A laser heating system is described for use with diamond anvil high pressure cells that directly senses and stabilizes visible thermal radiation emitted by hot samples. This technique stabilizes sample temperatures better than other methods and allows superior temperature control. Calibration of the system was checked by measuring the melting temperatures of five metals at ambient pressure. Assuming literature values for spectral emissivity, the calibration was found to be accurate to 3.3% (based upon one standard deviation of the percentage error from published melting temperatures). Performance of the laser heating system was verified by heating iron foil at 13 GPa. With the sample intensity unstabilized, mean temperature was 3003 K with a standard deviation of 144 K, while with it stabilized, mean temperature was 3051 K with a standard deviation of 8 K. For a given wavelength-dependent emissivity, the difference between the actual temperature and the greybody temperature increases as the temperature increases. Therefore, to accurately determine temperatures at the high temperatures applicable to solid Earth geophysics (1500–6000 K), wavelength-dependent emissivity cannot be ignored.

CuS, or covellite (hexagonal symmetry), was compressed in a diamond anvil cell at room temperature up to a pressure of 45 GPa, and studied using x rays from both a Mo Kα source and a synchrotron. The x-ray diffraction spectrum of CuS disappears by about 18 GPa. The presence of Cu fluorescence lines in all spectra and the reappearance of diffraction lines upon decompression confirm that CuS undergoes reversible pressure-induced amorphization at this pressure. A third-order Birch–Murnaghan equation of state fit to the diffraction data below 11 GPa yields a bulk modulus of 89±10 GPa with a pressure derivative of −2±2 for covellite. Further compression up to 45 GPa shows three to four diffraction lines of very low intensity, implying some high pressure ‘‘ordering’’ of the amorphous phase. The Raman spectra obtained indicate that the changes in structure are probably due to the twisting or the distortion of covalently bonded CuS4–CuS4 units in different directions.

Abstract. The compressibility of c~-Mns (alabandite) was determined by x-ray analysis using a Mao-Bell type diamond anvil cell. The zero pressure bulk modulus (Ko) is 74 + 2 GPa with the pressure derivative of the bulk modulus (K'o) fixed at four. Allowing K'o to vary yielded a statistically better fit with Ko = 88 _+ 6 GPa and K' o = 2.2 + 0.6. Our data combined with the data of McCammon (1991) gave Ko=73+ 1 GPa with K' o fixed at four. A fit with K' o allowed to vary yielded Ko = 75_+ 2 GPa and K'o = 3.7_+0.4. Alabandite transformed from the BI structure (NaCl-type) to an unknown high-pressure phase at 26 GPa. The high-pressure phase has lower than hexagonal symmetry and it is stable to at least 46 _+ 4 GPa.

Iron‐magnesium‐silicate perovskite was melted in a laser‐heated diamond anvil cell and monitored by thermal analysis. Two signals were identified at each pressure: a lower temperature signal and a higher temperature signal. The lower signal may correspond to the temperature where iron diffuses rapidly. The higher signal would then correspond to melting of magnesium‐enriched silicate perovskite. Alternatively, the lower signal may be the solidus where (Fe.14Mg.86)SiO3 undergoes incongruent melting to an iron‐magnesium‐enriched solid plus a silica‐enriched liquid. Then, the higher signal would be the liquidus. The slope for the melting curve (the higher signal) between 30GPa and 94GPa is slightly negative. Fitting to a straight line gives a value for the slope of −2.5 ± 0.6K/GPa. At 30GPa, the lower signal is ≈300K below the melting curve. They converge slightly at higher pressures and differ by ≈140K at 94GPa. Our melting curve is several hundred degrees (K) below previous estimates.

of Ca2+ is at a maximum and a minimum, respectively, and Kd is the dissociation constant of fura 2-AM for Ca2+ (240 nM). The value of b, which determines the degree of asymmetry, was 1.2. TEA was added by perfusion of 5 ml of a modified BSS solution containing 100 mM TEA and low NaCI (50 mM). Other components were not changed (see above for BSS composition). Bombsein was applied by addition of 1 ml of BSS plus 2 gM bombesin to a dish containing 1 ml of BSS (final bombesin concentration = 1 p.M). Solution were applied within 0.5 cm of the cells whose responses were measured.