Effect of Different Nitrogen Sources on the Cellular Form of Trigonopsis variabilis

Triangular cells are formed during early logarithmic growth of Trigonopsis variabilis. Good triangularity is obtained with methionine, proline, hydroxyproline, or alanine as a nitrogen source.     

Nuclear track registration in solids by etching

Summary A review is given on recent developments in the field of charged particle track registration in insulating solids by preferential etching. The basic mechanism of latent track formation in minerals and inorganic glasses seems to be a spike formation process. In the more sensitive organic polymers, radiation induced chemical changes along the track probably predominate. The sensitivity, etching kinetics, and stability of tracks in plastics and some of the factors which affect them are discussed on the basis of experimental data.Several microscopic and macroscopic methods for simplified or automatic track counting are described briefly. Among the many applications of the etching method, neutron dosimetry via (n, f), (n, ), and recoil reactions are discussed in some detail. Other applications in nuclear physics, chemistry, biology, space research, and for age determinations in geological and archeological samples are listed.Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation.Based on a lecture at the University of Tennessee, February 13, 1968.     

The effect of oxygen and humidity on charged particle registration in organic foils

The number and diameter of microscopically visible alpha-particle tracks which can be etched in the surface of sensitive plastic foils such as cellulose triacetate are increased by the presence of oxygen. Pre- or posttreatment of foils with water or humid air increases the etching speed but not the foils' sensitivity. Treatment of foils with diluted H202 increases the sensitivity slightly, but the etching speed considerably. Some parameters of the oxygen/humidity effect are described; its possible consequences for the interpretation of the latent track formation process and its practical applications are discussed briefly.