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  • 1
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    Validation of Saharan Dust Layer Characteristics with Lidar Observations (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Lidar backscattering profiles available from the LITE data set have been used to estimate the optical depths of the Saharan dust layer over West Africa and E. Atlantic regions, in the context of validating the 3-D conceptual model of the Saharan dust plume proposed by Karyampudi and Carlson. The aerosol extinction profiles and optical depths were retrieved from LITE using the Fernald et al. (1972) method. An extinction-to-backscattering ratio, S(sub a), of 25 was selected for optical depth calculations. The spatial analysis of total column and Saharan dust layer optical depths show higher optical depths over W. Africa that decrease westward over E. Atlantic. The higher optical depths over W. Africa, in general, are associated with heavy dust being raised from the surface in dust source regions. Rapid depletion of these heavy dust particles, perhaps due to sedimentation, appear to decrease the dust loading within the dust layer as the plume leaves the west African continent. Higher optical depths are generally confined to the southern edge of the dust layer, where the middle level jet appears to transport the heavy dust concentrations that tend to mix downward from vertical mixing associated with the strong vertical shears underneath the middle jet. Thus, LITE measurements although, in general, validate the Saharan dust plume conceptual model, show maximum values of optical depths near the southern edge of the dust plume over the E. Atlantic region instead of near the center of the dust plume as described in the conceptual model.
    Keywords: Geophysics
    Type: Nineteenth International Laser Radar Conference; Part 2; 685-690; NASA/CP-1998-207671/PT2
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
    Electronic Resource
    Electronic Resource
    Two Pheromones of Coniferophagous Bark Beetles Found in the Bark of Nonhost Angiosperms (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 805-816 
    Details
    ISSN: 1573-1561
    Keywords: Semiochemicals ; pheromones ; nonhost volatiles ; frontalin ; conophthorin ; 1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane ; (E)-7-methyl-1,6-dioxaspiro[4.5]decane ; Coleoptera ; Scolytidae ; Batesian mimicry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Volatiles from fresh bark of black cottonwood, Populus trichocarpa; trembling aspen, P. tremuloides; paper birch, Betula papyrifera; bigleaf maple, Acer macrophyllum; red alder, Alnus rubra; and Sitka alder, Alnus viridis, were collected on Porapak Q and subjected to coupled gas chromatographic–electroantennographic detection analyses by utilizing the antennae of several scolytid beetles (Dendroctonus pseudotsugae, D. rufipennis, D. ponderosae, Ips pini, and Dryocoetes confusus). Among the antennally active volatiles identified by coupled gas chromatographic-mass spectroscopic analysis were frontalin, 1,5-dimethyl-6,8-dioxabicyclo[3.2.1]-octane, in the two Alnus species and conophthorin, (E)-7-methyl-1,6-diox-aspiro[4.5]decane, in the other four species. Field trapping experiments demonstrated that conophthorin had a significant disruptant effect on the response to a pheromone-host kairomone blend by both Dendroctonus pseudotsugae and D. ponderosae. Our results, and the recent identification of other scolytid pheromones in various tree species, pose major questions regarding the evolution and ecological roles of these semiochemicals, including the possibility of Batesian mimicry by the beetles. They also suggest a need for comparative studies on the biosynthetic pathways for these compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020892700653
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    Paper (German National Licenses)
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