Proceedings of the Japan Academy, Series B

Stability of Magnesite under the Lower Mantle Conditions

Tomoo KATSURA, Yoshihiko TSUCHIDA, Eiji ITO, Takehiko YAGI, Wataru UTS ...

1991 Volume 67 Issue 4 Pages 57-60
Published: 1991
Released on J-STAGE: October 13, 2006

DOIhttps://doi.org/10.2183/pjab.67.57

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High-pressure and high-temperature stability of MgCO₃ magnesite was investigated using a lever and spring type of diamond anvil cell up to 55GPa at about 1300°C. No phase transformation was observed in magnesite at the pressures investigated. Magnesite would be a dominant carbon-reservoir in the lower mantle. The volume of magnesite at 55GPa is 77% of that at the atmospheric pressure. The compressibility in the c-axis is 8% larger than that in the a-axis.

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Bridgman Anvil with a Sintered Diamond Core for Phase Transformation Studies at High Pressures and High Temperatures

Masaki AKAOGI, Teruhiko YAMAZAKI

1991 Volume 67 Issue 4 Pages 61-65
Published: 1991
Released on J-STAGE: October 13, 2006

DOIhttps://doi.org/10.2183/pjab.67.61

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A new Bridgman anvil composed of tungsten carbide with a sintered diamond core is described. The truncated face of the anvil is 26mm in diameter, the central part of which consists of the sintered diamond core 15mm in diameter. Using the newly developed Bridgman anvils, pressures up to about 20.5GPa were successfully generated at room temperature. Phase transformation experiments were carried out using the Bridgman anvils with an internal heating system. 5-10mg sample was charged in a single high-pressure high-temperature run. The disproportionation boundary of Zn₂SiO₄ modified spinel to a mixture of ZnSiO₃ ilmenite and ZnO rocksalt was determined as P(GPa)=12.3+1.3×10^-3T(°C) by the Bridgman anvil apparatus.

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Phase Transition and Glass Transitions in Isocyanocyclohexane Studied by a Polaro-Calorimeter

Isao KISHIMOTO, Jean-Jacques PINVIDIC, Takasuke MATSUO, Hiroshi SUGA

1991 Volume 67 Issue 4 Pages 66-71
Published: 1991
Released on J-STAGE: October 13, 2006

DOIhttps://doi.org/10.2183/pjab.67.66

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Calorimetric and electric measurements have been performed simultaneously on Isocyanocyclohexane by using a polaro-calorimeter, which is essentially an adiabatic calorimeter with built-in electrodes in the sample cell. A phase transition between plastically crystalline and ordered low-temperature crystalline phases was found at 192.6 K. The corresponding enthalpy and entropy changes were determined to be 6.177kJ mol^-1 and 32.07J K^-1mol^-1, respectively. Glassy crystal was formed by supercooling the plastically crystalline state. It underwent three glass transitions at 55K, 130K and 160K. Results of the simultaneous measurement of relaxation of the enthalpy and electric polarization were adequately described by an empirical Kohlrausch-Williams-Watts function.

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High Coherence between the Most Refractory Siderophile Elements in Metallic Materials of Meteorites

Akimasa MASUDA, Takafumi HIRATA

1991 Volume 67 Issue 4 Pages 72-77
Published: 1991
Released on J-STAGE: October 13, 2006

DOIhttps://doi.org/10.2183/pjab.67.72

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Re and Os abundances in twelve iron meteorites of various groups and five stony iron meteorites have been determined by isotope dilution employing an inductively coupled plasma mass spectrometry (ICP-MS). Re and Os abundances were found to have a wide variation covering nearly four orders of magnitude, with a very high correlation coefficient (0.996), showing a slope very slightly gentler than unity. The regression line observed here covers various groups of iron meteorites and stony iron meteorites. This feature can be interpreted to reflect a single“universal”effect such as direct mixing of particles of most refractory metallic elements with gaseous cloud of less refractory matrix elements, predating the formation of meteorites, since Re and Os are predicted theoretically to be the first elements that condense as a solid phase from high temperature solar nebula. The aim of this paper is to study the relationship between the siderophile refractory elements, Re, Os and Ir, together with their bearings on Ni, and to draw some implications for the early sequences of the solar system.

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Cytoplasmic Movement in Spirogyra during and after Centrifugation

Kiyoko KURODA, Noburô KAMIYA

1991 Volume 67 Issue 4 Pages 78-82
Published: 1991
Released on J-STAGE: October 13, 2006

DOIhttps://doi.org/10.2183/pjab.67.78

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The mode of dislocation of the cell organelles in Spirogyra was observed while the algal filaments were being centrifuged at 600rpm (40g). When all the chloroplasts were packed at the centrifugal end of the cell together with the nucleus and most of the cytoplasm, a large clear area appeared in the centripetal end where only a thin layer of cytoplasm was left beneath the plasma membrane. Active movement of tubular organelles (endoplasmic reticulum, ER) was clearly seen in this area. With rhodamine-conjugated phalloidin, distinct fibrous structures (bundles of F actin) showed up running more or less longitudinally or transversally to the cell axis. By staining with DiOC₆(3), a faint fluorescent image coinciding with that of the moving tubular organelles became recognizable but only for a few seconds after blue light irradiation before it was rapidly transformed into a polygonal structure. The formation of the polygon was reversible, but it did not present the normal state of the ER. The movement of the tubular ER is supposed to be caused by the interaction of the cortical F actin bundles and putative myosin-like protein(s) attached to the ER.

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