The aims and methods used in this study were the same as in Report 1. This report concerns with the cohort survey on two groups of children who entered primary school in 1971 and 1972 which was ...continued untill 1977. The results were as follows. 1) The number of examinees were 457 of 1 st grade pupils of primary school in 1971 and 463 of 1st grade pupils of primary school in 1972, 920 children in total. The number of those used in analysing data were 358 and 367, respectively. 2) ΣCx (cumulative number of carious teeth up to the post-eruptive tooth age x-year per initial 100 teeth), Cx (number of teeth newly attacked by caries during the post-eruptive tooth age x-year per initial 100 teeth) and Mx (caries incidence rate of teeth during the post-eruptive tooth age x-year) by kinds of teeth were shown in Table 2.
The effect of pressure on the molar volumes of wüstite (Fe0.924O) and three spinel phases of Fe2SiO4, Fe1.8Mg0.2SiO4 and Fe1.6Mg0.4SiO4 has been determined by means of the X‐ray diffraction method at ...pressures up to 255 kb at room temperatures. The isothermal bulk moduli for these minerals have been evaluated at zero pressure from the volume data by a least‐squares fit to the Birch equation. The value for wüstite thus determined is 1.42±0.10 Mb. The values for the spinel phases of olivines range between 1.96 and 2.12±0.10 Mb and are indistinguishable from each other. The mean volume thermal expansivity for the spinel phase of Fe2SiO4 has been determined to be (23±1)×10−6 °C−1 at a pressure of 1 bar and a temperature range of 8°–396°C by means of the X‐ray diffraction technique. On the basis of these data, the stability boundary for an assumed reaction, Fe2SiO4 (spinel) = 2 FeO(wüstite) + SiO2(stishovite), has been estimated to be P (kb) = 227.5 ‐ 0.022 T(°C).
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