ABSTRACTS OF TECHNICAL ARTICLES 269 



hiouftht into agreement with tlieDretical i)redi('tions l)y distinguishing be- 

 tween grou]) velocity and i)aiti('le velocity of a jnilse of niinoi'ity caiiiers. 

 Corrected high tenii)eiatuie measurements of electron di'ift mobility- are 

 consistent witli the theoietical prediction ^ = AT^^'-. The experimentally 

 determined value of A is 2.0 X 10" cm- deg^/-/v()lt-sec. 



Reiss, H.i 



Chemical Effects Due to the Ionization of Impurities in Semicon- 

 ductors, J. C1iem. Phys., 21, p. 1209, July, 1953 (Monograph 2172). 



This ])aper contains a theoretical account of the possible effects which the 

 ionization of donor and acce])tor im]mrities can induce in the thermod}-- 

 namic phase relations involving their solutions with semiconductors. These 

 effects reflect the energy band structure of the semiconductor. Furthermore, 

 the phenomenon has an interest of its own, for within a certain range of 

 exi)erimental conditions the effects can be attributed to a chemical-like, 

 mass action behavior of the electrons which play the roles of negati\'e ions. 

 Section V is a brief discussion of a fine point concerning the Fermi level. It 

 is shown that although the Fermi level is certainly the electronic electro- 

 chemical potential, it is not the Giljbs free energy per electron unless the 

 density of electron energy levels is linear in the volume of the system. 



RoBBixs, R. L.i 



Measurement of Path Loss Between Miami and Key West at 3675 

 mc, I.R.E., Trans., P.G.A.P. 1, pp. 5-8, July, 1953. 



Radio transmission measurements ha\'e been made at 3,675 megac3'cles on 

 the 130-mile path between ^Nliami and Key West, Florida, which is largely 

 over watery wastes of the Everglades and shallow sea waters of the Florida 

 Keys. Path loss and fading characteristics for this terrain were not found 

 to differ materially from the characteristics of hilly oi' mountainous paths 

 in the northeastern section of the country. 



Ross, I. 'SI., see G. C. Dacey. 



Shanxox, C. E. 



Turing's Formulation of Computing Machines and Von Neumann's 

 Models of Self-reproducing Machines., I.R.E., Proc, 41, pp. 1235- 

 1241, Oct., 1953 (Monograph 2150). 



This paper reviews briefly some of the recent developments in the field of 

 automata and non-numerical computation. A number of typical machines 

 are descril^ed, including logic machines, game-]:)laying machines and learn- 

 ing machines. Some theoretical (luestions and developments are discussed, 

 such as a comparison of com])uters and the brain. 



1 Bell Telephone Laboratories. 



