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  • 1990-1994  (3)
  • microbial respiration  (2)
  • 71.55.Ht  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Charge compensation and the luminescence of Cr3+ in KMgF3 (1994)
    Springer
    Applied physics 59 (1994), S. 365-372 
    Details
    ISSN: 1432-0630
    Keywords: 71.70.Ch ; 71.55.Ht
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Studies of the photoluminescence spectra of Cr3+ ions in KMgF3 crystals co-doped with Cr3+ and Ni2+ ions are reported. Several crystal field sites are identified by the different R-line spectra due to the 2 E→4 A 2 transition and broadband luminescences associated with the 4 T 2→4 A 2 transitions. Cr3+ ions substituting without local charge compensation on the octahedral Mg2+ site give rise to a low temperature R line in photoluminescence at λ=702.3 nm with a radiative decaytime of 3 ms at T=14 K. At T=300 K this isotropic centre gives rise to an unpolarized broadband 4 T 2→4 A 2 emission, which results from the thermal occupancy of an excited 4 T 2 state just above the 2 E level which, at lower temperature, gives rise to emission in the R-line. Other crystal field sites are due to some Cr3+ ions having Mg2+ or K+ vacancies in nearest-neighbour positions, these vacancies being required to maintain charge neutrality in doped fluoride perovskites. The Cr3+−K+ vacancy complex results in the centre having trigonal symmetry, and low temperature, photoluminescence via R 1 and R 2 lines at 716.8 nm and 716.0 nm, respectively. Finally, Cr3+ ions having a nearest neighbour Mg2+ vacancy have tetragonal symmetry, experiencing weak crystal fields. In consequence, the 4 T 2 level lies below 2 E and the photoluminescence spectrum at low temperature takes the form of a polarized broad 4 T 2→4 A 2 band with peak at 760 nm and radiative decaytime of 54 μs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331713
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Soil phosphorus fractions, aluminum, and water retention as affected by microbial activity in an Ultisol (1990)
    Springer
    Plant and soil 122 (1990), S. 125-136 
    Details
    ISSN: 1573-5036
    Keywords: aluminum ; microbial respiration ; phosphorus fractions ; soil moisture ; soil organic matter ; soil phosphorus ; soil respiration ; soil structure ; ultisol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Increased organic matter input into weathered and infertile soils through agricultural techniques such as minimum tillage or agroforestry can improve P availability to crops. Organic matter is an energy source for microbes, and their activity may be responsible in part for increased levels of labile P. The objective of the work reported here was to examine, in a highly weathered Ultisol, the influence of microbial activity in mobilizing P, maintaining it in a plant-available state, and preventing its fixation, and the effect of N and biocides on these processes. Exchangeable aluminum and soil moisture were also determined, since they interact with microbes and soil P. Results showed that increased microbial activity reduced sorption of dissolved and organic P by soil, maintained inorganic P in soluble and labile pools, increased microbial P, decreased mineral P, increased exchangeable Al, and increased water retention. Additions of N and biocides had variable effects, probably due to complex interactions between N, degrading biocides, and microbial populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02444112
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Soil phosphorus fractions, aluminum, and water retention as affected by microbial activity in an Ultisol (1990)
    Springer
    Plant and soil 121 (1990), S. 125-136 
    Details
    ISSN: 1573-5036
    Keywords: aluminum ; microbial respiration ; phosphorus fractions ; soil moisture ; soil organic matter ; soil phosphorus ; soil respiration ; soil structure ; ultisol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Increased organic matter input into weathered and infertile soils through agricultural techniques such as minimum tillage or agroforestry can improve P availability to crops. Organic matter is an energy source for microbes, and their activity may be responsible in part for increased levels of labile P. The objective of the work reported here was to examine, in a highly weathered Ultisol, the influence of microbial activity in mobilizing P, maintaining it in a plant-available state, and preventing its fixation, and the effect of N and biocides on these processes. Exchangeable aluminum and soil moisture were also determined, since they interact with microbes and soil P. Results showed that increased microbial activity reduced sorption of dissolved and organic P by soil, maintained inorganic P in soluble and labile pools, increased microbial P, decreased mineral P, increased exchangeable Al, and increased water retention. Additions of N and biocides had variable effects, probably due to complex interactions between N, degrading biocides, and microbial populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00013105
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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