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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 49 (1997), S. 261-266 
    ISSN: 1573-0867
    Keywords: 13C abundance ; 13C discrimination ; soil organic carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Application of the carbon-13 (13C) tracer technique to soil organic carbon emission is relatively new to many researchers and only a few results have been reported to date. This mini-review paper cites some well-documented research in organic carbon pool studies using the 13C tracer technique. The 13C abundance in soil usually remains at a stable level under a set of natural conditions. Variations in 13C reflect different sources and types of organic components from natural environments. An important feature of 13C discrimination in the soil C pool has permitted researchers to assess the dynamic nature of the pool. This discrimination may reflect a selective preference at early stage of residue decomposition by soil microbes. Crop rotation and residue input to humic substances can change the 13C abundance, which is a possible way to estimate soil C emission. However, the dynamic relationship between 13C abundance in the soil C pool and C emission is still in an early stage of development. Restrictions due to requirement of long-term experiments and duration of vegetation changes may affect its wide-spread adoptions in C emission studies.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 95 (1994), S. 245-250 
    ISSN: 1573-7357
    Keywords: 74.72.−h ; 74.72.Bk ; 74.25.Jb ; 79.60.-i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic structures of Y Ba2Cu3Ox and YBa2Cu4O8 were studied by angleresolved photoemission with an energy resolution of better than 10 meV. A detailed study in the 1st and 2nd Brillouin zone of untwinned single crystals shows the presence of “extended” saddle point singularities in the band structure in the vicinity of the Fermi energy, which give rise to van Hove singularities in the density of states. The binding energy of the singularity depends on the doping. We show that this extended saddle point singularity leads to a density of states which diverges as ε−1/2, which in turn can lead to very high transition temperatures even in a BCS scheme with weak coupling.
    Type of Medium: Electronic Resource
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