Materials Literature
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Abstract The use of electron donor–electron acceptor groups to enhance miscibility in polymer blends has been investigated, using the immiscible binary pair polystyrene and polyisoprene as the basic materials. These polymers have been modified by copolymerization with monomers that are either donor or acceptor groups.…
Glucose isomerase from Streptomyces murinus has been crystallized in space group P4(1)2(1)2, cell dimensions a = b = 137.65 and c = 132.20 A. One dimer of the tetrametric molecule is found per asymmetric unit. An initial structure solution was obtained by the molecular replacement method. The crystallographic refineme…
Abstract A model for a twin consisting of two domains is proposed for a new pseudo-hexagonal modification of high-density boron nitride. A structure refinement based on high resolution diffraction data taken with 0.5 Å synchrotron radiation resulted in R factors below 0.015 for each domain. The refinement against detw…
Total photon mass attenuation of six multielement shielding materials (concrete, plaster of paris, quick lime, black cement, white cement, and silica) is measured in the 123- to 1250-keV energy range. The experimental results are analyzed in terms of cross sections, effective atomic numbers, and electron densities. Co…
Polyethylene and polyvinyl chloride pellets were introduced into concrete to improve its neutron attenuation characteristics while several types of heavy coarse aggregates were used to improve its gamma ray attenuation properties. Neutron and gamma ray attenuation were studied in concrete samples containing coarse agg…
<div class="htmlview paragraph">The effect of small amounts of silicate on coolant performance has been studied. The corrosion protection provided by different coolant technologies was evaluated for different silicate contents. This work includes results from electrochemical tests and static and dynamic heat-rej…
We show that transmission-mode perpendicular incidence ellipsometry, which yields the trivial values Psi =45 degrees , Delta =0 for an isotropic thin film, can be used to provide useful data during the vacuum deposition of anisotropic coatings. Thus the number of quarter-wave film thicknesses necessary for a quarter-w…
Air separation of a cholesteric liquid crystalline triheptyl cellulose/ethyl cellulose (3/97) binary composite membrane prepared from tetrahydrofuran, chloroform, and dichloromethane solutions was studied at different pressure differences across the membrane by the variable volume method. With an increasing pressure d…
Introduction Much work has been done on the phenomenon of electropolishing since it was discovered by Jaquat. Most of this work was directed towards the elucidation of the polishing mechanism as well as establishing conditions for polishing of different metals and alloys. Studies on the polishing mechanism have reveal…
A novel starburst molecule, 4,4′,4″-tri(N-phenoxazinyl)triphenylamine (TPOTA), has been synthesized, and its molecular properties and morphology investigated. TPOTA readily forms a stable amorphous glass with a glass transition temperature as high as 145[ddot]C when the melt sample is cooled down on standing, as chara…
By adjusting the particle size distribution of the Sm/sub 2/Fe/sub 17/ alloy-powder the density of cold isostatically pressed (p=200 MPa) magnets as well as of die-pressed (p=600 MPa) magnets could be improved up to 72% of the theoretical density. A remanent polarization and a coercivity of 0.77 T and 10.8 kA/cm could…
Cast thin films of the composites PVA-CrCl 3 were prepared. The absorption spectra, X-ray diffraction, hardness number and dielectric constant were measured before and after irradiation by neutrons in the fluence range of 3.4 × 10 5 to 1.68 × 10 8 n/cm 2 . The Racah constant was calculated to be 600 cm -1 which is abo…
Abstract The synthesis of styrenic monomers that have pyrazolic or bipyrazolic pendant groups is described. Their homopolymerization and their copolymerization with maleic anhydride (MA) and N ‐(3‐acetoxy propyl) maleimide is reported. The monomers were prepared from the Williamson reaction between 2‐pyridine carbinol…
The dependence on the substrate temperature and the flux rates of the behavior of impinging elemental Si and Ge fluxes on a SiO2 surface, including SiO2 etching and the deposition of polycrystalline Si and SiGe films, was investigated by using the solid source molecular beam epitaxy (MBE). Flux rates of the source bea…
Abstract For an electrocatalytic oxidation of cyclohexene in an air-equilibrated acetonitrile solution containing (5,10,15,20-tetraphenylporphyrinato)manganese(III) as a catalyst, benzoic anhydride as an acylating reagent and 1-methylimidazole as a ligand to Mn porphyrin, the addition of the compounds such as Methylen…
Two binary mixtures of polar liquid crystal materials were previously reported to exhibit three incommensurate smectic A phases predicted for such materials on the basis of phenomenological theory. Results of our recent high-resolution X-ray scattering experiments show that no incommensurate phases exist in the two sy…
Motivated by the need for highly efficient far-IR Fabry-Perot étalons for airborne and space astronomy, we have developed a high-yield photolithographic technique for producing low-loss metal-mesh reflectors. We describe the production technique and report on the mesh flatness and uniformity. Optical measurements of m…
A new first principle approach to the problem of ferroelectric instability is advanced. This model-free approach permits to investigate the role of dipolar forces in the origin of ferroelectric instability in crystals of arbitrarily low ionicity possessing finite but anyhow small dielectric gap width in the electronic…
SUMMARY The results of a laboratory study carried out to investigate copper deposition and localized corrosion on API N-80 carbon steel are presented. Hydrochloric acid-based stimulation fluids and a recovered worn-out acid sample from the field were used in the tests. To all the tested fluids a copper-based corrosion…
We have studied the static magnetic properties of nanocrystalline Co-Ti doped barium ferrite BaFe/sub 10.4/Co/sub 0.8/Ti/sub 0.8/O/sub 19/. The zero-field-cooled (ZFC) and field-cooled (FC) processes show the typical features of a small particle system. The dependence on temperature of the coercive field is discussed…