Evaluation of contrast in duplicated radiographs

This investigation evaluated changes in the contrast of duplicated radiographs made at different ultraviolet light exposures. Increasing ultraviolet light exposure had different effects on the duplicates of originals of different "background" densities. When correctly exposed, a duplicate radiograph enhanced contrast. When originals had the same contrast but different "background" densities, their duplicates did not have the same contrast. It was not possible to duplicate accurately all the different contrasts measured on an original. It was possible, however, to produce duplicates with all contrasts greater than those of the original.

Health complaints attributed to the use of carbonless copy paper (a preliminary report)

Persistent health complaints attributed to the use of carbonless copy paper by office workers on the campus of the University of Washington led to this preliminary study. The goals were to estimate the extent of the problem in a population of known carbonless copy paper users; to describe those health problems which the users attribute to the use of carbonless copy paper; and to make a preliminary determination of the chemical constituents of the paper. Participants were asked to complete a health questionnaire and to attach to it copies of the forms they used. A minimum estimate of 10.7 health complainants per 100 users was similar to that found by investigators in Denmark, but lower than that reported by other investigators and of anecdotal material reported to the study group. There was a statistically significant association between complainants and the amount of paper used. Reports of headaches and irritation of the skin, eye and respiratory tract were similar to those reported elsewhere. Concurrent factors such as poor ventilation, high temperature and/or low humidity need to be investigated for possible synergistic or additive effects.

Evaluation of the quality of duplicated radiographs

This experiment evaluated the image quality of duplicated radiographs made at different ultraviolet light exposures. Image quality was measured in terms of "residual" film fog, film density, mottle, image contrast, and resolution. The "residual" fog density of duplicates decreased with increases in ultraviolet exposures until it was less than the fog density of the original. The density of duplicates decreased with increases in ultraviolet exposures until it leveled off at a certain density, depending on the density of the original film. Mottle was less on lighter duplicates than on darker duplicates. Contrast of duplicates increased initially with increases in ultraviolet exposures and later decreased with further increases in ultraviolet exposures. Resolution of duplicates was nearly the same as the original as long as the duplicate had acceptable "residual" fog density.

A method for the duplication of complete dentures

A quick and easy technique for the duplication of a complete denture has been presented. This technique can be performed in the dentists' office without special equipment.

Mutagenic activity in photocopies

Extracts from several different photocopies were mutagenic in the Ames Salmonella assay. The mutagenic behavior was similar for extracts from copies and corresponding toners indicating that toners are directly responsible for the mutagenicity. The mutagenicity is caused by at least two classes of compounds which may be present either alone or in combination in any toner.

Nitropyrenes: isolation, identificaton, and reduction of mutagenic impurities in carbon black and toners

Extracts of selected xerographic toners and copies were found to be mutagenic in the Salmonella assay. The activity was independent of the xerographic hardware and process and was traced to nitropyrenes present as impurities in the carbon black, the toner colorant. Manufacturing process changes resulted in a substantial reduction of the nitropyrene content of the carbon black and thus in the mutagenicity of the corresponding toners. Nitropyrenes are potent frameshift mutagens, and possible mechanisms for their biological action are discussed.