Single crystal X ray experiments have been performed for calcite, calcite II, and calcite III at 300 K and pressures up to 4.1 GPa. The volume decrease from calcite to calcite II is estimated to be 0.54 cm 3 /mol (1.5 %) at 1.5 GPa, which compares well with the value 0.48 cm 3 /mol in the calcite to calcite II transition at 1.4 GPa reported previously based on piston cylinder volume compression experiments. The crystal data of calcite III have been determined using single crystal X ray analyses at 300 K and pressures between 2.3 and 4.1 GPa. The calcite III crystal is found to be monoclinic with the space group either C2, Cm, or C2/m from the systematic absence of reflections, and with the refined cell parameters of a = 8.707(7), b = 9.315(6), c = 6.154(4) A , and = 115.18(2) at 2.3 GPa. These crystal data of calcite III at 2.3 GPa yield a density of 2.94 g/cm 3 for Z = 8, which is much less than the previously estimated densities, ranging from 3.11 to 3.28 g/cm 3 at pressures from 1.9 to 2.9 GPa, using powder X ray analyses based on orthorhombic structural models for calcite III, but is generally consistent with the reported data by the piston cylinder experiments. Thus the present study reveals the density of calcite III is substantially less than that of aragonite (3.02 g/cm 3 at 2.3 GPa), indicating that calcite III is metastable with respect to aragonite at high pressures.

This paper proposes non-contact control of supporting of an elastic long shaft by using active magnetic bearing (AMB) system. We aimed to develop a magnetic bearing system that takes dynamic of the elastic body into consideration. An experimental system supporting the shaft with two AMBs is built and control experiments are carried out. As a first trial simple Proportional-Derivative (PD) feedback controllers are applied and levitation of the shaft is succeeded, while the 1st elastic mode of the shaft is appeared but undamped.

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