9,355 research outputs found
X-ray observations of the galaxy cluster PKS 0745-191: To the virial radius, and beyond
We measure X-ray emission from the outskirts of the cluster of galaxies PKS
0745-191 with Suzaku, determining radial profiles of density, temperature,
entropy, gas fraction, and mass. These measurements extend beyond the virial
radius for the first time, providing new information about cluster assembly and
the diffuse intracluster medium out to ~1.5 r_200, (r_200 ~ 1.7 Mpc ~ 15'). The
temperature is found to decrease by roughly 70 per cent from 0.3-1 r_200. We
also see a flattening of the entropy profile near the virial radius and
consider the implications this has for the assumption of hydrostatic
equilibrium when deriving mass estimates. We place these observations in the
context of simulations and analytical models to develop a better understanding
of non-gravitational physics in the outskirts of the cluster.Comment: 10 pages, 11 figures, accepted to MNRAS; expanded discussion of
analysis and uncertainties, results qualitatively unchange
"Valuing the Visual Disamenity of Offshore Wind Projects at Varying Distances from the Shore: An Application on the Delaware Shoreline"
Several offshore wind power projects are under consideration in the United States. A concern with any wind power project is the visual disamenity it may create. Using a stated preference choice model, we estimated the external costs to residents of the State of Delaware for offshore wind turbines located at different distances from the coast. The annual costs to inland residents was 9, 0 (200680, 35, and $27 for the same increments.Windfarms, View Disamenity, Valuation
Structural Control of Metamaterial Oscillator Strength and Electric Field Enhancement at Terahertz Frequencies
The design of artificial nonlinear materials requires control over the
internal resonant charge densities and local electric field distributions. We
present a MM design with a structurally controllable oscillator strength and
local electric field enhancement at terahertz frequencies. The MM consists of a
split ring resonator (SRR) array stacked above an array of nonresonant closed
conducting rings. An in-plane, lateral shift of a half unit cell between the
SRR and closed ring arrays results in a decrease of the MM oscillator strength
by a factor of 4 and a 40% change in the amplitude of the resonant electric
field enhancement in the SRR capacitive gap. We use terahertz time-domain
spectroscopy and numerical simulations to confirm our results and we propose a
qualitative inductive coupling model to explain the observed electromagnetic
reponse.Comment: 11 pages, 5 figure
Transiting Exoplanet Survey Satellite (TESS)
The Transiting Exoplanet Survey Satellite (TESS ) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its two-year mission, TESS will employ four wide-field optical CCD cameras to monitor at least 200,000 main-sequence dwarf stars with I_C (approximately less than) 13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from one month to one year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10-100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every four months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations
Paper Session III-C - Innovative Financing of a Large Space Project
This paper addresses the changes to the Space Frontier Operations, Inc. (SFO) Space Exploration Plan, (SEP) that was initially presented at the 37th. Space Congress in 1999.
Progress since last year will be presented briefly and the progress made in finding the correct financing vehicles will be presented in detail.
The SFO Space Exploration Project starts off as an international project that will present unique and difficult challenges to both the space and financial communities. The effects of these challenges will be discussed along with their impact to the process of raising capital for a project of this nature.
The rationale behind establishing a separate but complimentary corporation will be discussed. The relationship between the commercial corporation and SFO will be delineated. It will be shown that complimentary roles are not only possible but also highly desirable.
The way in which the SEP fits into the standard protocols used by the finance industry will be discussed. As the project proceeds to completion the issue of traditional financing with an Initial Public Offering will be addressed along with the possibility of bringing in one or more partners – either commercial or governmental.
Finally, the work of the supporting commercial corporation will be presented and the current status of the two corporations will be discussed
Decoupling Crossover in Asymmetric Broadside Coupled Split Ring Resonators at Terahertz Frequencies
We investigate the electromagnetic response of asymmetric broadside coupled
split ring resonators (ABC-SRRs) as a function of the relative in-plane
displacement between the two component SRRs. The asymmetry is defined as the
difference in the capacitive gap widths (\Delta g) between the two resonators
comprising a coupled unit. We characterize the response of ABC-SRRs both
numerically and experimentally via terahertz time-domain spectroscopy. As with
symmetric BC-SRRs (\Delta g=0 \mu m), a large redshift in the LC resonance is
observed with increasing displacement, resulting from changes in the capacitive
and inductive coupling. However, for ABC-SRRs, in-plane shifting between the
two resonators by more than 0.375Lo (Lo=SRR sidelength) results in a transition
to a response with two resonant modes, associated with decoupling in the
ABC-SRRs. For increasing \Delta g, the decoupling transition begins at the same
relative shift (0.375Lo), though with an increase in the oscillator strength of
the new mode. This strongly contrasts with symmetric BC-SRRs which present only
one resonance for shifts up to 0.75Lo. Since all BC-SRRs are effectively
asymmetric when placed on a substrate, an understanding of ABC-SRR behavior is
essential for a complete understanding of BC-SRR based metamaterials
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