Materials Literature
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Abstract Investigation of the clay mineralogy of forty-seven samples of sediments from boreholes in the western Nile Delta, an area little studied hitherto, and from surface sites on the mouth of the Nile and adjacent coast shows that the clay fractions consist of dominant iron-rich, dioctahedral, randomly interstrati…
The equilibrium shape of dissociated dislocations in thin foils of Cu-10 at.% Al is investigated by weak-beam electron microscopy. It is found that dislocations assume a truncated triangular shape caused principally by the reduction in line energy when Shockley partials rotate towards screw character. The effects of i…
An isolated acceptor impurity is shown to be responsible for the ∼113-meV deep luminescence band which is frequently seen in GaAs layers grown by molecular-beam epitaxy. We establish that this center, which is also observed in melt-grown and solution-grown GaAs and which has often been associated with the presence of…
Several electrochemical systems exhibit an intense color change when an electrochemical reaction is induced by an applied electrical field or current. The electrochemical and electro‐optical properties of several such systems have been investigated. These systems are termed electrochemichromic and they can be classifi…
Abstract The melting behavior of restrained isotactic polypropylene fibers is examined quantitatively in terms of the influence the anisotropic structural state of the polymer has on the observed properties. Two endotherm peaks are observed to occur in some of the samples. The formation and location of the multiple pe…
The effects of fabrication variables on the high‐temperature strength of hot‐pressed Si 3 N 4 containing 5 wt% Y 2 O 3 were studied. Materials containing a crystalline grain‐boundary phase, formed as a consequence of a high‐temperature presintering heat treatment and identified as Si 3 N 4 ·Y 2 O 3 , had high‐temperat…
Abstract The multiple melting transitions previously reported for cis ‐polyisoprene have been related to different morphological species observed in thin films using transmission electron microscopy. Two distinct types of spherulitic lamellar crystal have been identified which have characteristic growth rates, lamella…
In this paper a general spectral approximation theory is developed for compact operators on a Banach space. Results are obtained on the approximation of eigenvalues and generalized eigenvectors. These results are applied in a variety of situations.
The quantum efficiency of Dy 3+ ‐activated phosphors is reasonably high in lattices where a low activator concentration (≤ 1%) is already sufficient for effective energy transfer from the lattice to the activator ions. When more activator is needed for effective energy transfer, the quantum efficiency is limited due t…
Aspects of the behavior of the twist elastic modulus K22 of a lyotropic liquid crystal formed by the α-helical polypeptide poly-γ-benzyl-L-glutamate of three molecular weights (MW= 300 000, 310 000, and 550 000) in three solvents (dioxane, dichloromethane, and chloroform) were investigated as a function of concentrati…
The analysis of diffusional transport limitation of nutrient uptake rates by phytoplankton, derived earlier for spherical cells, is extended to include, in an approximate manner, cylindrical and disk‐shaped cells. Transport limitation of nutrient (NO 3 − and NO 2 − ) uptake rates by the marine diatom, Ditylum brightwe…
Characteristic electron-energy-loss processes in crystalline silicon foils are examined for scattering angles less than 2.5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ rad. The relatively high energy of the electron beam (75 keV), combined with a low angular divergence (8 \ifmmode\times\else\texttimes\…
Structural changes accompanying extreme boron-enrichment of boron carbide were deduced with Mo K0¢ X-ray diffraction data obtained from a twinned aggregate containing a minimal amount of carbon. The crystal system remains rhombohedral, probable space group R-3m, as for B4C, but unit-cell parameters show significant ex…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of molecular complexing on the properties of binary nematic liquid crystal mixturesJ. W. Park, C. S. Bak, and M. M. LabesCite this: J. Am. Chem. Soc. 1975, 97, 15, 4398–4400Publication Date (Print):July 1, 1975Publication History Published online1 May 2002Published i…
The rate of cooling of fused‐silica fibers and the generation of stress in clad fibers of fused silica and 96%‐silica glass (∼125 μm OD) pulled at 1750°C were studied. Experimental cooling rates reported by previous workers were fitted using low‐ and high‐temperature heat‐transfer coefficients derived from their data.…
Abstract A number of natural kaolinites from a variety of world sources have been investigated using electron spin resonance at both X-band and Q-band. The results show systematic differences some of which are related to the crystallinity of the material, some to the presence of transition metal ions other than Fe 3+…
A method is described for quantitatively determining the inhibitory activity of pure components, isolates, or mixtures of components (such as urine) on the growth of calcium oxalate crystals. Results with known calcium phosphate crystal growth inhibitors--magnesium, citrate, and pyrophosphate--suggest that these compo…
Previously derived formalisms for extinction are extended to include crystals of non-spherical shape and anisotropy of mosaic spread and particle size. Expressions derived for extinction in an ellipsoidal crystal are compared with numerical calculations on a polyhedral specimen. A pseudo-spherical approximation for po…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpectroscopic investigations of excited states of transition-metal complexesGlenn A. CrosbyCite this: Acc. Chem. Res. 1975, 8, 7, 231–238Publication Date (Print):July 1, 1975Publication History Published online1 May 2002Published inissue 1 July 1975https://pubs.acs.org/doi/1…
Abstract 1. Heat treatment of carbon black-rubber mixtures is a method of “in process” polymer grafting which gives a definite improvement in the dynamic properties of vulcanizates. 2. The heat treatment process can be more effective if chemical promoters are used. These chemical promoters function as coupling agents…