Materials Literature
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Abstract The molecular motion of unsintered polytetrafluoroethylene (PTFE) was studied by dynamic viscoelastic measurements. From results for variously heat treated suspension polymerized (molding powder) PTFE, the following conclusions are drawn. Molding powder, as received, has a high degree of crystallinity accordi…
Summary In contrast with some other hydrous aluminum phosphates, vashegyite is crystalline. Simultaneous application of several assumptions leads to the hypothesis that it has a structure analogous to that of kaolinite, and thus contains tetrahedral sheets, n [X 2 O 5 ], where X is both P and H 3 (in lieu of Si). Thus…
This article modifies the Almon polynomial distributed lag to allow for a lag of infinite length. Estimation of the model is considered, and an empirical example is given to illustrate the usefulness of the model
SUMMARY A case of polymorphism in the desmid Micrasterias pinnatifida (Kütz.) Ralfs is described. It is based on material collected from the overflow channel of a dam in Caeté, Minas Gerais State. After careful examination of nearly 500 specimens, 26 different morphological expressions of the alga were found which led…
A quick method is presented of determining the coincidence site lattice when the original lattice is primitive cubic.
The results of an experimental investigation of the surface flashover of high density alumina spacers in vacuum are presented. The insulators were subjected to a combination of a dc or 60-Hz prestress and a 1-50-us impulse stress. It is shown that the overall flashover voltage is strongly dependent upon the magnitude…
Light propagation along the helical axis of cholesteric liquid crystals, whose structure has been distorted by a magnetic or electric field perpendicular to the helix axis, is theoretically investigated. The solutions show several reflection bands whose centers are given by the Bragg condition mλm = 2S n (m is an inte…
As-grown CdSe single crystals exhibited mainly the emissions associated with excitons, and the diffusion of Li caused the intensity of edge emission to be marked. The difference in the peak wavelengths of edge emission at 4.2 K between the as-grown crystal and CdSe: Li seemed to be due to the difference in the donor-a…
The previous measurements of the first anisotropy constant, K1, of single crystal YCo5by Hoffer and Strnat were extended over a wider temperature range (4.2 to 900K) using their same sample. However, the measurements of magnetization parallel and perpendicular to the c-axis of the crystal were made using a vibrating s…
The lattice parameters of solid solutions of magnesium and silver in lithium have been measured by X-ray diffraction, using extruded wire specimens. The results for the LiMg alloys are compared with some previously published values. In the dilute (<0.5 at%Ag)LiAg alloys, a very rapid change in the lattice parameter of…
Abstract Oxidation kinetics of metallic uranium in moist gaseous media and its correlation to the surface morphology were studied by means of a gas chromatographic technique developed for this purpose. The results have substantiated the authors' earlier work which led to the concept of a hydride fracture mechanism for…
It is shown to be possible to predict the optical properties of evaporated films of antimony in the infrared as a function of their thickness and changes in free-carrier concentration. This is achieved by the interpretation of previous data on the optical properties of thin films of antimony, with the use of detailed…
The rate of nitrogen removal from liquid iron and iron alloys containing oxygen, sulphur, silicon, carbon, nickel, and chromium, respectively, was studied at 1600℃ using argon as a carrier gas. The results obtained are as follows:
This paper describes the breakdown characteristics of SF6 at pressures up to 15 kg/cm2 absolute at 20°C against power frequency, switching impulse and lightning impulse voltages in sphere and coaxial cylinder gaps.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermally induced degenerate skeletal rearrangement and isomerization reactions of cyclooctatetraenesLeo A. Paquette, Masayoshi Oku, William E. Heyd, and Robert H. MeisingerCite this: J. Am. Chem. Soc. 1974, 96, 18, 5815–5825Publication Date (Print):September 1, 1974Publicat…
The theoretical variation of the thermoelectric figure of merit of heavily doped polycrystalline hot-pressed germanium-silicon alloys is investigated as a function of carrier concentration. It is shown that in a material with a finite grain size (typically 10 −4 m to 10 −8 m) the figure of merit is increased and that…
In order to clarify the water treeing, the authors conducted a series of experiments on three types of specimen, namely, sheet samples, wires and cables.
Abstract Four polymers, viz. polystyrene, polycarbonate, poly(methyl methacrylate), and poly‐(vinyl chloride), were cooled from the melt to room temperature under hydrostatic pressures of 30 and 1000 atm. Cooling under high pressure increased the density by 0.4–0.6%, and the effect of this has been examined for the to…
Abstract The intrinsic viscosity and molecular weight of several samples of polyhydroxyethylaspartamide with differing degrees of polymerization were determined and related, according to the Mark‐Howink equation. The a exponent is consistent with a random‐coil structure. The average unperturbed dimensions of the polym…
Silica‐free phases which have a structure similar to that of mullite can be crystallized from gels in the Na 2 O‐Al 2 O 3 and (Na,K) 2 O‐BaO‐Al 2 O 3 systems. A gelation step appears to be necessary, since a solid‐state reaction between Na 2 CO 3 and Al(OH) 3 does not give the mullite‐type phase. Crystallization of th…