Maser polarization changes during a pulsation in the CSE of an AGB star are related in a complicated way to the magnetic field structure. 43 GHz SiO maser transitions are useful for polarization study because of their relatively simple Zeeman splitting structure and their location. This work uses 3D maser simulation to investigate the effect of the magnetic field on maser polarization with different directions. The results show that linear polarization depends on the magnetic direction while circular polarization is less significant. The EVPA changes through π/2 at an angle of around 50 degrees, approximately the Van Vleck angle. The EVPA rotation result from 3D maser simulation is consistent with results from 1D simulations, and may explain the 90 degree change of the EVPA within a single cloud in the observational cases of TX Cam and R Cas.

A spectroscopic study comparing the [Na/Fe] distributions of RGB and AGB stars in the Galactic globular cluster (GC) NGC 6752 found that there was no Na-rich, 2nd-generation star along the early-AGB of this cluster. This came as a surprise since in this GC, as well as other Galactic GCs studied so far, 1st- and 2nd-generation stars have usually been found from the main sequence turnoff up to the red giant branch. To investigate whether the failure of a significant fraction of stars to ascend the AGB also happens to other GCs, we studied a sample of AGB and RGB stars in NGC 2808 observed at the ESO/VLT with FLAMES. Contrary to NGC 6752, we find that the AGB and RGB stars we studied in NGC 2808 have comparable [Na/Fe] dispersions.