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  • Digitale Medien  (4)
  • 1990-1994  (2)
  • 1975-1979  (2)
Materialart
  • Digitale Medien  (4)
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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 5388-5401 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The adsorption of hydrogen on a cobalt(101¯0) surface was investigated in ultrahigh vacuum (UHV) between 85 and 500 K using Video-LEED, temperature-programmed thermal desorption (TPD), work function (ΔΦ) measurements, and high-resolution electron energy loss spectroscopy (HREELS). Between 90 and 200 K, hydrogen adsorbs dissociatively with high sticking coefficient (s0≥0.8) via precursor kinetics and forms, with increasing exposure, a c(2×4), a p2mg (2×1) and a (1×2) LEED structure (hydrogen coverages aitch-thetaH=0.5, 1.0, and 1.5, respectively). While the first two structures represent true ordered hydrogen phases there is strong evidence that the (1×2) phase is reconstructed, likely in a paired-row configuration. The formation of the (1×2) phase is slightly thermally activated; its decomposition produces a sharp thermal desorption maximum (α state) appearing on the low-energy side of a β-TPD signal which reflects the hydrogen desorbing from the unreconstructed surface. The activation energies for desorption from the α and β states are 62 and 80 kJ/mol, respectively. Chemisorption in the β state [(2×1) phase up to aitch-thetaH=1.0] is associated with a ΔΦ of +207 meV, while the fully developed (1×2) reconstructed phase (α state) causes a ΔΦ of approximately −122 meV resulting in an overall work function change of +85 meV at saturation. From HREELS, we determine the H adsorption site in all superstructures to be threefold with a local CS symmetry. Our results are discussed and compared with previous findings for similar metal–hydrogen interaction systems.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    ISSN: 1365-2958
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Medizin
    Notizen: Mutants (glk) of Streptomyces coelicolor A3(2) that are resistant to the non-utilizable glucose analogue 2-deoxyglucose are deficient in glucose kinase activity, defective in glucose repression, and usually unable to utilize glucose. A 2.9 kb Bcll fragment, previously shown to restore a wild-type phenotype to a glk deletion mutant that lacks the entire segment, contains two complete open reading frames that would encode proteins of 20.1 kDa (ORF2) and 33.1 kDa (ORF3). ORF3 is transcribed from its own promoter, and also from a promoter that initiates transcription upstream of ORF2. A derivative of the temperate phage πC31 containing ORF3 alone restored a wild-type phenotype when used to lysogenize the deletion mutant. The product of ORF3 is homologous to members of a family of repressor proteins encoded by xylR In Bacillus subtilis and Lactobacilius pentosus, and by nagC in Escherichia coli. Although this might suggest that ORF3 encodes a positive activator for glucose kinase, rather than the enzyme itself, ORF3 restored the ability to metabolize glucose to an E. coli glk mutant, and activity gels of cell extracts of E. coli containing ORF3 cloned in the pT7-7 expression vector demonstrated that the ORF3 product has glucose kinase activity.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 272 (1978), S. 410-414 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] A nucleotide sequence comprising 960 base pairs of bacteriophage λDNA has been determined. The sequence includes the entire genes of the regulatory proteins cro and cII, and part of the O gene, together with control elements for their transcription and translation. The right-hand boundaries ...
    Materialart: Digitale Medien
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  • 4
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The high strength to weight ratio of glass reinforced plastics (FRF) combined with their fabrication flexibility has led to increasing use in new applications that no other materials could satisfy. FRF often replaces metals in traditional applications. Increasingly stringent flammability requirements have led to the use of alumina trihydrate filler, usually in combination with halogenated rosins. However, difficulties in compounding and fabrication often limit, the alumina trihydrate loading. This requires substantial increments of halogenated resin to meet specific flammability restrictions. In such composites, the price of the compound may be too high for a given application and one must often compromise substantially on both processing and physical property performance. Alumina trihydrate filled systems commonly suffer from poor glass fiber wet out and mold flow, with reduced strength and uniformity in fabricated parts. This paper describes how a unique silane pretreatment for alumina trihydrate permits bulk molding compound (BMC)/sheet molding compound (SMC) formulations to be developed with increased loadings of the filler, reduced filler wet out time, and improvements in glass dispersion, mold flow out, strength and uniformity of the composite. The paper also shows how the halogenated resin content of flame retarded systems may be minimized by the use of this silane treated alumina trihydrate.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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