The radio spectra of reddened 2MASS QSOs: evidence for young radio jets

Multifrequency radio continuum observations (1.4-22 GHz) of a sample of reddened QSOs are presented. We find a high incidence (13/16) of radio spectral properties, such as low frequency turnovers, high frequency spectral breaks or steep power-law slopes, similar to those observed in powerful compact steep spectrum (CSS) and gigahertz-peaked spectrum (GPS) sources. The radio data are consistent with relatively young radio jets with synchotron ages <1e6-1e7yr. This calculation is limited by the lack of high resolution (milli-arcsec) radio observations. For the one source in the sample that such data are available a much younger radio age is determined, <2e3yr, similar to those of GPS/CSS sources. These findings are consistent with claims that reddened QSOs are young systems captured at the first stages of the growth of their supermassive black holes. It also suggests that expanding radio lobes may be an important feedback mode at the early stages of the evolution of AGN.Comment: 9 pages, to appear in MNRA

Safe Spacecraft Rendezvous and Proximity Operations via Reachability Analysis

The rapid expansion of the utilization of space by nations and industry has presented new challenges and opportunities to operate efficiently and responsibly. Reachability analysis is the process of computing the set of states that can be reached given all admissible controls and can be a valuable component in an autonomous mission planning system if conducted efficiently. In the current research, reachability analysis is used with several relative motion models to show that all ranges of orbits can be computed in milliseconds, and that it is a feasible approach for on-board autonomous mission planning. Reachability analysis is then combined with an Artificial Potential Function (APF) derived guidance control law to conduct safe spacecraft rendezvous between a deputy in a Natural Motion Circumnavigation (NMC) relative orbit around a chief while avoiding obstacles. While the APF employed in this research requires improvements for trajectory computation, this research demonstrates the feasibility of combining reachability analysis with an APF for safe, on-board, autonomous mission planning

On the type of triangle groups

We prove a conjecture of R. Schwartz about the type of some complex hyperbolic triangle groups.Comment: 10 pages, 3 figure

Investigation of electrodynamic stabilization and control of long orbiting tethers

The possibility of using electrodynamic forces to control pendular oscillations during the retrieval of a subsatellite is investigated. The use of the tether for transferring payloads between orbits is studied

Molecular modeling of -endotoxins from Bacillus thuringiensis.

Bacillus thuringiensis (Bt) is a Gram-positive entomotoxic bacterium widely used to control crop pests and disease vectors. Since the introduction of transgenic plants expressing Bt genes, it has been demonstrated that Bt-crops constitute an important tool in the increase of productivity and in the decrease of the use of chemical pesticides. Its success comes from the production of the ?-endotoxins (Cry). These toxins share a molecular mechanism of similar action or, at least, some common aspects

An approximation algorithm for the maximum cut problem and its experimental analysis

AbstractAn approximation algorithm for the maximum cut problem is designed and analyzed; its performance is experimentally compared with that of a neural algorithm and that of Goemans and Williamson's algorithm. Although the guaranteed quality of our algorithm in the worst-case analysis is poor, we give experimental evidence that its average behavior is better than that of Goemans and Williamson's algorithm