Carbon-14, decay

Thus, three species from the gas phase, O2, CO, and CO2, take part in the reaction, and the generalized volatiles component, L, is extracted. The following formulae for the volatiles extraction and carbon decay rates from the fth model... 

Dimerization was observed in 1 -3 and t-6, because the decay of the absorption of 1 -3 and 1-6 increased with increasing [S], respectively. The transient absorption of c-1 shifted to that of t-1 during the decay because of the bimolecular isomerization of c-1 to t-1 via a-12. Similarly, the transient absorption of c-2 shifted to that of t-2 " through bimolecular isomerization, = (2.0-4.3) x 10 sec were calculated from the dependence of kobs on [S] (Table 2). No dimerization of c-6 was observed, because kobs did not depend on [c-6]. The transient absorption of c-1 with p-MeO and methyl group (Me) on the olefinic carbon decayed with kobs according to first-order kinetics without any shifts or dependence of [c-7]. In other words, neither unimolecular isomerization nor dimerization was observed in c-7. ... 

Event II was the main plankton extinction and productivity crisis coimected to the rapid collapse of the surface-to-deep water carbon isotope gradient and drops in barium and carbonate accumulation rates. Curiously, there was a hundredfold increase in the concentration of foraminifera relative to total carbonate. It could be due to intensified deep circulation with winnowing of the fine fraction. Or possibly to better the preservation of the dissolution-prone planktonic forms through deepening of the CCD and/or lowered rates of in situ dissolution caused by decreased decay of organic carbon in sediment pore waters. There is support for this idea from the fact that coccoHths tend to be more dissolution-resistant than foraminifera, also from calcite dissolution above the calcite saturation horizon is driven mainly by titration by metabolic carbon dioxide derived from organic carbon decay at or near the sediment-water interface. 

Ammo acid racemization (Section 27 2) A method for dating archeological samples based on the rate at which the stereo chemistry at the a carbon of ammo acid components is ran domized It is useful for samples too old to be reliably dated by decay... 

One example of a characterization application is the determination of a sample s age based on the kinetics for the decay of a radioactive isotope present in the sample. The most common example is carbon-14 dating, which is used to determine the age of natural organic materials. 

What mass of carbon is needed to give a percent relative standard deviation of 1.0% for the activity of a sample if counting is limited to 1 h How long must the radioactive decay from a 0.50-g sample of carbon be monitored to give a percent relative standard deviation of 1 % for the activity ... 

To prevent such release, off gases are treated in Charcoal Delay Systems, which delay the release of xenon and krypton, and other radioactive gases, such as iodine and methyl iodide, until sufficient time has elapsed for the short-Hved radioactivity to decay. The delay time is increased by increasing the mass of adsorbent and by lowering the temperature and humidity for a boiling water reactor (BWR), a typical system containing 211 of activated carbon operated at 255 K, at 500 K dewpoint, and 101 kPa (15 psia) would provide about 42 days holdup for xenon and 1.8 days holdup for krypton (88). Humidity reduction is typically provided by a combination of a cooler-condenser and a molecular sieve adsorbent bed. 

Fig. 3. pH Dependence of total organic carbon (TOC) decay during the photooxidation of a landfill leachate using H2O2/uv. Initial TOC concentration,... 

Potable Water Treatment. Treatment of drinking water accounts for about 24% of the total activated carbon used in Hquid-phase apphcations (74). Rivers, lakes, and groundwater from weUs, the most common drinking water sources, are often contaminated with bacteria, vimses, natural vegetation decay products, halogenated materials, and volatile organic compounds. Normal water disinfection and filtration treatment steps remove or destroy the bulk of these materials (75). However, treatment by activated carbon is an important additional step in many plants to remove toxic and other organic materials (76—78) for safety and palatability. 

Adsorption of Radionuclides. Other appHcations that depend on physical adsorption include the control of krypton and xenon radionuchdes from nuclear power plants (92). The gases are not captured entirely, but their passage is delayed long enough to allow radioactive decay of the short-hved species. Highly rnicroporous coconut-based activated carbon is used for this service. 

Mass Spectrometer. The mass spectrometer is the principal analytical tool of direct process control for the estimation of tritium. Gas samples are taken from several process points and analy2ed rapidly and continually to ensure proper operation of the system. Mass spectrometry is particularly useful in the detection of diatomic hydrogen species such as HD, HT, and DT. Mass spectrometric detection of helium-3 formed by radioactive decay of tritium is still another way to detect low levels of tritium (65). Accelerator mass spectroscopy (ams) has also been used for the detection of tritium and carbon-14 at extremely low levels. The principal appHcation of ams as of this writing has been in archeology and the geosciences, but this technique is expected to faciUtate the use of tritium in biomedical research, various clinical appHcations, and in environmental investigations (66). 

Locations. Weld decay may affect welded stainless steels that have normal carbon contents and are not specifically inhibited for sensitization. Weld decay affects only the immediate weld area. 

Note that low carbon or stabilized grades of stainless steel do not possess intrinsically greater corrosion resistance than their unadjusted counterparts. Their sole value in typical cooling water systems results from their resistance to sensitization and potential weld decay that can result when the metals are welded. It is therefore not economically justifiable to specify low carbon or stabilized grades of stainless steel for typical cooling water system components that are not to be welded. 

Color None Decaying organic material and metallic ions causing color may cause foaming in boilers hinders precipitation methods such as iron removal, hot phosphate softening can stain product in process use Coagulation, filtration, chlorination, adsorption by activated carbon... 

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