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An overview is presented of experimental and theoretical work conducted at the Naval Research Laboratory on the reduction of hydrodynamic drag. The work establishes the effectiveness of certain chemical additives in reducing drag and defines the character of laminar, transitional, and turbulent flows when such additives are present. A variety of new additives for reducing drag have been developed during the program, and their unique properties are also summarized. Finally, the theoretical work is used as a basis for assessing the relative merits of proposed explanations for the drag reduction phenomenon.

The radioactive aerosol content of the surface air in Antarctica has been measured continuously since 1956, first at Little America station and later at the South Pole station. On‐site measurements were made daily of the radioactivity due to bomb‐produced fission products and to naturally occurring radionuclides of the radon and thoron series. Later, composite samples covering 3‐month periods were subjected to radiochemical analysis for such long‐lived radionuclides as Sr90, Cs137, Ce144, Pm147, and Pb210. The natural radioactivity was lower in Antarctica than has been observed at any other geographical location, as might be expected from, the small area of exposed land surface in the vicinity. Fission‐product concentrations, however, often exceeded those found in the southernmost part of South America and exhibited more well‐defined seasonal variations, with maximums in the antarctic summer.

Publication costs assisted by the Na val Research Laboratory Proton NMR relaxation times have been measured as a function of temperature for water adsorbed on zeolite 13-X at various coverages of water, various deuteration levels, and various degrees of hydrolysis. Hydrolysis produces a new surface proton site, which exchanges protons with the adsorbed water. The three limiting cases of rapid exchange, slow exchange, and exchange rate limited relaxation, as predicted by the theory of Zimmerman and Britten are observed; a quantitative fit of this theory to the relaxation data was carried out. The exchange reaction is half order with respect to water and first order with respect to the proton surface complex. Proton second moment data indicate an Al(OH)" structure for the proton surface complex. A new view of zeolite hydrolysis is proposed, in which it is shown that the removal of Na+ ions is not necessary in order for the structural aluminum to be hydrolyzed.

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