Materials Literature
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A study was undertaken to define better the concept of the statistical grain. A cube having edges of 52·1 mm was cut from a slowly cooled β-brass ingot which had equiaxed grains. The distributions of sizes and shapes of grain sections on the faces of the cube were determined. The grains were then separated in a soluti…
Abstract— The rate constant k 5 / > for physical quenching of singlet oxygen O 2 (δ 1 ;) by the sensitizer in dye‐sensitized photooxygenations is determined in the case of chlorophylls a and b (7.3 times 10 8 , 4.2 times 10 8 M ‐1 s ‐1 respectively), pheophytins a and b (7.4 times 10 7 , 3.0 times 10 7 M ‐1 s _1 re…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe preparation and structure of a dinuclear .eta.2-H2 complex (P-N)(.eta.2-H2)Ru(.mu.-Cl)2(.mu.-H)Ru(H)(PPh3)2, P-N = Fe[.eta.-C5H3(CHMeNMe2){P(iso-Pr)2}-1,2](.eta.-C5H5)Cashman. Hampton, William R. Cullen, Brian R. James, and Jean Pierre. CharlandCite this: J. Am. Chem. So…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUmuhengerin, a New Antimicrobially Active Flavonoid from Lantana trifoliaP. C. Rwangabo, M. Claeys, L. Pieters, J. Corthout, D. A. Vanden Berghe, and A. J. VlietinckCite this: J. Nat. Prod. 1988, 51, 5, 966–968Publication Date (Print):September 1, 1988Publication History Pub…
X-ray diffraction measurements have been made on the nematic phase of T15 (4-cyano-4′-n-pentyl-p-terphenyl), as well as on the nematic and smectic A phases of RNO2 [4′-nitrophenyl-4-(4′-n-hexyloxy-benzoyloxy)-cinnamate]. The x-ray equipment used allows comparably high resolution measurements of liquid crystals. The in…
Abstract We have reexamined the parallel Avrami model recently proposed by Velisaris and Seferis (1) to describe the non‐Isothermal crystallization of poly(etheretherketone), PEEK. We show that, based on considerations of morphology development, the crystallization process with the larger Avrami exponent has the highe…
Details are given of a new organic electro-optic crystal, 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole, having a reduced half-wave voltage of 370 V (approximately 8 times lower than lithium niobate). The molecular design, synthesis, and molecular characterization of this compound are outlined and a descript…
Analysis of the pH dependence of the kinetic parameters and competitive inhibitor Ki values for tryptophan indole-lyase suggests two enzymic groups must be unprotonated in order to facilitate binding and catalysis of tryptophan. The V/K for tryptophan and the pKi for oxindolyl-L-alanine, a putative transition state an…
Experiments were conducted on samples of depleted uranium and on intermetallic compounds of zirconium-cobalt and lanthanum-nickel-aluminide to evaluate the pyrophoricity of the activated materials and their hydrides and deuterides on exposure to air. None of the materials spontaneously ignited when exposed to room tem…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHeterogeneous acid-catalyzed amination of isobutene to tert-butylamineM. Deeba and M. E. FordCite this: J. Org. Chem. 1988, 53, 19, 4594–4596Publication Date (Print):September 1, 1988Publication History Published online1 May 2002Published inissue 1 September 1988https://pubs…
The mechanism controlling passivation of metal surface at tips of corrosion tunnels formed on aluminum by anodic etching in hot aqueous chloride solutions was studied. Theoretical considerations based on transport processes were used to rationalize SEM observations and potential measurements. In the mechanism proposed…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRigid-rod polymers with flexible side-chains. 6. Ordered phases from solid solutions of two-component blends as investigated by wide-angle x-ray scatteringR. Duran, M. Ballauff, M. Wenzel, and G. WegnerCite this: Macromolecules 1988, 21, 9, 2897–2899Publication Date (Print):…
Abstract Poly(hydroxamic acid) in gel or water soluble from was prepared from the reaction of poly(acrylamide) and hydroxylamine in basic aqueous solution (pH > 12) at room temperature. The polymers were composed of 70% hydroxamic acid groups, less than 5% carboxylic acid groups, and 25% unreacted amide groups. The…
Abstract The primary stages of the oxidation of NiCr23 and of NiCr21Fe12 and the final oxide layers were studied at room temperature and oxygen pressures between 10 −6 Pa and 10 −4 Pa using AES and XPS. The composition of the surface during oxygen exposure was monitored by continuous recording of the Auger transitions…
The behavior of metallic lithium electrodes with poly (ethylene oxide)‐based polymer electrolytes has been studied as a function of the nature and concentration of the salt, time, temperature, and current density. Impedance spectroscopy and galvanostatic polarization results are reported. Passivating film formation an…
Relationships among the apical pore field-bearing diatom genera Brebissonia, Cymbella, Gomphonema, Gomphoneis, Didymosphenia, Gomphocymbella, and Reimeria and their close ally Encyonema were evaluated using cladistics. These biraphid genera are a polythetic group defined by chloroplast number and type, mode of sexual…
The validity of the Hückel rule extends considerably further than hitherto assumed the limit is in no way already reached with the diatropic, aromatic [22]annulene. The deep-blue title compound was isolated as the octaethyl-N,N′,N″,N‴-tetramethyl dibromide. Its diamagnetic ring-current effect is unusually large; the s…
A computer simulation using discretized space and time is employed to examine the early stages of phase separation as described by the Cahn-Hilliard-Cook equation (CHCE). The relative simplicity of this simulation provides a direct test of various mathematical treatments of the nonlinear term in the CHCE. In particula…
Tubular blood-contacting polymeric materials were modified by plasma polymerization and evaluated in the baboon with respect to their capacity to induce both acute and chronic arterial thrombosis. Polymer surface composition was determined by electron spectroscopy for chemical analysis. Steady-state arterial thromboem…
A parallel detection system for electrons in the 10–800-kV energy range is described. The design is based on a 576×382 pixel charge-coupled device array operating at liquid-nitrogen temperature. This is coupled by fiber optics to a single-crystal YAG screen, which serves as the primary detection element. The performan…