Materials Literature
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Abstract The Diels‐Alder homopolycycloaddition of 2,5‐diphenyl‐3,4‐(5,6‐acenaphthylenylene)‐cyclopentadienone (VIII) affords a low molecular weight soluble ladder polymer having reduced specific viscosities between 0.17 and 0.25 dl/g in benzene and an insoluble fraction of higher molecular weight. The ladder polymers…
The energy levels of the I5 ground term of Ho3+ in single crystals of CaWO4 were established by absorption and fluorescence spectra measurements. The measurements were made using crystals at temperatures near 2, 20, and 85°K. Most of the observed transitions can be accounted for by the electric dipole selection rules.…
Measurements of the Mn 55 nuclear magnetic resonance, high-field susceptibility, magnetic anisotropy and electrical resistivity have been performed on intermetallic compound MnB 2 . It is proposed that MnB 2 is an antiferromagnet with a magnetic moment of about 3 µ B per Mn atom and a Néel point of 760°K. The weak fer…
Abstract Certain monocyclic and polycyclic tertiary amines initiate polymerization of, and copolymerize with, pivalolactone. These comprise three‐, four‐, and five‐membered monocyclic amines and 1‐azapolycyclic amines. The polymerization proceeds in three steps: (a) initiation to form a cyclic amine/pivalate betaine,…
The zero-field NMR of Mn 55 in ferromagnetic MnBi has been observed in the temperature range 4.2°K to 500°K. Resonance signals from nuclei in the domain and domain wall are separately observed at 225.01 MHz, and 206 MHz, respectively, at 294°K. As the temperature is decreased, the quadrupole splitting and the frequenc…
The pressure coefficient of the Curie temperature of CuCr 2 X 4 was obtained from the result of measurement of the variation with pressure in the self inductance of search coil wounded on the specimen vessel. The coefficients, d T c /d p , were founded to be -11.3×10 -4 °Kkg -1 cm 2 for CuCr 2 S 4 , -4.1×10 -4 °Kkg -1…
It is proposed that the various localized forms of corrosion (pitting, stress corrosion cracking, intergranular corrosion, crevice corrosion, filiform corrosion, tuberculation, and exfoliation) have the common feature of local acidification by hydrolysis. The acidity is viewed as having a responsible role in the self-…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of central and terminal groups on nematic mesophase stabilityMichael J. S. Dewar and Ronald S. GoldbergCite this: J. Org. Chem. 1970, 35, 8, 2711–2715Publication Date (Print):August 1, 1970Publication History Published online1 May 2002Published inissue 1 August 1970h…
Abstract Critical miscibility data obtained from measurements of phase‐volume ratios have been used to calculate the concentration dependence of the pair interaction parameter for the system polystyrene–cyclohexane. The measured temperature and concentration ranges are 11–30°C and 4–18% polymer by weight, respectively…
Electrical conductivity and Hall effect measurements have been made on a series of synthetic p-type semiconducting diamonds in the temperature range 80 to 450K. The dominant conductivity mechanism at low temperatures is shown to be impurity conduction, and effects have been isolated due both to impurity-band conductio…
Abstract The thioketo and thioenol tautomers of thioacetone have been separated by gas chromatography and characterized by infrared and NMR spectra at low temperatures. The pure thioketo tautomer polymerizes rapidly at room temperature, but the thioenol tautomer does not. At room temperature, the thioenol gradually di…
The anodic dissolution of Mo was studied in H2SO4-K2SO4 solutions (pH = 0.4-3.4) and K2SO4-K2CO3-KOH solutions (pH = 9.5-13.6) at 25 C (77 F). Faradaic efficiency studies showed the metal to be electrochemically oxidized to the Mo-VI state. Analysis of surface films and polarization measurements indicate the corrosion…
Photon scattering cross sections were measured with 70-keV resolution from 6 to 9 MeV in Sn, and from 8.5 to 12.5 MeV in Zr. A new method of analysis is used to infer relatively reliable total photon interaction cross sections. Both the elastic scattering and the total interaction cross sections vary more rapidly with…
Infrared and Raman spectra have been recorded for room-temperature phase powdered samples of Ca(NO3)2, Sr(NO3)2, Ba(NO3)2, and Pb(NO3)2. The spectra are interpreted in terms of a factor group analysis. Considerable multiplet band structure is reported for the first time.
We consider the scattering of two spin waves in a uniaxial (easy axis) Heisenberg ferromagnet with single-ion anisotropy. The two-spin-deviation problem is solved exactly at zero temperature. We find (for $S>\frac{1}{2}$), in addition to the usual two-spin-wave bound states, a new "single-ion bound state," in which…
Abstract Highly crystallized θ-alumina was obtained by a two-step treatment, by hydrothermal and thermal treatment, of η-alumina. Its X-ray-powder diffraction pattern was interpreted based on the structure of θ-gallia, and least-squares refinements were carried out. The electron diffraction pattern of θ-alumina from b…
1. A method is presented for the measurement of the elasticity of human skin in vivo. A simple suction cup device is applied to the intact skin and the distortion produced in response to pre-determined negative pressures recorded. By the use of appropriate formulae stress and strain may be calculated and a stress/stra…
Abstract Poisson's ratio for several low‐density plastic foams has been determined in both tension and compression. For polystyrene bead foams and a polyurethane foam, Poisson's ratio is greater in tension than compression. In compression, Poisson's ratio is not linear, showing a larger value below the yield strain an…
Crystallographic studies of Ba 2 NaNb 5 O 15 have shown that the possible space groups are D 6 2 , C 11 2v and D 19 2h . The coincidences between the infrared and Raman spectra support the conclusion, based on the ferroelectric properties of the crystal, that the space group is C 11 2v . The anomalous tantalum compoun…
The dielectric properties of annealed single crystals of SrTi${\mathrm{O}}_{3}$ have been measured over the temperature range from 5 to 300 \ifmmode^\circ\else\textdegree\fi{}K. At temperatures below 50 \ifmmode^\circ\else\textdegree\fi{}K, electric double hysteresis loops are observed and associated changes in weak-f…