Materials Literature
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Abstract Various theories accounting for the existence of a front factor in the equation of state for rubber elasticity are reviwed. It is shown that a front factor which may be different from unity exists whether or not intramolecular energy effects are present. A unified theory is presented which is applicable both…
Abstract The nonisothermal method of Freeman and Carroll is used to investigate the kinetics of the thermal degradation of polyethylene and polystyrene. The reactions were studied thermogravimetrically under a vacuum of 1 mm Hg. Decomposition appears to occur in stages. The rate parameters were determined for each reg…
The theory of sound attenuation in structurally perfect dielectric crystals is extended and applied to recent experiments on the absorption of acoustic waves in crystalline quartz at frequencies from ${10}^{9}$ cps to 2.4\ifmmode\times\else\texttimes\fi{}${10}^{10}$ cps. The sound wave is assumed to vary the frequenci…
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The Hall effect, thermoelectric power, and electrical conductivity have been measured as a function of temperature in crystals of $p$-type titanium sesquioxide. A transition is observed at about 450\ifmmode^\circ\else\textdegree\fi{}K. Below this temperature the crystals behave like semiconductors, while above it the…
Diffusion fronts in samples containing grain boundaries are spike shaped. Velocity of spike advance and angle between spike and boundary are measured. The "spike-velocity method" of analysis permits evaluation of two effective widths, ${W}_{D}$ and ${W}_{0}$, which describe the diffusion properties of the boundary. Th…
The lattice vibration spectrum of a solid can be characterized by one single frequency, which is defined as "the frequency of the center of gravity" of this spectrum or simply "center frequency." From its equality with the characteristic frequency of specific heat we have recently derived the "center law of the lattic…
Optical absorption cross sections and the fluorescent quantum efficiency in ruby have been determined. This data has been used to correlate calculations with the analysis of the preceding paper. Stimulated emission from ruby under pulsed excitation has been studied in some detail; the observations are found to depend…
Abstract Natürlich vorkommende organische Substanzen sind vielfach nach gewissen Regeln, Gesetzmäßigkeiten, gebaut. Solche Bauregeln sind nicht nur zur Konstitutionsaufklärung neuer Naturstoffe nützlich, sondern können, wie hier gezeigt wird, auch bei der Erforschung biochemischer Umsetzungen als Leitfaden dienen. Aus…
The safety problems of research reactors are discussed. Safety of these reactors depends principally from the rahin them, and the penetrating radiations emitted. The safety requirements for reactivity containments, control instruments and mechanisms, guaranteed supplies, and operations of the research reactors are des…