Radioactive tracing

Fig. in-12. Verification of the Gibbs equation by the radioactive trace method. Observed (o) and calculated (line) values for for aqueous sodium dodecyl sulfate solutions. (From Ref. 108.)... 

Radioactive traces Helpful in finding the region of actual placement ... 

Neurotransmitters in the body are not normally made of radioactive atoms. Researchers make radioactive versions by adding radioactive atoms to the solution in which chemical reactions produce the molecule. For example, hydrogen-3 can be incorporated into parts of a dopamine molecule instead of hydrogen-1. Brain tissue can be cut into thin slices, exposed to radioactive dopamine (or other radioactive molecules), and then examined for radioactive traces, indicating receptors to which dopamine has attached. These procedures are known as autoradiography. 

Pinder etal. (1985) deduced NSA values in the range 20-41 m2d kg-1 from measurements of 238Pu in corn near the Savannah River Plant. Similar values also apply to non-radioactive trace elements. Allcroft et al. (1965) made a series of measurements of fluorine in herbage on a farm near Stoke-on-Trent and also recorded fallout of fluorine in a nearby deposit gauge. During the period of study (1956-61) the productivity of the pasture was improved, and the yearly average NSA declined from 59 to 27 m2d kg-1 (Chamberlain, 1970). When productivity is low, the time T0 before maturity is increased, and so is the NSA (Table 2.17). Also XG may be increased, since the rate of field loss seems to be related to growth rate. 

In the specific case of the determination of trace amounts of actinides, it is interesting to compare the results obtained by TRES to those obtained by other techniques. This very brief presentation is based on a very detailed and comprehensive lecture on radioactive ultra-trace determination in the environment (Aupiais, 2001, in French). In order to detect radioactive traces in environmental samples, various techniques are available (a and ft liquid scintillation, y spectrometry, mass spectrometry,. ..), which most of the time are coupled to a preconcentration of the sample. Such methods allow isotope discrimination, which is impossible with TRES. Another restriction of TRES as compared to the other techniques available is that TRES is strictly limited to luminescent elements. On the other hand, liquid scintillation is a rather time-consuming method as compared to TRES. For example, detection limits with a liquid scintillation are equal to 2 x 10-10 mol for 238U and 9 x 10-19 mol for 244Cm but the acquisition time is on the order of a few days, to be compared with TRES acquisition times of a few minutes. In the case of Cm, the advantage of a liquid scintillation is clear but TRES appears to be competitive in the case of U, if no isotopic discrimination is required. 

Jordan, S. and Schikarski, W., Evaluation of radioactive and non-radioactive trace constituents emitted from fossil-fuel and nuclear power plants. In Environmental Behavior of Radionuclides Released in the Nuclear Industry, pp. 525-535. IAEA, Vienna, 1973. 

Bourlat et al. (1995) have presented results on the plutonium radioactivity levels in Mururoa lagoon water during the 1985-1991 period. The low radioactivity levels recorded, from 0.01 to 1.5 Bq/m are due to the slow solubilization of plutonium deposited in lagoon sediments following atmospheric experiments which took place from 1966 to 1974. The average concentrations of the lagoon water decrease from one year to the next. Since the Mururoa lagoon is open to the ocean, plutonium radioactivity traces are also detectable in the immediate vicinity of the atoll. 

Ehlken. S., and Kirchner, G. (2002). Environmental processes affecting plant root uptake of radioactive trace elements and variability of transfer factor data a review. J. Environ. Radioact. 58. 97-112. 

In Chapter 1, Fyfe, Mueller, and Kokotailo describe the applications of solid-state NMR to the study of zeolite molecular sieve catalysts and related systems. Zeolites provide an apt arena in which to demonstrate the capabilities of modern techniques such as sample spinning, cross-polarization, and multidimensional correlation spectroscopy. In Chapter 2, Karger, and Pfeifer consider the question of molecular diffusion in catalyst systems. Applications of NMR techniques such as imaging, lineshape analysis, relaxation, pulsed field gradient echo spectroscopy, and NMR tracer exchange are described and compared with other, more traditional techniques such as radioactive tracing. In Chapter 3, Haw discusses the use of NMR to probe catalytic processes, showing how the combination of temperature control with novel NMR probes makes it possible to elucidate reaction mechanisms in situ. 

Hevesy and Paneth, in the first application of radioactive trace elements, determine the solubility of PbCrO using RaD. 

Santschi, P., U. P. Nyffeler, R. F. Anderson, S. L. Schiff, P. O Hara R. H. Hesslein, 1984. Response of radioactive trace metals to acid-base titrations in controlled experimental ecosystems evaluation of transport parameters for application to whole lake radiotracer experiments. Can. J. Fish. Aquat. Sci. 43 60-77. 

Americium (am)— A silvery metal that is a man-made element whose isotopes am-237 through am-246 are all radioactive trace quantities of americium are widely used in smoke detectors and as neutron sources in neutron moisture gauges. 

Foster, R. F. 1959. Radioactive tracing of the movement of an essential element through an aquatic community with specific reference to radiophosphorus. Pubbl. Stn. ZooL Napoli 31(Suppl.) 34-62. 

Americium (am) a silvery metal that is a man-made element whose isotopes am-237 through am-246 are all radioactive trace quantities of americium are widely used in smoke detectors, and as neutron sources in neutron moisture gauges Analysis approach selecting one of two primary approaches for FEMA one is the hardware approach that lists individual hardware items and analyzes their possible failure modes and the second is the functional approach that recognizes that every item is designed to perform a number of outputs within a system... 

FIGURE 1 Radioactivity traces of MGDG fatty acid esters and molecular species separated by HPLC after a 3 min pulse and a 60 second chase... 

---