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  • disorder  (2)
  • Crassulacean acid metabolism (CAM)  (1)
  • Electron transport rate through photosystem II  (1)
  • Flooded tropical savannas  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Conductance distributions in random resistor networks. Self-averaging and disorder lengths (1994)
    Springer
    Journal of statistical physics 75 (1994), S. 135-151 
    Details
    ISSN: 1572-9613
    Keywords: Resistor networks ; hierarchical lattices ; disorder ; probability distributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The self-averaging properties of the conductanceg are explored in random resistor networks (RRN) with a broad distribution of bond strengthsP(g)∼g μ−1. The RRN problem is cast in terms of simple combinations of random variables on hierarchical lattices. Distributions of equivalent conductances are estimated numerically on hierarchical lattices as a function of sizeL and the distribution tail strength parameter μ. For networks above the percolation threshold, convergence to a Gaussian basin is always the case, except in the limit μ→0. Adisorder length ξD is identified, beyond which the system is effectively homogeneous. This length scale diverges as ξD∼∣µ∣−v (ν is the regular percolation correlation length exponent) when the microscopic distribution of conductors is exponentially wide (μ→0). This implies that exactly the same critical behavior can be induced by geometrical disorder and by strong bond disorder with the bond occupation probabilityp↔μ. We find that only lattices at the percolation threshold have renormalized probability distributions in aLevy-like basin. At the percolation threshold the disorder length diverges at a critical tail strength µc as ∣µ−∣−z withz∼3.2±0.1, a new exponent.Critical path analysis is used in a generalized form to give the macroscopic conductance in the case of lattices abovep c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02186283
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative measurements of chlorophyll a fluorescence, acid accumulation and gas exchange in exposed and shaded plants of Clusia minor L. and Clusia multiflora H. B. K. in the field (1997)
    Springer
    Trees 11 (1997), S. 240-247 
    Details
    ISSN: 0931-1890
    Keywords: Key words Chlorophyll a fluorescence ; Clusia ; Crassulacean acid metabolism (CAM) ; Electron transport rate through photosystem II ; Malate decarboxylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Changes in chlorophyll a fluorescence during the day and diurnal-changes of net CO2-exchange and organic acid contents were determined in two species of the genus Clusia during the dry season in Venezuela. The investigations included plants of the C3/CAM intermediate species Clusia minor and the C3 species C. multiflora growing at exposed and shaded sites. Both species showed a C3 pattern of net CO2-exchange at the exposed site. In the shade under extreme drought stress C. minor showed a weak expression of CAM without CO2-uptake during the afternoon (phase IV of CAM). C. multiflora growing in the shade exhibited a C3-pattern of net CO2-exchange and a small but significant nocturnal accumulation of citrate. Shaded plants of C. minor were able to double their light utilisation for electron transport and to reduce non-photochemical quenching during phase III compared to phase II of CAM. Furthermore, increase of electron transport rate through photosystem II in phase III of CAM is correlated to decarboxylation of malate. At the exposed site C. multiflora was less negatively affected by high PPFD than C. minor. This was shown by a lower reduction of potential electron quantum yield (Fv/Fm) and higher light utilisation of electron transport of C. multiflora compared to C. minor. At the exposed site C. minor did not make use of the CAM option to increase light utilisation of electron transport and to reduce non-photochemical quenching as did the plants growing in the shade.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009670
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrogen distribution and leaf area indices in relation to photosynthetic nitrogen use efficiency in savanna grasses (1998)
    Springer
    Plant ecology 138 (1998), S. 63-75 
    Details
    ISSN: 1573-5052
    Keywords: Canopy structure ; C3and C4grasses ; Flooded tropical savannas ; Leaf nitrogen content ; Optimality model ; Seasonal tropical savannas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf photosynthetic characteristics, distribution patterns of nitrogen content per unit leaf area (nL) and leaf area production per unit nLwere measured in natural stands of a C4 grass (Hyparrhenia rufa) from the seasonal savannas and of a C4grass (Paspalum fasciculatum) and two C3grasses (Leersia hexandra and Hymenachne amplexicaulis) from the flooded savannas in central Venezuela. Daily rates of canopy photosynthesis (PcD) as well as the optimal leaf area production per unit nLat which PcDfor a given total amount of nitrogen in the canopy (i.e., canopy-PNUE) is maximized were also calculated. The C3and C4species from the flooded savannas had similar light saturated rates of photosynthesis per unit nL(i.e. leaf-PNUE) and similar canopy-PNUEs which was in strong contrast with previous studies. Especially H. rufa but also L. hexandra and H. amplexicaulis had leaf- and canopy-PNUEs which were considerably higher than the values calculated for most other species with the same photosynthetic pathway (i.e., C3or C4). In contrast to previous studies, differences in the light gradient in the canopy between stands only partially explained differences in N distribution. Measured leaf area indices were greater and the average nL values were consequently smaller than the calculated optima. There was, however, a very strong linear correlation between the optimal and actual average nLindicating that even though the model overestimated average nL, it did predict the differences in leaf area production per unit nitrogen – the inverse average nL– very well. This result strongly indicates that leaf area production per unit of leaf nitrogen increases with leaf-PNUE and decreases with the extinction coefficient for light. Grass species from seasonal savannas have extremely high leaf-PNUEs and thus optimally produce large amounts of leaf area per unit nL. This helps explain how stands of these species may have high leaf area indices and achieve high photosynthetic productivity despite the very low nutrient availability at which they grow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009727822617
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Nonuniversality and analytical continuation in moments of directed polymers on hierarchical lattices (1993)
    Springer
    Journal of statistical physics 71 (1993), S. 967-980 
    Details
    ISSN: 1572-9613
    Keywords: Directed polymers ; hierarchical lattices ; disorder ; moments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We prove the moments of the directed polymer partition function GZ, using an exact position space renormalization group scheme on a hierarchical lattice. After sufficient iteration the characteristic functionf(n)=ln〈GZn〉 of the probability ℘(Z) converges to a stable limitf *(n). For smalln the limiting behavior is independent of the initial distribution, while for largen,f *(n) is completely determined by it and is thus nonuniversal. There is a smooth crossover between the two regimes for small effective dimensions, and the nonlinear behavior of the small moments can be used to extract information on the universal scaling properties of the distribution. For large effective dimensions there is a sharp transition between the two regimes, and analytical continuation from integer moments ton→0 is not possible. Replica arguments can account for most features of the observed results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049956
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    Paper (German National Licenses)
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