Other A BO 3 

 Compounds* E. A. Wood^ Bibliography. Acta Cryst., 4, pp. 353-362, 

 July, 1951. 



The first part of this paper presents the results of optical and X-ray studies 

 of the perovskite-t>'pe crystals, potassium niobate and sodium niobate. Potas- 

 sium niobate is orthorhombic at room temperature, changing to tetragonal at 

 about 225°C. and cubic near 435°C. Sodium niobate is orthorhombic at room 

 temperature, changing to tetragonal at about 370°C. and to cubic at about 

 640°C. 



The second part of the paper discusses relations among the structures of the 

 ABO3 compounds. 



Subjective Sharpness of Additive Color Pictures * M. W. Baldwin^ 

 Proc. I.R.E., 39, pp. 1173-1176, Oct., 1951. 



This is a report on the first numerical results to come from a laboratory 

 experiment on the subjective sharpness of additive three-color pictures. The 

 sharpness factor is isolated by using out-of-focus projection (of slides) instead 

 of actual television transmission. 



An observer's acuity for defocus is greatest for the green component and least 

 for the blue component, in an additive three-color picture. When the same 

 picture is reproduced in monochrome (white, red, green, or blue) at the same 

 brightness, the observer's acuity for defocus is equal to that found for the 

 green component. 



Frequency-Modulation Terminal Equipment for the Transcontinental 

 Relay System * J. G. Chaffee^ and J. B. Maggio^ Elec. Eng., 70, pp. 

 880-883, Oct., 1951. 



To meet the exacting requirements of the new transcontinental microwave 

 relay system, specially designed frequencj'-modulation terminal equipment was 



* A reprint of thi.s article may be obtained on request. 

 iBell Tel. Labs. 



