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  • Chemistry  (2)
  • Key wordsNeisseria meningitidis  (2)
  • 74.25.Bt  (1)
  • 1
    ISSN: 1573-7357
    Keywords: 74.25.Bt ; 74.25.Fy ; 74.62.Dk ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the anisotropic electrical resistivity, the Hall Effect, and the specific heat anomaly at Tc of Ca-doped YBa2Cu3Ox single crystals of various Ca and O contents are presented. The transport properties are discussed in terms of charge and spin separated quasiparticles and confirm that by doping Ca onto Y sites the hole concentration, nh, can be extended beyond the value achieved with O-doping alone at x=7.0. The jump in the specific heat at Tc which increases monotonously with x up to x=7.0 in Ca-free crystals displays a maximum in highly oxygenated Ca-doped crystals. This maximum, however, is displaced from the Tc(nh) maximum to higher values of nh, consistent with the model of induced superconductivity in the CuO chains.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 259 (1998), S. 363-371 
    ISSN: 1617-4623
    Keywords: Key wordsNeisseria meningitidis ; Shuttle mutagenesis ; Signature-tagged mutagenesis ; Transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Shuttle mutagenesis using signature-tagged transposons was employed to generate a library of individually tagged mutants of the Neisseria meningitidis strain B1940, which belongs to serogroup B. The use of tagged transposons allowed us to monitor for enrichment for single mutants during the process of shuttle mutagenesis, by amplification of the tags and subsequent sequence determination. Enrichment of a single clone occurred during the transformation of the meningococci with transposon-containing plasmid DNA. Sequence determination around the site of transposon insertion revealed that the transposon had mutagenized a previously unknown locus, which was designated hrtA (high rate of transformation). hrtA-mediated transformation was independent of TnMax5 and tag sequences, and it most probably involved recombination events. The hrtA locus is restricted to meningococci and gonococci and is present in few apathogenic neisserial species. Chromosomal mapping of hrtA and six further hrt sites revealed a random distribution of highly transforming DNA fragments on the meningococcal chromosome. In conclusion, our data demonstrate that shuttle mutagenesis of naturally competent bacteria using signature-tagged transposons allows the isolation of chromosomal DNA fragments, which exhibit a high transformation efficiency, and which, therefore, are likely to be involved in horizontal gene transfer.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1617-4623
    Keywords: Key wordsNeisseria meningitidis ; Capsule synthesis ; Polysialyltransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The serogroups B, C, W135 and Y of Neisseria meningitidis express chemically and immunologically distinct capsular polysaccharides containing sialic acid. In the case of serogroup B meningococci sialic acid is synthesized by the gene products of a locus termed sia and forms the homopolymers of the capsule. The organization of the genes required for sialic acid synthesis in serogroups B, C, W135 and Y was elucidated by PCR technology. Cloning, sequencing and the functional expression of the polysialyltransferase (PST) genes of serogroups B and C demonstrated that the difference in capsule composition derives from the presence of related, but distinct siaD genes coding for PSTs. Analysis of meningococci of serogroups W135 and Y expressing sialic acid heteropolymers revealed that the DNA sequences of the corresponding genetic loci in these serogroups were highly homologous, but differed completely from the siaD genes of serogroups B and C. This finding suggests that enzymes unrelated to those of serogroups B and C are required for the formation of sialic acid heteropolymers characteristic of the capsules of serogroups W135 and Y.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 934-943 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Extractives from Cneoraceae, II. Studies on the Hydrogenation, Alkali Degradation, and Synthesis of ChromonesChromon-A (1) is hydrogenated to give mainly a tetrahydro-derivative and, in addition, the hexahydro-derivatives 3and 5. Its alkaline degradation yields 8and 9. The naturally occuring chromones 1, 12, and 13are synthesized. Structure 15is confirmed for chromone-B by catalytic hydrogenation.
    Notes: Die aus Chromon-A (1) erhaltenen Hexahydroderivate haben die Strukturen 3und 5, die mit Alkali erhaltenen Abbauketone die Strukturen 8und 9. Durch Synthese werden die natürlichen Chromone 1, 12und 13dargestellt. Für Chromon-B wird die Struktur 15durch katalytische Hydrierung bewiesen.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 10 (1979), S. 191-200 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Explosive Welding as a Technique for Cladding of Precious MetalsThe method of explosive welding and the importance of the cladding parameters are described. The “Explosive Weldability Window” is experimentally determined for the material combination AgCu 10/Fe. The behaviour of explosive claddings produced under different conditions during rolling is investigated.Best results are obtained with samples with a wavy interphase, produced under the following cladding parameters: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {10^ \circ \le \beta \le 18^ \circ} \\ {1400 \le {\rm v}_{\rm K} \le 2600{{\rm m} \mathord{\left/ {\vphantom {{\rm m} {\rm s}}} \right. \kern-\nulldelimiterspace} {\rm s}}} \\ \end{array} $$\end{document}It is shown, that in comparison with conventional methods explosive cladding has advantages both in processing and quality.
    Notes: Die Grundlagen des Explosivschweißens werden geschildert und die Bedeutung der Plattierparameter aufgezeigt. Das „Explosive Weldability Window“ wird für die Werkstoffpaarung AgCu 10/Fe experimentell entwickelt.Das Verhalten der bei unterschiedlichen Bedingungen hergestellten Explosivplattierungen beim Auswalzen wird untersucht. Die besten Ergebnisse werden für Verbindungen mit welliger Verbindungsfläche erzielt, die mit den Plattierparametern \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {10^ \circ \le \beta \le 18^ \circ} \\ {1400 \le {\rm v}_{\rm K} \le 2600{{\rm m} \mathord{\left/ {\vphantom {{\rm m} {\rm s}}} \right. \kern-\nulldelimiterspace} {\rm s}}} \\ \end{array} $$\end{document} hergestellt werden.Es wird gezeigt, daß gegenüber konventionellen Verfahren das explosive Plattieren verfahrenstechnische und qualitative Vorteile hat.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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