A Parametric Study of the Acoustic Mechanism for Core-Collapse Supernovae

We investigate the criterion for the acoustic mechanism to work successfully in core-collapse supernovae. The acoustic mechanism is an alternative to the neutrino-heating mechanism. It was proposed by Burrows et al., who claimed that acoustic waves emitted by $g$-mode oscillations in proto-neutron stars (PNS) energize a stalled shock wave and eventually induce an explosion. Previous works mainly studied to which extent the $g$-modes are excited in the PNS. In this paper, on the other hand, we investigate how strong the acoustic wave needs to be if it were to revive a stalled shock wave. By adding the acoustic power as a new axis, we draw a critical surface, an extension of the critical curve commonly employed in the context of neutrino heating. We perform both 1D and 2D parametrized simulations, in which we inject acoustic waves from the inner boundary. In order to quantify the power of acoustic waves, we use the extended Myers theory to take neutrino reactions into proper account. We find for the 1D simulations that rather large acoustic powers are required to relaunch the shock wave, since the additional heating provided by the secondary shocks developed from acoustic waves is partially canceled by the neutrino cooling that is also enhanced. In 2D, the required acoustic powers are consistent with those of Burrows et al. Our results seem to imply, however, that it is the sum of neutrino heating and acoustic powers that matters for shock revival.Comment: 20 pages, 19 figures, accepted by Ap

Strictosidine, the common precursor for monoterpenoid indole alkaloids with 3 α and 3 β configuration

Recently we reported that strictosidine (l> is the key intermediate in the formation of the three classes (ASDidOf3DeIm5, Iboga, Corynanthe) of monoterpenoid indole alkaloids In Catharanthus roseus and a variety of other plant species in cell culture using in vivo and in vitro techniques"2. These results were independently confirmed In Manchester 394 and subsequently also Scott et a1.5 were able to confirm the precursor role of (1) using Catharanthus material. All these results are in accord with reports on the biosynthesis of an alkaloid of taxonomically distant origin, camptothecln, for which strictosidine la&am6 was previously found to be a precursor, and recently7 also (1). The key intermediate in the biosynthesis of the majority of mono-terpenoid alkaloids is therefore (1) with 3 a (2) configuration, rather than vincoside (2) with 3 13 (lX> configuration as had previously been assumeda. However, a generalization of this precursor function of (1

S-adenosyl-L-methionine: (S)-scoulerine 9-O-methyltransferase, a highly stereo- and regio-specific enzyme in tetrahydroprotoberberine biosynthesis

Suspension cultures of Berberis species are useful sources for the detection and isolation of a new enzyme which transfers the methyl group from S-adenosyl-L-methionine specifically to the 9-position of the (S)-enantiomer of scoulerine, producing (S)-tetrahydrocolumbamine. The enzyme was enriched 27-fold; it is not particle bound, has a pH optimum of 8.9, a molecular weight of 63 000 and shows a high degree of substrate specificity