Materials Literature
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A modification of an earlier technique, to measure the distribution of space charge in the insulation of a coaxial cable, under both DC and AC electric fields, is described. The mathematical analysis is developed on the basis of acoustic waves propagating in media with cylindrical geometry. In order to measure the cha…
Raman spectra of diamond powders with size less than 2 μm have been measured as a function of the particle size. The Raman line was found to become more asymmetric with some tailing towards lower Raman shifts, broader, and weaker with decreasing particle size. The observed result can be explained by a phonon confineme…
Abstract The performance of acrylic (50:50 MMA/BuA) latexes was investigated as a function of fusion level using high speed tensile testing. The structure of the copolymer was varied via the addition of molecular weight modifiers to the emulsion polymerizations. Chain transfer agent (CBr 4 ) was used to reduce the cop…
Abstract Surface graft polymerization of a hydrophobic monomer, 2,2,3,3,3‐pentafluoropropyl methacrylate (5FMA), onto hydrophilic poly(vinyl alcohol) (PVA) and cellulose films was studied after corona discharge of the films. It was found that grafting strongly depended on the reaction medium; especially, addition of a…
Abstract The depression of the glass transition temperature by water was studied in a set of polyurethanes in which the soft segment consisted of polyethylene oxide (sample I) or a block copolymer of poly(propylene oxide) terminated with poly(ethylene oxide) in various proportions (sample set II). DSC measurements wer…
We have performed the first computer simulation of a twisted nematic liquid crystal using non-spherical hard particles in modified periodic boundary conditions. The director profiles are stable, suggesting that the technique may usefully complement conventional simulations of unperturbed liquid crystals. We make preli…
The demagnetizing tensor for ferromagnets is generalized to include interactions between uniformly magnetized bodies. This “mutual” demagnetizing tensor is symmetric, has a trace of zero, and has other simple geometric properties. The tensor is then used to develop an expression for the macroscopic magnetic field in n…
Adenosine 5'-monophosphate (AMP) deaminase from baker's yeast is an allosteric enzyme containing a single AMP binding site and two ATP regulatory sites per polypeptide [Merkler, D. J., & Schramm, V. L. (1990) J. Biol Chem. 265, 4420-4426]. The enzyme contains 0.98 +/- 0.17 zinc atom per subunit. The X-ray crystal stru…
The authors have measured angle-resolved ultraviolet photoemission spectra from epitaxially grown thin films of CuBr with (111) orientation. Their analysis allows the determination of an experimental valence band dispersion very near Gamma -L-direction of the bulk Brillouin zone. These results show fair agreement with…
We describe reversible holographic effects in azo-dye doped liquid crystals. Surface-stabilized holograms are recorded at 514 nm using beams polarized parallel to the molecular director of the liquid crystals. While these holograms persist for several hours in the dark, complete erasure is achieved in a few seconds by…
New lines in the low temperature luminescence spectra of lightly aluminum doped p-type films of 3C, 6H, and 4H SiC are identified and associated with the recombination of a neutral aluminum acceptor four particle bound exciton complex.
We studied the change in electrical conductivity of deposits from focused electron beam induced dissociation of W(CO)6 for different exposure conditions. Lines were deposited by scanning repeatedly to build up the same total electron dose; with different electron doses per scan, resistance differences of more than one…
Hall-effect and resistivity measurements were performed on simultaneously deposited B-doped homoepitaxial and polycrystalline diamond films, as well as a (100)-oriented type-IIb natural diamond crystal, over a temperature range of 140–600 K. At 298 K, the respective Hall mobilities for the homoepitaxial and polycrysta…
In a Langmuir monolayer of NBD-stearic acid, long rods (\ensuremath{\sim}1 mm long, \ensuremath{\sim}20 \ensuremath{\mu}m wide) of a two-dimensional solid phase are obtained at the liquid-solid phase transition. A rod bent in the plane of the water under the effect of a bending stress breaks after a clearly defined de…
The kinetics of photoinduced defect formation in high-purity silicas has been studied by femtosecond transient absorption spectroscopy in the visible and ultraviolet. Band edge two-photon excitation produces singlet excitons which decay in 0.25 ps into defects with the absorption spectra of nonbridging oxygen hole cen…
Abstract Starch‐ g ‐poly(methyl acrylate) copolymers (S‐ g ‐PMA) containing 10, 30, 46, and 58% PMA, by weight, were prepared by ceric ammonium nitrate‐initiated polymerization of methyl acrylate onto granular cornstarch. Graft copolymers were extrusion‐processed through a strand die with water contents of 10 and 30%…
Abstract The effect of uniaxial and biaxial film‐processing parameters on the orientation of the phenyl ring in the crystalline and amorphous phases has been evaluated using a variety of techniques. It has been demonstrated that the total phenyl ring orientation factor (PROF) measured from refractive indices can refle…
Tyrosyl ring motions in alpha-lytic protease were investigated by solid-state deuterium nuclear magnetic resonance (NMR) spectroscopy in lyophilized enzyme powder, in powder suspended in organic solvents, and in aqueous crystals. Ring flipping rates were determined by examining deuterium quadrupole echo line shapes. O…
The synthesis of poly(phenylcarbyne), one of a class of carbon-based random network polymers, is reported. The network backbone of this polymer is composed of tetrahedrally hybridized carbon atoms, each bearing one phenyl substituent and linking, by means of three carbon-carbon single bonds, into a three-dimensional r…
We have thus far dealt with the resistance to crack propagation at opposite extremes of material representation, continuum solid and atomic lattice. It is now appropriate to investigate the problem at an intermediate level, that of the microstructure . By ‘microstructure’ we mean the compositional configuration of dis…