A new style of diamond anvil cell (DAC) has been designed and built for conducting research in fluids at pressures to 2.5 GPa and temperatures from-190 to 1200 "C. The new DAC has been used for optical microscope observations and synchrotron x-ray diffraction studies. Fringes produced by interference of laser light reflected from top and bottom anvil faces and from top and bottom sample faces provide a very sensitive means of monitoring the volume of sample chamber and for observing volume and refractive index changes in samples that have resulted from transitions and reactions. X-ray diffraction patterns of samples under hydrothermal conditions have been made by the energy dispersive method using synchrotron radiation. The new DAC has individual heaters and individual thermocouples for the upper and lower anvils that can be controlled and can maintain temperatures with an accuracy of ho.5 "C. Low temperatures are achieved by introducing liquid nitrogen directly into the DAC. The equation of state of Hz0 and the a-0 quartz transition are used to determine pressure with an accuracy of f 1% in the aqueous samples. The new DAC has been used to redetermine five isochores of Hz0 as well as the dehydration curves of brucite, Mg(OH)z, and muscovite, Kkl,(Si,Al)O,,(OH),.-2340 Rev. Sci. Instrum.

Encapsulating Earth's deep water filter Small inclusions in diamonds brought up from the mantle provide valuable clues to the mineralogy and chemistry of parts of Earth that we cannot otherwise sample. Tschauner et al. found inclusions of the high-pressure form of water called ice-VII in diamonds sourced from between 410 and 660 km depth, the part of the mantle known as the transition zone. The transition zone is a region where the stable minerals have high water storage capacity. The inclusions suggest that local aqueous pockets form at the transition zone boundary owing to the release of chemically bound water as rock cycles in and out of this region. Science , this issue p. 1136

BACKGROUND: At academic medical centers, attending rounds (AR) serve to coordinate patient care and educate trainees, yet variably involve patients.

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