Materials Literature
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Some polymer radicals have been proposed as potential organic magnetic materials. In order to determine where to place the doublet or triplet centers on the side chains of a conjugated polymer chain, we have studied model dimers, i.e., isomeric bis(nitrenophenyl)acetylenes and diacetylenes. They were generated by phot…
Since polyimides were invented more than 30 years ago, several books dealing with the subject have been published [33, 34, 40u, 48b, 55, 64]. While some of these books [33–35] have very thorough and systematic coverage of the chemistry and general physical, mechanical, and electrical properties of polyimides, most of…
For light propagation in stratified media the normal component of the Poynting vector is defined as an indefinite scalar product. The vanishing of this scalar product for two waves is regarded as proof of their mutual orthogonality. Orthogonality in this sense is an inherent property of optical eigenmodes with differe…
We have established a simple icosahedral to face-centred icosahedral ordering transformation in Al–Mn quasicrystals. This result strongly supports the view that the recently discovered face-centred icosahedral quasicrystal in ternary Al–Cu–Fe and related alloys represents a long-range superstructure of simple icosahed…
Ce modele considere la fissuration comme un processus de Markov vectorise 2D. Deux lois de propagation des fissures de fatigue sont utilisees pour l'analyse, et une methode des integrales finies modifiee est proposee pour determiner les parametres du modele stochastique. Ce modele utilise les donnees de Virkler. Excel…
The annealing effect on the lattice distortion of porous silicon (PS) layers have been studied mainly by X-ray multiple-crystal diffractometry and infrared spectroscopy. The lattice spacing of PS layers changed with increasing annealing temperature and finally became smaller than that of the unanodized Si substrate ab…
The RHEED specular beam profiles produced by GaAs vicinal surfaces are examined and correlated with the surface topography. It is found that the shape of split peaks produced with the incident beam normal to step edges is a measure of surface orientation over lengths on the order of terrace widths, but is not sensitiv…
A dense (97% of theoretical density) Si 3 N 4 —SiC composite containing 10 wt%β‐SiC was prepared by introducing a SiC phase by the pyrolysis of a polymeric SiC precursor. The composite material was produced by mixing an alkyl/aryl‐substituted polysilane with Si 3 N 4 powder and, by subsequently forming green compacts,…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of optically active polyacetylene containing an asymmetric silicon by using organotransition-metal complexes as catalystsBen Zhong Tang and Norio KoteraCite this: Macromolecules 1989, 22, 11, 4388–4390Publication Date (Print):November 1, 1989Publication History Pub…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectronic properties of polypyrrole/n-Si heterojunctions and polypyrrole/metal contactsAkira Watanabe, Syuuji Murakami, Kunio Mori, and Yasube KashiwabaCite this: Macromolecules 1989, 22, 11, 4231–4235Publication Date (Print):November 1, 1989Publication History Published on…
The decoupling of short-range valence-bond states into topologically distinct sectors is discussed. On a square-lattice strip with odd width, this decoupling implies that short-range resonating-valence-bond (RVB) states are doubly degenerate. This result is precisely equivalent to the Lieb-Schultz-Mattis (LSM) theorem…
Abstract The pure γ‐form of isotactic poly(propylene) can be obtained by melt‐crystallization starting from a fraction of a random ethylene‐propene copolymer (ethylene content 4 wt.‐%) soluble in p ‐xylene at 28°C. Some structural models previously reported are tested by comparing calculated wide‐angle X‐ray diffracti…
Large thermally induced changes in the end-interface reflectance and transmittance of silica fibers coated with vanadium dioxide films have been observed.
We report the DNA sequence and in vivo transcription start of pdxB, which encodes a protein required for de novo biosynthesis of pyridoxine (vitamin B6). The DNA sequence confirms results from previous minicell experiments showing that pdxB encodes a 41-kilodalton polypeptide. RNase T2 mapping of in vivo transcripts a…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectrochemical, theoretical, and ESR characterizations of porphycenes. The .pi. anion radical of nickel(II) porphyceneM. W. Renner, A. Forman, W. Wu, C. K. Chang, and J. FajerCite this: J. Am. Chem. Soc. 1989, 111, 23, 8618–8621Publication Date (Print):November 1, 1989Publi…
Using nuclear extracts from Bombyx mori middle silk glands (MSG) where the sericin-1 (Ser-1) mRNA is produced specifically, we have studied the in vitro transcription of the Ser-1 gene. To determine the sites required for the promoter function of the Ser-1 gene and characterize the factors binding to these sites, the…
Humic substances, the dark-colored, natural organic polyelectrolytes that are found in practically all soils, sediments, and natural water, strongly interact with both inorganic and organic pollutants. Inorganic cationic species generally undergo complexation reactions with humic substances. The binding of cations, su…
Since its development in the early 1970s, synchrotron‐based X ray absorption spectroscopy (XAS) has proven to be a versatile structural probe for studying the local environments of cations in a variety of earth materials ranging from crystalline solids, silicate glasses, and high‐temperature silicate melts to aqueous…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics and mechanisms of the thermal dehydration of dilithium sulfate monohydrateNobuyoshi Koga and Haruhiko TanakaCite this: J. Phys. Chem. 1989, 93, 23, 7793–7798Publication Date (Print):November 1, 1989Publication History Published online1 May 2002Published inissue 1 No…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe first structural characterization of a nickel(I) macrocyclic system: structure of nickel(I) diphenyldi-p-toyl-21-thiaporphyrinLechoslaw Latos-Grazynski, Marilyn M. Olmstead, and Alan L. BalchCite this: Inorg. Chem. 1989, 28, 22, 4065–4066Publication Date (Print):November…