Browsing Research Articles, Department of Geosciences by Issue Date
Now showing items 1-20 of 30
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Stability of zircon u-pb systematics in a greenschist-grade mylonite - an example from the rockfish valley fault zone, central Virginia, USA
(University of Chicago Press, 1992-09)The mid-Paleozoic, greenschist-grade Rockfish Valley Fault Zone (RVFZ) of central Virginia cuts the Grenville-aged Pedlar River Charnockite Suite (PRCS) and contains zircons that underwent brittle failure during ductile ... -
Structure of the subducting Nazca plate beneath Peru
(American Geophysical Union, 1994-05)Arrival times from intermediate-depth (110-150 km) earthquakes within the region of flat subduction beneath the subandean zone and foreland basins of east-central Peru provide constraints on the geometry and velocity ... -
First-principles study of several hypothetical silica framework structures
(American Physical Society, 1995-09-15)Several hypothetical silica structures have been generated using a simulated-annealing strategy with an ab initio based covalent-bonding potential. First-principles total-energy pseudopotential methods have been used to ... -
Lithospheric structure of the Chaco and Parana Basins of South America from surface-wave inversion
(American Geophysical Union, 1997-02)Surface-wave data from a portable broadband array have been used to invert for the velocity structure of the crust and upper mantle beneath the Chaco and Parana Basins of central South America. The upper-mantle velocity ... -
Location of the southern edge of the Gorda slab and evidence for an adjacent asthenospheric window: Results from seismic profiling and gravity
(American Geophysical Union, 1998-12)As the Mendocino Triple Junction migrates northward along the California margin it is widely presumed to leave a "slab-free" or "asthenospheric" window in its wake. A 250-km-long south-north seismic refraction-reflection ... -
Crustal structure beneath southern Africa and its implications for the formation and evolution of the Kaapvaal and Zimbabwe cratons
(American Geophysical Union, 2001-07-01)The formation of Archean crust appears to involve processes unique to early earth history. Initial results from receiver function analysis of crustal structure beneath 81 broadband stations deployed across southern Africa ... -
Crustal thicknesses in SE Brazilian Shield by receiver function analysis: Implications for isostatic compensation
(American Geophysical Union, 2002-01)[1] The Brazilian Lithosphere Seismic Project (BLSP, a joint project by University of Sao Paulo and Carnegie Institution, 1992-1999) operated more than 20 temporary broadband stations in the southeastern Brazilian shield. ... -
Constraints on the S wave velocity structure in a continental shield from surface wave data: Comparing linearized least squares inversion and the direct search Neighbourhood Algorithm
(American Geophysical Union, 2002-05)[1] In their study of upper mantle structure beneath the Parana Basin of SE Brazil, Snoke and James [1997] concluded, on the basis of a linearized least squares inversion (LLSI) of surface wave dispersion data, that a ... -
Fluorinert as a pressure-transmitting medium for high-pressure diffraction studies
(AIP Publishing, 2003-10)Fluorinert is a liquid pressure-transmitting medium that is widely used in high-pressure diffraction work. A systematic study of five different fluorinerts was carried out using single-crystal x-ray diffraction in a ... -
General rules for predicting phase transitions in perovskites due to octahedral tilting
(American Physical Society, 2005-07-08)Recent experiments on several oxide perovskites reveal that they undergo tilt phase transitions to higher-symmetry phases on increasing pressure and that dT(c)/dP < 0, contrary to a general rule previously proposed for ... -
Cell adhesion of Shewanella oneidensis to iron oxide minerals: Effect of different single crystal faces
(American Institute of Physics, 2005-12)The results of experiments designed to test the hypothesis that near-surface molecular structure of iron oxide minerals influences adhesion of dissimilatory iron reducing bacteria are presented. These experiments involved ... -
Cell adhesion of Shewanella oneidensis to iron oxide minerals: Effect of different single crystal faces
(American Institute of Physics, 2005-12-30)The results of experiments designed to test the hypothesis that near-surface molecular structure of iron oxide minerals influences adhesion of dissimilatory iron reducing bacteria are presented. These experiments involved ... -
Increased susceptibility to repeated freeze-thaw cycles in Escherichia coli following long-term evolution in a benign environment
(2006-12-05)Background In order to study the dynamics of evolutionary change, 12 populations of E. coli B were serially propagated for 20,000 generations in minimal glucose medium at constant 37°C. Correlated changes in various other ... -
Climate model boundary conditions for four Cretaceous time slices
(Copernicus Publications, 2007)General circulation models (GCMs) are useful tools for investigating the characteristics and dynamics of past climates. Understanding of past climates contributes significantly to our overall understanding of Earth's climate ... -
Structural refinement of neutron powder diffraction data of two-stage martensitic phase transformations in Ti50.75Ni47.75Fe1.50 shape memory alloy
(Cambridge University Press, 2007-09)Transformation behaviors of the technologically important polycrystalline Ti50.75Ni47.75Fe1.50 shape memory alloy were investigated using differential scanning calorimeter (DSC) and powder diffraction techniques. DSC ... -
In situ structural and texture analyses of monoclinic phase for polycrystalline Ni-rich T49.86Ni50.14 alloy from neutron diffraction data
(Cambridge University Press, 2008-03)Phase transformation temperatures of a polycrystalline Ni-rich Ti49.86Ni50.14 shape memory alloy were investigated using a differential scanning calorimeter. In situ structural and texture analyses of the monoclinic ... -
Pressure-induced phase transition in PbSc0.5Ta0.5O3 as a model Pb-based perovksite-type relaxor ferroelectric
(American Physical Society, 2008-07-04)We report pressure-induced structural changes in PbSc0.5Ta0.5O3 studied by single-crystal x-ray diffraction and Raman scattering. The appearance of a soft mode, a change in the volume compressibility, broadening of the ... -
Effect of Ba incorporation on pressure-induced structural changes in the relaxor ferroelectric PbSc0.5Ta0.5O3
(American Physical Society, 2009-09-28)Pressure-induced structural changes in the canonical relaxor Pb0.78Ba0.22Sc0.5Ta0.5O3 were studied with both in-house and synchrotron single-crystal x-ray diffraction as well as Raman spectroscopy at pressures up to 9.8 ... -
Texture and structural refinement using neutron diffraction data from molybdite (MoO3) and calcite (CaCO3) powders and a Ni-rich Ni50.7Ti49.30 alloy
(Cambridge University Press, 2009-12)Preferred orientation or texture is a common feature of experimental powder patterns. The mathematics of two commonly used models for preferred orientation-the March-Dollase and the generalized spherical-harmonic models-is ... -
A-site doping-induced renormalization of structural transformations in the PbSc0.5Nb0.5O3 relaxor ferroelectric under high pressure
(American Physical Society, 2010-05-01)The effect of A-site incorporated Ba2+ and Bi3+ on the pressure-driven structural transformations in Pb-based perovskite-type relaxor ferroelectrics has been studied with in situ x-ray diffraction and Raman scattering of ...
