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  • Chemistry  (2)
  • continental dust  (2)
  • 1
    ISSN: 1573-0662
    Keywords: continental dust ; Antarctica ; palco-environment ; climatic cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The soluble and insoluble parts of 4 major components (Al, Ca, K and Mg) of the continental dust input over East Antarctica, as well as size, distribution parameters of the insoluble part of this dust, have been studied along an ice core which spanns the last climatic cycle (160 kyr). These results provide a better understanding of the respective impact of the different potential dust sources. While Al and K were probably entrapped in illite originating from arid areas and in a lesser extent from shallow marine sediments, Ca and Mg inputs were dominated by marine carbonate of exposed continental shelves emissions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-0662
    Keywords: continental dust ; Antarctica ; paleo-environment ; glacial age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We have studied the distribution of 327 clay mineral particles retrieved from four Antaretic ice smaples corresponding to present and Last Glacial Maximum (LGM) climate conditions. Illite, chlorite, smectite and kaolinite were identified in all samples. Focusing on kaolinite, because of its use as a possible tracer of low latitude soils, we find a significantly smaller amount for LGM samples while the dust concentration in snow during the LGM was about 30 times higher than for present climate conditions. This can be interpreted as change in the contribution of the Australian source with climate. A second approach was based on the modeling of the desert dust cycle using an Atmospheric General Circulation Model (AGCM) under both present-day and ice age conditions. Unlike mineralogical results, the model suggests the prevalence of the Australian dust source in the deposits over East Antarctica under both present-day and LGM climate conditions. However the model fails to reproduce the strong increase in dust deposits during the LGM. This discrepancy could be partly due to the lack of a higher latitude dust source in the model. The stronger dust input recorded in ice cores for the LGM could be related to an additional active high latitude source (possibly close to South America) overlapping the atmospheric background coming from low latitude areas.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectra of II-VI semiconductor nanocrystals embedded in silicate glass matrices with near-resonance and resonance excitation in the range of electron transitions between size-quantized energy levels were studied. It is shown that only the transitions with angular momentum l = 0, 2 contribute to the resonance Raman enhancement. The influence of the electron-phonon interaction on the Raman excitation profiles of the LO phonons and elastic vibrations of nanocrystals is analysed. The effect of the matrix on the intensities and frequencies of the low-frequency Raman (LFR) bands and the possibilities of determining the particle size determination using LFR spectra are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The surface-enhanced resonance Raman and surfaces enhanced hyper-Raman (SERHR) spectra of a photochromatic indigoid dye were obtained. The influence of stationary additional lighting (AL) at the absorption bands of the photoisomers on the SERHR intensities was observed. This is connected not only with the changes in the photoisomer concentration on the silver surface under AL but also with different scattering intensities of the resonance hyper-Raman spectra of isomers due to their different symmetries.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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