Materials Literature
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Abstract Small‐angle x‐ray scatting (SAXES) and transmission electron microscopy (TEM) have been applied to study polymer morphologies of CO 2 ,‐blown rigid polyurethane foam samples of varying isocyanate index. The results are consistent with an irregular (meso) phase segregated structure with phase boundaries showin…
We report lattice and electronical properties of BaTiO3:La powders and ceramics with 0<xLa<20 at.%. Dielectric measurements and x-ray scattering evidence a continuous decrease of the ferroelectric transition temperature when the La content is increased. For xLa=20 at.%, no dielectric maximum is found for temperatures…
Optically controlled planar orientation of liquid crystal molecules with polarized light is used to make phase gratings in liquid crystal media. The electro-optical properties of liquid crystal linear and chirped gratings are discussed.
We report on detailed neutron diffraction studies of both pinned and moving magnetic flux line lattices in $2H\ensuremath{-}\mathrm{Nb}{\mathrm{Se}}_{2}$. For field-cooled, pinned lattices, we are able to make a detailed quantitative comparison with the theory of Larkin and Ovchinnikov and find excellent agreement. In…
Using helium atom scattering Hulpke and L"udecke recently observed a giant phonon anomaly for the hydrogen covered W(110) and Mo(110) surfaces. An explanation which is able to account for this and other experiments is still lacking. Below we present density-functional theory calculations of the atomic and electronic s…
The crystal structure of beta-D-cellotetraose shows the same molecule packing as cellulose II, with two antiparallel molecules in the unit cell: For cellulose II, the orientation of the C6-O6 bonds has been described as gauche-trans and trans-gauche, respectively, for the two antiparallel molecules, which otherwise ha…
The ferroelectric polarization of perovskite oxides is much larger than implied by displacement of static ionic charges. We use an explicitly correlated scheme to investigate the phenomenon; charge transport is evaluated as a geometric quantum phase. Both covalence and electron-electron interaction enhance polarizatio…
The encapsulation of graphite-type carbon wires in the regular, 3-nanometer-wide hexagonal channels of the mesoporous host MCM-41 is reported. Acrylonitrile monomers are introduced through vapor or solution transfer and polymerized in the channels with external radical initiators. Pyrolysis of the intrachannel polyacr…
An exact result is calculated numerically for the dilute limiting, zero shear viscosity of bimodal suspensions of hard spheres. The required hydrodynamic functions are calculated from recent results for the resistivities of unequal spheres. Both the hydrodynamic and Brownian contributions to the Huggins coefficient ex…
In this paper we calculate how a pendant drop evolves at the end of a nozzle when the volume of the drop increases steadily with time. We find that the character of the evolution is strongly dependent on the growth rate of the drop and the radius of the nozzle. Typically we find that once the drop has become unstable,…
Extensive LDA and quasi-particle calculations have been performed on boron nitride (BN) single-wall and multi-wall nanotubes. Strain energies are found to be smaller for BN nanotubes than for carbon nanotubes of the same radius, owing to a buckling effect which stabilizes the BN tubular structure. For tubes larger tha…
A reciprocal space formulation of the Cluster Variation is used in order to extract effective pair interactions in alloys from experimental short-range order diffuse intensities. The method is applied to the analysis of the short range order contribution to the neutron diffuse scattering of a $Fe-19.5 {\%} Al$ single…
A fourth fatty acid condensing enzyme was isolated from Escherichia coli by its ability to restore elongating activity to a protein extract which had been treated with cerulenin, a condensing enzyme-specific inhibitor. The purified beta-ketoacyl-[acyl carrier protein] (ACP) synthase IV [3-oxoacyl-ACP synthase; acyl-AC…
The crystal structure of an allosteric chorismate mutase, the Thr-226-->Ile mutant, from yeast Saccharomyces cerevisiae has been determined to 2.2-A resolution by using the multiple isomorphous replacement method. Solvent-flattening and electron-density modification were applied for phase improvement. The current crys…
Two decay components of luminescence of oxygen-vacancy centres were observed in alkaline-earth fluoride and barium fluorohalide crystals at 17-300 K. We denoted them as slow and very slow components. Very slow components are observed in all crystals except for type II oxygen centres in BaFBr. Above 100-150 K the integ…
Linear as well as non-linear contributions to the Zeebeck and Peltier coefficients of a metallic film in contact with the equilibrium metal are calculated within a simple model. The non-linear part of the thermoelectric response survives down to a very low temperature which in principle permits thermoelectric cooling…
We present the first low frequency (0.1-20 Hz) measurements of the complex elastic constant on KSCN single crystals. Our measurements show very slow sample-size dependent elastic relaxations, at temperatures ranging from ${T}_{c}\ensuremath{-}40$ K up to the order-disorder phase transition temperature ${T}_{c}$. The d…
A ferroelectric instability is predicted to occur in an experimentally accessible temperature range in a main-chain (semiflexible) liquid crystalline polymer with directed polar mesogenic segments. The long-range part of the dipole-dipole interaction is separated and its effect is completely accounted for in the avera…
Effects of compression on the Raman and IR modes of KOH(D), RbOH(D) and CsOH(D) have been measured at pressures up to 20 GPa and temperatures down to 100 K using the diamond anvil technique. For all three hydroxides an ordering transition into the respective hydrogen-bonded low-temperature phases was found below 1 GPa…
Optical spectra are measured for transparent and colorless TbAlO3 single crystals grown by the Czochralski method in a reducing atmosphere, although those grown in an inert atmosphere show blackbody color due to broadband absorption of Tb4+ ions. This is a report on strong Tb3+ emission spectrum at room temperature of…