8,339 research outputs found
Heating and cooling a tri-level house with a hydronic baseboard-valance system
Cover title.Prepared as part of an investigation conducted by the Engineering Experiment Station, University of Illinois at Urbana-Champaign
A Persistent High-Energy Flux from the Heart of the Milky Way : Integral's view of the Galactic Center
The Ibis/Isgri imager on Integral detected for the first time a hard X-ray
source, IGR J17456-2901, located within 1' of Sgr A* over the energy range
20-100 keV. Here we present the results of a detailed analysis of ~7 Ms of
Integral observations of the GC. With an effective exposure of 4.7 Ms we have
obtained more stringent positional constraints on this HE source and
constructed its spectrum in the range 20-400 keV. Furthermore, by combining the
Isgri spectrum with the total X-ray spectrum corresponding to the same physical
region around SgrA* from XMM data, and collected during part of the Integral
observations, we constructed and present the first accurate wide band HE
spectrum for the central arcmins of the Galaxy. Our complete analysis of the
emission properties of IGR shows that it is faint but persistent with no
variability above 3 sigma contrary to what was alluded to in our first paper.
This result, in conjunction with the spectral characteristics of the X-ray
emission from this region, suggests that the source is most likely not
point-like but, rather, that it is a compact, yet diffuse, non-thermal emission
region. The centroid of IGR is estimated to be R.A.=17h45m42.5,
decl.=-28deg59'28'', offset by 1' from the radio position of Sgr A* and with a
positional uncertainty of 1'. Its 20-400 keV luminosity at 8 kpc is L=5.4x10^35
erg/sec. Very recently, Hess detected of a source of ~TeV g-rays also located
within 1' of Sgr A*. We present arguments in favor of an interpretation
according to which the photons detected by Integral and Hess arise from the
same compact region of diffuse emission near the central BH and that the
supernova remnant Sgr A East could play an important role as a contributor of
very HE g-rays to the overall spectrum from this region.Comment: 14 pages, 11 figures, Accepted for publication in Ap
Troubles with Bayesianism: An introduction to the psychological immune system
A Bayesian mind is, at its core, a rational mind. Bayesianism is thus well-suited to predict and explain mental processes that best exemplify our ability to be rational. However, evidence from belief acquisition and change appears to show that we do not acquire and update information in a Bayesian way. Instead, the principles of belief acquisition and updating seem grounded in maintaining a psychological immune system rather than in approximating
a Bayesian processor
Io: IUE observations of its atmosphere and the plasma torus
Two of the main components of the atmosphere of Io, neutral oxygen and sulfur, were detected with the IUE. Four observations yield brightnesses that are similar, regardless of whether the upstream or the downstream sides of the torus plasma flow around Io is observed. A simple model requires the emissions to be produced by the interaction of O and S columns in the exospheric range with 2 eV electrons. Cooling of the 5 eV torus electrons is required prior to their interaction with the atmosphere of Io. Inconsistencies in the characteristics of the spectra that cannot be accounted for in this model require further analysis with improved atomic data. The Io plasma torus was monitored with the IUE. The long-term stability of the warm torus is established. The observed brightnesses were analyzed using a model of the torus, and variations of less than 30 percent in the composition are observed, the quantitative results being model dependent
Association of Mesocotyl and Coleptile Elongation with Seeding Vigor in Rice
Three experiments were conducted to evaluate the relationship of mesocotyl and coleoptile elongation to seedling vigor and plant height in rice (Oryza sativa). A laboratory experiment was conducted to evaluate the potential lengths of the mesocotyl and coleoptile of semidwarf and standard rice genotypes. Four genotypes exhibited inherent differences in their ability for mesocotyl and coleoptile elongation. The semidwarf genotypes (\u27M-101 \u27 and RU 7703008) showed reduced mesocotyls, coleoptiles, and total lengths (mesocotyl + coleoptile); whereas, the tall plant type (\u27L-201\u27 and \u27Labelle\u27) had comparatively longer mesocotyls, coleoptiles, and total lengths. Itis assumed that mesocotyl elongation is the most important of the three parameters evaluated in seedling vigor, but total length is the least variable. Significant differences were detected among seeding depths and genotypes in the greenhouse experiment for emergence percentage, emergence index, coleoptile, and mesocotyl lengths. The field experiment verified that the low seedling vigor was due to the shorter mesocotyls and coleoptiles of the semidwarf genotypes in this test and was primarily responsible for poor stand establishment
The Proposed High Energy Telescope (HET) for EXIST
The hard X-ray sky now being studied by INTEGRAL and Swift and soon by NuSTAR
is rich with energetic phenomena and highly variable non-thermal phenomena on a
broad range of timescales. The High Energy Telescope (HET) on the proposed
Energetic X-ray Imaging Survey Telescope (EXIST) mission will repeatedly survey
the full sky for rare and luminous hard X-ray phenomena at unprecedented
sensitivities. It will detect and localize (<20", at 5 sigma threshold) X-ray
sources quickly for immediate followup identification by two other onboard
telescopes - the Soft X-ray imager (SXI) and Optical/Infrared Telescope (IRT).
The large array (4.5 m^2) of imaging (0.6 mm pixel) CZT detectors in the HET, a
coded-aperture telescope, will provide unprecedented high sensitivity (~0.06
mCrab Full Sky in a 2 year continuous scanning survey) in the 5 - 600 keV band.
The large field of view (90 deg x 70 deg) and zenith scanning with
alternating-orbital nodding motion planned for the first 2 years of the mission
will enable nearly continuous monitoring of the full sky. A 3y followup pointed
mission phase provides deep UV-Optical-IR-Soft X-ray and Hard X-ray imaging and
spectroscopy for thousands of sources discovered in the Survey. We review the
HET design concept and report the recent progress of the CZT detector
development, which is underway through a series of balloon-borne wide-field
hard X-ray telescope experiments, ProtoEXIST. We carried out a successful
flight of the first generation of fine pixel large area CZT detectors
(ProtoEXIST1) on Oct 9, 2009. We also summarize our future plan (ProtoEXIST2 &
3) for the technology development needed for the HET.Comment: 10 pages, 13 figures, 2 tables, SPIE Conference "Astronomical
Telescopes and Instrumentation 2010"; to appear in Proceedings SPIE (2010
Dynamics of Dissipative Quantum Systems--from Path Integrals to Master Equations
The path integral approach offers not only an exact expression for the non-
equilibrium dynamics of dissipative quantum systems, but is also a convenient
starting point for perturbative treatments. An alternative way to explore the
influence of friction in the quantum realm is based on master equations which
require, however, in one or the other aspect approximations. Here it is
discussed under which conditions and limitations Markovian master equations can
be derived from exact path integrals thus providing a firm basis for their
applicability.Comment: 10 pages, 1 figur
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