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  • 1
    ISSN: 1572-879X
    Keywords: absolute surface intermediate concentration ; ethylene hydrogenation ; reaction intermediates in catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The first measurement of a turnover rate with respect to surface intermediate concentration in a high pressure heterogeneous catalytic reaction is reported. By using infrared-visible sum frequency generation to study the hydrogenation of ethylene on Pt(111), it was found that the surface concentration of π-bonded ethylene, the key reaction intermediate, represented approximately 4% of a monolayer. Thus the absolute turnover rate per surface adsorbed ethylene molecule is 25 times faster than the rate measured per platinum atom. To explain these results, we propose a model of weakly adsorbed ethylene intermediates reacting on atop sites.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 62 (1996), S. 263-268 
    ISSN: 1432-0630
    Keywords: PACS: 78.20. ; e; 41.20. ; q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  The PhotoAcoustic (PA) method has been used to study the optical resonance absorptions on corrugated surfaces. The resonance absorptions due to the excitations of surface plasmons and guide-waves of corrugated surfaces have been measured experimentally, and the effects of the groove depth and period of the corrugated surface on the absorption curve have been observed. Moreover, the differential method based on the rigorous use of electromagnetic theory is used to calculate the parameters of the grooves and the optical absorptivities of the samples. The theoretical results on the resonance absorption peaks are in good agreement with those of the PA experiments. Then, the parameters of the grooves can be estimated by the PA investigations.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 62 (1996), S. 263-268 
    ISSN: 1432-0630
    Keywords: 78.20. — e ; 41.20. — q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The PhotoAcoustic (PA) method has been used to study the optical resonance absorptions on corrugated surfaces. The resonance absorptions due to the excitations of surface plasmons and guide-waves of corrugated surfaces have been measured experimentally, and the effects of the groove depth and period of the corrugated surface on the absorption curve have been observed. Moreover, the differential method based on the rigorous use of electromagnetic theory is used to calculate the parameters of the grooves and the optical absorptivities of the samples. The theoretical results on the resonance absorption peaks are in good agreement with those of the PA experiments. Then, the parameters of the grooves can be estimated by the PA investigations.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1996), S. 279-282 
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A low-temperature plasma-enhanced chemical vapour deposition (PECVD) technique has been employed to produce ultrafine tin oxide powders. The structural features and phase transition of this material have been characterized using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction, infrared spectroscopy (IR) and transmission electron microscopy (TEM). The oxygen absorption behaviour and gassensing properties have been investigated by electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and electrical measurements. Thick film gas sensors made from such ultrafine SnO2 powders yield better sensitivities than those of normal undoped SnO2 gas sensors. A gas-sensing reaction mechanism is also proposed.
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  • 5
    ISSN: 1573-5060
    Keywords: Oryza sativa ; cytoplasmic male sterility (CMS) ; fertility-restoring reversion ; radiation mutation ; genetic analysis, rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A male fertile revertant was isolated from M1 of a cytoplasmic male sterile indica rice line II-32A, the dry seeds of which were treated with 60Co-γ rays at a dose of 290 Gy. The acquired revertant T24 was morphologically and agronomically similar to II-32B, the maintainer of II-32A. Testcrosses of the revertant with II-32A and Zhenshan 97A showed that the revertant was able to restore the fertility of CMS lines. Genetic analysis of the progenies between T24 and II-32A, Zhenshan 97A XieqingzaoA and DZhenshan 97A, which have different cytoplasms, showed that the fertility restoration of four CMS lines by T24 involved one nuclear gene, indicating that T24 was a result of the mutation of one nuclear gene. The mechanism of the restoration of CMS line by T24 was obviously different from other restorers such as Minghui 63 and 20964, which were shown to behave in two gene mode in fertility restoration. The discovery of the revertant T24 contributes to the understanding of CMS and fertility restoration of CMS in rice. The T24 and its parent II-32A may constitute a pair of near isogenic lines for the restoring gene, which should be valuable materials for molecular genetic analysis of CMS.
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  • 6
    ISSN: 1573-5060
    Keywords: Beta ; genetic resources ; RAPD ; annual beets ; molecular marker ; polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Annual beets in the genus Beta section Beta represent an important genetic resource. Representative accessions of annual beets from a beet germplasm collection were analysed using RAPD to assess the patterns of variation and relationships among them. Using arbitrary primers, markers showing variation across accessions were identified. A dendrogram of similarity was produced using these molecular markers. All the accessions analysed were classified into three major groups corresponding to species or subspecies macrocarpa, adanensis and maritima. Macrocarpa was shown to be the most divergent group in this section. Using RAPD molecular markers, it was possible to ascribe an accession to one of three taxonomic groups and overcome much of the confusion encountered when morphological traits are used for identification. The group of maritima was found to be more polymorphic than either the group of macrocarpa or adanensis at both accession and subspecies levels.
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  • 7
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A cosmid mapped to human Chromosome (Chr) 17q21, c140c10, was found to contain a CpG island. We completed the sequence analysis of c140c10 because of two considerations: the cosmid contained an STS from the 17-β-hydroxysteroid dehydrogenase gene (17-HSD), which was believed to be a neighbor of the breast cancer susceptibility gene, BRCA1; CpG islands are usually associated downstream and/or upstream of human genes. Computer-based exon trapping of the cosmid sequence revealed putative additional exons. With two of those exons used as a probe to screen human placental cDNA libraries, two cDNA isoforms for a novel gene, designated as ufHSD, were isolated. The amino acid sequence of the open reading frames of the cDNA showed no significant homology to any protein in the data base. However, it is possible that our cDNAs are from the gene for α-acetylglucosaminidase, which has recently been localized to the same region. Northern analyses show that the major isoform is expressed in all tissues tested, with the highest expression in blood leukocytes and lowest in brain. Finally, our study has shown that the 46.7-kb cosmid c140c10 encompasses loci for five genes and pseudo-genes: ΨPTP4A, ufHSD, 17-HSDI, 17-HSDII, and 22A1.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Packed capillary columns ; Liquid crystalline polysiloxane ; Polymer encapsulated particles ; Vitamins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid crystal polysiloxane stationary phases were prepared by coating two different polymers on deactivated porous silica particles (10 μm diameter, 80 Å pores). Deactivation of the silica particles before coating was necessary to prepare highly efficient and inert stationary phases for supercritical fluid chromatography (SFC). Fat-soluble vitamins E, A, K1, K2, D2, and D3 were separated on these columns using neat supercritical CO2 as mobile phase. The analyses were completed within 40 min at 70 °C. The results were compared to those obtained using a capillary column packed with less ordered liquid crystalm,m-cyanobiphenyl-substituted polysiloxane coated particles. Reduced shape selectivity was observed with this cyanobiphenyl phase. The response factors of vitamins A, E, K1, K2, D2, and D3 when using the flame ionization detector (FID) were determined to be very similar.
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  • 9
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Packed capillary columns ; Polyethylene oxide coated phases ; Polymer encapsulated particles ; Amines and acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polyethylene oxide (PEO)-based polymers with hydroxy, methoxy, and aminopropoxy terminal groups were coated on diol functionalized and hexamethyldisilazane end-capped silica particles. Proton-donor and proton-acceptor test solutes, including carboxylic acids, hydroxy-containing compounds, arylamines, and alkylamines were used to evaluate the chromatographic performances of these polymer coated particles under SFC conditions with neat CO2 as mobile phase. It was found that the particles coated with hydroxy-terminated PEO were suitable for the separation of proton-donor compounds such as hydroxy-containing compounds and carboxylic acids, and the particles coated with aminopropoxy-terminated PEO could be used for the separation of amines. That is, the proton-accepting stationary phase is suitable for the separation of proton accepting solutes, including strong basic alkylamines (pKb≈4), using neat CO2 as mobile phase, while the protondonating stationary phase is suitable for the separation of proton-donating compounds such as carboxylic acids (pKa≈4). Hydrogen bond basicity was found to be a critical factor for the chromatography of basic amines. Low volatility acidic and basic drugs were chromatographed using the new stationary phases. The stability of the PEO coated particles was determined by measuring the loss of organic carbon under SFC conditions. It was found that approximately 18 % of the coating (average molecular weight of 15,000) was washed out of the particles by supercritical CO2 after 7 h at 350 atm and 50°C
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 80 (1996), S. R61 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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