Bestimmung der resorptionsverfügbaren PCDD/PCDF aus Kieselrot

For the estimation of intestinal absorption of polychlorianted dibenzodioxins/dibenzofurans (PCDD/F), ain-vitro model was developed in order to study PCDD/F mobilization by digestion of technogenic soils using ?Kieselrot” (red slag) as substrate and digestive juice model mixtures. Red slag samples were shaken successively with model mixtures of saliva, gastric juice, duodenal juice and bile. The solids were separated, the aqueous phase was extracted with hexane, the hexane extract analyzed for PCDD/F. Additionally, the PCDD/F-content of the red slag was determined. Extraction efficiency was tested with three different digestive juice model mixtures and also tap water for comparision. The percentage of PCDD/F transferred from the red slag sample into the digestive juice mixture was defined as absorption availability. In our experiments, a maximum absorption availability of 2 % was found.     

Pigeon homing: Different effects of olfactory deprivation in different countries

Summary This study compares the orientation of untreated pigeons and pigeons subjected to olfactory deprivation at two lofts near Pisa, Italy, at a loft at Ithaca, New York, USA, and at a loft at Frankfurt a.M., FRG. The experimental birds were rendered anosmic by nasal plugs until Gingicain, a local anaesthetic, was applied shortly before release. The Italian and American control pigeons appeared to orient towards home equally well, while the control pigeons in Germany frequently preferred directions that deviated significantly from the home direction. The effect of olfactory deprivation was small in the USA and in Germany; it was significantly larger in Italy, indicating that Italian pigeons depend on olfactory information to a much greater extent. These findings suggest that there are important regional differences in the strategies and cues pigeons use to navigate. The varied roles of olfactory information, and the reasons for these differences are discussed.     

Femtosecond time-resolved spectroscopy of elementary molecular dynamics

Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (CARS) is applied in order to prepare and monitor laser-induced vibrational coherences (wave packets) of different samples mainly in its electronic ground state but also in excited states. The time evolution of these wave packets gives information on the dynamics of molecular vibrations. In a first example the femtosecond (fs) CARS transients of iodine are investigated. By changing the relative delay between the applied laser pulses of this non-degenerated four-wave mixing technique, both the wavepacket motion on the electronically excited and the ground states can be detected as oscillations in the coherent anti-Stokes signal. Second we report on selective excitation of the vibrational modes in the electronic ground state of polymers of diacetylene by means of a femtosecond time-resolved CARS scheme. This selectivity is achieved by varying the phase shape (chirp) and the relative delay between the exciting laser pulses.     

Lyman α in der Milchstraße

W. K. möchte sich bei R. Schaaf für mehrere klärende Diskussionen bedanken sowie bei D. Osterbrock für einen Brief.