Decay, correction for

F = fraction of total activity assigned to measured radiation D = decay correction for interval between time for which activity is determined and sample is measured... 

Short half-lives enable identification by decay measurement. They also require precise records of the time of sample collection, separation from the longer-lived parent, and the beginning and end of counting to calculate ingrowth and decay. Decay correction for reporting the activity at the time of collection is needed for all radionuclides, but is significant under usual sample analysis scheduling only for radionuclides with short and intermediate half-lives Sr is an example of the latter. 

The C content of a sample is described in a similar manner. The basis for Rq is an oxalic acid standard of the US National Bureau of Standards normalized for C fractionation and corrected for radioactive decay since a reference date January 1, 1950 (Stuiver and Polach, 1977). The absolute value of Rq is 1.176-10 (Stuiver et al, 1981). 

Measured concentrations of Th and Pa in marine sediments consist of three components that scavenged from seawater that supported by U contained within lithogenic minerals and that produced by radioactive decay of authigenic U. Most of the proxies described in this paper make use of only the scavenged component. Measured °Th and Pa must therefore first be corrected for the presence of the other two... 

Where all nuclide measurements are expressed in activities. In both expressions, the first term in curly brackets corrects for Th (or Pa) supported by U in lithogenic material, and the second term in curly brackets corrects for °Th (or Pa) ingrown from authigenic U. For samples that are known to be young, such as sediment trap or core-top samples, t = 0 and this second term equals zero reflecting the lack of time for decay of authigenic U in such samples. 

Age correction is also generally required in order to correct for the decay of excess °Th (or Pa) since the formation of the sediment. Only by such a correction can the conditions at the time of sediment formation be determined. For °Thxs, this correction is given by ... 

The unit cell (Table 1) and orientation matrix were determined from the XYZ centroids of 8192 reflections with I > 20c(7). The intensities (SAINT [8]) were corrected for beam inhomogeneity and decay, and the esd s adjusted using SADABS [9]. An absorption correction was applied (Tmin 0.949, Tmsx 0.983) and symmetry and multiply measured reflections averaged with SORTAV [10]. 

FRET applications employing CFP and YFP are complicated due to considerable bleed-through between CFP and YFP fluorescence (Figs. 5.5B and 5.6B). Direct excitation of YFP and bleed-through of CFP fluorescence into the YFP detection channel have to be corrected for as shown in Chapters 7 and 8. The multiexponential fluorescence decay of all CFP variants complicates the quantification of FRET by donor lifetime methods. Altogether these factors make quantitative analysis of the FRET efficiency relatively difficult. 

If we choose a much larger than 1 (thin samples d<0.5L) or h pL (thick samples d>>L), the final steady-state exhalation deviates very little from the free exhalation rate and we do not need to know the reshaping time or use Equation 2 for corrections. An air grab sample taken at any time (and corrected for radioactive decay if necessary) after closure, will yield the free exhalation rate to a good approximation, provided that the can is perfectly radon-tight. 

Burns and Curtiss (1972) and Burns et al. (1984) have used the Facsimile program developed at AERE, Harwell to obtain a numerical solution of simultaneous partial differential equations of diffusion kinetics (see Eq. 7.1). In this procedure, the changes in the number of reactant species in concentric shells (spherical or cylindrical) by diffusion and reaction are calculated by a march of steps method. A very similar procedure has been adopted by Pimblott and La Verne (1990 La Verne and Pimblott, 1991). Later, Pimblott et al. (1996) analyzed carefully the relationship between the electron scavenging yield and the time dependence of eh yield through the Laplace transform, an idea first suggested by Balkas et al. (1970). These authors corrected for the artifactual effects of the experiments on eh decay and took into account the more recent data of Chernovitz and Jonah (1988). Their analysis raises the yield of eh at 100 ps to 4.8, in conformity with the value of Sumiyoshi et al. (1985). They also conclude that the time dependence of the eh yield and the yield of electron scavenging conform to each other through Laplace transform, but that neither is predicted correctly by the diffusion-kinetic model of water radiolysis. 

Rzad et al.( 1970) compared the consequences of the lifetime distribution obtained by ILT method (Eq. 7.27) with the experiment of Thomas et al. (1968) for the decay of biphenylide ion (10-800 ns) after a 10-ns pulse-irradiation of 0.1 M biphenyl solution of cyclohexane. It was necessary to correct for the finite pulse width also, a factor rwas introduced to account for the increase of lifetime on converting the electron to a negative ion. Taking r = 17 and Gfi = 0.12 in consistence with free-ion yield measurement, they obtained rather good agreement between calculated and experimental results. The agreement actually depends on A /r, rather than separately on A or r. 

Fig. 5. Retention of 144Ce in lung, liver, skeleton, and soft tissue remainders of Beagle dogs after inhalation of l44Ce chloride in Cs chloride aerosol particles. Average values and total ranges of data are shown in the upper figure along with solid line curves which were projected from the biological model, all of which include physical decay. The lower figure shows the same model projections only corrected for physical decay.

Pulmonary retention functions are given as fractions of the initial pulmonary burden and are not corrected for radioactive decay of lMCe Ti/> = 285 d). 

Data are not corrected for physical decay and are listed in approximate order of decreasing radioactivity concentrations. h Tissue weights were normalized to a total body weight of 10 kg. c L.N. indicates Lymph Nodes. 

However for several of the molecules shown in Figures 1 and 2, DNA has only a small effect on the observed fluorescence lifetime. These molecules include trans-7,8-dihydroxy-7,8-dihydro-BP (15,18,19), trans-4,5-dihydroxy-4,5-dihydro-BP (15,18), BPT (7,18), 1,2,3,4-tetrahydro-BA (12), 8,9,10,11-tetrahydro-BA (14), 5,6-dihydro-BA (12), anthracene (12) and DMA (14). Typical decay profiles obtained in fluorescence lifetime measurements of trans-7,8-dihydroxy-7,8-dihydro-BP and of 8,9,10,11-tetrahydro-BA are shown in Figure 6. The lifetimes extracted from the decay profiles shown here have been obtained by using a least-squares de-convolution procedure which corrects for the finite duration of the excitation lamp pulse (77). 

Procedures for pretreatment of soil samples and synthesis of sample benzene for 14C analysis had been described in Chen et al. (2002b). Sample benzene was often left for 3-4 weeks to allow any radon with half-life of 3.82 days that may be present to decay. 14C activity of the CgFL was then determined using a 1220-QUANTULUS ultralow-level liquid scintillation spectrometer manufactured by WALLAC Company, Sweden. The 14C analyses were conducted at the Guangzhou Institute of Geochemistry, CAS. Results are reported as A14C, in parts per thousand of the 14C/12C ratio from that of the standard (oxalic acid decay corrected to 1950) (Stuiver and Po-lach 1977), and corrected for bomb 14C (Chen et al. 2002b), where ... 

---