Yttrium estimator method

In the Exposure Factors Handbook, US-EPA (1997) has identified seven key studies which employ methods based on measurements of tracer elements, and nine other studies on soil intake among children. The individual key studies used between three and eight different tracer elements. Not all the tracer elements turned out to be useful for estimation of the daily soil intake aluminum, silicon, and yttrium appeared to be the most reliable. The results of the studies are summarized in Table 7.4. 

A similar approach can be applied for the Y atom insertion into the C-H bond of alkenes and other alkanes. Our calculation by the Cl method in a 6-311-H-G(2d,2p) basis set with a complete active space for 8 electrons in 8 orbitals (Is orbital of carbon atom is frozen) predicts that the vertical S-T excitation energy in methane is around 11 eV (11.37 eV or 262 kcal/mol). Following the above approximation it is equal -2 Jch- From Eq. (9) the activation energy for the yttrium atom insertion reaction, Eq. (1) M=Y, should be 17.6 kcal/mol. This simple estimation is in a good agreement with very accurate ab initio calculations, Ea = 20.7 kcal/mol [15]. 

There are no measurements of the heat capacity of ThD2(cr) or ThT2(cr), but Flotow et al. [1984FLO/HAS] have estimated the following values by modelling the heat capacity contributions from the lattice vibrations, represented by an Einstein function, conduction electrons and acoustic modes. This method had been shown to be valid for the deuterides of uranium, yttrium and zirconium. 

Coehoorn (1991) used a similar method to calculate electronic structures of rare-earth-transition-metal compounds. Figure 4b shows schematic representations of his calculation of the dependence of the average magnetic moment on cell volume in bcc-Fe and Y2Fei7. In the case of yttrium-iron compounds, we can estimate the volume dependence of the magnetic properties of the Fe sublattice because of the lack of 4f electrons at rare-earth sites. The cross denotes the moment at the equihbrium volume. 

One additional method used to study single phase /3-Ce is by alloying with an element which stabilized the /3-phase field such as lanthanum (Roberts and Lock, 1957) or yttrium (Panousis and Gschneidner, 1972). The properties of the pure /3-phase may be estimated by extrapolation of data measured at several alloy compositions to 100% /3-Ce. 

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