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.     

The detonation wave from solid explosives

It has been shown that the detonation wave from a solid explosive changes in velocity after leaving the explosive. In the case of some low-velocity explosives, e.g., about 2400 metres per second, the velocity of the detonation wave increases by approximately 100–200 metres per second. With other high-velocity explosives, 5000–6000 m./sec., the velocity may decrease to around 4400 metres in some cases.Careful measurements have shown that a zone of uniform velocity exists beyond the surface of the explosive, the dimensions of the zone depending on the diameter of the sphere of the explosive or the diameter of the cartridge detonated. In the case of a $\text{1}\text{1}\text{4}$-inch dynamite cartridge, the zone of uniform velocity extended for about ten inches, while, with a sphere of explosive four inches in diameter, the zone extended for about 25 inches.An explanation of the reason for the high velocity of the detonation wave in the gaseous medium is suggested, linking it up with either the velocity of sound at the temperatures prevailing or the kinetic velocity of the gaseous particles themselves, the latter explanation appearing to be more in accordance with the determined facts. Such an explanation implies the assumption of extremely high momentary temperatures at the wave front, in some cases of over 40,000° C. These extremely high temperatures are due partly to the heat of combustion of the explosive ingredients but more to the heating effect resulting from the enormous pressures developed at the moment of explosion, as previously applied by Berthelot and Dixon in the study of gaseous explosions. Adiabatic conditions are assumed in such calculations. With such an explanation, reasonable agreement between theory and fact is obtained for a number of explosives, and the discrepancies that exist are in cases where discrepancies might be expected.     

Some measurements of the spectral components of planetary radiation and planetary temperatures

The object of the present paper is (1) to describe further measurements of the radiation emitted by planets; (2) to give an radiation into spectral components; and (3) to give estimates of planetary temperatures.     

The dynamics of nuclear reactions

The dynamics of nuclear reactions are surveyed on an elemental basis with emphasis upon the c.g. system of coordinate axes. Corrections are given for angular distributions, angular straggling, and thin target straggling.     

Display and interaction features of instructional texts and computers

The design of instructional texts is an area of educational technology which is attracting considerable interest, much of it centered on the display of information and on student-text interaction. This article discusses whether techniques found useful in text design can be transposed to the display of CAL materials. Each medium has its problems and advantages; at present, little is directly transferable from one medium to the other. The computer-presented 'dynamic book' concept provides an example of how to combine giving learners control over the presentation with book-style indexing and browsing.