Biodeterioration of standard reference materials

Microbial resistance to heavy metals

“…The enzymes carrying out the forward reactions are coded by DNA on bacterial plasmids and transposonsthe latter is a small amount of DNA transferable between closely related microorganisms-and not by normal chromosomal genes (24-26). Therefore, it is not too surprising that mercuric and organomercurial strains of bacteria have been isolated from a variety of ecosystems such as soil, water, and marine sediments (27)(28)(29)(30)(31)(32).…”

Environmental factors and mechanisms controlling degradation of Tb(III) chelates: development of effective new Tb phosphors for postage stamp use

“…Aging beyond 280 hours reveals additional differences between sample I, which retains its phosphorescence, and V, which decays to about 10 percent of the maximum. Inferentially , phosphor decay is a result of interactions between each phosphorescent coating system and its environment including gummed backing on stamp papers.…”

“…After coating, test papers were dried at 66^C for 15"20 min, or until visibly and palpably dry. These experiments continued through summer, fall and winter months, during which the relative humidity in NBS buildings averages about 50 %, but may occasionally range from 33"73i6 (10) oculars and a 1.25X optovar setting for a total magnification of 125X. A 2.5 mm pinhole stop below the photometer gave a 50 urn diameter field for luminescence intensity measurements.…”

Microbial resistance to heavy metals

“…The enzymes carrying out the forward reactions are coded by DNA on bacterial plasmids and transposonsthe latter is a small amount of DNA transferable between closely related microorganisms-and not by normal chromosomal genes (24-26). Therefore, it is not too surprising that mercuric and organomercurial strains of bacteria have been isolated from a variety of ecosystems such as soil, water, and marine sediments (27)(28)(29)(30)(31)(32). The enzymology of methylmercury hydrolysis and mercuric ion reduction is now understood in some detail (24)(25)(26).…”