602 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1952 



homogeneous fields at least partially account for the inhomogeneities in bom- 

 bardment conduction. 



Serious errors in the normal estimates of range and mobility of electrons or 

 holes in insulators can be introduced by neglecting these field inhomogeneities. 



Diffusion in Alloys and the Kirkendall Effect. J. Bardeen and C. 

 Herring^ Pp. 87-111. Am. Soc. for Metals. Atom movements; a semi- 

 nar . . . held during the thirty-second National Metal Congress and 

 Exposition, Chicago, Oct. 21-27, 1950. Cleveland, Ohio, Am. Soc. for 

 Metals, 1951. 240 p. 



Some Roots of an Equation Involving Bessel Functions. B. P. Bogert . 

 Jl. Math. Phijs., 30, pp. 102-105, July, 1951. (Monograph 1903). 



Creep Test Methods for Determining Cracking Sensitivity of Poly- 

 ethylene Polymers. W. C. Ellis^ and J. D. Cummings\ A.S.T.M. Bull., 

 No. 178, pp. 47-49, Dec, 1951. 



Conventional creep testing methods for evaluating the cracking sensitivity 

 of polyethylene polymers are described. The tests show that sensitivity to 

 cracking in the presence of an active agent decreases with increasing average 

 molecular weight of the poljmier. For a given stress condition and environment, 

 there appears to be a threshold value of stress and strain for the occurrence of 

 cracking. 



Observer Reaction to Video Crosstalk. A. D. Fowler . J. Soc. Motion 

 Picture and Television Engrs., 57, pp. 416-424, Nov., 1951. (Monograph 

 1928). 



Presented here are results of tests to determine how much video crosstalk 

 can be tolerated in black-and-white television pictures. Experienced observers 

 viewed a television picture and rated the disturbing effects of controlled amounts 

 of crosstalk from another video system. Crosstalk couj)ling was simultated by 

 a network which permitted changes in frequency characteristic as well as in 

 coupling loss. Tolerable limits for crosstalk coupling are derived from the test 

 results. 



Mass Spectrometric Studies of Molecidar Ions in the Noble Gases. 

 J. A. Hornbeck^ and J. P. Molnar\ Phys. Rev., 84, pp. 621-625, 

 Nov. 15, 1951. 



Molecular ions of the rare gases (He2"'', Ne2'*', A2"'', Kr2+, and Xe2"'") produced 

 by electron impact at gas pressures from 10^'' to lO"^ mm Hg have been studied 

 with a small mass spectrometer. The ion intensity increased linearly with elec- 

 tron current and with the square of the gas pressure. The form of the ionization 

 versus electron energy curves resembles closely curves of excitation probabilitj' 

 by electron collision. The appearance potentials of the molecular ions were less 



^ Bell Telephone Laboratories 



