Applying artificial intelligence to the control of space telescopes (extended abstract)

The field of astronomy has recently benefited from the availability of space telescopes. The Hubble Space Telescope (HST), for instance, despite its problems, provides a unique and valuable view of the universe. However, unlike HST, a telescope need not be in low Earth orbit to escape our thickening atmosphere: it is currently technologically feasible to put a telescope on the moon, and there are excellent reasons for doing this. Either in low Earth orbit or on the moon, a space telescope represents an expensive and sought-after resource. Thus, the planning, scheduling, and control of these telescopes is an important problem that must be seriously studied

Efficient Auction-Based Grid Reservation using Dynamic Programming

Abstract — Auction mechanisms have been proposed as a means to efficiently and fairly schedule jobs in high-performance computing environments. The Generalized Vickrey Auction has long been known to produce efficient allocations while exposing users to truth-revealing incentives, but the algorithms used to compute its payments can be computationally intractable. In this paper we present a novel implementation of the Generalized Vickrey Auction that uses dynamic programming to schedule jobs and compute payments in pseudo-polynomial time. Additionally, we have built a version of the PBS scheduler that uses this algorithm to schedule jobs, and in this paper we present the results of our tests using this scheduler. I

Which drugs are most effective for moderate to severe depression in adolescents?

Fluoxetine is the only selective serotonin-reuptake inhibitor (SSRI) approved by the US Food and Drug Administration (FDA) to treat depression in children 8 years of age and older; it also has the most favorable benefit-to-risk profile compared with placebo in trials lasting up to 12 weeks (strength of recommendation [SOR]: A, meta-analysis). Fluoxetine combined with cognitive behavioral therapy (CBT) is superior to fluoxetine alone, CBT alone, or placebo (SOR: B, single well-done randomized controlled trial [RCT]). Further research is needed to address the long-term efficacy of fluoxetine treatment

Which drugs are safest for moderate to severe depression in adolescents?

Selective serotonin-reuptake inhibitors (SSRIs) appear to be the safest, given current data. Major safety concerns--prompting a US Food and Drug administration (FDA) black box label warning--have been raised about increased risk of suicidality (ideation, behavior, and attempts) among adolescents receiving antidepressant therapy. Information about the safety of tricyclic antidepressants in young people is limited because adverse effects have not been systematically reported in trials (SOR: A, meta-analysis)

Alpha Enhancement and the Metallicity Distribution Function of Plaut's Window

We present Fe, Si, and Ca abundances for 61 giants in Plaut's Window (l=-1,b=-8.5) and Fe abundances for an additional 31 giants in a second, nearby field (l=0,b=-8) derived from high resolution (R~25,000) spectra obtained with the Blanco 4m telescope and Hydra multifiber spectrograph. The median metallicity of red giant branch (RGB) stars in the Plaut field is ~0.4 dex lower than those in Baade's Window, and confirms the presence of an iron abundance gradient along the bulge minor axis. The full metallicity range of our (biased) RGB sample spans -1.5<[Fe/H]<+0.3, which is similar to that found in other bulge fields. We also derive a photometric metallicity distribution function for RGB stars in the (l=-1,b=-8.5) field and find very good agreement with the spectroscopic metallicity distribution. The radial velocity and dispersion data for the bulge RGB stars are in agreement with previous results of the BRAVA survey, and we find evidence for a decreasing velocity dispersion with increasing [Fe/H]. The [alpha/Fe] enhancement in Plaut field stars is nearly identical to that observed in Baade's window, and suggests that an [alpha/Fe] gradient does not exist between b=-4 and -8. Additionally, a subset of our sample (23 stars) appear to be foreground red clump stars that are very metal--rich, exhibit small metallicity and radial velocity dispersions, and are enhanced in alpha elements. While these stars likely belong to the Galactic inner disk population, they exhibit [alpha/Fe] ratios that are enhanced above the thin and thick disk.Comment: Accepted for publication in ApJ. 38 pages, 11 figures, and 2 tables. Requests for higher resolution figures and electronic versions of tables 1 and/or 2 in advance of publication may be sent to cijohnson[at]astro.ucla.ed

Several Developments in Space Tethers

Five reports address different aspects of development of tethers to be deployed from spacecraft in orbit around the Earth. The first report discusses proposed optoelectronic tracking of retroreflective objects located at intervals or of retroreflective coats along the entire length of a tether to measure lateral motions. The second report describes digitally controlled spooling machinery that retracts or extends a tape tether at controlled speed and tension in the spool isolated from uncontrolled tension on the outside. The third report discusses part of this machinery that pivots to accommodate misalignments between the deployed and spooled portions of the tether and contains rollers used to exert tension and speed control. The fourth report discusses aspects of designs of proposed electrodynamic tethers, which would be electrically conductive and would interact with the magnetic field of the Earth to exert forces to modify orbits of deploying spacecraft. The fifth report discusses electrical aspects of designs of electrodynamic tape tethers, including the use of solar cells or motional electromagnetic force to generate currents in tethers and the use of electron emitters and electron and ion collectors at opposite ends of tethers to make electrical contact with the thin plasma in surrounding space