A series of experiments was performed to constrain the chemical and isotopic evolution of insoluble organic material (IOM) during hydrothermal alteration at temperatures ranging from 250 degrees C to 450 degrees C at 50 MPa. Experiments involved IOM that was extracted from the Murchison (CM2) meteorite or synthesized by aqueous carbonization of dextrose. Flash (dry) pyrolysis experiments at 400 - 1000 degrees C were also conducted with Murchison IOM to distinguish between the effects of hydrothermal and thermal degradation. Extended reaction times (up to 3905 h) were employed to establish D/H equilibria between IOM and H2O. The H isotope compositions of the H2O used in the experiments ranged from delta D= -447 parts per thousand to 3259 parts per thousand. Results revealed that the extent of the IOM H isotope evolution strongly depends on the delta D composition of the coexisting H2O with minimal temperature effects. The empirical relationship that describes the isotope exchange between IOM and H2O is as follows:

We report first principles density functional calculations of the Born effective charges and electronic dielectric tensors for the relaxor PMN (PbMg1/3Nb2/3O3). Visualization of the Born charge tensors as "charge ellipsoids" have provided microscopic insights on the factors governing piezoelectric enhancements with polarization rotation. Several 15 and 30-atom ferroelectric and antiferroelectric supercells of PMN involving 1:2 and 1:1 chemical ordering have been studied. A cascading set of ferroelectric phonon instabilities lead to several low symmetry monoclinic structures. We find a ground state with a 15-atom unit cell with 1:2 chemical ordering along [111] with a monoclinic C2 structure. (c) 2006 Elsevier B.V. All rights reserved.

We compute the c/a lattice strain versus temperature for nonmagnetic hcp iron at high pressures using both first-principles linear response quasiharmonic calculations based on the full potential linear-muffin-tin-orbital (LMTO) method and the particle-in-cell (PIC) model for the vibrational partition function using a tight-binding total-energy method. The tight-binding model shows excellent agreement with the all-electron LMTO method. When the hcp structure is stable, the calculated geometric-mean frequency and the Helmholtz free energy of epsilon-Fe from PIC and the linear response lattice dynamics agree very well, as does the axial ratio as a function of temperature and pressure. On-site anharmonicity proves to be small up to the melting temperature, and PIC gives a good estimate of its sign and magnitude. At low pressures, epsilon-Fe becomes dynamically unstable at large c/a ratios, and the PIC model might fail where the structure approaches lattice instability. The PIC approximation describes well the vibrational behavior away from the instability, and thus is a reasonable approach to compute high temperature properties of materials. Our results show significant differences from earlier PIC studies, which gave much larger axial ratio increases with increasing temperature, or reported large differences between PIC and lattice dynamics results.

We investigate the elastic and isotropic aggregate properties of ferromagnetic bcc iron as a function of temperature and pressure by computing the Helmholtz free energies for the volume-conserving strained structures using the first-principles linear response linear-muffin-tin-orbital method and the generalized-gradient approximation. We include the electronic excitation contributions to the free energy from the band structures, and phonon contributions from quasiharmonic lattice dynamics. We make detailed comparisons between our calculated elastic moduli and their temperature and pressure dependences with available experimental and theoretical data. The isotropic aggregate sound velocities obtained based on the calculated elastic moduli agree with available ultrasonic and diamond-anvil-cell data. Birch's law, which assumes a linear increase in sound velocity with increasing atomic density, fails for bcc Fe under extreme conditions. First-principles linear-response lattice dynamics is shown to provide a tractable approach to examine the elasticity of transition metals at high pressures and high temperatures.

A complete set of elastic and piezoelectric constants for single-domain rhombohedral Pb(Zn1/3Nb2/3)O-3-4.5%PbTiO3 is obtained using Brillouin scattering. The bulk modulus and elastic constants agree with the values obtained from ultrasonic methods, but the piezoelectric constants are smaller. Differences in piezoelectric constants from different techniques are due to frequency dispersion and the contributions of domain boundaries. The pressure dependence of the Brillouin shifts of amorphous BeH2 was measured from ambient pressure to 17 GPa. The equation of state is deduced from the pressure dependence of the sound velocity; the bulk modulus is 14.2 (3.0) GPa and its pressure derivative is 5.3 (0.5). (c) 2006 Elsevier B.V. All rights reserved.

The All Sky Extrasolar Planet Survey (ASEPS) would use the Sloan 2.5-m wide field telescope and new generation multiple object high throughput Doppler instruments to undertake a large-scale visible and near-IR band Doppler survey of up to similar to 250,000 relatively bright stars (generally V up to < 13 for the visible and J < 11 for the near IR) for extrasolar planets between 2008-2013. An extended survey continuing until similar to 2020 could survey an additional similar to 250,000 stars and obtain information on long-period planets from the earlier detected planet sample, possibly detecting many solar analogs. ASEPS aims to increase the number of extrasolar planets by nearly two orders of magnitude (up to similar to 10,000 planets in the 12-year survey using all clear nights). This dramatic increase in the number of known planets would allow astronomers to study correlations among the diverse properties of extrasolar planets much more effectively than at present. Additionally, the large number of planet discoveries will enable the detection of rare planets that may have eluded previous planet searches, as well as transiting planets, and interacting multiple planet systems. In March-June 2006, a single full-scale multi-object W.M. Keck Exoplanet Tracker (Keck ET) with 60 object capability was commissioned and a trial planet survey of similar to 420 V=8-12 solar type stars has been conducted at Sloan telescope. Since the 2006 August engineering run, the instrument performance (throughput, image quality, and Doppler precision) has been substantially improved. Additional stars are being searched for planets.