129 research outputs found
Kinetics data for diffusion of outgas species from RTV 560
A detailed analytical and experimental study was made of the outgassing behavior of RTV 560 silicone rubber. The four outgas species which predominate in the temperature range of 285 K to 425 K were separately identified. The initial concentration of these species in the parent material and their bulk volatilities were determined. The diffusion coefficients and activation energy for diffusion of the two major species were deduced from outgassing rate data. It is shown that by using these data in a diffusion theory model, the outgassing rates of these major species can be predicted for arbitrary geometry and any temperature within the range studied
Ground-state properties of rutile: electron-correlation effects
Electron-correlation effects on cohesive energy, lattice constant and bulk
compressibility of rutile are calculated using an ab-initio scheme. A
competition between the two groups of partially covalent Ti-O bonds is the
reason that the correlation energy does not change linearly with deviations
from the equilibrium geometry, but is dominated by quadratic terms instead. As
a consequence, the Hartree-Fock lattice constants are close to the experimental
ones, while the compressibility is strongly renormalized by electronic
correlations.Comment: 1 figure to appear in Phys. Rev.
CrO2: a self-doped double exchange ferromagnet
Band structure calculations of CrO2 carried out in the LSDA+U approach reveal
a clear picture of the physics behind the metallic ferromagnetic properties.
Arguments are presented that the metallic ferromagnetic oxide CrO2 belongs to a
class of materials in which magnetic ordering exists due to double exchange (in
this respect CrO2 turns out to be similar to the CMR manganates). It is
concluded that CrO2 has small or even negative charge transfer gap which can
result in self-doping. Certain experiments to check the proposed picture are
suggested.Comment: 4 pages, 4 Figure
On the optical properties of Ag^{+15} ion-beam irradiated TiO_{2} and SnO_{2} thin films
The effects of 200-MeV Ag^{+15} ion irradiation on the optical properties of
TiO_{2} and SnO_{2} thin films prepared by using the RF magnetron sputtering
technique were investigated. These films were characterized by using UV-vis
spectroscopy, and with increasing irradiation fluence, the transmittance for
the TiO_{2} films was observed to increase systematically while that for
SnO_{2} was observed to decrease. Absorption spectra of the irradiated samples
showed minor changes in the indirect bandgap from 3.44 to 3.59 eV with
increasing irradiation fluence for TiO_{2} while significant changes in the
direct bandgap from 3.92 to 3.6 eV were observed for SnO_{2}. The observed
modifications in the optical properties of both the TiO_{2} and the SnO_{2}
systems with irradiation can be attributed to controlled structural
disorder/defects in the system.Comment: 6 pages, ICAMD-201
Label-free segmentation of co-cultured cells on a nanotopographical gradient
The function and fate of cells is influenced by many different factors, one of which is surface topography of the support culture substrate. Systematic studies of nanotopography and cell response have typically been limited to single cell types and a small set of topographical variations. Here, we show a radical expansion of experimental throughput using automated detection, measurement, and classification of co-cultured cells on a nanopillar array where feature height changes continuously from planar to 250 nm over 9 mm. Individual cells are identified and characterized by more than 200 descriptors, which are used to construct a set of rules for label-free segmentation into individual cell types. Using this approach we can achieve label-free segmentation with 84% confidence across large image data sets and suggest optimized surface parameters for nanostructuring of implant devices such as vascular stents
Transport Properties, Thermodynamic Properties, and Electronic Structure of SrRuO3
SrRuO is a metallic ferromagnet. Its electrical resistivity is reported
for temperatures up to 1000K; its Hall coefficient for temperatures up to 300K;
its specific heat for temperatures up to 230K. The energy bands have been
calculated by self-consistent spin-density functional theory, which finds a
ferromagnetic ordered moment of 1.45 per Ru atom. The measured
linear specific heat coefficient is 30mJ/mole, which exceeds the
theoretical value by a factor of 3.7. A transport mean free path at room
temperature of is found. The resistivity increases nearly
linearly with temperature to 1000K in spite of such a short mean free path that
resistivity saturation would be expected. The Hall coefficient is small and
positive above the Curie temperature, and exhibits both a low-field and a
high-field anomalous behavior below the Curie temperature.Comment: 6 pages (latex) and 6 figures (postscript, uuencoded.) This paper
will appear in Phys. Rev. B, Feb. 15, 199
First-principles study of a tilt grain-boundary in rutile
[[abstract]]The atomic and electronic structure of a tilt grain boundary in rutile TiO2 has been calculated in an ab initio manner. The method employs a plane-wave basis set and optimized pseudopotentials and is carried out within the local-density approximation of density-functional theory. The study focuses on the structure and energy of the ∑=15 36.9° (210)[001] tilt boundary, which is relaxed to equilibrium using a conjugate gradients iterative minimization technique. The calculations confirm the stability of a proposed atomic model for the boundary and provide some insight into its electronic structure.[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子
Electron transport in TiO2 probed by THz time-domain spectroscopy
Euan Hendry, F. Wang, J. Shan, T. F. Heinz, and Mischa Bonn, Physical Review B, Vol. 69, article 081101 (2004). "Copyright © 2004 by the American Physical Society."Electron transport in crystalline TiO2 (rutile phase) is investigated by frequency-dependent conductivity measurements using THz time-domain spectroscopy. Transport is limited by electron-phonon coupling, resulting in a strongly temperature-dependent electron-optical phonon scattering rate, with significant anisotropy in the scattering process. The experimental findings can be described by Feynman polaron theory within the intermediate coupling regime and allow for a determination of electron mobility
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