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81.
Summary A crystallite modulus of native cellulose along the chain axis has been calculated based on the X-ray analysed molecular conformation and the force constants used in the vibrational analysis. The calculated values are 172.9 GPa and 70.8 GPa for the cases with and without the intramolecular hydrogen bondings taken into account, respectively. The intramolecular hydrogen bondings have been found to play an important role on the determination of crystallite modulus and the chain deformation mechanism, based on the calculation of the strain energy distribution to the internal coordinates such as bond lengths, bond angles, and so on. 相似文献
82.
T. Negishi T. Ogura T. Masumoto T. Goto K. Fukuoka Y. Syono H. Ishii 《Journal of Materials Science》1985,20(2):399-406
Amorphous Ni75Si8B17 and Pd78Cu6Si16 alloy powders were dynamically compacted using a propellant gun. The degree of compaction increases with increase in the magnitude of shock pressure. The shock pressure giving the highest degree of compaction is lower in Pd78Cu6Si16 than in Ni75Si8B17. The progress of compaction-induced crystallization is faster in Pd78Cu6Si16 than in Ni75Si8B17, reflecting the difference in their exothermic characteristics during heating. Evidence was found for a melting and solidification mechanism of dynamic compaction of amorphous powders. 相似文献
83.
84.
Simulation of photoelectric conversion in the photosynthetic reaction centre by a monomolecular layer assembly was successfully attained by using a newly synthesized linear A-S-D triad as a charge separation unit and an antenna pigment for light harvesting. The synthetic amphiphilic triad molecule has three functional moieties within a molecule, i.e. a hydrophilic electron acceptor viologen (A), a hydrophobic sensitizer perylene (S) and a hydrophobic electron donor ferrocene (D) moiety. The amphiphilic antenna molecule has a light-harvesting pyrene (H) moiety in the middle of the alkyl chain of fatty acid. Because of overlap of the emission spectrum of the antenna pyrene and the absorption spectrum of the sensitizer perylene moiety of the triad, light energies harvested by the antenna molecules were efficiently transferred to the sensitizer moiety of the triad and finally converted to electrical energies via multistep electron transfer across the monolayer through the charge separation unit of the triad molecule in the highly oriented monolayer assembly. 相似文献
85.
Selective Cation Exchange in Substituted Tobermorites 总被引:1,自引:0,他引:1
Selective cation exchange in tobermorites with three levels of Al3+ and Na+ substitution for Si4+ has been investigated. The cation exchange selectivity for a tobermorite with 2 mol% Al3+ and 0 mol% Na+ substitution increased as follows: Mg2+ > Ba2+ > Sr2+ . Cation exchange in the above tobermorite is postulated to take place mainly from edge and planar surface sites and apparently from interlayer Ca2+ sites. Tobermorites with 10 and 15 mol% Al3+ (and Na+ ) substitution have additional Na+ exchange sites in the interlayers and show the following selectivity: Ba2+ > Sr2+ > Mg2+ . The cation exchange selectivity in the substituted tobermorites can be explained by the hydrated radii of cations and the steric limitations of the ion exchange cavity in tobermorite; the latter was determined by 27 Al and 29 Si magic angle spinning nuclear magnetic resonance spectroscopy. These basic selective cation exchange studies of substituted tobermorites are of relevance in nuclear waste treatment and disposal. 相似文献
86.
A. Trunschke H. -C. Böttcher A. Fukuoka M. Ichikawa H. Miessner 《Catalysis Letters》1991,8(2-4):221-228
Molybdenum promoted Rh/SiO2 catalysts have been prepared by using the heteronuclear cluster (C5H5)3RhMo2(CO)5 as well as metal salt precursors. The promoting effect of molybdenum has been studied for the hydroformylation of ethene and propene and the hydrogenation of acetaldehyde. It has been found that molybdenum, especially on the cluster-derived catalyst, increases both the hydrogenation and the hydroformylation rate of the olefins. No specific influence on the CO insertion reaction could be obtained. As an explanation, the promotion of the initial step to form intermediate surface alkyl groups has been proposed as the rate determining step for ethene hydroformylation. The promotion of the alcohol formation by bimetallic centers having Rh and Mo in close vicinity has been supported by the results of the hydrogenation of acetaldehyde. 相似文献
87.
88.
Paresh L. Dhepe Masataka Ohashi Shinji Inagaki Masaru Ichikawa Atsushi Fukuoka 《Catalysis Letters》2005,102(3-4):163-169
Mesoporous silicas are modified with sulfonic acid groups either by one-pot or by grafting method. In the hydrolysis of sucrose and starch, the sulfonated mesoporous silicas work as water-tolerant recyclable solid acid catalysts, showing higher conversion and turnover frequency than conventional Amberlyst-15, Nafion-silica and HZSM-5 catalysts. 相似文献
89.
T Ohmachi R Fukuoka Y Kimura Y Asada HL Ennis 《Canadian Metallurgical Quarterly》1998,62(10):2008-2015
Two Dictyostelium discoideum ribosomal protein genes, denoted DdL27a and DdL37a, were isolated and sequenced. The DdL27a gene contained an open reading frame of 148 amino acids coding for a putative 16,407 Da protein, which was similar to rat L27a (82.6% similarity) and to ribosomal proteins from other species. The gene contained a 311-bp intron downstream from the ATG initiation codon with an A+T content of 75%. The DdL37a gene encoded a 9,999 Da protein consisting of 91 amino acids, which had high sequence similarity to rat, human, and chicken ribosomal protein L37a, and was interrupted by two introns of 254 bp and 75 bp in length. The DdL37a protein contained a typical zinc finger motif (Cys-X2-Cys-X14-Cys-X2-Cys), which may be involved in the interaction of proteins with nucleic acids. Genomic DNA blot analysis indicated that the DdL27a and DdL37a genes are present in single copies in the Dictyostelium haploid genome. The DdL27a and DdL37a mRNA were expressed maximally in growing amoebae, and their levels decreased during multicellular development, coordinately with the observed decrease in ribosome accumulation during later development. 相似文献
90.
Kazuhiko Kandori Masamichi Fukuoka Tatsuo Ishikawa 《Journal of Materials Science》1991,26(12):3313-3319
The effects of citrate ions on the formation of - and -FeOOH particles were investigated using various techniques. The formation and crystallization of both particles were inhibited by citrate ions, and their particle sizes decreased with increase in the concentration of these ions. Finally, aggregated amorphous particles were formed. The effects of citrate ions appeared to be more significant for -FeOOH than for -FeOOH. This difference could be explained by the pH dependence of the affinity of citrate ions to Fe3+ ions. The amorphous -FeOOH particles prepared in the presence of > 10 mol% citrate ions selectively adsorbed water molecules. 相似文献