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  • 1985-1989  (2)
  • 1880-1889
  • 14C uptake  (1)
  • 23.40.Z  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Light and dark uptake and loss of 14C: methodological problems with productivity measurements in oceanic waters (1989)
    Springer
    Hydrobiologia 173 (1989), S. 95-105 
    Details
    ISSN: 1573-5117
    Keywords: 14C uptake ; 14C loss ; productivity ; assimilation number ; oligotrophic water ; phytoplankton ; bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurements of the uptake and loss of 4C in the light and in the dark in the Tasman and Coral Seas have revealed methodological problems with the estimation of productivity in these waters. Rates of productivity estimated without replication, time series incubations and dark controls frequently overestimated the true rates of autotrophic production. The data showed unexpectedly high rates of both uptake and loss in the dark in oligotrophic waters. In oligotrophic oceanic waters, dark incorporation of 14C sometimes equalled the uptake of 14C in the light bottle. Rapid uptake of isotope in the dark controls appeared to be the result of rapid bacterial growth and metabolism. This problem was exacerbated by agitation of the sample before or during the incubation. Tropical samples were particularly susceptible to problems arising from the agitation of the samples. Latitudinal gradients of dark uptake and loss were revealed in these incubations. The loss of label during 8–12 hours in the dark (after 12 hr in the light) was as high as 50% in subtropical waters. The loss was frequently unmeasurable (〈 10%) in temperate waters. The time course of 14C uptake indicated active grazing in the bottles and suggested that most of the nighttime losses of label were due to grazing by microheterotrophs. Respiratory losses appeared to be small. Calculated values of the assimilation number (or photosynthetic capacity) which did not correct for dark 14C uptake were too high to be biochemically realistic. The errors were due to the heterotrophic uptake of label and the lack of dark controls. Rapid release of 14C in the dark after incubation in the light meant that the estimate of ‘productivity’ was dependant on the trophic state of the sample and on the period of incubation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015519
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The study of prompt and delayed muon induced fission (1987)
    Springer
    The European physical journal 328 (1987), S. 37-47 
    Details
    ISSN: 1434-601X
    Keywords: 23.40.Z ; 24.75.t ; 25.85.G ; 25.85.J ; 27.90 ; 36.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mass yield and total kinetic energy release (TKE) distributions of fragments from prompt and delayed muon induced fission, separately, have been measured for the isotopes235U,238U,237Np and242Pu. The distributions from prompt muon induced fission are compared with the corresponding distributions from hadronic reactions and from spontaneous fission (s.f.). The distributions from the delayed muonic fission processes are compared to the distributions for neutron and proton-induced fission. No mass distributions measured in the prompt muonic fission process show any signature, which can be attributed to the presence of the muon. Differences observed between the TKE distributions of prompt muon induced and hadron induced fission can be explained by the screening effect of the negative charge of the muon bound in the orbit of one of the fission fragments. The observed yield of symmetric muon induced fission was found to be defined merely by the value of the excitation energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01295181
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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