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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 250 (1996), S. 81-88 
    ISSN: 1617-4623
    Keywords: Key words glyA mutations ; Serine hydroxymethyltransferase ; Regulatory gene ; Regulatory mutations ; One-carbon metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We used an Escherichia coli strain blocked in serine biosynthesis and carrying a partial glyA deletion to isolate strains with altered regulation of the glyA gene. The glyA deletion results in 25% of the normal serine hydroxymethyltransferase activity. Three classes of mutants with increased glyA expression were isolated on glycine supplemented plates. One class of mutations increased glyA expression 10-fold by directly altering the −35 consensus sequence of the glyA promoter. The two other classes increased glyA expression about 2- and 6-fold, respectively. The latter two classes of mutations also affected regulation of the metE gene of the folate branch of the methionine pathway, but not metA in the nonfolate branch of the methionine pathway, or the gcv operon, encoding the glycine cleavage enzyme system. The mutations were mapped to about minute 85.5 on the E. coli chromosome.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 75 (1996), S. 169-183 
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract For a number of important questions in VHE/UHE cosmic ray physics wide angle air Cerenkov detectors offer superior performance compared to scintillator arrays or air Cerenkov telescopes. On hand of the HEGRA air Cerenkov detector AIROBICC the general principle and performance will be discussed. Ideas and prospects for a detector with an energy threshold around 1 to 3 TeV will be presented.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 47 (1996), S. 495-504 
    ISSN: 0947-5117
    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: Metal dusting von NickelbasislegierungenMetal dusting, der Zerfall metallischer Materialien in feinste metallische Partikel und Graphit, wurde für Nickel, Eisen-Nickel-Legierungen und kommerzielle Nickel-Basis-Legierungen in CO—H2—H2O-Gemischen bei Temperaturen zwischen 450-750°C untersucht. Bei Kohlenstoffaktivitäten ac 〉 1 können alle Metalle, in die Kohlenstoff gelöst eindringen kann, durch metal dusting zerstört werden, hoch nickelhaltige Legierungen direkt durch Graphitwachstum in das Material und in dem Material, Stähle über die Bildung eines instabilen Karbides M3C als Zwischenprodukt. Schutz ist möglich durch Verhinderung des Eindringens von Kohlenstoff. Die Bildung von Chromoxid ist die beste Möglichkeit des Schutzes, dieses wird begünstigt durch hohe Chromkonzentrationen in den Legierungen und durch Oberflächenbehandlungen, die schnelle Diffusionswege für die Anlieferung von Chrom an die Oberfläche erzeugen.Das metal dusting-Verhalten von Alloy 600 wird im Detail beschrieben. Weiterhin wurde durch Auslagerungen bei 650°C und 750°C für verschiedene kommerzielle Nickel-Basis-Legierungen eine Rangfolge bezüglich des Widerstands gegen metal dusting erhalten.
    Notes: Metal dusting, the disintegration of metallic materials into fine metal particles and graphite was studied on nickel, Fe—Ni alloys and commercial Ni-base alloys in CO—H2—H2O mixtures at temperatures between 450-750°C. At carbon activities ac 〉 1 all metals can be destroyed into which carbon ingress is possible, high nickel alloys directly by graphite growth into and in the material, steels via the intermediate formation of instable carbide M3C. Protection is possible only by preventing carbon ingress. Chromium oxide formation is the best way of protection which is favoured by a high chromium concentration of the alloy and by a surface treatment which generates fast diffusion paths for the supply of chromium to the surface.The metal dusting behaviour of Alloy 600 is described in detail. A ranking of the metal dusting resistance of different commercial nickel-base alloys was obtained by exposures at 650°C and 750°C.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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