Close associations of certain lepidopteran taxa with pyrrolizidine alkaloids (PAs), a typical class of plant secondary metabolites, have been well documented from the perspective of evolutionary ecology. Male danaine butterflies are thought to utilize PAs as precursors for the production of dihydropyrrolizines [e.g. danaidone (DO) and hydroxydanaidal (HD)] in their two distinct androconial organs, viz. alar scent organs (sex brands) and abdominal hairpencils. However, little is known about the quantitative profiles of these compounds in danaines, the mechanism for their formation in the androconial organs, or their biological functions, particularly in mating behaviour. The present study addressed these unanswered questions posed for males of the danaine butterfly, Parantica sita. Chemical analyses of androconial extracts revealed considerable seasonal/regional and individual variations of the amounts of DO (the major dihydropyrrolizine produced) and 7R‐HD (the 7R‐enantiomer of HD detected in this study) found in the two organs. These variations seemed to depend primarily on the age of the male and the phenological traits of PA‐containing plants available. Males were found to acquire an adequate capability to produce DO ~1 week after eclosion. DO was shown to be produced exclusively in the sex brand and subsequently physically transferred to the hairpencil through a contact behaviour between the two organs, here termed ‘perfuming behaviour’. The results of behavioural experiments with PA‐fed and PA‐unfed males that were allowed to compete for mates, combined with the positive electroantennographic (EAG) responses of the female, to both DO and 7R‐HD, led to the conclusion that either or both of these compounds can act as the sex pheromone. Oral administration of PAs to males indicated that DO can be biosynthesized from various PA precursors, while 7R‐HD, unlike in arctiid moths, is derived only from PAs with the 7R‐configuration. The putative biosynthetic pathways of DO and 7R‐HD, and the evolutionary provenance of the binate androconial system in the Danainae are also discussed.
By using a meamfield approximation we give a semianalytical method for reducing data on metal-hydrogen systems, which allows for hydrogen-hydrogen (H-H) interactions beyond the level of pair'interactions. Interactions up to the niplet level are explicitly included here, althoub the method allows for interactions up lo any finite order. The model fits lowconcentration data at one temperature and then predicts pressures, lattice expansion and various energies as functions of concentcations for a range of temperahlres. A Monte Carlo simulztion is used to lend support to the approximate validity of the mean-field approximation for calculating the entropy in the regime of low concentrations. We find an increasingly negative average triplet interaction energy as the H concentration is increased. Although the mean-field approach is not an adequate description of clustering phenomena leading to the a-p phase transition, nevertheless OUT finding of a more negative triplet energy with increased concentration may indicate the importance of beyond-pair interactions in the phase m i t i o n .Our philosophy is to assume that the microscopic energy of a metal-hydrogen system is the sum of the site occupation energies together with the pair, triplet, quadruplet, . . . ntuplet terms. We then use a mean-field model to show that, at a low hydrogen concentration r, the effects of these terms on thermodynamic quantities go as 1, r, r z , r3, etc. Hence this hierarchy of interactions can be truncated in the low-concentration a-phase where r is small. This model, which we will term the minimization model, was carried out in practice up to triplet hydrogen interactions, as well as incorporating the experimentally measured change
and The COSY-TOF Collaboration: H. Brand,' S. Brand,' P. Cloth,' M. Dahmen,' V. Druke,' W. E y r i~h ,~
AbstractExperiments on light meson production and ppbremsstrahlung as planned for the initial stage at COSY are discussed. Special emphasis will be placed on near-threshold behaviour where due to kinematics all particles are forced into a rather narrow cone around the beam axis. A specially designed charged particle detector system will be used which not only covers the complete forward hemisphere of 2n in the laboratory system but additionally shows maximum resolution in the extreme forward direction with only moderate cuts in the minimally required energy of all ejectiles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.