Materials Literature
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A brief outline is given of the spin-wave approximation to the near ground states of ferromagnetism and antiferromagnetism. Simple pictorial models of spin waves are introduced. These models clarify the striking difference between ferromagnetic spin waves, which obey the dispersion law ω ∝ k2, and antiferromagnetic sp…
Summary In his recent theory of work hardening, Mott assumes that face-centred cubic crystals usually contain, prior to deformation, a network of dislocations, as suggested first by Frank; and he computes the decrease in the modulus of rigidity due to the existence of such a network. His computation may be extended to…
Electron beam contamination has been studied in simple vacuum systems to determine how it originates and methods by which it may be prevented. It is concluded that the contamination is formed by the interaction of the electrons with organic molecules adsorbed on the bombarded surfaces, the molecules being replenished…
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In contrast to other inorganic solids, glasses may be permanently compacted by application of pressures of the order of 104 to 105 atmospheres. This effect was studied on two simple oxide glasses (SiO2 and B2O3) and several silicate glasses. The effect of compacting was studied by measuring the densities, dimensions,…
Abstract The Hall coefficient and resistivity of a range of polycrystalline graphites with different crystal sizes and a single crystal of Travancore graphite have been measured over a wide range of temperature. The number of free electrons has been found to be approximately 6x1018 per cm3 at room temperature; the var…
Abstract In liquids the molecular configuration is a function of temperature. If in a given substance super-cooling of the liquid is possible to such a low temperature—the ‘transformation temperature’ (Tg)—that the viscosity reaches about 1013 poises, the required changes in configuration become impossible and at all…
INTRODUCTION The following described materials have been unearthed partly during the construction of the Ch ngtu-Chungking Railway mainly in 1951 and partly during the clearing away the building foundation in Tatienwan, a suburb of Chungking.
Mole\`ere's theory of multiple scattering of electrons and other charged particles is here derived in a mathematically simpler way. The differential scattering law enters the theory only through a single parameter, the screening angle ${{\ensuremath{\chi}}_{a}}^{\ensuremath{'}}$, Eq. (21). The angular distribution, ex…
Abstract Several configurations of polypeptide chains involving planar amide groups with the dimensions found by experiment for simple substances, and hydrogen bonds between the NH groups and the carbonyl oxygen atoms, have been discovered. One of these structures, the α-helix, with about 3·7 amino-acid residues per t…
Since the first studies with bacterial corrosion of underground pipe lines in 1939 in the United States chief interest has been centered in this subject in the Eastern states. Indications are that the causative sulfate-reducing bacteria and the characteristic anaerobic soils associated with their corrosive action are…
Paul R. Kent, MSC, USN, J. Howard Steeve, MSC, USN; Convergence Insufficiency: Incidence Among Military Personnel and Relief by Orthoptic Methods, The Mili
The mineral gyrolite was discovered in Skye by T. Anderson in 1851. He showeditto be ahydratedcaleiumsilicateofapproximate composition 2CaO.3SiO 2 .3H 2 O. Subsequently gyrolite has been found in other localities, and has been prepared hydrothermally by Flint, McMurdie, and Wells. The ratio of lime to silica found by…
Abstract Die Darstellung von Mangan(VII)‐oxyd aus Kaliumpermanganat und konz. Schwefelsäure wird beschrieben, Mangan(VII)‐oxyd ist eine in der Aufsicht grüne, in der Durchsicht rote, ölige Flüssigkeit vom Smp. 5,9° und dem Zersetzungspunkt ∼55°. D = 2,396; elektr. Leitfähigkeit x < 4 · 10 −9 Ohm −1 · cm −1 . Dielek…
When an alloy develops an ordered structure, new Brillouin zone boundaries are formed corresponding to the extra Bragg reflections. It is shown that, in this process, the Fermi energy is lowered, and this tends to stabilize the superlattice. The theory is applied to the superlattices in CuPt, CuAu and Ag 3 Mg, where t…
A study of the thermal decomposition of nitromethane was made by the flow method, with nitrogen as carrier gas, the reaction being followed by polarographic analysis of the effluent from the furnace for nitromethane. When carefully dried nitrogen was used the rate of disappearance of nitromethane became erratic; it wa…