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  • 1990-1994  (3)
  • 12.20.Fv  (1)
  • 34.80.Kw  (1)
  • Cumulant generating function  (1)
  • intercropping
  • mungbean
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  • 1
    ISSN: 1434-601X
    Keywords: 14.80.Pb ; 13.10. + q ; 12.20.Fv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Motivated by the observation of energy- and momentum-correlatede + e − pairs in heavy ion collisions, a search for resonances ine + e − scattering at the corresponding energies has been made. Thee + e − decay channel is analyzed in a time window from ∼ 10−13 s to ∼ 10−11 s with a set-up optimized for low-background detection of delayede + e − decays. The two-photon decay channel of a hypothetical resonance is investigated by measuring the two-photon annihilation-in-flight excitation function. New upper limits for the partiale + e − decay width Γee of a few meV are derived for total centre-of-mass energies √s between 1.78 and 1.92 MeV, taking into account the dilepton as well as the two-photon decay of a neutral resonance.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical biology 28 (1990), S. 529-565 
    ISSN: 1432-1416
    Keywords: Space time ; Integral equation ; Dispersal ; Asymptotic velocity of propagation ; Approximation formulae ; Cumulant generating function ; Fisher/Skellam diffusion model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We consider the velocity with which an invading population spreads over space. For a general linear model, originally due to Diekmann and Thieme, it is shown that the asymptotic velocity of population expansion can be calculated if information is available on: (i) the net-reproduction, R o; i.e. the expected number of offspring produced by one individual throughout its life, and (ii) the (normalized) reproduction-and-dispersal kernel, β(a, χ − ξ); i.e. the density of newborns produced per unit of time at position χ by an individual of age a born at ξ By means of numerical examples we study the effect of the net-reproduction and the shape of the reproduction-and-dispersal kernel on the velocity of population expansion. The reproduction-and-dispersal kernel is difficult to measure in full. This leads us to derive approximation formulas in terms of easily measurable parameters. The relation between the velocity of population expansion calculated from the general model and that from the Fisher/Skellam diffusion model is discussed. As a final step we use the model to analyse some real-life examples, thus showing how it can be put to work.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-6079
    Keywords: 34.80.Kw ; 32.30.Rj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The x-ray spectra induced by spontaneous capture of free cooling electrons into bare and hydrogenlike heavy ions have been observed. Au78+, Au79+ and U91+ ions were stored in the storage ring ESR at velocities between 60% and 65% of the velocity of light and the x rays were measured in coincidence with stored particles having captured one electron in the electron cooler. The lines observed can be attributed to the direct transition of cooling electrons into theK shell of the projectile and to the characteristicL →K transitions. The latter are mainly induced by capture into higher shells and subsequent cascade transitions. The measurements are compared to detailed calculations within the framework of presently available theories. Although the relative structure of the measured spectra is in fair agreement with the theoretical prediction, the total charge-changing rate in the electron cooler is about a factor of three smaller than expected.
    Type of Medium: Electronic Resource
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