Decay correction factor

It is not uncommon to supply air into the room with jets attached both to the ceiling and to the wall surfaces. Air jets can be parallel to both surfaces or be directed at some angle to one or both surfaces (Fig. 7.28). Studies of compact wall jets supplied parallel to both surfaces reported by Grimitlyn show that the correction factor value is in the range from 1.6 to 1.7, which means that restriction of entrainment from two sides reduces velocity decay by 20% to 30% compared to the case of a wall jet. 

Requirements for standards used In macro- and microspectrofluorometry differ, depending on whether they are used for Instrument calibration, standardization, or assessment of method accuracy. Specific examples are given of standards for quantum yield, number of quanta, and decay time, and for calibration of Instrument parameters. Including wavelength, spectral responslvlty (determining correction factors for luminescence spectra), stability, and linearity. Differences In requirements for macro- and micro-standards are considered, and specific materials used for each are compared. Pure compounds and matrix-matched standards are listed for standardization and assessment of method accuracy, and existing Standard Reference Materials are discussed. 

The actual curve, however, is somewhat modified by Coulomb interaction between the electron or positron and the nucleus. This is allowed for by multiplication with a dimensionless function F(Z p), which leads to a correction factor / for the total decay rate, and it is the product ft that is used for purposes of comparing measured lifetimes with theory. The most rapid decays, with ft = 103 to 104 s, are known as super alio wed . These include 0+ to 0+ decays having A//, 2 = 2 and ft is found experimentally to be close to 3000 s, giving the coupling constant for the Fermi interaction... 

The correct normalization from the photoionization process gives a factor (47i)2a ph/3 and that from the Auger decay a factor coJAn, which finally leads to... 

Table 1 Composite of our own SW data [14] on the chemically induced variations of the EC decay constant X of Cr" with the corresponding SR-SW results [13] (in parentheses, the Bahcall correction factors have been introduced by us, for the sake of comparability).

After Lp, absorption and radiation damage decay corrections to the integrated intensities the observed structure factors (Fobs) are obtained. Each measured reflection thus will have the corresponding Fobs- In other words, Fobs is the square root of the measured intensity of a given reflection corrected for effects that come from the properties of the crystal itself. 

Measurements of the solid fat content are made by taking the amplitude of the FID at two times (typically 10 and 70 /is) following the 90° pulse. The first amplitude is proportional to the total number of protons (solid plus liquid phase) whereas the second amplitude depends only on the number of liquid-phase protons. The rapid decay of the solid-phase signal requires that a correction factor is determined to allow for the decay of the signal during the spectrometer dead-time. The correction factor is determined using calibration standards of known composition. Details of calibration methods, tempering procedures for fats and a comparison of NMR with other methods can be found in a review.22 Other publications in this area are listed in Table 8. 

Neutron absorption in fission products has a small effect on decay-heat power for r < 10 s and is treated by a correction factor G. The corrected total decay-heat power is given by the ANS Standard, in terms of thermal-neutron flux (in neutrons/cm s), reactor operating time T (in s), and cooling time t (in s) as... 

For a focal length/ = 2 mm this correction factor rj is depicted in Figure 8.4. Its value at the focal point F becomes significant for small values of the wave vector k = co Jc. This corresponds to cases in which the two-level system is close to the mirror surface, i.e., z +f < X. However, for larger values of k the variations of r] are shifted toward the mirror surface. Far away from the mirror r] tends to unity so that the decay rate reduces to its free-space value. According to these results modifications of fhe spontaneous decay rate could be observable on a scale of 100 nm buf only within a distance of the order of the wavelength from the mirror surface. 

The decay or ingrowth factor T) is a correction factor for decay or ingrowth of the radionuclide before and during counting. For the simple situation where the radionuclide of interest is not supported by a parent in the sample, the decay factor is given by... 

Here X denotes the radionuclide decay constant,fo denotes the time from sample collection to the start of sample counting, and denotes the real time, or clock time, of the sample counting measurement, which may be longer than the live time Ic- When the time r is short relative to the half-life of the radionuclide, the product XfR may be very small, and as XtR approaches zero, the correction factor for decay during counting, (1 - e )/XtR, approaches 1. If the value of this factor is sufficiently close to 1, it may be omitted from the expression for D. When it is included, it must be calculated carefully to avoid large round off errors when XtR is small. 

If ipn is the approximate wave function, then in (12.2.1) the factor li/>n(0)P can be corrected into (0) 2(1 — yo s/7r). The correction factor, in this approach, is uncomfortably large. The relativistic kinematic terms, which are ignored in (12.2.1), are likely to be relevant only for decay into T+r pairs. 

Plate the Th (Section 13.7.7). Count lli in the alpha spectrometer. Count the beta activity using a thin plastic cover (eg., overhead sheet, 0.1mm polyester, 14mg/cm ) to absorb Th alphas and most (78 %) of Th betas. This cover lets most (91 %) of the 234mpg betas through. Calculate the Ih activity (see below for calibration factor). For decay correction, use the time of Fe(OH)3 precipitation as the time of U and Th separation. Tliis introduces some error, as some U is copredpitated and only removed in the chloride column. The contribution of other beta emitters can be quantified by repeating the beta countings and fitting the results to the decay rate of Th (Buesseler et al., 1994). 

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