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A summarizing account is given of the research on barium titanate in progress at the Laboratory for Insulation Research at M. I. T. since 1943. The investigations have led to an understanding of the mechanism of ferroelectricity in the titanates and to discoveries such as the piezoelectric effect in the ceramics and t…
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The field and lens constants are calculated for two typical magnetic lenses as used in electron microscopes, using the relaxation method developed by Southwell for the solution of potential problems The results are compared with those based on simple analytic approximations to the field distribution in the work of Gla…
The highly symmetrical SO 4 2 ‐ group is not easily distorted and consequently does not lend itself readily to glass formation, Vitreous sulfates of cations of the noble‐gas type are unknown. However, by combining a large cation with a weak positive force field (K + ) with the strong field of the proton (H + ), it bec…
Emulsion-type polymerization reactions have been accelerated by irradiation with ultrasonic energy. A magnetostriction oscillator at 15 kc gave essentially the same results as a piezoelectric oscillator at 500 kc. The rate of formation of polystyrene was doubled and higher final yields obtained using about 0.03 watt o…
Abstract Dichtemessungen und Röntgenuntersuchungen an Mg 2 Pb und Mg 2 Sn ergeben eine Anomalie in der Art, daß der röntgenographisch berechnete Wert der Dichte kleiner als der pyknometrisch gemessene ist. Mg 2 Ge zeigt diese Anomalie nicht mehr. Die Zusammensetzung der Verbindungen ist exakt formelgemäß. Bei Mg 2 Pb…
In a former paper the authors suggested the following equation of state, (P+π)(V−ω)=RT, where π is the internal pressure (or cohesive energy density) and ω is the volume at absolute zero. It was found that this equation was in good agreement with data on the thermal expansivity and isothermal compressibility of polyst…
The use of a steel microtome knife in cutting sections for electron microscopy has certain disadvantages, especially in the achievement and maintenance of a sufficiently sharp edge, which involve a considerable expenditure of time. The search for a knife material having homogeneity and hardness without excessive britt…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Vapor Pressure of Inorganic Substances. II. B2O31Rudolph Speiser, Sam Naiditch, and Herrick L. JohnstonCite this: J. Am. Chem. Soc. 1950, 72, 6, 2578–2580Publication Date (Print):June 1, 1950Publication History Published online1 May 2002Published inissue 1 June 1950https…
Therecentobservation of orthorhombic α'‐Ca 2 Si0 4 (bredigite) at all temperatures between about 850° and 1450°C. leads to a rational interpretation of the polymorphism of this substance, which is very satisfactory from the crystal‐chemical point of view. The so‐called β phase, of as yet unknown, complex structure, ex…
ADVERTISEMENT RETURN TO ISSUEArticleNEXTThe Penetration of Cellulose Fibers.Alfred J. Stamm and Harold. TarkowCite this: J. Phys. Chem. 1950, 54, 6, 745–753Publication Date (Print):June 1, 1950Publication History Published online1 May 2002Published inissue 1 June 1950https://doi.org/10.1021/j150480a001RIGHTS & PERMISS…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Gelation of Sodium Silicate. Effect of Sulfuric Acid, Hydrochloric Acid, Ammonium Sulfate, and Sodium Aluminate.Reynold C. Merrill and Robert W. SpencerCite this: J. Phys. Chem. 1950, 54, 6, 806–812Publication Date (Print):June 1, 1950Publication History Published online…
The subject of this paper is treated mainly from the standpoint of cotton cellulose. The concept of crystallinity is discussed not simply in the narrow sense of degree of crystallinity but in the broader sense, which involves the whole fine structure of cellulose. With respect to crystallinity in the latter sense, the…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPeriodate Oxidation of DextranAllene Jeanes and C. A. WilhamCite this: J. Am. Chem. Soc. 1950, 72, 6, 2655–2657Publication Date (Print):June 1, 1950Publication History Published online1 May 2002Published inissue 1 June 1950https://pubs.acs.org/doi/10.1021/ja01162a086https://…
Like the chemical properties of the elements, the work function φ is a periodic function of atomic number, as shown clearly by a new compilation of published data for 57 elements. The progressive rise and fall of work function values throughout the table of the elements appears to be sufficiently regular to permit app…
Models, largely based on the assumptions introduced by Peierls and Nabarro in dealing with a single dislocation, are used in calculations on three types of intercrystalline boundaries, namely, (I) a boundary due to a difference of atomic spacing, (II) a twist boundary, and (III) a symmetrical tilt boundary. With these…
Dilatometric and viscometric data on fractionated polystyrenes containing diethylbenzene end groups are presented over wide temperature ranges. The second-order transition temperature, viscosity-temperature coefficient, and specific volume all change rapidly with increasing molecular weight toward asymptotic limits wh…
Abstract In the first part of this paper, simple approximate methods have been developed for evaluating the electrical conductivity of films and wires of a size comparable with the mean free path of the conduction electrons. In the second part, a rigorous theory has been given of the electrical conductivity of a thin…
Evidence is presented for three new, light neptunium isotopes formed by deuteron bombardments of ${\mathrm{U}}^{233}$, ${\mathrm{U}}^{235}$, and ${\mathrm{U}}^{238}$. The isotope ${\mathrm{Np}}^{231}$ has a half-life of 50\ifmmode\pm\else\textpm\fi{}3 min. and emits alpha-particles of 6.28-Mev energy; the proportion o…
When a crystal of magnetite has been cooled through the low temperature transition (near -164\ifmmode^\circ\else\textdegree\fi{}C) in a demagnetized state, the magnetization undergoes a large and abrupt increase in the three principal crystallographic directions [100], [110], and [111] upon warming. The behavior of th…