Materials Literature
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Liquid-crystal cells shaped like a plano-convex lens or a plano-concave lens are prepared. The focal length can be varied from the value f e for an extraordinary ray, where the liquid-crystal cell takes a homogeneous alignment, to f o for an ordinary ray, where it takes a homeo-tropic alignment, by applying an electri…
Symmetrical effective-medium theory is used to find the conductivity and Hall effect of a two-dimensional binary mixture. Results are given in detail in the limit of low applied magnetic field, when the expressions for the Hall coefficients simplify to linear combinations of the corresponding quantities for the compon…
The phase behavior and structures of several liquid crystals of the $n\mathrm{O}.m$ (${\mathrm{C}}_{n}{\mathrm{H}}_{2n+1}\ensuremath{-}\mathrm{OPhCHNPh}{\mathrm{C}}_{m}{\mathrm{H}}_{2m+1}$) series of compounds have been established by a variety of experiments. The hexagonal close-packed layers of the ${S}_{B}$ phases…
Abstract Systematics in the X-ray photoelectron spectra (X. p. e. s.) of Ti, V, Cr, Mn and Nb oxides with the metal ion in different oxidation states as well as of related series of mono-, sesqui- and di-oxides of the first row transition metals have been investigated in detail. Core level binding energies, spin-orbi…
Measurements of conductance and capacitance are made on polycrystalline β″-alumina over a range of frequencies from 10 to 107 Hz and temperatures from −130 to 400 °C. The results are analyzed using complex impedance plots which exhibited a bulk and grain boundary component. Above 220 °C the resistance of the grains ex…
The dynamic mechanical properties of poly(p-phenyleneterephthalamide) fiber were investigated. Measurements of the dynamic mechanical properties were carried out on samples of low crystallinity and low orientation over a temperature range from −100 to +500°C at a frequency of 110 Hz, at a heating rate of 5°C/min. Five…
A family of ’’polarization models’’ has been generated for description of polarizable and deformable molecules in condensed phases. Within these models the intermolecular forces are not pairwise additive, but have a many-body component that generalizes the polarization interactions present in conventional electrostati…
A numerical procedure is presented for implementing the Green’s function method of sensitivity analysis in chemical kinetics. The procedure is applied to three sets of chemical reactions: the Chapman mechanism for ozone kinetics, a mechanism for methane combustion and a model for formaldehyde oxidation in the presence…
Smectic–nematic phase boundaries that resemble arcs of ellipses can be analyzed by a quadratic expansion in temperature and pressure of the change ΔG of Gibbs function. If the change of entropy or volume is known, ΔG and its first two derivatives can be determined. Data on 8OCB and mixtures of 8OCB and 6OCB and of CB9…
We report time-resolved studies of luminescence excited in nominally pure single-crystal MgO by short pulses of 500-keV electrons at sample temperatures from 10 to 500 K. The principal luminescence bands have peaks at approximately 4.9, 3.3, and 1.7 eV. The decay kinetics and spectral shift of the 4.9-eV luminescence…
The energy position of the occupied and unoccupied $4f$ levels relative to the Fermi energy is studied for the rare-earth metals. This is done by treating the excited state as an impurity in an otherwise perfect crystal. This picture is first considered in the complete screening approximation. In this approximation th…
The bond lengths and bond angles of orthorhombic black phosphorus have been determined as a function of hydrostatic pressures to 26.6(5) kbar using time-of-flight neutron powder diffraction. We show that the markedly anisotropic compression reported previously results from a large pressure-induced shortening of the va…
The band structure and electronic properties of pure and heavily doped polyacetylene (both as grown and stretch oriented) have been investigated by a combination of optical-absorption and -reflection measurements in the frequency range from the middle ir (0.1 eV) through the visible (4.0 eV). The absorption data are c…
Aqueous solutions of methyl and hydroxypropyl methylcellulose are known to gel upon heating. These gels are completely reversible in that they are formed upon heating yet will liquefy upon cooling. The precipitation temperature, gelation temperature, and gel strength of these methylcellulose solutions were determined…
A detailed investigation of ${\mathrm{V}}_{2}$${\mathrm{O}}_{5}$, V${\mathrm{O}}_{2}$, ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$, and V metal is presented. The vanadium core lines in the x-ray photoelectron spectra are anomalously wide for ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ and V${\mathrm{O}}_{2}$. It is shown that this…
On 24 January 1978 the Russian satellite Cosmos-954 reentered the atmosphere over northern Canada. By use of high-altitude balloons, the atmosphere was sampled during 1978 up to an altitude of 39 kilometers to detect particulate debris from the reactor on board the satellite. Enriched uranium-bearing aerosols at conce…
Abstract A vibronic centre with a zero phonon line at 2.367 eV is produced in type Ib diamond by electron irradiation. The absorption system associated with the centre is strongly photochromic, and at low temperature (less than 200 K) may be bleached to less than 10% of its original strength; as the 2.367 eV system is…
Abstract The infrared and Raman spectra were studied for polycrystalline TlNO 3 in the modifications γ‐D or C , β‐C , and α‐O . The site group and factor group analysis of the NO − 3 anion, own symmetry D 3h , was carried out for the space groups considered. The following site groups are possible for the various modif…
Abstract A recent method for the determination of Clebsch‐Gordan coefficients is applied to the crystallographic space groups.
Manganese-rich Mn-Cu alloys quenched from the high temperature γ-phase state are known to show a high damping capacity, which has been revealed to be associated with the fcc → fct transformation of the metastable γ-phase. The γ-phase of high manganese Mn-Fe alloys is also reported to show tetragonality when quenched.