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  • 1
    Electronic Resource
    Electronic Resource
    Study on the synthesis of brassinolide and related compounds III - Stereoselective synthesis of typhasterol from hyodeoxycholic acid
    Amsterdam : Elsevier
    Tetrahedron 43 (1987), S. 3705-3712 
    Details
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0040-4020(01)86858-7
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    Paper (German National Licenses)
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  • 2
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    Interactions of meteoric smoke particles with sulphuric acid in the Earth's stratosphere (2012)
    Copernicus
    Details
    Publication Date: 2012-05-16
    Description: Nano-sized meteoric smoke particles (MSPs) with iron-magnesium silicate compositions, formed in the upper mesosphere as a result of meteoric ablation, may remove sulphuric acid from the gas-phase above 40 km and may also affect the composition and behaviour of supercooled H2SO4-H2O droplets in the global stratospheric aerosol (Junge) layer. This study describes a time-resolved spectroscopic analysis of the evolution of the ferric (Fe3+) ion originating from amorphous ferrous (Fe2+)-based silicate powders dissolved in varying Wt % sulphuric acid (30–75 %) solutions over a temperature range of 223–295 K. Complete dissolution of the particles was observed under all conditions. The first-order rate coefficient for dissolution decreases at higher Wt % and lower temperature, which is consistent with the increased solution viscosity limiting diffusion of H2SO4 to the particle surfaces. Dissolution under stratospheric conditions should take less than a week, and is much faster than the dissolution of crystalline Fe2+ compounds. The chemistry climate model UMSLIMCAT (based on the UKMO Unified Model) was then used to study the transport of MSPs through the middle atmosphere. A series of model experiments were performed with different uptake coefficients. Setting the concentration of 1.5 nm radius MSPs at 80 km to 3000 cm−3 (based on rocket-borne charged particle measurements), the model matches the reported Wt % Fe values of 0.5–1.0 in Junge layer sulphate particles, and the MSP optical extinction between 40 and 75 km measured by a satellite-borne spectrometer, if the global meteoric input rate is about 20 tonnes per day. The model indicates that an uptake coefficient ≥0.01 is required to account for the observed two orders of magnitude depletion of H2SO4 vapour above 40 km.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 3
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    Unknown
    Interactions of meteoric smoke particles with sulphuric acid in the Earth's stratosphere (2012)
    Copernicus
    Details
    Publication Date: 2012-01-17
    Description: Nano-sized meteoric smoke particles (MSPs) with iron-magnesium silicate compositions, formed in the upper mesosphere as a result of meteoric ablation, may remove sulphuric acid from the gas-phase above 40 km and may also affect the composition and behaviour of supercooled H2SO4-H2O droplets in the global stratospheric aerosol (Junge) layer. This study describes a time-resolved spectroscopic analysis of the evolution of the ferric (Fe3+) ion originating from amorphous ferrous (Fe2+)-based silicate powders dissolved in varying Wt % sulphuric acid (30–75%) solutions over a temperature range of 223–295 K. Complete dissolution of the particles was observed under all conditions. The first-order rate coefficient for dissolution decreases at higher Wt % and lower temperature, which is consistent with the increased solution viscosity limiting diffusion of H2SO4 to the particle surfaces. Dissolution under stratospheric conditions should take less than a week, and is much faster than the dissolution of crystalline Fe2+ compounds. The chemistry climate model UMSLIMCAT (based on the UKMO Unified Model) was then used to study the transport of MSPs through the middle atmosphere. A series of model experiments were performed with different uptake coefficients. Setting the concentration of 1.5 nm radius MSPs at 80 km to 3000 cm−3 (based on rocket-borne charged particle measurements), the model matches the reported Wt % Fe values of 0.5–1.0 in Junge layer sulphate particles, and the MSP optical extinction between 40 and 75 km measured by a satellite-borne spectrometer, if the global meteoric input rate is about 20 t d−1. The model indicates that an uptake coefficient ≥0.01 is required to account for the observed two orders of magnitude depletion of H2SO4 vapour above 40 km.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 4
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    A DOAS-like method for total column of CO2 from ground-based FTS measurements of the direct solar beam (2014)
    Copernicus
    Details
    Publication Date: 2014-03-11
    Description: A new algorithm, similar to that of DOAS method, is developed to retrieve the total column CO2 from the ground-based hyper-spectral measurements of direct solar beam. Other than spectrum fitting method, which is generally used in the optimal estimation algorithm, the radiances ratio at two wavelength named channel pair, where one is of weak and the other is of relatively strong absorption, is used to retrieve the total column CO2 in the Short Wave InfraRed(SWIR) band. Sensitivity studies show that this DOAS-like method is less dependent on the model parameters such as aerosols, water vapor, surface pressure, temperature, wavelength shift and signal noise, and the pairs of channels are carefully selected based on the sensitivity studies. To validate the algorithm, the FTS measurements located at Xi'Chong astronomical observatory are used to derive the total column CO2 amount, 272 pairs ratios are used in the retrieval and the results agree very well with that of GOSAT, which shows that the DOAS-like method could give reasonable value of XCO2.
    Electronic ISSN: 1867-8610
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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