Materials Literature
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Effects of manganese oxide on the initial sintering kinetics of compacts of 5‐μ diameter alumina were studied by isothermal shrinkage measurements from 1450° to 1650°C. The observed rates were characterized by assuming a volume‐diffusion mechanism. Variations in sintering rate with both oxygen partial pressure in the…
The kinetics of the delayed elasticity in inorganic glasses is explained by a molecular rearrangement mechanism with a distribution of activation energies. An experimental method is described by means of which the spectrum of activation energies for the recovery creep process can be determined. Two such spectra, for a…
The theory of low-spin d 5 octahedral complexes is re-examined, and it is found that excited states can contribute significantly to the magnetic properties of the ground state. Electron spin resonance experiments have been performed on (IrX 6 ) 2- complexes (X = F, Cl, Br), and analysis of the data using the more deta…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLow-temperature hydrogen adsorption on copper-nickel alloysD. A. Cadenhead and N. J. WagnerCite this: J. Phys. Chem. 1968, 72, 8, 2775–2781Publication Date (Print):August 1, 1968Publication History Published online1 May 2002Published inissue 1 August 1968https://pubs.acs.org…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTests of the singlet mechanism for cis-trans photoisomerization of the stilbenesJack Saltiel, Oliver C. Zafiriou, Eldon D. Megarity, and Angelo A. LamolaCite this: J. Am. Chem. Soc. 1968, 90, 17, 4759–4760Publication Date (Print):August 1, 1968Publication History Published o…
Abstract The Huggins constant k ′ in the expression for the viscosity of dilute nonelectrolytic polymer solutions, η = η(1 + [η] c + k ′[η] 2 c 2 + …), is calculated. For polymers in the theta condition, k ′ is estimated to be 0.5 < k θ ′ ≤ 0.7. For good solvent systems, the Peterson‐Fixman theory of k ′ has been m…
Abstract A quantitative infrared spectroscopic study of a model urethane‐type compound was carried out in order to obtain basic data on hydrogen bonding in polyurethanes. First, the absolute intensity of free NH groups of N ‐phenylurethane, which was adopted as the model urethane, was determined by Wilson‐Wells' meth…
Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans the biological, physical, and social sciences.
The polarized absorption spectra of ferrimyoglobin cyanide, ammonia, azide, fluoride, formate, and water (acid ferrimyoglobin) complexes in single crystals are described. Special emphasis is placed on the polarization-ratio (PR) spectrum—the spectrum of the intensity ratio for light absorbed along and perpendicular to…
The room-temperature properties of sputtered niobium films can be made to approach those of the bulk metal either by deposition after extensive presputtering on substrates heated to ∼700°C, or by the application of a small negative bias to unheated substrates. The effectiveness of the former method is associated with…
It has recently been observed that cristobalite can hetero‐geneously nucleate and grow internally in vitreous silica. When the glass‐crystal composite is cooled to room temperature, β‐cristobalite is metastably retained as a result of the large tensile stresses developed during cooling. Although these crystals are not…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of new high-pressure pyrochlore phasesR. D. Shannon and A. W. SleightCite this: Inorg. Chem. 1968, 7, 8, 1649–1651Publication Date (Print):August 1, 1968Publication History Published online1 May 2002Published inissue 1 August 1968https://pubs.acs.org/doi/10.1021/ic…
Abstract The absorption of biologically important purines, pyrimidines, and nucleosides by Li-, Na-, Mg-, and Ca-montmorillonite has been studied in aqueous solutions over a range of pH values 2–12. The initial organic concentrations were about 1 m.molar. The ratio clay to organic compounds was such that only up to 25…
High temperature gas reaction specimen chamber for an electron microscope has been constructed. The specimen under electron microscopic observation can be heated at about 1000°C in a gas layer at a pressure of about 300 Torr. The specimen is placed on a film covering the minute hole in the platinum ribbon and heated b…
Abstract Dielectric properties of four methacrylate polymers (methyl, ethyl, n ‐butyl and n ‐octyl) were studied in the frequency range 0.0001 cps–300 kcps at temperatures above and below the glass transition temperature and at various pressures up to 2500 atm. At temperatures well above T g a single relaxation peak (…
Abstract The mechanism of boron uptake by clays, especially illitic clays, and the factors which control such uptake have long been debated issues. In an attempt to answer some of the questions of the controversy, three illites were treated in solutions containing boron. In the study, boron concentration, salinity, te…
THE VIEW THAT THE PLANT CELL GROWS BY THE YIELDING OF THE CELL WALL TO TURGOR PRESSURE CAN BE EXPRESSED IN THE EQUATION: rate = cell extensibility x turgor. All growth rate responses can in principle be resolved into changes in the 2 latter variables. Extensibility will relate primarily to the yielding properties of t…
A new electro-optic effect is presented, based on guest-host interactions in nematic liquid crystals. The ability of a nematic liquid crystal to cooperatively align in an electric field is used to orient ``guest'' dichroic dye molecules (molecules whose absorption spectrum is a function of the molecular orientation wi…
A new allotropic form of carbon occurs in shock-fused graphite gneisses in the Ries Crater, Bavaria. The assemblage in which it occurs consists of hexagonal graphite, rutile, pseudobrookite, magnetite, nickeliferous pyrrhotite, and baddeleyite. Electron-probe analyses indicate that the new phase is pure carbon. It is…
A fourteen-faced space-filling polyhedron which closely approximates the actual distribution of four-, five- and six-sided polygons found in packings of soap bubbles and biological cells is proposed as an alternative to the Kelvin tetrakaidecahedron as the ideal polyhedron for these packings. This polyhedron may also…