Materials Literature
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Abstract A simple method combining macroscopic and microscopic features is proposed to calculate approximate values for Meyer's piezoelectric coefficients. The numerical result suggests that the piezoelectricity of liquid crystals is weak and its effect on alignment fluctuations mostly negligible.
The Percus–Yevick equation has been adapted for a two-dimensional system of particles interacting via noncentral forces. A pair potential operating between two particles has been constructed with the intention of reproducing some properties of a sample of such particles which will be similar to the ones encountered in…
Abstract The mobilities of polymer chain segments in mixtures of rubber and carbon black were investigated by nuclear magnetic resonance. Spin–spin relaxation time ( T 2 ) measurements on cis ‐polybutadiene and ethylene–propylene–diene rubber (EPDM) bound rubbers detected at least two relaxing regions: an immobile reg…
The crystal chemistry of point defects in lead zirconate‐titanate is discussed. The results are used to interpret sintering and grain‐growth behavior. Lattice vacancies are created thermally, by substitutional impurities with incorrect valences, and by changes in stoichiometry. Charged O vacancies are introduced when…
As a preliminary to describing the dislocation distribution in deformed alloys of copper containing a small volume fraction of SiO2 particles, the stress distribution in such an alloy is calculated on the assumption that no plastic relaxation takes place around the particles. The continuum approximation is used, and i…
A study by transmission electron microscopy of plastic relxation at undeformable spherical silica particles in a matrix of copper which has undergone plastic deformation leads to an understanding of the dislocation processes involved. The major process is the formation of dipoles of prismatic loops, either of primary…
Abstract Carbon black does not exist as single spherical particles but forms itself into a rodlike primary structure. These rodlike structures then form into an aggregated secondary network. This secondary network is believed to be held together by Van der Waals-London attraction forces. The decrease in shear modulus…
The elastic, piezoelectric, and dielectric constants, and their temperature dependence within the range 0°–110°C, have been determined for single crystals of lithium tantalate and lithium niobate. For each material, the constants were extracted from a combination of many ultrasonic phase-velocity measurements, the mea…
Abstract The synthesis of poly(lactic acids) from the cyclic lactides and properties of the polymers prepared have been described. Degradation rates in vitro under homogeous and heterogeneous conditions have been measured. The kinetics of deesterification under homogeneous conditions is second order and an activation…
Data on the infrared spectra of aliphatic nitro-compounds and their salts are discussed and summarised. Relations are established between the position of the nitro-stretching bands in the absorption spectrum and the structure of the radical. A fairly large number of examples are given of the use of infrared spectrosco…
Abstract Zur Untersuchung der chiroptischen (ORD/ZD) Eigenschaften diastereomerer Chlorin‐Derivate werden durch Reduktion der 9‐Carbonyl‐Gruppe von Methylphäophorbid a ( 2a ) die diastereomeren Alkohole 4a (9R, 10R), 4b (9S, 10R) und 5b (9S, 10S) dargestellt. Die Bestimmung der absoluten Konfiguration an C‐9 und C‐10…
Abstract Die Metall‐acetylacetonate M(acac) 2 (M = Mg, Co, Ni, Cu, Zn), M(acac) 3 (M = Al, Sc, V, Cr, Mo, Mn, Fe, Co, In, Ce), MO(acac) 2 (M = Ti, V), MoO 2 (acac) 2 und M(acac) 4 (M = Zr, Th) werden mit Octaäthylporphin [ 1 ; (OÄP)H 2 ] umgesetzt (Tabb. 1 und 2). Abgesehen von Komplexen der Metalle Ce und Th werden d…
Among the factors contributing to the "hazards of hospitalization,"1 or for that matter, the hazards of practicing good medicine, are dangerous complications due to purely diagnostic procedures. One such well recognized though fortunately relatively infrequent complication is the development of acute renal insufficien…
The linearized hydrodynamic behavior of liquid crystals is systematically deduced and earlier theories reconciled and simplified. Predictions for ordinary and depolarized light scattering are obtained and the latter compared with experiment.
Abstract Using a modified Extended Hückel (S. C. C.) procedure the structure of the ferrocenyl‐methyl cation has been calculated. The result is a structure (V) with about equal overlap population between all FeC bonds. The methylene group is bent towards the iron atom and both rings are tilted.
The optical absorption of thin films of silver monofluoride has been investigated in the visible and ultraviolet region of the spectrum at room and low temperatures. Exciton peaks have been observed at 4.63 and 6.34 eV for samples at 4.8 \ifmmode^\circ\else\textdegree\fi{}K. The first exciton peak is considerably lowe…
The paper describes pulse measurements on threshold switches based on thin layers (∼1μ) of multicomponent chalcogenide glasses. By means of voltage reversals prior to switching and monitoring of the corresponding switching delays, it has been demonstrated that switching in these systems is not essentially a thermal pr…
Neutron diffraction analysis of the cubic phase of CaC2 has revealed the characteristics of the hindering potential for rotation of the C2 group, i.e., the body diagonal axes being the easiest direction for the C2 random orientation, the face diagonals being the next easiest and the cube axes being by far the hardest.…
Measurement of the second-order nonlinear optical susceptibility of trigonal selenium yielded d11 = (9.7 ± 2.5) × 10−11 m/V. This value was obtained by cw SHG with a 10.6-μm CO2 laser at a phase-matching angle of 5.5° ± 0.3° to the optic axis. Factors affecting this measurement are discussed along with data on absorpt…
We investigate the properties of binary mixtures of hard-sphere fluids with nonadditive diameters: calling Rij the distance of closest approach between particles of species i and j we assume R12 = 12(R11 + R22) + α with α ≠ 0. We find the exact correlation functions as well as the solution of the Percus–Yevick integra…