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Concrete thermal treatments. 2nd part

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Nature of self-seeding polyethylene crystal nuclei

In a limited temperature range above the clearing point of crystal suspensions, submicroscopic entities representing unmeasurably small portions of the original crystal population may survive whose existence is revealed by crystals nucleated on subsequent cooling [1]. Factors influencing the number of these nuclei and…

Theoretical Calculation of Atomic Spectra Using Digital Computers*

For an arbitrary electron configuration l1n1l2n2l3n3⋯, analytical expressions are derived for the energy-matrix coefficients of the electrostatic-interaction parameters Fk(li,lj) and Gk(li,lj) and of the spin–orbit parameters ζ(li). A computer program is described which calculates decimal values of these coefficients…

Ferroelectric Tungsten Bronze-Type Crystal Structures. I. Barium Strontium Niobate Ba0.27Sr0.75Nb2O5.78

Ferroelectric Ba0.27Sr0.75Nb2O5.78, with Tc = 348° ± 15°K, is a tungsten bronze-type structure crystallizing in the tetragonal system, with lattice constants a = 12.43024 ± 0.00002 and c = 3.91341 ± 0.00001 Å at 298°K, space group P4bm, and five formulas in the unit cell. The integrated intensities of 6781 structure f…

Regulation of glutamine synthetase. XII. Electron microscopy of the enzyme from Escherichia coli

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRegulation of glutamine synthetase. XII. Electron microscopy of the enzyme from Escherichia coliR. C. Valentine, B. M. Shapiro, and E. R. StadtmanCite this: Biochemistry 1968, 7, 6, 2143–2152Publication Date (Print):June 1, 1968Publication History Published online1 May 2002P…

Superconducting Phosphorus

Phosphorus, the element itself, becomes superconducting near 4.7 degrees K and at pressures exceeding 100 kilobars. This constitutes one of the four last missing links in the proof that superconductivity is normal behavior for every truly metallic sp element. The three remaining ones are arsenic, sulfur, and iodine.

Crystals from Cocoons of Malacosoma neustria testacea

The crystalline material covering the cocoon of Malacosoma neustria testacea (Lasiocampidae, Lepidoptera) was analyzed physically and chemically. The mean component was identified as calcium oxalate monohydrate, and the crystals were found to be whewellite in form.

Anionic polymerization of β‐substituted acrylic esters

Abstract Anionic polymerizations of methyl and other n ‐alkyl cinnamtes with organometallic catalysts were studied. Calcium‐zinc‐tetraethyl showed the greatest catalytic activity for the polymerization of the above monomers. In copolymerization of cis and trans isomers of methyl crotonate and isopropyl crotonate the t…

Relationship between the Macroscopic and Microscopic Theory of Crystal Elasticity. II. Nonprimitive Crystals

A recent microscopic elasticity formalism is generalized to nonprimitive, nonpiezoelectric crystals, and extended to treat long-range electrostatic interactions explicitly. Its relationship with the macroscopic theory of crystal elasticity is established for this type of crystal up to, and including, third order. The…

Ternary Hydrides Possessing the Cubic Perovskite Structure. I. A Neutron-Diffraction Study of BaLiH3 and BaLiD3

Neutron-diffraction studies on powered samples of BaLiH3 and BaLiD3 have shown that the structure is of the inverted perovskite type with the atomic positions of space group Pm3m: Ba in (0, 0, 0), Li in (12, 12, 12), and H or D in (12, 12, 0; 0, 12, 12; 12, 0, 12). The SrLiH3 and EuLiH3 are presumably isostructural. T…

Proton Spin–Lattice Relaxation in Hexagonal Ice

The results of measurements of the proton spin–lattice relaxation time T1 in ice are reported. The ice samples were single crystals grown by zone refining at atmospheric pressure. The measured activation energy for the T1 process is 14.1 ± 0.1 kcal/mole. No anisotropy of T1 is observed. A theoretical calculation of T1…

Spontaneous Emission Probabilities and Quantum Efficiencies for Excited States of Pr3+ in LaF3

Spontaneous emission probabilities for electric- and magnetic-dipole transitions from several electronic states of Pr3+ in LaF3 are calculated using the Judd–Ofelt theory and experimental intensity parameters. The calculated radiative decay probabilities are combined with observed fluorescence lifetimes to determine t…

Temperature Dependence of the Ferroelectric Mode in KH2PO4

Raman-scattering measurements on K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$ reveal a broad, low-frequency ferroelectric mode which can be represented by a simple damped-harmonic-oscillator function. The resultant characteristic frequency and reciprocal zero-frequency susceptibility approach zero while the damping factor r…

Optical Absorption Edge of Magnetic Semiconductors

Received 29 January 1968DOI:https://doi.org/10.1103/PhysRevLett.20.1045©1968 American Physical Society

Electric-Field-Induced Phase Change in Cholesteric Liquid Crystals

Abstract Optically-negative cholesteric liquid-crystal films can be transformed to an optically-positive state by applying high d-c electric fields. A phase transformation occurs in which the helicoidal cholesteric structure is converted to either a planar smectic, or a linear nematic, structure. The threshhold field…

Effects of substitution of triphenylmethyl groups into cellulose on the fine structure and thermal properties of the products

Abstract Mercerized cellulose in the form of 7/2 yarn was reactivated with 17.5% sodium hydroxide and then heated at 100°C. with 5 moles of trityl chloride, in pyridine, per anhydroglucose unit. The time of reaction was varied, giving ether derivatives of the cellulose containing 0.31–0.79 triphenylmethyl groups (DS)…

EXPLOSIONS IN SNOW

Abstract : Tables, curves, equations, and example problems presented in the report make it possible, within the range of the experiments, to accurately predict any desired dimensions of the limit of complete rupture.

Wave Propagation in Anisotropic Bars of Rectangular Cross Section. Part I. Longitudinal Wave Propagation

An approximate solution is obtained for the problem of steady-state longitudinal-wave propagation in anisotropic bars of infinite length and rectangular cross section by employing the variational method of Ritz. The first three dispersion curves are presented for orthotropic, tetragonal, hexagonal, cubic, and isotropi…

A podsol derived from serpentine rocks in Hokkaido, Japan

Because of its high magnesium content and relatively small anount of silica, iron and aluminum, the weathering process of serpentine rock is very different from other aluminosilicate rocks. Generally it has been thought that podsolization does not occur in the soil derived from this rock.