1561 References Cited U.S. PATENT DOCUMENTS 3,792,423 2/1974 Becker et al. ......................... 73/620 3,979,712 9/1976 Ettenhofer et al. . 4,028,934 6/1977 Sollish ................................... 73/620 4,327,576 5/1982 Dickey et al. ................... 73/40.5 A 4,640,121 2/1987 Leuker et al. ................... 73/40.5 A 4,641,526 2/1987 Izumi et al. ........................... 73/5...

2014 Tunneling spectroscopy at high bias has proved to be useful as a tool for studying electronic excitations in junctions although one major difficulty encountered is the huge background in the second derivative of the tunneling characteristics I(V). This background however depends on which second derivative is used. We compare the sensitivity of the functions d2V/dI2, d2I/dV2 and 1/03C3.d03C...

A mutant, USDA 206C, of Rhizobium fredii USDA 206 was obtained by passage on acridine plates. This mutant was cured of its 197-megadalton Sym plasmid but retained its symbiotic effectiveness. Multiple plasmid and chromosomally borne nif gene copies have previously been shown in R. fredii USDA 206. HindIII and EcoRI restriction enzyme digests of plasmid and total DNA showed that at least two nif...