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An analysis is presented of the compatible subgroups which can arise by second-order phase transition from the perovskite structure, without change of unit cell. The symmetry analysis is based upon the subduction-criterion simplification of the thermodynamic Landau theory. The possible displacements from the perovskit…
Measurements at room temperature of the infrared reflectivity of oriented samples of orthorhombic NaN${\mathrm{O}}_{2}$ crystals have been carried out and analyzed by Kramers-Kronig relations to obtain the principal dielectric response functions. The eight infrared dispersion frequencies found are well accounted for b…
The temperature dependences of the hyperfine magnetic fields at ${\mathrm{Fe}}^{57}$ nuclei in $A$ and $B$ sites of ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ have been determined with the M\"ossbauer-effect technique. A comparison with neutron diffraction data shows that the ${H}_{\mathrm{hpf}}$-versus-$T$ curves follow t…
The low-lying phonon and magnetic excitations of CoO have been studied experimentally and theoretically, both above and below the antiferromagnetic ordering temperature. The experiments were performed using the technique of inelastic scattering of slow neutrons with the aid of a triple-axis crystal spectrometer. These…
A gallstone of almost perfect octahedral symmetry was composed of a mixture of crystallites of the three polymorphous forms of calcium carbonate: calcite, aragonite, and vaterite.
Abstract The low polymerization of ethylene oxide with sodium dimethyldithiocarbamate in a homogeneous system was studied. This reaction was verified as proceeding through a step-by-step addition mechanism, due to the enhanced nucleophilicity of the dithiocarbamate anion in dipolar aprotic solvents. The solvent effect…
A method has been developed for obtaining lattice spacings of powder samples by x-ray diffraction in times potentially as short as 1 second. The sample is irradiated with polychromatic radiation from an x-ray tube, and the energy spectrum of x-rays scattered at a given angle is observed with a semiconductor radiation…
Abstract The self-diffusion coefficient of ions or atoms in such crystals as halides, oxides and sulfides can be determined from the rate of the diffusion-controlled solid-state reaction as well as by the tracer method. In the present study, the self-diffusion coefficient of nickel atoms in nickel sulfide was determin…
An account is given of an investigation of the effects of fibre type (rayon, acrylic fibre, wool, and cotton) and dimensions on the properties of needled fabrics, the test methods used being those described in a previous paper. Some fabrics show a stick-slip behaviour in extension; others deform smoothly. Rayon webs c…
The reaction kinetics of graphite with hydrogen at high temperatures and pressures was studied by measuring the rate of weight loss and surface recession of graphite samples. Under experimental conditions, methane and acetylene were the predominant products. From previous studies, surface reaction mechanisms were assu…
Abstract The solubility of cellulose triacetate in a range of solvents was measured, and the results for tetrachloroethane, chloroform, and acetic acid were compared with those from initial phase separation in solvent–nonsolvent mixtures and viscosity–concentration studies. The correlation found between solubilities,…
Vaporization experiments with liquid samples of TiO, Ti3O5, Ti4O7, Ti5O9, and TiO2 were performed, and the residues were analyzed by x-ray diffraction procedures. The results show that the congruently vaporizing composition lies between the composition Ti3O5 and the composition Ti4O7 instead of at the composition Ti3O…
Axisymmetric plastic buckling of axially compressed cylindrical shells is studied for semi-infinite shells and shells of finite length subject to free-edge boundary conditions. It is shown that the length of the cylinder has a negligible effect on the buckling load. Reductions in buckling stresses from the classical s…
The preparation of homopolymers of cyclohexyl isonitrile by cat-ionic initiators has been investigated.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFar-infrared spectra of compounds containing the M6X12 metal atom clusterRaymond A. Mackay and Robert Fournier SchneiderCite this: Inorg. Chem. 1968, 7, 3, 455–459Publication Date (Print):March 1, 1968Publication History Published online1 May 2002Published inissue 1 March 19…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe application of the Pfeiffer effect to the resolution of dissymmetric coordination compoundsStanley Kirschner and Nasir AhmadCite this: J. Am. Chem. Soc. 1968, 90, 7, 1910–1911Publication Date (Print):March 1, 1968Publication History Published online1 May 2002Published in…
Glass compositions are correlated with published data for refractive index, specific volume, and fluidity, which indicate the presence of different structural types in silicate glasses. These structural types are shown to be uniquely related to the composition areas of primary crystallization phase fields. It is sugge…
Summary The compositions of more than eighty synthetic members of the apatite group with the general formula A 10 ( X O 4 ) 6 Z 2 have been used as a basis for classifying the apatites into three groups. The ratios of the mean sizes of the ‘ A ’ ions to those of the ‘ X ’ ions for all these compositions lie between th…
The electron spin resonance of Gd 3+ has been studied in the orthorhombic and rhombohedral phases of BaTiO 3 . The main features of Gd 3+ resonances are summarized in their relation to Fe 3+ resonances as follows: (1) The axis of the axial crystalline field in the orthorhombic phase is parallel to the <110> polar axis…
Abstract The preparation and properties of films and fibers of highly disordered cellulose are described; the basis of the preparation is the regeneration of cellulose from cellulose derivatives in non‐aqueous media. These cellulose are at least 97% hydrogen‐bond disordered (as measured by the infrared‐deuteration tec…