Materials Literature
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The quality of hot-filament chemical-vapor-deposited diamond films has been quantitatively assessed by 1H and 13C nuclear-magnetic-resonance (NMR) spectroscopy. As the carbon mole fraction increases from 0.053 to 0.074 in the gas phase, film quality in terms of sp2 carbon content, bonding disorder, and spin-lattice re…
The spin dependence of low-energy electron absorption and reflection from ferromagnetic Fe(110) is investigated using the normalized difference between the absorption (or reflection) of electrons polarized parallel and antiparallel to sample magnetization. The resulting absorption and reflection spin asymmetries are f…
The temperature-dependent optical spectra of the major insulating forms of polyaniline—the fully reduced leucoemeraldine base, half-oxidized emeraldine base (EB), and fully oxidized pernigraniline base (PNB)—and of two oligomeric model compounds for polyaniline are reported. All three forms of the polymer possess a ∼3…
Depolarized Rayleigh spectra of ortho-terphenyl (OTP) were measured in the temperature range from Tg to Tg+190 K. Two samples prepared with and without ‘‘clusters’’ were used for the measurement. Four different Fabry–Perot interferometers covering the time range from about 0.5 ps to 100 ns were employed. Two relaxatio…
Studies have been conducted to further characterize overoxidized polypyrrole films grown on carbon electrodes. Differences in apparent diffusion coefficients for various probes are interpreted via a model based on both hydrophobic and electrostatic interactions between the probe and polymer film. These electrode coati…
The crystal structure of the histidine-containing phosphocarrier protein (HPr) of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) from Bacillus subtilis has been determined at 2.0-A resolution and refined to a crystallographic residual error R-factor of 0.150. The secondary-structure folding topology of…
I describe a systematic study of the effects of vapor-transport growth conditions on the properties of ${\mathrm{NbSe}}_{3}$. Pinning of charge-density waves (CDW's) in ${\mathrm{NbSe}}_{3}$ that is not intentionally doped is primarily by impurities rather than by intrinsic defects. A substantial fraction of these imp…
Abstract Segmented polyurethane elastomers based on a mixture of castor oil and poly(propylene glycol), 4,4'‐diphenylmethane diisocyanate, and 1,4‐butanediol were prepared. The ultimate, thermal, dynamic mechanical behavior and morphology were studied. The use of castor oil shifts the main transition region of the sof…
Abstract Hydrogenated nitrile rubber was prepared by using palladium acetate as the homogeneous catalyst system. The effect of different reaction parameters on the level of hydrogenation was studied. The extent of hydrogenation increased with increase in reaction time, temperature, pressure, and catalyst concentration…
The band structures of \ensuremath{\alpha}-rhombohedral ${\mathrm{B}}_{12}$ (\ensuremath{\alpha}-r-${\mathrm{B}}_{12}$) and \ensuremath{\alpha}-tetragonal ${\mathrm{B}}_{50}$ (\ensuremath{\alpha}-t-${\mathrm{B}}_{50}$) crystals have been calculated by means of the first-principles orthogonalized linear combination of…
An accurate first-passage simulation technique formulated by the authors [J. Appl. Phys. 68, 3892 (1990)] is employed to compute the effective conductivity σe of distributions of penetrable (or overlapping) spheres of conductivity σ2 in a matrix of conductivity σ1. Clustering of particles in this model results in a ge…
An attempt has been made to clarify the anisotropy in the optical absorption and nanostructure of thin films prepared by oblique codeposition of Ag and SiO2. At a low concentration of Ag, the columnar structure grows toward the incident direction of vapor flux of SiO2, and Ag is dispersed in that structure as small me…
Abstract The effect of heating on four chemically synthesized polyanilines, three of which were doped by HCI, H 2 SO 4 , HCIO 4 , and one sample which was dedoped, was investigated. The structural variations during thermal decomposition were studied by real‐time synchrotron radiation diffractometry and correlated with…
We report the results of a seiies of ab initio calculations on the structure and on the vibrational spectra of pyrrole and pyrrole oligomers performed with double zeta quality basis set.
This paper compares the biophysical and mechanistic properties of a typical type I dehydroquinase (DHQase), from the biosynthetic shikimate pathway of Escherichia coli, and a typical type II DHQase, from the quinate pathway of Aspergillus nidulans. C.d. shows that the two proteins have different secondary-structure co…
Abstract The dielectric relaxation behavior of poly(phenylene sulfide), PPS, has been investigated from room temperature to 180°C. This study was undertaken to examine the mobility of the amorphous phase through the glass transition region, to determine the contribution that rigid amorphous phase material makes to the…
We study the effects of electron-electron interactions in halogen-bridged mixed-valence transition-metal linear-chain complexes (MX chains) applying a simple 3/4-filled two-band discrete tight-binding (extended) Peierls-Hubbard model with both on-site and intersite electron-phonon couplings. We employ a variety of met…
We consider a 3/4-filled, two-band discrete tight-binding Peierls-Hubbard model for an isolated chain of a halogen-bridged, mixed-valence, transition-metal linear-chain complex (HMMC or MX chain). We have employed the adiabatic approximation in which the quantum fluctuations associated with phonons are implicitly trea…
Raman-scattering spectra of LO-phonon modes in CdSe microcrystals of various sizes in a germanate glass matrix are measured. The frequency of the peak shifts towards the lower-frequency side and the bandwidth broadens with decreasing microcrystal size. The size dependences of the peak shift and the broadening of the b…
Long-time self-diffusion coefficients in concentrated colloidal dispersions of silica spheres, with various interaction potentials, were measured with the fluorescence recovery after photobleaching technique. Charge stabilized spheres were measured in solutions of LiCl in dimethylformamide with varying ionic strength.…