Materials Literature
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Taraxerol, careaborin (taraxeryl trans-p-hydroxycinnamate), and the novel triterpenoid taraxeryl cis-p-hydroxycinnamate were isolated from the leaves of Rhizophora apiculata. © 1990, American Chemical Society. All rights reserved.
We consider two simplified models of the formation of patterns emerging from the growth and coalescence of water droplets on a substrate (breath figures). The study is restricted here to the case of a one-dimensional substrate. In the first model we assume a monodisperse distribution of droplet sizes. In the second mo…
Dense, polycrystalline AlN samples of grain size between 1.8 and 19 μm were fabricated by hot‐pressing. Bar‐shaped samples were subjected to creep in four‐point bending under static loads in nitrogen atmosphere. The outer fiber stress was varied between 20 and 140 MPa and the temperature between 1650 and 1940 K. Stead…
Abstract Wegen der Sprödigkeit Keramischer Bauteile kommt deren oberflächennahen Werkstoffzuständen für das Festigkeitsverhalten eine besondere Bedeutung zu Neben der Oberflächentopographie und den vorliegenden Gefügezuständen sind dabei insbesondere die auftretenden Eigenpannungen wichtig Für die Analyse oberflächenn…
In fatigue both monotonic and cyclic plastic zones are formed ahead of the crack tip, inside which the strain history can be studied on the basis of stable hysteresis loops and structure anticipated in the crack-tip process zone and in the area of the maximum tensile stress (MTS) ahead of the crack tip. With these mat…
A test methodology that uses thermal resistance-time curves deter mined on thin shces of the foam and the scaling technique to relate aging time to the specimen thickness, was applied to evaluate long-term thermal performance of six polyurethane foams manufactured with the same polymer but different blowing agents. Th…
Abstract A set of Ni/SiO 2 catalysts with metal loadings between 1 and 8% by weight has been prepared by several methods. Metal dispersions have been determined by H 2 chemisorption and x‐ray line broadening analysis, giving metal particle sizes from ∼30 to 250 Å. XPS analysis of the samples has been recorded after re…
The Eu3+ and Y3+ complexes of 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N, N' - diacetic acid (K22DA), 1,7-diaza-4,10,13-trioxacyclopentadecane-N, N' - diacetic acid (K21DA), and the open-chain analogue ethylene glycol bis (ß-aminoethyl ether) - N,-N,N',N'-tetraacetic acid (EGTA) have been characterized in solution…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and characterization of new polymers exhibiting large optical nonlinearities. I. Ladder polymers from 3,6-disubstituted 2,5-dichloroquinone and tetraaminobenzeneLuping Yu and Larry R. DaltonCite this: Macromolecules 1990, 23, 14, 3439–3444Publication Date (Print):J…
Abstract Examination of clothing in forensic science cases often involves forming an opinion as to the age and cause of any damage present. This study, involving a range of possible weapons, clothing types, and types of damage, showed that it is possible to distinguish a cut from a tear and a slash from a stab. The ef…
Abstract Auger electron spectroscopy (AES), x‐ray photoelectron spectroscopy (XPS) and factor analysis of the MVV Auger spectra and the Cr 2p XPS spectra were applied to study quantitatively the initial stages of the oxidation of polycrystalline chromium. Application of factor analysis allows the identification of up…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA 1:1 complex of silver with a cofacial stilbene: [(Z)-2,2,5,5-tetramethyl-3,4-diphenylhex-3-ene]silver(I) triflateJames E. Gano, Girija Subramaniam, and Ronald BirnbaumCite this: J. Org. Chem. 1990, 55, 15, 4760–4763Publication Date (Print):July 1, 1990Publication History P…
An approach was developed to determine triplet quantum yields, ΦT, which overcomes most of the difficulties usually encountered in flash photolysis studies of triplet states. The combined application of near-IR emission and optoacoustics yields ΦT values which are independent of the absorption properties of the triple…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNew aspects of chiral heteroorganocuprates and an x-ray crystal structure with unprecedented magnesium-sulfur bondsD. Martin Knotter, Wilberth J. J. Smeets, Anthony L. Spek, and Gerard Van KotenCite this: J. Am. Chem. Soc. 1990, 112, 15, 5895–5896Publication Date (Print):Jul…
Abstract The acidic Cs salt of 12-tungstophosphoric acid (Cs/polyanion = 2.5) was much more active for liquid phase decomposition of cyclohexyl acetate than Nafion, HY-zeolite, H-ZSM-5, Al3+-exchanged montmorillonite, and SO42−/ZrO2.
A novel method of crystal growth which utilizes an axial submerged heater is proposed and numerically simulated. Single crystals should be grown by directional solidification in vertical bottom seeded crucibles. Submerged in the melt, the heater supplies the heat axially downward, enclosing and stratifying a small act…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and high temperature chemistry of methylsilsesquioxane polymers produced by titanium-catalyzed redistribution of methylhydridooligo- and -polysiloxanesRichard M. Laine, Jeffrey A. Rahn, Kay A. Youngdahl, Florence Babonneau, Martin L. Hoppe, Zhi Fan Zhang, and John…
The lumazine synthase-riboflavin synthase complex (heavy riboflavin synthase) of Bacillus subtilis consists of an icosahedral capsid of 60 beta-subunits containing a core of three alpha-subunits. The enzyme has been purified from the derepressed mutant H 94 of B. subtilis by a novel efficient procedure using column ch…
Backscattered electron (BSE) imaging is being developed into an accurate and useful technique for determining changes in bone morphology, histometry, and mineral content. BSE is currently used as a tool for quantifying the response of mineralized tissue to biomaterials. This paper briefly discusses the physics of BSE…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPentaammineruthenium(III) phenylcyanamide complexes: crystal structure determination and the dependence of b1*.rarw. b1 LMCT oscillator strength on the nature of the phenylcyanamide ligandRobert J. Crutchley, Kierstan McCaw, Florence L. Lee, and Eric J. GabeCite this: Inorg.…