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  • Excitons and related phenomena (including electron-hole drops)  (1)
  • Foliar nitrogen  (1)
  • Genetic code  (1)
  • Springer  (3)
  • American Chemical Society
  • Cell Press
  • 1995-1999  (3)
  • 1970-1974
Collection
Publisher
  • Springer  (3)
  • American Chemical Society
  • Cell Press
Years
  • 1995-1999  (3)
  • 1970-1974
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 40 (1995), S. 545-550 
    ISSN: 1432-1432
    Keywords: Genetic code ; Aminoacyl-tRNA synthetases ; Ribozyme ; Protein design ; Leucine zippers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aminoacyl-tRNA synthetases exist as two enzyme families which were apparently generated by divergent evolution from two primordial synthetases. The two classes of enzymes exhibit intriguing familial relationships, in that they are distributed nonrandomly within the codon-amino acid matrix of the genetic code. For example, all XCX codons code for amino acids handled by class II synthetases, and all but one of the XUX codons code for amino acids handled by class I synthetases. One interpretation of these patterns is that the synthetases coevolved with the genetic code. The more likely explanation, however, is that the synthetases evolved in the context of an already-established genetic code—a code which developed earlier in an RNA world. The rules which governed the development of the genetic code, and led to certain patterns in the coding catalog between codons and amino acids, would also have governed the subsequent evolution of the synthetases in the context of a fixed code, leading to patterns in synthetase distribution such as those observed. These rules are (1) conservative evolution of amino acid and adapter binding sites and (2) minimization of the disruptive effects on protein structure caused by codon meaning changes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1447-1452 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Optical properties of thin films, surfaces, and layer structures (superlattices, heterojunctions, and multilayers) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We investigate the absorption spectrum and the distribution of radiative decay times for two-dimensional excitons in semiconductor quantum wells, as affected by an adiabatic white-noise random potential. Such a potential could result from atomic-scale fluctuations in the composition of an alloy semiconductor, or in quantum well thickness. We find in general that the shortest radiative decay time is directly proportional to the inhomogeneous width of the exciton line in absorption, itself proportional to the correlation parameter for the random potential.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5052
    Keywords: Biomass ; Foliar nitrogen ; Foliar phosphorus ; Interspecific competition ; Resource allocation ; Shoot: Root ratio ; Wetland plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the importance of nutrients, soil moisture, arbuscular mycorrhizal fungi (AMF), and interspecific competition levels on the biomass allocation patterns of three wetland perennial plant species, Carex stricta Lam., Phalaris arundinacea L., and Typha latifolia L. A factorial experiment was conducted with high-low nutrient levels, high-low soil moisture levels, and with and without AMF inoculation. Under the experimental conditions, plant inoculation by AMF was too low to create a treatment and the AMF treatment was dropped from the total analysis. P. arundinacea and T. latifolia biomass were 73% and 77% higher, respectively, in the high nutrient treatment compared to the low nutrient treatment. Biomass allocation between shoots and roots remained relatively constant between environmental treatments, although shoot:root ratios of P. arundinacea declined in the low nutrient treatment. For C. stricta, the high nutrient and soil moisture treatments resulted in an increase in biomass of 50% and 15%, respectively. Shoot:root ratios were nearly constant among all environmental conditions. Biomass of T. latifolia and C. stricta was greatly decreased when grown with P. arundinacea. The rapid, initial height growth of P. arundinacea produced a spreading, horizontal canopy that overshadowed the vertical leaves of T. latifolia and C. stricta throughout the study. This pattern was repeated in both high and low nutrient and soil moisture treatments. When grown with P. arundinacea, C. stricta and T. latifolia significantly increased their mean shoot height, regardless of the nutrient or soil moisture level. The results of this experiment suggest that C. stricta and T. latifolia were light limited when growing with P. arundinacea and that canopy architecture is more important for biomass allocation than the other environmental conditions tested. The results also suggest that Phalaris arundinacea is an inherently better competitor (sensu Grime 1979) than C. stricta or T. latifolia.
    Type of Medium: Electronic Resource
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