Dredge second

This relationship has been predicted by the stellar evolution theory, as resulting essentially from the so called first and second dredge-up episodes. In Fig. la we see the corresponding predictions by the theory (Marigo, 2001). The sensitivity of the predicted abundances both to the metallicity at the epoch of formation of the progenitors and to their stellar mass in the Main Sequence is evident, making such diagrams powerful tools to trace back the evolutionary history of individual PNe. Uncertainties prevent however us to pursue now this... 

Fig. 5.18. Interior composition of a model 7 MQ star during the second dredge-up phase. After Iben (1991).

The sediment from Amerikahaven (site 10) was found to contain unexpectedly low contaminant levels during sampling in 1996 (see also De Boer et al., 2001). This was attributed to repeated dredging activity. The sediment was therefore sampled a second time in September 1997 at a non-dredged site. Analysis of this sediment showed considerably higher contaminant levels. These results are considered more representative of this location and were therefore used instead of the 1996 data in the multivariate statistical analysis of biomarker data. Sediment bioassays were however conducted with the material collected in 1996 and these data for location no. 10 were used for multivariate analysis when sediment chemistry was included. 

There are four processes which can produce chemical peculiarities in AGB stars the first, second and third dredge-up events and envelope (or hot-bottom) burning. 

The Cult of Isis, dredged up in modem format, was the official ideology of leading British politicians, financiers, and literary figures during the previous century. Its great public exponent was the colonial secretary during the Second Opium War,... 

Becker S. A. and Iben L, Jr. (1979) The asymptotic giant branch evolution of intermediate-mass stars as a function of mass and composition I. Through the second dredge-up phase. Astrophys. J. 232, 831-853. 

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