Materials Literature
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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…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInduced chain rigidity, splay modulus and other properties of nematic polymer liquid crystalsGert Jan Vroege and Theo OdijkCite this: Macromolecules 1988, 21, 9, 2848–2858Publication Date (Print):September 1, 1988Publication History Published online1 May 2002Published inissu…
Diffusion coefficients D of 59Fe have been measured in single crystal α-Zr in the range 765-1193 K (in directions both parallel (D∥) and perpendicular (D⊥) to the c axis) and in a polycrystalline Zr–0•28 at.% Fe alloy, in the range 733–1070 K. The single-crystal results show that D∥/D⊥ has values between 2•2 and 5•9,…
Abstract Two major problems which exist in the use of illite crystallinity to define low‐grade metamorphic zones are the variety of values chosen for the zone boundaries and the persistent use of three different indices of crystallinity. Although measurement techniques, which cause much of the interlaboratory variatio…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReactions of unsaturated compounds with iodine and bromine on .gamma. aluminaRichard M. Pagni, George W. Kabalka, Richard Boothe, Kevan Gaetano, Lyman J. Stewart, Richard Conaway, Christopher Dial, Donna Gray, Steven Larson, and Teresa LuidhardtCite this: J. Org. Chem. 1988,…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe nature of the thermal transitions in poly(p-oxybenzoate)J. Economy, W. Volksen, C. Viney, R. Geiss, R. Siemens, and T. KarisCite this: Macromolecules 1988, 21, 9, 2777–2781Publication Date (Print):September 1, 1988Publication History Published online1 May 2002Published i…
The preparation, spectroscopic investigation, structure determination, conformational analysis, and modeling of the Dewar pyrimidinone photoproduct of thymidylyl-(3'----5')-thymidine, previously referred to as TpT3 [Johns, H. E., Pearson, M. L., LeBlanc, J. C., & Heilleiner, C. W. (1964) J. Mol. Biol. 9, 503-524], is…
A decagonal quasicrystal with a periodicity of 1·6 nm along the tenfold axis, similar to that in Al─Pd and Al─Co, has been found in a rapidly solidified Al6Ni alloy containing a few per cent of silicon. In addition, a new decagonal phase has been found in Al4Ni which has a periodicity of 0·4 nm along the tenfold axis.…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReductive chemistry of nickel hydroporphyrins. Evidence for a biologically significant difference between porphyrins, hydroporphyrins, and other tetrapyrrolesAlan M. Stolzenberg and Matthew T. StershicCite this: J. Am. Chem. Soc. 1988, 110, 19, 6391–6402Publication Date (Pri…
X-ray scattering and optical studies reveal two key features of Surface Stabilized Ferroelectric Liquid Crystal (SSFLC) cell structure: (1) The temperature dependence of the layer thickness is an important effect in determining both the layer and director-polarization structure; and (2) There exists in some SSFLC cell…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of thermal history on crystallization of poly(ether ether ketone) (PEEK)Youngchul Lee and Roger S. PorterCite this: Macromolecules 1988, 21, 9, 2770–2776Publication Date (Print):September 1, 1988Publication History Published online1 May 2002Published inissue 1 Septem…
The requirements for ferroelectric liquid crystals (FLC) for an application in fast-switching electro-optic devices are summarized. Typical molecular structures for FLC-mixtures are discussed. New non-chiral SmC-substances as well as some chiral dopants are shown. Important material parameters which are presented incl…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSurface and bulk phase separation in block copolymers and their blends. Polysulfone/polysiloxaneNiranjan M. Patel, David W. Dwight, James L. Hedrick, Dean C. Webster, and James E. McGrathCite this: Macromolecules 1988, 21, 9, 2689–2696Publication Date (Print):September 1, 19…
Chiral smectic C compounds having an ester group in the central core, an optically active tail group (alkoxy or alkoxycarbonyl), and an electronegative substituent (halogen or cyano) ortho to the chiral tail were synthesized. The effect of the ortho substitution on the characteristics, especially on spontaneous polari…