285 research outputs found
Abstract Games of Argumentation Strategy and Game-Theoretical Argument Strength
We define a generic notion of abstract games of argumentation strategy for (attack-only and bipolar) argumentation frameworks, which are zero-sum games whereby two players put forward sets of arguments and get a reward for their combined choices. The value of these games, in the classical game-theoretic sense, can be used to define measures of (quantitative) game-theoretic strength of arguments, which are different depending on whether either or both players have an “agenda” (i.e. an argument they want to be accepted). We show that this general scheme captures as a special instance a previous proposal in the literature (single agenda, attack-only frameworks), and seamlessly supports the definition of a spectrum of novel measures of game-theoretic strength where both players have an agenda and/or bipolar frameworks are considered. We then discuss the applicability of these instances of game-theoretic strength in different contexts and analyse their basic properties
Current and Nascent SETI Instruments
Here we describe our ongoing efforts to develop high-performance and
sensitive instrumentation for use in the search for extra-terrestrial
intelligence (SETI). These efforts include our recently deployed Search for
Extraterrestrial Emissions from Nearby Developed Intelligent Populations
Spectrometer (SERENDIP V.v) and two instruments currently under development;
the Heterogeneous Radio SETI Spectrometer (HRSS) for SETI observations in the
radio spectrum and the Optical SETI Fast Photometer (OSFP) for SETI
observations in the optical band. We will discuss the basic SERENDIP V.v
instrument design and initial analysis methodology, along with instrument
architectures and observation strategies for OSFP and HRSS. In addition, we
will demonstrate how these instruments may be built using low-cost, modular
components and programmed and operated by students using common languages, e.g.
ANSI C.Comment: 12 pages, 5 figures, Original version appears as Chapter 2 in "The
Proceedings of SETI Sessions at the 2010 Astrobiology Science Conference:
Communication with Extraterrestrial Intelligence (CETI)," Douglas A. Vakoch,
Edito
Status of the UC-Berkeley SETI Efforts
We summarize radio and optical SETI programs based at the University of
California, Berkeley. The SEVENDIP optical pulse search looks for ns time scale
pulses at visible wavelengths using an automated 30 inch telescope. The ongoing
SERENDIP V.v sky survey searches for radio signals at the 300 meter Arecibo
Observatory. The currently installed configuration supports 128 million
channels over a 200 MHz bandwidth with ~1.6 Hz spectral resolution. SETI@home
uses the desktop computers of volunteers to analyze over 160 TB of data at
taken at Arecibo looking for two types of continuous wave signals and two types
of pulsed signals. A version to be released this summer adds autocorrelation
analysis to look for complex wave forms that have been repeated (and overlayed)
after a short delay. SETI@home will soon be processing data of Kepler exoplanet
systems collected at the GBT. The Astropulse project is the first SETI search
for s time scale dispersed pulses in the radio spectrum. We recently
reobserved 114 sky locations where microsecond pulses were detected. This data
is in process of being transferred to Berkeley for analysis.Comment: 8 pages, including 1 figure. Presented at SPIE Conf. 8152, San Diego,
CA, Aug 25, 201
Traintracks Through Calabi-Yaus: Amplitudes Beyond Elliptic Polylogarithms
We describe a family of finite, four-dimensional, -loop Feynman integrals
that involve weight- hyperlogarithms integrated over -dimensional
elliptically fibered varieties we conjecture to be Calabi-Yau. At three loops,
we identify the relevant K3 explicitly; and we provide strong evidence that the
four-loop integral involves a Calabi-Yau threefold. These integrals are
necessary for the representation of amplitudes in many theories---from massless
theory to integrable theories including maximally supersymmetric
Yang-Mills theory in the planar limit---a fact we demonstrate.Comment: 4+2 pages, 4 figures; references adde
Rosat, Asca and Osse Observations of the Broad Line Radio Galaxy 3C120
We present simultaneous observations of the superluminal radio galaxy 3C120
performed with the ASCA and GRO (OSSE) satellites on February-March 1994, as
well as an analysis of all the ROSAT archival data. The ASCA spectrum of this
object can be described by an absorbed (N_H=1.6e^21 cm^-2) power law with
photon index Gamma_ASCA=2 and a very broad sigma>0.8 keV intense iron line
(EW>400 eV) at ~ 6 keV. The combined ASCA--OSSE data do not exclude the
presence of a narrower (sigma=0.4 keV) and less intense (EW<300 eV) iron line
plus a hard component, corresponding either to reflection from an accretion
disk or to a flatter power law from a jet. However a single power law plus
broad Fe line is preferred from a statistical point of view by the ASCA data.
The ROSAT data yield a column density in excess of the Galactic value. The
spectral slopes, ranging from Gamma_ROSAT=2.5 to 3.3, are steeper than that
measured by ASCA, suggesting the presence of a soft excess. The 0.1-2 keV
power-law slope is variable and softer at higher intensity. These results show
that the combined soft and hard X-ray spectrum of 3C120 is rather complex. The
intrinsic absorption, the soft excess, and the iron line indicate that the
X-ray emission from this blazar-like radio galaxy is dominated by a
Seyfert-like component, at least in the 0.1-10keV energy band. The jet
contribution, if present, becomes important only at higher energies.Comment: 25 pages, Latex, 8 PostScript figures, to appear in The Astrophysical
Journa
Magnetic fields and accretion flows on the classical T Tauri star V2129 Oph
From observations collected with the ESPaDOnS spectropolarimeter, we report
the discovery of magnetic fields at the surface of the mildly accreting
classical T Tauri star V2129 Oph. Zeeman signatures are detected, both in
photospheric lines and in the emission lines formed at the base of the
accretion funnels linking the disc to the protostar, and monitored over the
whole rotation cycle of V2129 Oph. We observe that rotational modulation
dominates the temporal variations of both unpolarized and circularly polarized
line profiles. We reconstruct the large-scale magnetic topology at the surface
of V2129 Oph from both sets of Zeeman signatures simultaneously. We find it to
be rather complex, with a dominant octupolar component and a weak dipole of
strengths 1.2 and 0.35 kG, respectively, both slightly tilted with respect to
the rotation axis. The large-scale field is anchored in a pair of 2-kG unipolar
radial field spots located at high latitudes and coinciding with cool dark
polar spots at photospheric level. This large-scale field geometry is unusually
complex compared to those of non-accreting cool active subgiants with moderate
rotation rates. As an illustration, we provide a first attempt at modelling the
magnetospheric topology and accretion funnels of V2129 Oph using field
extrapolation. We find that the magnetosphere of V2129 Oph must extend to about
7R* to ensure that the footpoints of accretion funnels coincide with the
high-latitude accretion spots on the stellar surface. It suggests that the
stellar magnetic field succeeds in coupling to the accretion disc as far out as
the corotation radius, and could possibly explain the slow rotation of V2129
Oph. The magnetospheric geometry we derive produces X-ray coronal fluxes
typical of those observed in cTTSs.Comment: MNRAS, in press (18 pages, 17 figures
World checklist of hornworts and liverworts
A working checklist of accepted taxa worldwide is vital in achieving the goal of developing an online flora of all known plants by 2020 as part of the Global Strategy for Plant Conservation. We here present the first-ever worldwide checklist for liverworts (Marchantiophyta) and hornworts (Anthocerotophyta) that includes 7486 species in 398 genera representing 92 families from the two phyla. The checklist has far reaching implications and applications, including providing a valuable tool for taxonomists and systematists, analyzing phytogeographic and diversity patterns, aiding in the assessment of floristic and taxonomic knowledge, and identifying geographical gaps in our understanding of the global liverwort and hornwort flora. The checklist is derived from a working data set centralizing nomenclature, taxonomy and geography on a global scale. Prior to this effort a lack of centralization has been a major impediment for the study and analysis of species richness, conservation and systematic research at both regional and global scales. The success of this checklist, initiated in 2008, has been underpinned by its community approach involving taxonomic specialists working towards a consensus on taxonomy, nomenclature and distribution
Dark sectors 2016 Workshop: community report
This report, based on the Dark Sectors workshop at SLAC in April 2016,
summarizes the scientific importance of searches for dark sector dark matter
and forces at masses beneath the weak-scale, the status of this broad
international field, the important milestones motivating future exploration,
and promising experimental opportunities to reach these milestones over the
next 5-10 years
Research activity and the association with mortality.
INTRODUCTION: The aims of this study were to describe the key features of acute NHS Trusts with different levels of research activity and to investigate associations between research activity and clinical outcomes. METHODS: National Institute for Health Research (NIHR) Comprehensive Clinical Research Network (CCRN) funding and number of patients recruited to NIHR Clinical Research Network (CRN) portfolio studies for each NHS Trusts were used as markers of research activity. Patient-level data for adult non-elective admissions were extracted from the English Hospital Episode Statistics (2005-10). Risk-adjusted mortality associations between Trust structures, research activity and, clinical outcomes were investigated. RESULTS: Low mortality Trusts received greater levels of funding and recruited more patients adjusted for size of Trust (n = 35, 2,349 £/bed [95% CI 1,855-2,843], 5.9 patients/bed [2.7-9.0]) than Trusts with expected (n = 63, 1,110 £/bed, [864-1,357] p<0.0001, 2.6 patients/bed [1.7-3.5] p<0.0169) or, high (n = 42, 930 £/bed [683-1,177] p = 0.0001, 1.8 patients/bed [1.4-2.1] p<0.0005) mortality rates. The most research active Trusts were those with more doctors, nurses, critical care beds, operating theatres and, made greater use of radiology. Multifactorial analysis demonstrated better survival in the top funding and patient recruitment tertiles (lowest vs. highest (odds ratio & 95% CI: funding 1.050 [1.033-1.068] p<0.0001, recruitment 1.069 [1.052-1.086] p<0.0001), middle vs. highest (funding 1.040 [1.024-1.055] p<0.0001, recruitment 1.085 [1.070-1.100] p<0.0001). CONCLUSIONS: Research active Trusts appear to have key differences in composition than less research active Trusts. Research active Trusts had lower risk-adjusted mortality for acute admissions, which persisted after adjustment for staffing and other structural factors
The Iso2k Database: A global compilation of paleo-δ18O and δ2H records to aid understanding of Common Era climate
Reconstructions of global hydroclimate during the Common Era (CE; the past ~ 2000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ2H) isotopic composition of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 756 isotope records from the terrestrial and marine realms, including: glacier and ground ice (205); speleothems (68); corals, sclerosponges, and mollusks (145); wood (81); lake sediments and other terrestrial sediments (e.g., loess) (158); and marine sediments (99). Individual datasets have temporal resolutions ranging from sub-annual to centennial, and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and non-experts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across diverse archives and with climate model simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model-data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at: https://doi.org/10.6084/m9.figshare.11553162 (McKay and Konecky, 2020)
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