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  • 1
    ISSN: 1573-4994
    Keywords: Fluorescent probe ; ultrafast spectroscopy ; barrierless twisting ; charge shift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The quenching of Auramine fluorescence in ethanol is studied by two ultrafast spectroscopy techniques. The gain band, probed by transient absorption spectroscopy, vanishes in a few picoseconds, while a transient absorption band rises and the ground-state repopulation is delayed. In up-conversion experiments, nonexponential wavelength-dependent fluorescence decays are observed. The average decay times increase with the wavelength and the reconstructed instantaneous spectrum exhibits a few hundred-wavenumber red shift and a broadening while its intensity drops. The previously proposed relaxation model, involving a barrierless internal twisting motion toward a transient dark state, is further examined. In particular, the extinction coefficients of the transient state are extracted from the differential absorption spectra. The band is found to lie in the same wavelength range as the dimethylaniline cation radical. This result is discussed as a possible support for an internal twisting process involving a charge shift.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Precision agriculture 2 (2000), S. 377-388 
    ISSN: 1573-1618
    Keywords: decision support ; site-specific ; weed ; crop injury ; herbicide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract While uniform broadcast application (BC) of soil-applied herbicides is the norm, advances in geospatial technologies have enabled the deployment of site-specific herbicide application (SS). Since there are several, largely-untested decision rules for SS herbicide use, the objective of this work was to evaluate crop/weed outcomes and isoxaflutole use for a number of BC and SS strategies. Field experiments were established where isoxaflutole dose response functions were quantified from early-season Zea mays (L.), Sorghum bicolor (L.) Moench., and Abutilon theophrasti Medic. response data at multiple plots (64 in 1999; 62 in 2000) throughout a variable field. These data were then used to infer crop and weed outcomes from simulated application strategies. While BC and SS strategies that relied on the product label were similar in terms of total herbicide use, extent of crop tolerance, and A. theophrasti efficacy, the SS strategy resulted in a significant redistribution of herbicide. Using biologically effective doses (ED) resulted in the highest efficacy and herbicide use was highly species-dependent. By using a historical weed map of the field to guide herbicide application, herbicide use could be reduced some 20–48% when following the product label where seedlings were present, or 〉90% when using the ED for A. theophrasti. In order to maximize the potential agronomic benefits of SS, biological and spatial information of both the weed and soil should be taken into account.
    Type of Medium: Electronic Resource
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