Materials Literature
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Abstract We have been studying crystallization and melting behavior of high performance semicrystalline polymers to increase our understanding of the effects of processing on microstructure. Questions on development of morphology center around whether single or dual populations of crystals exist after melt processing,…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthetic nickel-iron NiFe3Q4 cubane-type clusters (S = 3/2) by reductive rearrangement of linear [Fe3Q4(SEt)4]3- (Q = sulfur, selenium)Stefano Ciurli, Shi Bao Yu, R. H. Holm, K. K. P. Srivastava, and E. MunckCite this: J. Am. Chem. Soc. 1990, 112, 22, 8169–8171Publication D…
The host-vector system for an extreme thermophile, Thermus thermophilus HB27, was developed. The host strain has a mutation in tryptophan synthetase gene (trpB), and the mutation was determined to be a missense mutation by DNA sequence analysis. A Thermus-E. coli shuttle vector pYK109 was constructed. pYK109 consists…
Abstract To determine the mechanisms of the electron-hole processes in a-Al2O3:C crystals, characteristics of their thermo- and photo-stimulated exoelectron emission (TSEE, PSEE) and luminescence have been studied. It is shown that the emission of F+ centres takes place with the temperature shift relative to the emiss…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn unprecedented, bridged dihydrogen complex of a cofacial metallodiporphyrin and its relevance to the bimolecular reductive elimination of hydrogenJames P. Collman, James E. Hutchison, Paul S. Wagenknecht, Nathan S. Lewis, Michel Angel Lopez, and Roger GuilardCite this: J.…
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SUMMARY For proper understanding of image formation using charge carriers, it is shown that signal detection by means of induction must be considered. This explains the possibility of imaging insulators as well as other phenomena especially in the conditions of the environmental scanning electron microscope. In additi…
The dynamical properties of two measures to probe ergodic behavior in Hamiltonian systems with a large number of degrees of freedom are investigated. The measures, namely, the energy metric d(t) and the fluctuation metric \ensuremath{\Omega}(t) are both based on the time-averaged energies of the individual particles c…
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Abstract Secondary minerals formed during simulated weathering of nuclear waste glasses have been identified by analytical electron microscopy. A complete description of the reacted glass, from the outermost surface in direct contact with the leachant solution to the reacting front that migrates into the bulk glass, w…
Heavy-ion irradiation (14 MeVu−1 Pb ions) of zircon crystals gives rise to linear latent tracks of 80 Å diameter and length 140 μm. Direct observation of the track core, by high-voltage high-resolution electron microscopy at atomic resolution, reveals a core having roughly circular cross-section, with some facetting o…
Abstract The response of glasses to three‐step thermal cycles in which the glass is poorly stabilized prior to reheating has been examined both theoretically and experimentally. Theory predicts that, during the heating stage of these cycles, a type of peak (called an upper peak) occurs which is quite different from th…
The reaction layers between silicon carbide continuous fibers (Nicalon) and a calcium aluminosilicate glass‐ceramic (anorthite composition) matrix in hot‐pressed composites have been characterized both structurally and chemically using high‐resolution, field‐emission scanning transmission electron microscopy. Chemical…
An experimental study of the temporal evolution of two-dimensional drained soap froths is presented. The long-time behavior of the froth shows a linear dependence of the average bubble area on time. By keeping nearly constant and thin plateau borders at all times, deviations from 120\ifmmode^\circ\else\textdegree\fi{}…
Development of epilithic algal communities was monitored in fast- (29 cm∙s −1 ) and slow-current (12 cm∙s −1 ) outdoor experimental stream channels for 33 d following a simulated spate. Disturbance reduced diatom densities in both current regimes to equal levels, but recovery was more rapid in slow current. Maximum al…
Abstract Utilizing a newly developed apparatus, force‐length measurements were performed on a series of unfractionated random ethylene copolymers having different counit types and a wide composition range. By controling crystallization conditions, crystallinity levels could be varied over wide extremes and a complete…
The surface of titanium has been modified by covalent attachment of an organic monolayer anchored by a siloxane network. This coating completely covers the metal and allows controlled modification of surface properties by the exposed chemical endgroups of the monolayer forming surfactant. The attachment of such a film…
The triplet energy of alpha-terthienyl has been determined by heavy atom-induced optical absorption: the value of 39.7 +/- 1.5 kcal/mol is consistent with earlier energy transfer work. Combining this result with calorimetric data from optoacoustic calorimetry indicates that intersystem crossing occurs with at least 90…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and characterization of highly crosslinked poly(acrylamides) and poly(methacrylamides). A new class of macroporous polyamidesKenneth J. Shea, G. J. Stoddard, D. M. Shavelle, F. Wakui, and R. M. ChoateCite this: Macromolecules 1990, 23, 21, 4497–4507Publication Date…
A series of 66 terpolymers of dl-lactide, glycolide, and epsilon-caprolactone was synthesized for the purpose of identifying those materials which exhibited rapid degradation in vitro. Polymers having half-lives from a few weeks to several months were identified. The morphology of each material was characterized by di…