Natural radioactivity in Indian tea

Summary The paper presents the results of measurements on tea samples collected during 1962 and 1973–1983 period for their natural radioactivity content. The radioisotopes studied under this programme are radium-226, thorium-228, and potassium-40. Tea was found to contain higher concentration of these radionuclides compared to other foodstuffs having vegetative origin. Interpretation for higher concentrations in tea compared to other foodstuffs is briefly given on the basis of agroclimatic conditions.     

Preparation of tritium-labeled tetrahydropteroylpolyglutamates of high specific radioactivity

Tritium-labeled [6S]-tetrahydropteroylpolyglutamates of high radiospecific activity were prepared from the corresponding pteroylpolyglutamates. Malic enzyme and D,L-[2-3H]malate were used as a generating system to produce [4A-3H]NADPH which was coupled to the dihydrofolate reductase-catalyzed reduction of chemically prepared dihydropteroylpolyglutamate derivatives. Passage of the reaction mixtures through a column of immobilized boronate effectively removed NADPH, and the tetrahydropteroylpolyglutamates were subsequently purified by chromatography on DEAE-cellulose. Overall yields of the [6S]-tetrahydro derivatives were 18-48% and the radiospecific activities were 3-4.5 mCi X mumol-1.     

黄土区土壤放射性的生物循环

研究了不同类型土壤中放射性物质的生物学循环和平衡问题。结果表明,土壤中放射性核素剖面分布的总趋势是沿发生层往下逐步减少。其生物积聚系数因不同核素而变动在1.06—1.44间。放射性物质在各类植物体内的含量顺序是:牧草>农业作物≥灌木≥果树>乔木。植物对α放射性的富集系数一般均小于0.10,而β放射性的富集系数大都处于0.5—1.0间.不同土地利用情况下土壤放射性可分为积累、消耗和中间3种平衡类型。     

Enzymatic lactate-specific radioactivity determination in biological samples

A method for the measurement of specific lactate radioactivity in biological samples is presented. It is based on the following steps: (a) enzymatic conversion of lactate to pyruvate, (b) pyruvate conversion to 2,4-dinitrophenylhydrazone, (c) concentration-separation of the latter in reusable Amberlite XAD-7 polymeric adsorbent columns, and finally (d) estimation of the radioactivity thus retained compared with that of enzymatically untreated aliquots of the same samples. Specificity was ensured by the use of lactate dehydrogenase as specific recognizing agent for lactic acid. No interference from glucose, lactate, or amino acids was observed. The method presented is simple and can be applied in routine multiple estimations of lactic acid radioactivity in conjunction with the enzymatic measurement of lactate in biological samples in tracer metabolic studies.     

Studies of radioactivity in the ores and mineral products

Mineral ores and products made of them were studied by gamma-spectrophotometry. Regularities of radionuclide content in ores and products were found. A possibility of deactivation of ores and mineral products by the technology of aerohydrodynamic concentration was shown.     

Discussing possible standards of natural radioactivity in building materials

Summary This paper discusses different possibilities of deriving reference values for the natural radioactivity concentrations in building materials to estimate possible additional radiation exposure for the population. Based on comprehensive experimental and theoretical investigations the consequences of the resulting hypothetical reference activity concentrations in building materials, applying different dose limits, were examined. The calculation of the activity concentration standards was performed for standard conditions obtained by earlier studies on exhalation of Radon-222 and Radon-220 from building materials.Dedicated to Prof. L.E. Feinendegen on the occasion of his 60th birthday