An eigenfunction expansion method for the analysis of exponential decay curvesA frequently encountered problem in many branches of science involves the resolution of experimental data into a sum of independent exponential curves of the formin order to estimate the physically significant parameters N, and Ai. Such problems arise, for example, in the analysis of multicomponent radioactive decay curves, and in the study of the dielectric properties of certain compounds. This paper is concerned with the numerical evaluation of a mathematical approach to the problem. The approach is based on the inversion of the Laplace integral equation by a method of Fourier transforms. The results of the analysis appear in the form of a frequency spectrum. Each true peak in the spectrum indicates a component, the abscissa value at the center of the peak is the decay constant Ai, while the height of the peak is directly proportional to Ni/A •. Results obtained on an IBM 650 computer indicate that the method may possess certain advantages over previous methods of analysis.

gives a positive uranium test and should never be used. CONCLUSIONSOn the basis of the tests several conclusions were reached relative to the fixing of natural water samples for uranium analysis.

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Activationanalysts have been carried out for 6 trace clcmcnts-vanadium, arsenic, molybdenum, tungsten, rhenium, and gold-in the ashes of several different types of marine organisms. Radiochemical procedures coupled with gamma-ray mcasuremcnt permitted unambiguous dctcrmination of submicrogram amounts of these elements.No reagent blank corrections were nccdcd. Experimental sensitivities for each element are given. INTRODUCTIONMany studies have been made on the abundance of trace elements in marine organisms. Early data have been summarized in Vinogradov's (1953) comprehensive compilation and current periodicals continually supplement this information.Nevertheless, systematic studies of trace element abundance are far from complete because of the inherent difficulties in the analytical methods and because of the many varieties included in the category of marine organisms. The importance of these studies has been emphasized in the last decade in connection with the radioactive contamination caused arouncl the Equatorial Pacific by atomic explosions. The cycle of trace elements in marine organisms has become an important basic problem to bc solved early in the atomic age because of questions arising from the disposal and dispersal of radioactive wastes in the sea.In the past spectrographic and spectrophotometric methods have been widely applied to these trace element studies. These methods are, however, restricted for some elements in this type of sample because of insufficient sensitivity and large reagent blanks, Activation analysis can overcome these disadvantages in many cases since it -- has excellent sensitivity for many elements for which the conventional methods present difficulties.In addition, problems of reagent blanks are eliminated.Therefore, activation analysis should play an important role in supplying complementary or unknown information on trace elements in marine organisms (Fukai and Meinke 19591). Bowen (1956) h as applied activation analysis to various types of marine samples and sea water to determine strontium and barium. Rubidium and cesium in sea water and seaweeds were analyzed by Smales and Salmon (1955) using this method. Among these elements, the newly obtained abundance of barium and cesium was less by a factor of 10 than the previously accepted value. Activation analysis has also been applied to the estimation of arsenic ( Smales and Pate 1952)) gold ( Hummel 1957)) and uranium ( Stewart and Bentley 1954) in sea water, although these measurements were not extended to biological materials.In order to re-examinc existing data and to obtain new information, ashes of 6 different marine samples have been analyzed for vanadium, arsenic, molybdenum, tungsten, rhenium, and gold by activation analysis ( Fukai and Meinke 1959b).Recently the authors ( 1959a) compiled from existing clata a generalized table for the average abundance of trace elements in marine organisms and in sea water. In this table the four groups, seaweeds, mollusks, crustaceans, and fishes, were chosen as represe...

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S-The radiochemical separation of strontium by an amalgamexchange technique has been critically evaluated with a saturated aqueous solution of potassium chloride as an exchange medium. With an optimised procedure strontium yields of about 34% were obtained, although mineral acids and alkalies above O*lM decrease this yield considerably because of decomposition of the amalgam. In studies with tracers of 16 different elements, representative of the Periodic Table, this technique gave considerably better decontamination than does the fuming nitric acid procedure. The simple separation can be carried out in 8 min with no special equipment required, while application of the method to fallout rain-water samples requires about 40 min. This procedure can also be easily adapted to the preparation of a SOY-free. source of O"Sr.