Hologram writer using a plasma display panel

A hologram writer for a read-only page-oriented hologram memory has been developed. Data masks are produced by photographing dot patterns of a plasma display panel on a long-size film. A data pattern is obtained by covering a fixed bit mask with each data mask and stored in a small hologram. A hologram memory plate with total capacity of 2 x 10(7) bits was prepared by this hologram writer. This paper describes the construction and features of this hologram writer, as well as the characteristics of the hologram memory plate produced on a trial basis.

Isolation of Hfr strains from R+ and ColV2+ strains of Escherichia coli and derivation of an R'lac factor by transduction

Temperature-resistant revertants were isolated from Escherichia coli strains carrying a temperature-sensitive dnaA mutation (initiation of chromosome replication) and either a repressed or a derepressed F-like R factor or a ColV2 factor. Many of the revertants had all the properties of Hfr strains, with a variety of directions and origins of transfer. From one such revertant, episomes carrying the R factor and part of the lac region (R'lac) could be isolated by transduction. This system offers a good selection for Hfr strains produced by integration of various episomes and for the isolation of R' factors.