Materials Literature
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The major thrust in the area of composite materials has been directed towards the development and study of high performance materials like glass, carbon, kevlar and boron fibres in appropriate polymer or metal matrices. Natural fibres like jute and sisal have the advantage of low cost and are likely to be useful in a…
A wide number and great variety of clinically important cardiovascular implants and devises exist. Some (e.g., catheters) may only contact the blood once, and for a relatively short time; others (e.g., kidney dialyzers and blood oxygenators) may be exposed to blood for hours, while tissue implants (e.g., heart valves…
The specific heat of the linear-chain magnet ${\mathrm{CsNiF}}_{3}$ has been measured at temperatures between 4 and 18 K, in magnetic fields up to 8 kG (0.8 T). A rounded peak is observed in both the temperature and field dependence. The peak positions in the field dependence are in qualitative agreement with classica…
Further calcul.ations have shown that Eqs. ( 1) and (2) in the Letter cannot be applied to the case under discussion, and the approximation men- tioned in Ref. 15 there is incorrect.A better calculation based on the exact solution of Max- well's equations for multiple reflections in ab- sorbing media will be published…
The synthesis of elastomers by step, chain, and ring-opening polymerizations is reviewed. These reactions are characterized as to the process variables which must be controlled to achieve the synthesis and crosslinking of an elastomer of the required structure. Both radical and ionic chain polymerizations are discusse…
Tetragonal and cubic CuFe2O4 are prepared and studied by Mössbauer-effect technique at room temperature and at 4.2 K with and without applied strong magnetic fields. The cation distributions and the hyperfine parameters are determined and compared with magnetization measurements. The results show that tetragonal CuFe2…
The magnetic interaction between local magnetic moments in an insulator or a semiconductor host is theoretically studied. For a dilute concentration of magnetic ions, the dominant mechanism for magnetic interaction could be the exchange polarization of the valence-band electrons of the host lattice. Its properties are…
Results are described for the field and temperature dependences of the electrical resistivity, Hall effect, and transverse magnetoresistance of ferromagnetic, antiferromagnetic, and diamagnetic Heusler alloys. The experiments cover the approximate ranges 2-300 K and 0-4.8\ifmmode\times\else\texttimes\fi{}${10}^{6}$ ${…
The theory of surface-enhanced second-harmonic generation at a metallic grating is developed. Using the form of the nonlinear source polarization given by Bloembergen et al. [Phys. Rev. 174, 813 (1968)], we solve Maxwell's equations to obtain the fields at the second-harmonic frequency. The calculations are done up to…
Abstract Crosslinking efficiency of isotactic polypropylene was studied as a function of the initiator used and of the reaction temperature. The decomposition rate of the initiator was found to be of prime importance for attaining the gel point. The over‐all efficiency of the process is strongly influenced also by the…
We report studies of sputtered iridium oxide films (SIROF's) by differential thermal analysis, evolved-gas analysis, scanning electron microscopy, x-ray diffraction, and electrical-conductivity measurements. SIROF's undergo an irreversible exothermic transition at \ensuremath{\sim}300\ifmmode^\circ\else\textdegree\fi{…
The electrical properties of single crystals of yttria-stabilized zirconia [${(\mathrm{Z}\mathrm{r}{\mathrm{O}}_{2})}_{0.88}$-${({\mathrm{Y}}_{2}{\mathrm{O}}_{3})}_{0.12}$], known to be an essentially anionic conductor, are studied in wide ranges of temperature (400-1100 K) and frequency (1.6 Hz-100 kHz). The dc elect…
Surface optical phonons have been detected on both the polar (100) and nonpolar (110) faces of GaAs, InP, and GaP with the use of high-resolution electron-energy-loss spectroscopy. The observed frequencies (GaAs: 291, InP: 337, GaP: 396 ${\mathrm{cm}}^{\ensuremath{-}1}$) on all surfaces are in excellent agreement (wit…
Abstract Um Einblick in die Bildungstendenz der Porphyrine zu gewinnen, wurde die säurekatalysierte Kondensation linearer Oligopyrrole 12a–d , 18 und 19 in verschiedenen Kombinationen untersucht. Obwohl hierbei im Prinzip die Bildung cyclischer Tetra‐, Penta‐, Hexa‐ und Heptapyrrole möglich wäre, erfolgte in jedem Fal…
Site selective spectroscopy has been performed for CaF2:Eu3+ samples as a function of annealing temperature and dopant concentration. The Eu3+ lines have been classified into five sites, two of which correspond with Eu3+ clusters. High annealing temperatures dissociate the clusters and leave Eu3+ ions in cubic and tet…
We extend the generalized van der Waals theory to the case of aligned nematic liquids which are subjected to curvature (i.e., “splay’’, “twist’’, and “bend’’) deformations. The Helmholtz free energy is written as an explicit functional of both the orientational distribution f(Ω) and the spatial variation n̂(R) of the…
We report photoemission spectra and intensity profiles of the $3d$ emission and the resonant valence-band satellites in Cu, ${\mathrm{Cu}}_{2}$O, and CuO. By analyzing the satellite separation energies, the multiplet structure, and the resonance shifts, we show that alternative resonance mechanisms are observed on Cu…
Detailed quantitative studies of the visible near-ir absorption spectra of trans-${(\mathrm{CH})}_{x}$ have been carried out in the semiconducting, transitional, and metallic regimes. With the use of the opto-electrochemical technique to take advantage of the control and precision of electrochemical doping, the absorp…
The following new phenomena recently brought to light by the Lorenz–Mie theory of scattering of electromagnetic radiation by spheres are reviewed: invisible particles, negative absorption, photophoresis, anisotropic photoelectron emission, Raman and fluorescent scattering by molecules embedded in dielectric spheres, e…
The electrical resistivity of pure hexagonal boron nitride in the c direction was measured from 700 degrees C to 1400 degrees C. Special attention was paid to allowance for electrical leakage of the measurement rig. The logarithm of the resistivity increased linearly with the reciprocal of absolute temperature, sugges…