Materials Literature
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Abstract Certain rare diamonds have had epochs of growth during which they were bounded by two surface forms: normal {111} facets together with non-flat surfaces of mean {100} orientation (‘cuboid’ surfaces). Differences of lattice imperfection content in octahedral and cuboid growth sectors (i. e. in regions that ha…
A straightforward attempt to estimate the influence of the first vertex correction for a homogeneous electron gas is made. The approximation scheme is also tested on a solvable model of a core electron coupled to an electron gas.
For a constant rate G of generation of electron-hole pairs, lg J ph (J ph is the photocurrent) increases as T -1 at high temperatures and reaches a maximum value of J m at T=T m . Thereafter, lg J ph decreases as T -1 with further decrease in temperature and finally, at low temperatures, J ph becomes independent of te…
The magnetic properties of the distorted perovskite GdCrO 3 have been investigated by magnetic moment measurements in the temperature range below 100K and specific heat measurements below 10K. Measurements show that the canting of the Cr 3+ ions from a simple antiferromagnetic alignment is due to antisymmetric exchang…
Hot-pressed ceramics of the lead titanate zirconate system with different grain sizes were prepared and some of their electrical properties measured. The values of the dielectric and piezoelectric properties were analysed together with information on barium titanate ceramics already published in the literature. Many s…
An exact solution to the one-dimensional electron gas with a particular attractive-interaction strength for scattering across the Fermi "surface" is given. It is shown that conductivity enhancement occurs for physically interesting values of the coupling constants. Scaling arguments are advanced to demonstrate that th…
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.