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  • 1
    Electronic Resource
    Electronic Resource
    Sauerstoffeffekt nach konventioneller Röntgen- und hoch energetischer Elektronenbestrahlung bei einer Strahlenmodifikation (Phänokopie) (1963)
    Springer
    Radiation and environmental biophysics 1 (1963), S. 51-59 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Zusammenfassung 1 Durch Bestrahlung 5stündiger Vorpuppen von Drosophila melanogaster wird die Flügelstellung der adulten Fliege im Sinne einer Spreizung verändert. Die Entstehung dieser Strahlenmodifikation, die gleichzeitig eine Phänokopie darstellt, ist von genetischen Faktoren abhängig, da sich zwei verschiedene Inzuchtstämme der Wildform in ihrer Strahlensensibilität voneinander unterscheiden. 2. Ultraharte, energiereiche Betatronstrahlen (30-MeV-Elektronen und 31-MeV-Photonen) sind in ihrer biologischen Wirksamkeit den gleichen Meßwerten von 180-keV-Strahlen deutlich unterlegen. Interessanterweise liegt die RBW für 31-MeV-Photonen mit 0,8 höher als die RBW für 30-MeV-Elektronen mit dem Werte von 0,7. Die 31-MeV-Photonen mit einer durchschnittlichen linearen Ionisationsdichte von 6,3 Ionenpaaren/μ sind damit biologisch effektiver als die schnellen 30-MeV-Elektronen, bei denen entlang der primären Bahnspur mit lediglich 3 Ionenpaaren/μ zu rechnen ist. 3. Bestrahlung in reinem N2 verhindert drastisch die Entstehung der Anomalie (Reduktion einer 98% igen Schädigung nach 5000 r 30-MeV-Elektronen auf 5%). Es konnte kein Unterschied im Ausmaß des Schutzeffektes für 30-MeV-Elektronen und 180-keV-Photonen festgestellt werden. 4. Es wird die Entstehung der Entwicklungsstörung diskutiert. Die gleichzeitige Abhängigkeit des Effektes vom Sauerstoffgehalt des Milieus und von der linearen Energieübertragung spricht für die große Beteiligung chemisch aktiver Bestrahlungsprodukte des Wassers an der Strahlenschädigung. Als weitere Hypothese zur Deutung des Sauerstoffeffektes wird eine Blockierung von Vorgängen im makromolekularen Bereich (Entstehung von RNS, usw.) durch Sauerstoffentzug postuliert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01192567
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    Paper (German National Licenses)
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  • 2
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    Pasture degradation modifies the water and carbon cycles of the Tibetan highlands (2014)
    Copernicus
    Details
    Publication Date: 2014-06-12
    Description: The Tibetan Plateau has a significant role with regard to atmospheric circulation and the monsoon in particular. Changes between a closed plant cover and open bare soil are one of the striking effects of land use degradation observed with unsustainable range management or climate change, but experiments coupling changes of surface properties and processes with atmospheric feedbacks are rare and have not been undertaken in the world's two largest alpine ecosystems, the alpine steppe and the Kobresia pygmaea pastures of the Tibetan plateau. We coupled measurements of micro-lysimeter, chamber, 13C labeling, and eddy-covariance and combined the observations with land surface and atmospheric models, adapted to the highland conditions. This allowed us to analyze how three degradation stages affect the water and carbon cycle of pastures on the landscape scale within the core region of the Kobresia pygmaea ecosystem. The study revealed that increasing degradation of the Kobresia turf affects carbon allocation and strongly reduces the carbon uptake, compromising the function of Kobresia pastures as a carbon sink. Pasture degradation leads to a shift from transpiration to evaporation while the total sum of evapotranspiration remains unaffected. The results show an earlier onset of convection and cloud generation, likely triggered by enhanced evaporation. Consequently, precipitation starts earlier and clouds decrease the incoming solar radiation. In summary, the changes in surface properties by pasture degradation found on the highland have a~significant influence on larger scales.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 3
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    Pasture degradation modifies the water and carbon cycles of the Tibetan highlands (2014)
    Copernicus
    Details
    Publication Date: 2014-12-02
    Description: The Tibetan Plateau has a significant role with regard to atmospheric circulation and the monsoon in particular. Changes between a closed plant cover and open bare soil are one of the striking effects of land use degradation observed with unsustainable range management or climate change, but experiments investigating changes of surface properties and processes together with atmospheric feedbacks are rare and have not been undertaken in the world's two largest alpine ecosystems, the alpine steppe and the Kobresia pygmaea pastures of the Tibetan Plateau. We connected measurements of micro-lysimeter, chamber, 13C labelling, and eddy covariance and combined the observations with land surface and atmospheric models, adapted to the highland conditions. This allowed us to analyse how three degradation stages affect the water and carbon cycle of pastures on the landscape scale within the core region of the Kobresia pygmaea ecosystem. The study revealed that increasing degradation of the Kobresia turf affects carbon allocation and strongly reduces the carbon uptake, compromising the function of Kobresia pastures as a carbon sink. Pasture degradation leads to a shift from transpiration to evaporation while a change in the sum of evapotranspiration over a longer period cannot be confirmed. The results show an earlier onset of convection and cloud generation, likely triggered by a shift in evapotranspiration timing when dominated by evaporation. Consequently, precipitation starts earlier and clouds decrease the incoming solar radiation. In summary, the changes in surface properties by pasture degradation found on the highland have a significant influence on larger scales.
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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