... DACs[*]
Figures 6, 7, 9, 10, 12, 13, 15 and 16 are only available inelectronic form at http://www.edpsciences.org
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
...[*]
Only the figures for $\beta =1$ are included in the printed version; the rest are available online as supplementary material.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Copyright ESO 2004