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Abstract Thermal conversion rates of the polyamic acid derived from pyromellitic dianhydride and 4,4′‐diaminodiphenyl ether are presented. Formation of the imide ring proceeds by fast and slow first‐order processes. Tertiary amines give ring closures faster by a factor of 10 than the free acid. The enhancement is an a…
Fluorescence yields of solutions of several chelates of europium and terbium have been measured: (a) upon excitation in the ligand absorption bands and (b) upon selective excitation to individual upper levels of the rare-earth ion. Yields with upper-ion-level excitation are lower than when the emitting level is excite…
Variational principles have been applied to aggregates of randomly oriented pure-phase polycrystals having tetragonal symmetry. The bounds of the effective elastic moduli obtained in this way show a substantial improvement over the bounds obtained by means of the Voigt and Reuss assumptions. The Hill average is found…
Four rules are proposed to explain the photoluminescent efficiency of Eu3+-activated oxides: (a) uv absorbing groups in the host lattice should be nearest neighbors in the crystal structure to have sufficient wavefunction overlap; (b) the emission spectrum of the absorbing group should overlap the absorption spectrum…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhosphonitrilic Compounds. VI. High Molecular Weight Poly(alkoxy- and aryloxyphosphazenes)H. R. Allcock, R. L. Kugel, and K. J. ValanCite this: Inorg. Chem. 1966, 5, 10, 1709–1715Publication Date (Print):October 1, 1966Publication History Published online1 May 2002Published…
Machine learning (ML) is transforming all areas of science. The complex and time-consuming calculations in molecular simulations are particularly suitable for an ML revolution and have already been profoundly affected by the application of existing ML ...Read More
The detailed movement of a dislocation line through a random array of point obstacles in the glide plane has been examined, using a digital computer, on the basis of the line tension approximation. The breakaway criterion at each obstacle is a critical angle between the arms of the dislocation, corresponding to a crit…
The solubility of stibnite ( Sb(2)S(3)) was measured at 25 degrees C and 1 atmosphere in solutions ranging from 0.45 to 7.16 percent Na(2)S by weight. Sb(2)S(3): Na(2)S mole ratios of saturated solutions range from 0.238 to 0.403. Stibnite solubility increases at an increasing rate with rising Na(2)S concentration. Th…
Single crystals of potassium chloride were grown from aqueous solutions under carefully controlled conditions of supersaturation, agitation, and impurity lead chloride concentration. The growth rate of the (100) face was determined. It was found that PbCl2 concentrations as low as 10−8 moles PbCl2/mole KCl decreased t…
Equilibrium constants have been measured for the following displacement reactions between copper(II) and zinc(II) with hematoporphyrin IX.[Formula: see text]Preliminary measurements have also been made for the reactions of Mn(II) and Co(II) with hematoporphyrin IX in glacial acetic acid solutions.
The X-band electron paramagnetic resonance spectra of Cu+ + ions doped into amorphous, tetragonal, and hexagonal GeO2 have been observed at 295°K. Optical absorption and reflection data for, respectively, the doped glass and polycrystalline samples were also obtained. From the experimental results, the symmetry of the…
The radical ions SO4− and S2O3−, trapped in γ-irradiated K2SO4 and Na2S2O3·5H2O crystals, respectively, have been identified by their ESR spectra. In the preceding paper molecular orbital calculations were described the results of which predict a ···1t163t262a1, 2A1 (symmetry Td) configuration for SO4− and a ···5e45a1…
The Raman and infrared spectra of the aluminate ions in alkaline solutions have been measured. Two ionic species, one predominant from pH 8 to pH 12 and the other predominant above pH 13, may be identified from the spectra. At intermediate pH's both forms are present. The selection rules and the polarization of the li…
The radial and longitudinal development of electron-photon showers has been measured in copper and lead at 1 GeV. A new technique using the thermoluminescent property of LiF has been employed to measure energy deposition. The resultant radial distributions and transition curves show good agreement with Monte Carlo cal…
The characteristics of phonon-terminated coherent oscillation associated with ${\mathrm{Ni}}^{2+}$, ${\mathrm{Co}}^{2+}$, and ${\mathrm{V}}^{2+}$ ions in rutile and perovskite fluorides are described. Continuous tunability over portions of the vibronic continuum of ${\mathrm{Ni}}^{2+}$ in Mg${\mathrm{F}}_{2}$ has been…
Abstract In agreement with the results of dynamic experiments of Stratton and Ferry, this study of relaxation of rubber vulcanizates entirely confirms the existence of peculiar, slow, viscoelastic processes in high polymer networks. Characteristic differences with the rheological behavior of unvulcanized polymers are…
Abstract Measurements of Young's modulus of vulcanized rubbers containing thermal carbon black show the predicted dependence on the volume concentration given by relationships derived for a suspension of spherical particles, for example, that due to Guth, Simha, and Gold which gives E=E 0 (1+2.5c+14.1c 2 ) . A simple…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbon Monoxide Reactions. I. A Novel Synthesis of Acid ChloridesWarren A. ThalerCite this: J. Am. Chem. Soc. 1966, 88, 18, 4278–4279Publication Date (Print):September 1, 1966Publication History Published online1 May 2002Published inissue 1 September 1966https://pubs.acs.org…
rings, in which the Ge is tetrahedrally coordinated, linked through octahedrally coordinated Ge atoms to form a three-dimensional Ge-O network. All Ge polyhedra are linked by corner sharing. The Ba ions occupy positions in channels of the network.
The temperature, pressure, and time dependence of bulk density and the compressive strength of clay and boehmite compacts subjected to reactive hot‐pressing were determined. The strength and the bulk density are linearly related to the extent of the dehydroxylation reaction which occurs during reactive hot‐pressing. I…