USE OF A RADIO-ACTIVE TRACER FOR THE MEASUREMENT OF SEDIMENT TRANSPORT IN THE NETHERLANDS

The "Rijkswaterstaat" has developed a method based on the use of radio-active tracers for the evaluation of sediment transport due to the combined action of waves and currents. The results of preparatory studies and a laboratory test were published in a previous report by J.J. Arlman, P. Santema and J.N. Svasek [1]. The main principles of the method were 1. Detection by a sledge-mounted unit towed by a survey vessel and continuous registration on board of the radio-activity measured on the sea bottom. 2. Employment of low specific radio-activity of tracer material and a large quantity thereof. 5> Use of a long-life isotope and high radio-activity. k. Measurement of the vertical distribution of radioactivity in core samples or if possible by discrimination. In March 1958 the first lot of tracer material was placed on the sea bed. The tracer material consisted of the radio-active isotope Scandium^" emitting 2 curies incorporated in 100 kg "greensand". Scandium^" has a half-life of 8^ days and emits strong gramma radiations with energies of 0.89 and 1.12 MeV. Afterwards, in 1959, two series of measurements were taken near the entrance to the Rotterdam Waterway. Four droppings formed one series; they were generally carried out in the following manner: 50 kg greensand labeled with 2 Curies Scandium was dropped in k places at a safe distance from each other. 2 of the 8 portions consisted of smaller quantities of both radio-activity and greensand. In the following paragraphs the preparation, dropping and detection of the tracer, the working out of the registrations and the interpretation of the results of the 1959 measurements are discussed.

Extraction of Trace Components from Large Quantities of Ice in Bore Holes

A melting probe system has been gerveloped which can be lowered down to 400 m in an ice bore hole of 135-165 mm diameter. At the gersired gerpth, a section of the bore hole is isolated and evacuated. Afterwards several tons of ice are melted under vacuum with an electrical heater. The inclusions which are principally gaseous, may be collected both during or after the melting procedure. The application of this system is mainly in the field of dating polar ice by radio-active isotope analysis.

Extraction of Trace Components from Large Quantities of Ice In Bore Holes

A melting probe system has been gerveloped which can be lowered down to 400 m in an ice bore hole of 135-165 mm diameter. At the gersired gerpth, a section of the bore hole is isolated and evacuated. Afterwards several tons of ice are melted under vacuum with an electrical heater. The inclusions which are principally gaseous, may be collected both during or after the melting procedure. The application of this system is mainly in the field of dating polar ice by radio-active isotope analysis.

The utilization of potassium by Bact. ladis aerogenes

As the potassium-ion concentration of synthetic media is decreased the total population (n 8 ) of Bact. lactis aerogenes which they support tends towards zero. Added potassium gives nearly linear increases in n 8 . The use of the radioactive isotope shows that the cells take up nearly all the potassium from the medium over wide ranges of concentration. Sodium cannot replace potassium, and the use of the active isotope shows that it is probably not taken up by the cells. Rubidium replaces potassium with about quarter efficiency, but lithium and caesium have only very small effects. The potassium appears to play the part of an enzyme-activator and in glucose-ammonium sulphate media it is displaced by the acid formed during growth. A quantitative treatment of the competition between K+ and H+ for an array of negative sites on an enzyme surface is attempted. On the assumption that a certain critical area of K+ activated sites is necessary for growth to continue, a relationship between n8 and the [K+] is developed and shown to be in general agreement with the experimental facts. The relation between n8 and potassium concentration varies from one medium to another. In glycerol-ammonium sulphate media, where n 8 is insensitive to the initial pH, the amounts of potassium present in the ammonium or sodium salts of the buffer support considerably greater populations them they can in the glucose medium. Further increases, however, demand much greater potassium concentrations, the results being in accord with the view that other products formed in the glycerol medium can displace potassium from the relevant enzyme and limit growth.

The utilization of potassium by Bact. lactis aerogenes

As the potassium-ion concentration of synthetic media is decreased the total population ( n s ) of Bact. lactis aerogenes which they support tends towards zero. Added potassium gives nearly linear increases in n s . The use of the radioactive isotope shows that the cells take up nearly all the potassium from the medium over wide ranges of concentration. Sodium cannot replace potassium, and the use of the active isotope shows that it is probably not taken up by the cells. Rubidium replaces potassium with about quarter efficiency, but lithium and caesium have only very small effects. The potassium appears to play the part of an enzyme-activator, and in glucose-ammonium sulphate media is displaced by the acid formed during growth. A quantitative treatment of the competition between K + and H + for an array of negative sites on an enzyme surface is attempted. On the assumption that a certain critical area of K + -activated sites is necessary for growth to continue, a relationship between n s and the [K + ] is developed and shown to be in general agreement with the experimental facts. The relation between n s and potassium concentration varies from one medium to another. In glycerol-ammonium sulphate media, where n s is insensitive to the initial pH, the amounts of potassium present in the ammonium or sodium salts of the buffer support considerably greater populations than they can in the glucose medium. Further increases, however, demand much greater potassium concentrations, the results being in accord with the view that other products formed in the glycerol medium can displace potassium from the relevant enzyme and limit growth.

Self-Diffusion in Tin Crystals

The rate of self-diffusion in single crystals of white tin of various orientations has been measured using the radio-active isotope Sn113. The ratio of the diffusion coefficients parallel and perpendicular to the tetragonal (c) axis is approximately 2 at 180 �C. and approximately 3 at 223 �C. The diffusion coefficients in both directions at various temperatures are given by the Arrhenius expressions Dc= 1.2 x 10-5e-10,1500/RT cm.2sec.-1 and Da=3.7 X 10-8e-5,900/RT cm.2sec.-l. The anisotropy is discussed in terms of the vacancy mechanism of diffusion.