1 STRUCTURE AND EVOLUTION OF NEARBY OB ASSOCIATIONS
We present the rst results of a comprehensive census of the stellar content of the nearby OB associations based on Hipparcos positions, proper motions and parallaxes for 12842 candidate member stars distributed over 21 elds on the sky. We use a new method to identify moving groups in these elds (see de Bruijne et al., these proceedings). Previously, astrometric membership in nearly all the nearby OB associations was known only for stars with spectral types earlier than B5. The Hipparcos measurements now allow us to identify members down to late F. This census provides a rm basis for studies of galactic and extragalactic star forming regions.
Stellar evolution and nucleosynthesis: an introduction to nuclear astrophysics
The new book, An Introduction to Nuclear Astrophysics, by Jean Audouze and Sylvie Vauclair, fills the tremendous need for a work of book length that is more modern than the 1968 textbook. Audouze and vauclair excellently summarize the current status of the field. The book is written at a level that would be quite suitable for use in a beginning graduate or upper division undergraduate course. Audouze and Vauclair, both active French astrophysicists, have made numerous contributions to our understanding of nuclear astrophysics. Audouze in particular, is well known for his work on light element synthesis and on the chemical evolution of the galaxy, so it is understandable that these sections are extraordinarily well treated. However, the authors have also done quite an admirable job in treating the rest of the field: Big Bang nucleosynthesis, nuclear reaction rates, explosive nucleosynthesis and the synthesis of the heavy elements as well as the problems regarding the isotopic anomalies in the early solar system and the use of radioactive decay for estimating the age of the universe.
Microwave source with enhanced radiation power based on orbitron MASERs
We have proposed the design of high power microwave source in a vacuum tube based on the theory of negative mass instability. The proposed source does not operate based on a slow-wave structure but instead makes use of accelerated charged particles. In our structure, an electron emitter injects the charged particles into to the cavity. Emitted particles move around the anode, which leads to electron acceleration and emission of electromagnetic waves with a specific frequency. In this paper, we have enhanced the output power and frequency of microwave source by variation of particles initial energy and the number of anodes incorporating their specific arrangement and applied voltages. Working at room temperature, compactness, wide bandwidth, and tunability of output frequency are among the advantages of the proposed source.