Radioactivity carbon

OtherApphca.tlons. Many appHcations of adsorption involving radioactive compounds simply parallel similar appHcations involving the same compounds in nonradio active forms, eg, radioactive carbon-14, or deuterium- or tritium-containing versions of CO2, H2O, hydrocarbons. For example, molecular sieve 2eohtes are commonly employed for these separations, just as for the corresponding nonradio active uses. 

Even higher organisms can be used for the production of labeled compounds. Plants, tobacco, or Canna indica for example, when grown in an exclusive atmosphere of radioactive carbon dioxide, [ 002], utilize the labeled precursor as the sole source of carbon for photosynthesis. After a suitable period of growth, almost every carbon atom in the plant is radioactive. Thus, plants can serve as an available source of C-labeled carbohydrates (9). 

When a plant or animal dies, the intake of radioactive carbon stops. Consequently, the radioactive decay of carbon-14... 

It is immediately clear that Acanthomyops need not rely on dietary sources of terpenes but can synthesize citronellal and citral from either acetate or mevalonate. The higher total activity of the citronellal as compared with the citral probably reflects the natural preponderance of citronellal (ca. 90%) in the ant secretion. As the specific activities show, these results are consistent with a common biogenetic origin of both terpenes. In the mevalonic acid pathway as described from other organisms (13), the radioactive carbon of l-C14-mevalonate is lost upon formation of isopentenyl pyrophosphate. 

In the production of TNT from the reaction between toluene and mixed acids (nitric/sulfuric), TeNMe forms in amounts between 0.2—0.4% of the total wt of TNT. This TeNMe has been held responsible for several expins which have occurred in TNT plants, causing fatal injuries to personnel and severe damage to facilities. These expins were attributed to the presence of TeNMe in the acid fume lines and the acid storage tanks. Mixts of TeNMe and readily oxidizable materials are known to form very powerful and sensitive expl mixts. Since TeNMe is also isolated from the nitration of Nitrobenzene (NB), the TeNMe formed in the nitration of toluene may arise from the oxidation of the aromatic ring and/or methyl group. In an effort to gain more informa-. tion on the origin of TeNMe from TNT production, radioactive carbon-14 (14C) was used as a tracer to determine the extent to which each of the carbon atoms in the toluene skeleton of the various nitro-substituted isomers contributes to... 

The ratio Nq j N must be a number greater than one, because the amount of radioactive carbon always decreases with time. The fraction for the shroud, 1.09, is significantly smaller than the ratio expected for a 2000-year-old object, 1.274. The smaller ratio means that less radioactive carbon has disintegrated, indicating that the object is not as old as 2000 years. 

C22-0114. The amount of radioactive carbon in any once-living sample eventually drops too low for accurate dating. This detection limit is about 0.03/g min, whereas fresh samples exhibit a count rate of 15.3/g min. What is the upper limit for age determinations using carbon dating ... 

Soon after their creation, the newly formed radiocarbon atoms react with atmospheric oxygen to form radioactive carbon dioxide, molecules of carbon dioxide in which the carbon atom is radiocarbon ... 

Allen, M. B., and S. Ruben Tracer Studies with Radioactive Carbon and... 

Experiments involving the release of radioactive carbon dioxide from MSMA-14C treated soils were conducted in a system consisting of two test tubes connected in series. One tube contained 5g of treated soil (at 10 and lOOppm of monosodium methane arsenic acid carbon dioxide while a second tube contained a trapping mixture, 2-methoxyethanol and monoethanolamine (7-10, v/v). Carbon dioxide-free air was passed over the soil and metabolic 14CO was collected in the trapping solution. The soils studied were Sharkey cldy, Hagerstown silty clay loam, Cecil sandy loam, and Dundee silty clay loam. All soils were initially adjusted to field capacity and maintained at 28-30°C the evolved 14CO was sampled periodically. Some properties of these soils are shown in Tabfe 13.1. 

Matsson and coworkers have measured the carbon-1 l/carbon-14 kinetic isotope effects for several Menshutkin reactions (equation 35) in an attempt to model the S/v2 transition state for this important class of organic reaction. These isotope effects are unusual because they are based on the artificially-made radioactive carbon-11 isotope. The radioactive carbon-11 isotope is produced in a cyclotron or linear accelerator by bombarding nitrogen-14 atoms with between 18- and 30-MeV protons (equation 36). 

Radioactive Carbon of High Specific Activity. Physic. Rev. 73, 254... 

Ruben, S., and M. D. Kamen Longlived Radioactive Carbon C14. Physic. 

When 23 reacts in this ANRORC process, in fact two intermediates, a cyanoimidoyl chloride (24) and a dicyanoazadiene (25), can be postulated (Scheme 11.16). When the dicyano compound 25 is the transient open-chain intermediate, scrambling of the radioactive carbon over both cyano groups takes place, and consequently after ring closure (route a), incorporation of the C-label into the pyrimidine ring should be expected (Scheme 11.16). 

Wolfe has presented an excellent description of the systematic application of stable and radioactive isotope tracers in determining the kinetics of substrate oxidation, carbon dioxide formation (including C02 breath tests), glucose oxidation, and fat oxidation in normal and diseased states. Quantification of the rate and extent of substrate oxidation can be achieved by using a specific or C-substrate which upon oxidation releases radioactive carbon dioxide. 

The method builds on the fundamentals of radiocarbon dating via analysis, an analytical method that relies on the nuclear decay of radioactive carbon that is incorporated from the atmosphere into all living, respiring plants. The is present in the atmosphere as " C02. The level of is extremely low, only one part per trillion of the natural abundance of carbon in the atmosphere. When plant respiration ceases, the uptake of stops, but the slow radioactive decay of... 

The volatile metabolites comprised 6% of the radioactivity. Carbon dioxide formed the main component. Other compounds, including carbonyl sulfide, were detected only in traces below 0.04%. 

Beryllium nitride is used in nuclear reactors and to produce radioactive carbon-14 isotope for tracer applications. 

McCollister DD, Beamer WH, Atchison GJ, et al. 1951. The absorption, distribution and elimination of radioactive carbon tetrachloride by monkeys upon exposure to low vapor concentrations. J Pharmacol Exp Therap 102 112-124. 

Radioactive elements are ones in which the atoms break up, changing into atoms of other elements. The time taken for half the original element to disappear is called the half-life. The man-made element fermium has a half-life of 80 days. Thus, if a gramme of fermium were made today, less than one-sixteenth of a gramme would be left at the end of a year. The half-life can be very useful. By measuring the amount of radioactive carbon left in fossil remains, or other matter that was once alive, scientists can determine their age. 

This is well known data but unfortunately it has never been published. It was given at the London Coordination Conference. The reaction involved the addition of radioactive carbon monoxide to methylmanganese pentacarbonyl. The carbon monoxide entering did not go in the acyl position but went exclusively in a coordination position. It seems that at least in this one example it is a coordinated ligand that is inserting. 

The polymer obtained in these tests was found to be always radioactive. It is most likely that the radioactive carbon found in the polymer comes from the ethyl groups initially contained in the catalytic complexes bound to the active centers of the a-titanium trichloride surface. The results obtained in such measurements are summarized in Table X (49). 

It has been assumed that all radioactive carbon found in the polymer is contained in it as —C2H6 groups. 

When compounds enriched in the heavy-carbon isotope 13C and the radioactive carbon isotopes nC and 14C became available about 60 years ago, they were soon put to use in tracing the pathway of carbon atoms through the citric acid cycle. One such experiment initiated the controversy over the role of citrate. Acetate labeled in the carboxyl group (designated [1-14C] acetate) was incubated aerobically with an animal tissue preparation. Acetate is enzymatically converted to acetyl-CoA in animal tissues, and the pathway of the... 

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