Tracers technique

Isotopes sufficiently long-Hved for work in weighable amounts are obtainable, at least in principle, for all of the actinide elements through fermium (100) these isotopes with their half-Hves are Hsted in Table 2 (4). Not all of these are available as individual isotopes. It appears that it will always be necessary to study the elements above fermium by means of the tracer technique (except for some very special experiments) because only isotopes with short half-Hves are known. 

If the source fingerprints, for each of n sources are known and the number of sources is less than or equal to the number of measured species (n < m), an estimate for the solution to the system of equations (3) can be obtained. If m > n, then the set of equations is overdetermined, and least-squares or linear programming techniques are used to solve for L. This is the basis of the chemical mass balance (CMB) method (20,21). If each source emits a particular species unique to it, then a very simple tracer technique can be used (5). Examples of commonly used tracers are lead and bromine from mobile sources, nickel from fuel oil, and sodium from sea salt. The condition that each source have a unique tracer species is not often met in practice. 

Tracer technique The use of a tracer gas in air for the study of air movement within a space. 

All isotopes of element 85, astatine, are intensely radioactive with very short half-lives (p. 795). As a consequence weighable amounts of the element or its compounds cannot be prepared and no bulk properties are known. The chemistry of the element must, of necessity, be studied by tracer techniques on extremely dilute solutions, and this introduces the risk of experimental errors and the consequent possibility of erroneous... 

Fluid Velocity. The flow of air is usually measured at or near atmospheric pressure. The typical instruments to measure fluid velocity are airborne tracer techniques, anemometers, pilot-static tubes, measuring flow in ducts. 

Brune, D., Kjaerheim, A., Hensten-Pettersen, A. and Marion, L. Corrosion of Dental Alloys Studied by Implantation and Nuclear Tracer Technique , Acta Odontologia Scandanavia, 41. 129-134 (1983)... 

Schmidt, L. B., A Special Mold Tracer Technique for Studying Shear Exten-sional. 

Tracer techniques are used widely in biology. Botanists, for example, work to develop new plant hybrids that grow more rapidiy. One common way to determine how fast plants grow is to measure how quickly they take up elemental phosphorus from the soil. New hybrids can be planted in a plot and fertilized with phosphoras enriched 32 32... 

Van Lieshout, M., West, C.E., and Van Breemen R.B., Isotopic tracer techniques for smdying the bioavaUability and bioefficacy of dietary carotenoids, particularly P-carotene, in humans a review. Am. J. Clin. Nutr, 77, 12, 2003. 

This project was supported by the Deutsche Forschungsgemeinschaft (BL 231/25 -1) and by the German Academic Exchange Service (DAAD), which are thus gratefully acknowledged. We thank D.-H. Tang for the measurements with the conventional tracer technique, K. Kupferschlager, M. Adams and G. Schroeder for technical support, and A. Jess and M. Liauw for helpful discussions. 

While methods employing radiaoactive tracer techniques have become a classical tool for the study of adsorption on electrodes, optical methods for the study of electrodes and processes occurring on them at an atomic or molecular level have undergone enormously rapid progress, which is characteristic for the contemporary development of electrochemistry. 

Radioactive tracer techniques. In electrochemistry, the procedure is essentially the same as in studies of chemical reactions the electroactive substance or medium (solvent, electrolyte) is labelled, the product of the electrode reaction is isolated and its activity is determined, indicating which part of the electroactive substance was incorporated into a given product or which other component of the electrolysed system participated in product formation. Measurement of the exchange current at an amalgam electrode by means of a labelled metal in the amalgam (see page 262) is based on a similar principle. 

Methane emission from ruminants can be estimated by using the ERUCT technique (Emissions from Ruminants Using a Calibrated Tracer). The tracer can either be isotopic or nonisotopic. Isotopic tracer techniques generally require simple experimental designs and relatively straightforward calculations [31]. Isotopic methods involve the use of (3H-)CH4 or (14C-)CH4 and ruminally cannulated animals. 

Nonisotopic tracer techniques are also available for measurement of CH4 production. Johnson et al. [32] described a technique using SF6, an inert gas tracer. This method has been... 

More recently, Arnstein and Bentley66 applied the isotopic tracer technique in their studies of kojic acid. First, they investigated the mechanism of the alkaline cleavage and degradation of di-O-methylkojic acid (XXXIII).66 Yabuta4 had found that treatment of XXXIII with barium... 

Dispersion in packed tubes with wall effects was part of the CFD study by Magnico (2003), for N — 5.96 and N — 7.8, so the author was able to focus on mass transfer mechanisms near the tube wall. After establishing a steady-state flow, a Lagrangian approach was used in which particles were followed along the trajectories, with molecular diffusion suppressed, to single out the connection between flow and radial mass transport. The results showed the ratio of longitudinal to transverse dispersion coefficients to be smaller than in the literature, which may have been connected to the wall effects. The flow structure near the wall was probed by the tracer technique, and it was observed that there was a boundary layer near the wall of width about Jp/4 (at Ret — 7) in which there was no radial velocity component, so that mass transfer across the layer... 

At this point we are really at the closest approach to a Comprehensive Theory, because the initiation by AlX+2, expressed by Equation (iv), has now been proved for isobutene and made very probable for styrene and norbornadiene by a radio-tracer technique which leaves little room for any alternative explanation [8]. 

We thank Prof. J. C. Bevington for providing facilities for D.W.G. to learn radio-tracer techniques, Prof. E. J. Goethals for helpful comments, and the Science Research Council for equipment. 

Anker,3 5 using isotope tracer technique, found in a mixed laboratory strain of rats (Wistar) no significant conversion of pyruvic acid to acetic acid. This was in contrast to the results obtained with the Sprague-Dawley strain of rats in which either such a conversion did take place or else pyruvic acid was utilized directly for acetylation. Exactly what constitutes the enzymic difference between the two strains is not known, but it is clear that a striking and potentially important difference exists. From the genetic standpoint one should not expect precisely the same metabolic results from rats of different strains or even from individual rats within the same strain, but the difference here reported is perhaps more fundamental than one might anticipate. If this difference is real, presumably other differences exist which have not been looked for, and one should be extremely careful about accepting the results from one strain as applicable to another. 

The routes followed by plants in the biosynthesis of hgnin have been widely studied using tracer techniques, principally with radiocarbon. By comparing the specific activities of the precursors fed to plants with the... 

Steric effects, molecular rearrangements, anchimeric assistance, and the use of tracer techniques have provided useful information about the nature of catalytic sites of aluminas and have led to a unified mechanism of their action. 

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