Determination from radioactivity

The two preceding methods have been combined to determine the tritium isotope effect. In a tritium-labeled substrate in D20, the change in infrared radiation absorption arises almost entirely from release of protons because the concentration of the tritium species in the reactant is small. Thus, the rate constant kH (determined by the change in the DOH absorption) represents release of protons. The constant kT for release of tritium to the solvent is determined from radioactivity measurements of water from the same reaction mixture. In the enolization of... 

Other isotopes can be used to determine the age of samples. The age of rocks, for example, has been determined from the ratio of the number of radioactive atoms to the number of stable gfPb atoms produced by radioactive decay. For rocks that do not contain uranium, dating is accomplished by comparing the ratio of radioactive fgK to the stable fgAr. Another example is the dating of sediments collected from lakes by measuring the amount of g Pb present. 

Answer Review the plant s design to determine how radioactive water could get from the plant to the river. Some ways are i) through the heat exchanger and through the condenser, ii) from the closed circuit water into the service water, iii) from the spent fuel storage pool, and iv) from the sump. Prepare fault trees or adapt existing fault trees to determine the probability of each of these release paths. Obtain reliability data for the components that are involved and evaluate the fault trees to determine the probability of each type of failure. For those pathways with a probabilit >7/y,... 

Radioactivity Analysis. Samples of urine, feces, and tissues were combusted to COo and analyzed for radioactivity (5). By using this method the recovery of radioactivity from samples spiked with C was 95 dt 5%. To determine the radioactivity expired as CO2, 5-ml aliquots of the solution used to trap the CO2 were added to 15 ml of a scintillation counting solution containing 4 grams 2,5-diphenyloxazole (PPO) and 0.1 grams l,4-bis-2(5-phenyloxazolyl)-benzene (POPOP) per liter of 1 1 toluene 2-methoxyethanol. Samples were counted for radioactivity in a Nuclear Chicago Mark II liquid scintillation counter. Counting eflSciency was corrected by the internal standard technique. 

FIGURE 1 Biodegradation of unsterilized NET microcapsules (63-125 pm) as determined by radioactive recoveries from injection sites of rats. (From Ref. 38.)... 

The area under the PCP concentration-time curve (AUC) from the time of antibody administration to the last measured concentration (Cn) was determined by the trapezoidal rule. The remaining area from Cn to time infinity was calculated by dividing Cn by the terminal elimination rate constant. By using dose, AUC, and the terminal elimination rate constant, we were able to calculate the terminal elimination half-life, systemic clearance, and the volume of distribution. Renal clearance was determined from the total amount of PCP appearing in the urine, divided by AUC. Unbound clearances were calculated based on unbound concentrations of PCP. The control values are from studies performed in our laboratory on dogs administered similar radioactive doses (i.e., 2.4 to 6.5 pg of PCP) (Woodworth et al., in press). Only one of the dogs (dog C) was used in both studies. 

Witschi and colleagues19 identified the requirement for metabolic activation of BHT in determining that radioactivity from 14C-labeled BHT became covalently bound to proteins in mouse lung. Both toxicity and protein binding were prevented when mice were treated with cytochrome P450 inhibitors, thereby indicating the... 

After the end of the 4-day exposure, the detectors were returned to EML for analysis. The amount of radon adsorbed on the carbon device was determined by counting the gamma rays of radon progeny in equilibrium with radon. The concentrations of radon in the buildings were determined from the radioactivity in the device and the calibration factor, obtained in a radon chamber, that takes into consideration the length of exposure and a correction for the amount of water vapor adsorbed during the exposure. The lower limit of detection with this technique is 0.2 pCi/1 for a measurement period of 4 days when the test sample is counted for 10 min, 4 days after the end of exposure. More than 90% of the radon monitoring devices were analyzed successfully. Most of the unsuccessful measurements were due to delays or losses caused by the participants. 

The enteral absorption of bromocriptine from an aqueous solution amounts to 30 - 40 % as determined from the sum of the cumulative biliary and urinary excretion of radioactivity (parent drug + metabolites) in bile duct cannulated animals. 

The radiochemical assays were done as follows At the end of a polymerisation experiment, when the conductivity had become constant, a ten-fold excess of tritiated water was added from a burette (see Figure 1), the cell was warmed rapidly to room temperature, and any polymer which had been precipitated during the polymerisation was allowed to re-dissolve. It was always noted that no hydrolysis occurred until the solutions reached 0 °C. This could be seen from a rapid drop of conductivity to a very low value. The solvent and most of the tritiated water were then distilled out, within about 15 minutes. The polymer was then dissolved in toluene, also run from a burette into the reaction vessel, which was then cut from the vacuum line. The polymer was precipitated in methanol and prepared for the determinations of radioactivity and DP. For the radiochemical assay the polymers were dissolved in toluene, re-precipitated in methanol, dried, weighed, re-dissolved in toluene, and the activity determined. The processes of precipitation and dissolution were repeated until the activity of the polymer became constant, (up to 7 repetitions). It was assumed that when the activity had become constant, all the excess of tritium had been removed. 

Mass-spectroscopic technique has also been used with non-fissile targets after pile or cyclotron bombardment to determine the mass-numbers of radioactive nuclides. In one case, the branching ratios of certain isotopes for and electron capture decay (where different elements are produced by the two routes) were determined from the amount of the stable end-products of radioactive decay, using the mass-spectrometer to identify the isotopes concerned and to correct for any stable impurities of the elements concerned (98). For some purposes, mass-spectroscopic separations could be very valuable technically such as the... 

These rules can now be applied to the three radioactive series in Figs. 1.1 and 1.2. The names of the various elemental materials are given in the figures. The atomic weights of each can be determined from the rules above, given the respective atomic weights of the parent of each series, taken here as UrI = 238.5, Th = 232.4, and... 

Such a mechanism is not incompatible with a Haven ratio between 0.3 and 0.6 which is usually found for mineral glasses (Haven and Verkerk, 1965 Terai and Hayami, 1975 Lim and Day, 1978). The Haven ratio, that is the ratio of the tracer diffusion coefficient D determined by radioactive tracer methods to D, the diffusion coefficient obtained from conductivity via the Nernst-Einstein relationship (defined in Chapter 3) can be measured with great accuracy. The simultaneous measurement of D and D by analysis of the diffusion profile obtained under an electrical field (Kant, Kaps and Offermann, 1988) allows the Haven ratio to be determined with an accuracy better than 5%. From random walk theory of ion hopping the conductivity diffusion coefficient D = (e /isotropic medium. Hence for an indirect interstitial mechanism, the corresponding mobility is expressed by... 

The intrinsic variable expressed as units of radioactivity (in becquerels or, more traditionally, curies) per mole of a substance. One Bq corresponds to 1 disintegration per second (dps) and one Ci to 3.70 x 10 ° Bq. This parameter is especially useful in quantifying the amount of substance in biological samples. For example, if SAs is the standard specific radioactivity (say, x dps/y mol) of a standard, and if SAg is the experimental specific activity (say, x dps/(y + z) mol), then the content z in a sample can be determined from the expression (SAs/ SAe) = (y + z)/y or z = y ([SAj/SAg] - 1). This intrinsic variable can also be expressed as the gram-atom excess of a stable isotope per mole of a substance. The numerator is typically determined using a ratio mass spectrometer, and the denominator can be estimated by chemical and/or spectroscopic techniques. 

Salicylic acid and Its metabolite were separated by two methods. The first was thin layer chromatography on cellulose with BAW solvent as for the In vivo metabolism studies. A quicker separation was achieved with a polyamide column. The entire 400 pL from an individual assay was placed on top of a 0.8 x 2.0 cm column packed with Polyamide-6 (Accurate Chemical and Scientific Corp.). The salicylic acid metabolite was eluted with 6 mL water but salicylic acid was retained. 3a70B scintillation fluid (Research Product International Corp.) was used to determine the radioactive content of the entire 6 mL of eluant. Separation of salicylic acid and its metabolite by polyamide column chromatography was verified by thin layer chromatography. 

The element may be determined from its radioactivity using tracer techniques. Isotopes of the element may be identified by mass spectrometry. 

Professor of physics at MoGill, Manchester, and Cambridge Universities. He identified the three types of radiations from radioactive substances, and devised methods for counting alpha particles and for determining the number of free positive electrons in the nucleus of an atom. 

Theodore William Richards, 1868-1928. Director of the Wolcott Gibbs Memorial Laboratory at Harvard University. The precision of his atomic weight determinations has never been surpassed. He discovered the anomalous atomic weights of lead from radioactive minerals. 

The production of Pb by radioactive decay of U may also affect the oxidation state of uraninite by a process called auto-oxidation (Frondcl 1958 Finch Murakami 1999). Radiogenic Pb4+ is a strong oxidizer and due to its instability in the presence of U4+, it is reduced to Pb2+ while simultaneously U4+ oxidizes to U6"1" leading to elevated U6+/U4+ ratios in uraninite. The U6+/U4+ ratios determined from XPS spectra of uraninite from Cigar Lake can be... 

Table 3 shows the coupling efficiency as a function of the desactivation temperature. It gives also the amount of radioactive groups C- l labeled C = 0 or C = NH groups derived from CN, as determined by radioactivity measurements. It can be noticed that the polymers present only a low amount of C, ranging from 0.1 % to about b % of the theoretical value by considering the reaction mechanism or . The reaction mechanism 0 seems therefore... 

Cosmic-ray exposure ages are determined from spallation-produced radioactive nuclides. Cosmic-ray irradiation normally occurs while a meteoroid is in space, but surface rocks unshielded by an atmosphere may also have cosmogenic nuclides. These measurements provide information on orbital lifetimes of meteorites and constrain orbital calculations. Terrestrial ages can be estimated from the relative abundances of radioactive cosmogenic nuclides with different half-lives as they decay from the equilibrium values established in space. These ages provide information on meteorite survival relative to weathering. 

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