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  • Articles: DFG German National Licenses  (3)
  • 2005-2009
  • 1995-1999  (3)
  • 1945-1949
  • Alkaloids  (1)
  • Caribbean  (1)
  • Commercial steel  (1)
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  • Articles: DFG German National Licenses  (3)
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  • 1
    ISSN: 1433-075X
    Keywords: Key words Surface transformation ; Commercial steel ; Multiple pulsed laser radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  A key innovation in materials processing of pre-formed metal parts is reported herein. The ”QQC Process” involves the judicious selection of exposure parameters to three pulsed lasers (excimer, Nd-YAG and CO2) simultaneously for treatment of the work piece. Pre-formed commercial steel parts are hardened and/or toughened, and/or clad with TiC improving performance by at least one order of magnitude. Two examples are detailed: a punch for aluminum can production and a fuel injector nozzle. In the latter case it has been shown that some tens of microns of the metal are transformed to a noncrystalline phase, in the middle of the workpiece.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-1561
    Keywords: Alkaloids ; mass spectrometry ; infrared spectroscopy ; amphibians ; ants ; decahydroquinolines ; quinolizidines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Three alkaloids—two minor decahydroquinolines (DHQs) and a major quinolizidine—were detected in an extract of a Brazilian myrmicine ant (Solenopsis (Diplorhoptrum) sp. picea group). One DHQ (3) was identical to a known frog-skin alkaloid, cis-195A (cis-5-methyl-2-propyldecahydroquinoline), while the second DHQ, an isomer of 3, designated 195J, was assigned a tentative cis-2-methyl-5-propyldecahydroquinoline structure (2) based on mass and infrared spectra. The third alkaloid proved identical to the frog-skin alkaloid 195C, for which a structure had not been previously proposed. Mass and infrared spectral analysis, including chemical ionization tandem mass spectrometry, indicated a 4-methyl-6-propylquinolizidine structure (1) for 195C. The four possible diastereomers were synthesized and the (6Z,10E)-4-methyl-6-propylquinolizidine diastereomer (1b) was identical to the natural alkaloid. Skin extracts of a population of a Madagascan mantelline frog contained, among other alkaloids, minor amounts of the same alkaloid triad 1–3 with 1 again predominating. The common occurrence of alkaloids 1–3 in both ant and frog supports the hypothesis that ants are a likely dietary source for sequestered frog-skin alkaloids and brings to six, the alkaloid classes common to ant and frog.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biodiversity and conservation 6 (1997), S. 1103-1121 
    ISSN: 1572-9710
    Keywords: Caribbean ; insects ; island ; equilibrium ; extinction ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ants were studied on Puerto Rico and 44 islands surrounding Puerto Rico. Habitat diversity was the best predictor of the number of species per island and the distributions of species followed a nested subset pattern. The number of extinctions per island was low, approximately 1–2 extinctions per island in a period of 18 years, and the rates of colonization seem to be greater than the extinction rates. Ant dynamics on these islands do not seem to support the basic MacArthur and Wilson model of island biogeography. The MacArthur and Wilson equilibrium is based on the notion that species are interchangeable, but some extinctions and colonizations can change the composition and number of species drastically.
    Type of Medium: Electronic Resource
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