The slow neutron-induced radioactivities of nuclear explosions

The slow neutron-induced radioactivities of nuclear explosions have been evaluated for infinite media of filtered Schuylkill water and the earth's crust. The magnitudes of these effects are compared with the activity of the fission fragments, and the conditions under which they may be of importance are considered.It has been assumed that a gram-molecule of neutrons is liberated in the blast.     

Theory of the halftone process. III. Dot size and halftone density

The theoretical and experimental quantitative relationships between the dot diameter, dot area, and density of a halftone are given. Experimental results do not agree exactly with the theoretical relationships except for screen negatives and positives with sharp dots.For accurate rendering, highlight dots in a reproduction must increase extremely rapidly in size for small density increments in the highlights of an original. A “emi-dark-field” densitometer is described which eliminates the effect of dot fringe in measuring densities of screen positives. The relationship between density of screen positive and density of proof is briefly discussed.     

Theory of the halftone process. II. The diffraction theory-calculation of the light distribution

An approximate method of calculating the light distribution in the dots formed behind a halftone screen from the Fresnel diffraction theory is described, and in a typical case, the distribution is found to check closely with that determined experimentally, being very different from that calculated from geometrical optics.