3,577 research outputs found
Three secrets of survival in science advice
The offices that give science advice to politicians are among the most important public bodies you’ve never heard of. Some nations — notably the United States and Denmark — have closed or stopped funding them. Elsewhere, these bodies are thriving: in the United Kingdom and France, for example. Differences between the healthy and the defunct hold lessons for countries that hope to improve the use of science in law-making and political debate. Spain’s national parliament, for instance, plans to open a science and technology advisory unit this summer. In the United States, hopes have been raised this past year of the return of something like the much-missed Office of Technology Assessment (OTA), shuttered in the mid-1990s. This spring, Congress is likely to consider funding for science and technology advice in its budget appropriations for the legislative branch. Here we offer a three-step survival guide for legislative science and technology advisory bodies (LSTABs). Our recommendations are based on the key functions and factors that seem to have led to the long-term success or failure of such bodies
Electrodynamic Structure of an Outer Gap Accelerator: Location of the Gap and the Gamma-ray Emission from the Crab Pulsar
We investigate a stationary pair production cascade in the outer
magnetosphere of a spinning neutron star. The charge depletion due to global
flows of charged particles, causes a large electric field along the magnetic
field lines. Migratory electrons and/or positrons are accelerated by this field
to radiate curvature gamma-rays, some of which collide with the X-rays to
materialize as pairs in the gap. The replenished charges partially screen the
electric field, which is self-consistently solved together with the
distribution functions of particles and gamma-rays. If no current is injected
at neither of the boundaries of the accelerator, the gap is located around the
conventional null surface, where the local Goldreich-Julian charge density
vanishes. However, we first find that the gap position shifts outwards (or
inwards) when particles are injected at the inner (or outer) boundary. Applying
the theory to the Crab pulsar, we demonstrate that the pulsed TeV flux does not
exceed the observational upper limit for moderate infrared photon density and
that the gap should be located near to or outside of the conventional null
surface so that the observed spectrum of pulsed GeV fluxes may be emitted via a
curvature process. Some implications of the existence of a solution for a super
Goldreich-Julian current are discussed.Comment: 17 pages, 12 figures, submitted to Ap
Large-Scale Image Processing with the ROTSE Pipeline for Follow-Up of Gravitational Wave Events
Electromagnetic (EM) observations of gravitational-wave (GW) sources would
bring unique insights into a source which are not available from either channel
alone. However EM follow-up of GW events presents new challenges. GW events
will have large sky error regions, on the order of 10-100 square degrees, which
can be made up of many disjoint patches. When searching such large areas there
is potential contamination by EM transients unrelated to the GW event.
Furthermore, the characteristics of possible EM counterparts to GW events are
also uncertain. It is therefore desirable to be able to assess the statistical
significance of a candidate EM counterpart, which can only be done by
performing background studies of large data sets. Current image processing
pipelines such as that used by ROTSE are not usually optimised for large-scale
processing. We have automated the ROTSE image analysis, and supplemented it
with a post-processing unit for candidate validation and classification. We
also propose a simple ad hoc statistic for ranking candidates as more likely to
be associated with the GW trigger. We demonstrate the performance of the
automated pipeline and ranking statistic using archival ROTSE data. EM
candidates from a randomly selected set of images are compared to a background
estimated from the analysis of 102 additional sets of archival images. The
pipeline's detection efficiency is computed empirically by re-analysis of the
images after adding simulated optical transients that follow typical light
curves for gamma-ray burst afterglows and kilonovae. We show that the automated
pipeline rejects most background events and is sensitive to simulated
transients to limiting magnitudes consistent with the limiting magnitude of the
images
Dynamics of adaptive agents with asymmetric information
We apply path-integral techniques to study the dynamics of agent-based models
with asymmetric information structures. In particular, we devise a batch
version of a model proposed originally by Berg et al. [Quant. Fin. 1 (2001)
203], and convert the coupled multi-agent processes into an effective-agent
problem from which the dynamical order parameters in ergodic regimes can be
derived self-consistently together with the corresponding phase structure. Our
dynamical study complements and extends the available static theory. Results
are confirmed by numerical simulations.Comment: minor revision of text, accepted by JSTA
Approximating RR Lyrae light curves using cubic polynomials
In this paper, we use cubic polynomials to approximate RR Lyrae light curves
and apply the method to HST data of RR Lyraes in the halo of M31. We compare
our method to the standard method of Fourier decomposition and find that the
method of cubic polynomials eliminates virtually all ringing effects and does
so with significantly fewer parameters than the Fourier technique. Further, for
RRc stars the parameters in the fit are all physical. Our study also reveals a
number of additional periodicites in this data not found previously: we find 23
RRc stars, 29 RRab stars and 3 multiperiodic stars.Comment: 6 pages, MNRAS accepte
Status of the Whipple Observatory Cerenkov air shower imaging telescope array
Recently the power of the Cerenkov imaging technique in Very High Energy gamma-ray astronomy was demonstrated by the detection of the Crab nebula at high statistical significance. In order to further develop this technique to allow the detection of weaker or more distant sources a second 10 m class reflector was constructed about 120 m from the original instrument. The addition of the second reflector will allow both a reduction in the energy threshold and an improvement in the rejection of the hadronic background. The design and construction of the second reflector, Gamma Ray Astrophysics New Imaging TElescope (GRANITE) is described
The Exceptionally Luminous Type Ia Supernova 2007If
SN 2007if was the third over-luminous Type Ia supernova (SN Ia) detected after 2003fg and 2006gz. We present the photometric and spectroscopic observations of the SN and its host by ROTSE-III, HET, and Keck. From the H a line identified in the host spectra, we determine a redshift of 0.0736. At this distance, the SN reached an absolute magnitude of -20.4, brighter than any other SNe Ia ever observed. If the source of luminosity is radioactive decay, a large amount of radioactive nickel (similar to 1.5 M(circle dot)) is required to power the peak luminosity, more than can be produced realistically in a Chandrasekhar mass progenitor. Low expansion velocity, similar to that of 2003fg, is also measured around the maximum light. The observations may suggest that SN 2007if was from a massive white dwarf progenitor, plausibly exploding with mass well beyond 1.4 M(circle dot). Alternatively, we investigate circumstellar interaction that may contribute to the excess luminosity.NASA NNX-08AN25G, NNX-08AV63GNSF AST-0707769, PHY-0801007Australian Research CouncilUniversity of New South WalesUniversity of TexasUniversity of MichiganAstronom
New Methods in Creating Transdisciplinary Science Policy Research Agendas: The Case of Legislative Science Advice
In transdisciplinary fields such as science policy, research agendas do not evolve organically from within disciplines but instead require stakeholders to engage in active co-creation. ‘Big questions’ exercises fulfill this need but simultaneously introduce new challenges in their subjectivity and potential bias. By applying Q methodology to an exercise in developing an international collaborative research agenda for legislative science advice (LSA), we demonstrate a technique to illustrate stakeholder perspectives. While the LSA international respondents—academics, practitioners, and policymakers—demonstrated no difference in their research priorities across advisory system roles, the analysis by developing and developed nation status revealed both common interests in institutional- and systems-level research and distinct preferences. Stakeholders in developing nations prioritized the design of advisory systems, especially in low- and middle-income countries, while those in developed countries emphasized policymaker evidence use. These differences illustrate unique regional research needs that should be met through an international agenda for LSA
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