Isotopic tracers, use

Miller et al., 1989 n = 6 children n = 3 n — 3 Age range 11-17 years 250 mg Ca as CCM enriched with tracer in form of chewable tablets Stable dual isotope tracers used to quantify CaAbs in urine and serum. Comparison of CCM chewable versus CCM swallowable supplements and CaCOa from data collected previously in same subjects Based on urinary excretion which correlated with serum data (r = 0.85) x SD% CaAbs from chewable CCM for molar ratio 6 2 3 (41.4 8.2%) > swallowable CCM for molar ratio 5 1 1 (39.5 10.6%) > CaCOa (26.7 7.8%) Chewable CCM > CaCOa (p =. 047) and swallowable CCM > CaCO (p =. 094)... 

Canuel, E.A., Cloern, J.E., Ringelborg, D.B., Guckert, J.B., and Rau, G.H. (1995) Molecular and isotopic tracers used to examine sources or organic matter and its incorporation into food webs of San Francisco Bay. Limnol. Oceanogr. 40, 67-81. 

Friel, J. K., Longerich, H. P., and Jackson, S. E. (1993). Determination of isotope ratios in human tissues enriched with zinc stable isotope tracers using inductively coupled plasma-mass spectrometry (ICP-MS). Biol. Trace Elem. Res. 123-136. 

Patterson, K.Y. (1997). Optimization in the analysis of nutritionally important stable isotope tracers using inductively coupled plasma-mass spectrometry. Unpublished Ph.D. Thesis, University of Maryland, College Park. 

Patterson, K.Y.,Veillon, C., Hill, A. D., and Moser-Veillon, P. B. (1999). Measurement of calcium stable isotope tracers using cool plasma ICP-MS.J.Atutl.At. Spectrom. 14(11), 1673. 

Equations 13.31 and 13.32 are only valid if the radioactive element in the tracer has a half-life that is considerably longer than the time needed to conduct the analysis. If this is not the case, then the decrease in activity is due both to the effect of dilution and the natural decrease in the isotope s activity. Some common radioactive isotopes for use in isotope dilution are listed in Table 13.1. 

Table 13.1 provides a list of several isotopes commonly used as tracers. The half-lives for these isotopes also are listed. What is the rate constant for the radioactive decay of each isotope ... 

Nuclear reaction analysis (NRA) is used to determine the concentration and depth distribution of light elements in the near sur ce (the first few lm) of solids. Because this method relies on nuclear reactions, it is insensitive to solid state matrix effects. Hence, it is easily made quantitative without reference to standard samples. NRA is isotope specific, making it ideal for isotopic tracer experiments. This characteristic also makes NRA less vulnerable than some other methods to interference effects that may overwhelm signals from low abundance elements. In addition, measurements are rapid and nondestructive. 

The neutron activation technique mentioned in the preceding paragraph is only one of a range of nuclear methods used in the study of solids - methods which depend on the response of atomic nuclei to radiation or to the emission of radiation by the nuclei. Radioactive isotopes ( tracers ) of course have been used in research ever since von Hevesy s pioneering measurements of diffusion (Section 4.2.2). These techniques have become a field of study in their own right and a number of physics laboratories, as for instance the Second Physical Institute at the University of Gottingen, focus on the development of such techniques. This family of techniques, as applied to the study of condensed matter, is well surveyed in a specialised text... 

The purpose of this article is to focus on a single series of reactions and to illustrate some of these uses of isotopic tracers. The set of reactions involves the dehydrocyclization of n-paraffins into aromatics over non-acidic Te NaX zeolite (4-7). 

In summary, the results from the fixed bed reactor study provided evidence as to the effect of Au and KOAc on the performance of the catalyst, though, these experiments did not give any information on the perturbation of the reaction pathways with the addition of Au and KOAc. For this type of information, additional experiments were performed using the TAP reactor with 1,2 C-labeled ethylene used as an isotopic tracer of the kinetics. 

Henderson GM (2002b) New oceanic proxies for paleoclimate. Earth Planet Sci Lett 203 1-13 Henderson GM, Burton KW (1999) Using ( " U/ U) to assess diffusion rates of isotopic tracers in Mn cmsts. Earth Planet Sci Lett 170(3) 169-179... 

Two important geochemical characteristics make Ra isotopes potentially useful as an estuarine tracer 1) having highly particle reactive Th isotopes residing largely in sediments as its direct radiogenic parents, which ties Ra directly to bottom sediments, and 2) exhibiting vastly different environmental behavior in fresh water and saltwater systems. 

Thus we shall be concerned with properties that furnish information about the nature of the ligands, the oxidation state of the metal, and the geometry of the field of ligands. Techniques such as radio-isotope tracer studies, neutron-activation analysis, and electron microscopy are powerful methods for locating a metal within constituents of the cell and are particularly suited to heavy-metal rather than organic drugs but since they do not provide information about the chemical environment of the metal they will not concern us here. After each section below we shall give an example, not necessarily from platinum chemistry, where the method has been used with success in biochemistry. 

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. 

Rabinowitz M, Wetherill GW, Kopple JD. 1974. Studies of human lead metabolism by use of stable isotope tracers. Environ Health Perspect 7 145-153. 

The characteristics of nuclei described here are intimately related to how certain species figure prominently in chemistry (such as dating materials by determining their carbon-14 content). The use of isotopic tracers is a technique that finds applications in all areas of chemistry. 

NO. The same parameters were then used to predict the responses for the isotopic tracer experiments reported in Figs. 9 and 10. 

To further test the model, calculations were performed to simulate the isotopic tracer experiments presented in Figs. 9 and 10. It should be noted that while the tracer experiments were performed at 438K, the rate coefficients used in the model were chosen to fit the experiments in which chemisorbed NO was reduced at 423 K. Figures 21 and 22 illustrate the nitrogen partial pressure and surface coverage responses predicted for an experiment in which 5 0 is substituted for l NO at the same time that H2 is added to the NO flow. Similar plots are shown in Figs. 23 and 24 for an experiment in which NO is substituted for during steady-state reduction. 

We have developed an in vitro digestion procedure, not as a substitute for in vivo studies, but as a useful adjunct. Our initial objective was to develop an in vitro procedure for measuring exchangeability, the fraction of the food mineral which exchanges with an extrinsic isotope tracer added to the food. This was expected to facilitate the measurement of food mineral absorption in humans by the extrinsic tag method. Secondary objectives were to determine if in vitro mineral solubility could be used to estimate potential... 

Radioactive isotopes provide a very convenient way of monitoring the fate or metabolism of compounds that contain the isotopes. When used in this way, the isotope is described as a tracer and compounds into which the radioactive atom has been introduced are said to be labelled or tagged. The labelled molecules need only comprise a very small proportion of the total amount of the unlabelled radioactive substance because they act in the same way as the non-radioactive substance but can be detected very much more easily. The varied applications of tracers in biochemistry range from studies of metabolism in whole animals or isolated organs to sensitive quantitative analytical techniques, such as radioimmunoassay. Phosphorus-32 is used in work with nucleic acids, particularly in DNA sequencing and hybridization techniques. In these instances the isotope is used as a means of visualizing DNA separations by autoradiographic techniques. 

Ogston, A.G. (1948). Interpretation of experiments on metabolic processes using isotopic tracer elements. Nature, London, 162, 963. 

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. 

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