726 research outputs found

    Initial test results on state estimation on the SCOLE mast

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    Modal state estimation tests are performed on the SCOLE mast for the fixed Shuttle platform case. Kalman filter state estimation results from a five mode computer model of the SCOLE mast, developed from a finite element analysis, are compared with those state estimates obtained from laboratory tests. Two comparison runs are presented, one an excitation of the first two bending modes, another, an excitation of the first torsional mode of the mast. Results from both runs show poor agreement in modal estimation between the computer model simulations and the laboratory test data. At present, the reason(s) for this poor performance is unknown. Both the laboratory hardware and software and the computer model are being checked for possible sources of errors. Further computer simulations as well as laboratory testing will be performed

    Electronic structure of NiS1x_{1-x}Sex_x across the phase transition

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    We report very highly resolved photoemission spectra of NiS(1-x)Se(x) across the so-called metal-insulator transition as a function of temperature as well as composition. The present results convincingly demonstrate that the low temperature, antiferromagnetic phase is metallic, with a reduced density of states at EF_F. This decrease is possibly due to the opening of gaps along specific directions in the Brillouin zone caused by the antiferromagnetic ordering.Comment: Revtex, 4 pages, 3 postscript figure

    Using infrared imagery to estimate white-tailed deer populations on the Pine Bluff Arsenal

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    Military installations present unique challenges to natural resource managers managing wildlife populations. For those species that are hunted or trapped, it is important to provide data to these installations for achieving sustainable harvests. Pine Bluff Arsenal (PBA), a military installation in southeastern Arkansas, manages for a host of wildlife species including white-tailed deer (Odocoileus virginianus). However, baseline data regarding population size for deer are lacking. We used infrared technology and distance sampling to estimate the size of the winter, post-harvest deer population on PBA. We identified 9 competing models. The best model provided an estimate of density of 0.245 deer/ha (CV = 43%) with a mean group size of 3.3 deer. This density estimate will serve as a baseline value for evaluating future management actions

    The Luminosity Function of Early-Type Galaxies at z~0.75

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    We measure the luminosity function of morphologically selected E/S0 galaxies from z=0.5z=0.5 to z=1.0z=1.0 using deep high resolution Advanced Camera for Surveys imaging data. Our analysis covers an area of 48\Box\arcmin (8×\times the area of the HDF-N) and extends 2 magnitudes deeper (I24I\sim24 mag) than was possible in the Deep Groth Strip Survey (DGSS). At 0.5<z<0.750.5<z<0.75, we find MB5logh0.7=21.1±0.3M_B^*-5\log h_{0.7}=-21.1\pm0.3 and α=0.53±0.2\alpha=-0.53\pm0.2, and at 0.75<z<1.00.75<z<1.0, we find MB5logh0.7=21.4±0.2M_B^*-5\log h_{0.7}=-21.4\pm0.2. These luminosity functions are similar in both shape and number density to the luminosity function using morphological selection (e.g., DGSS), but are much steeper than the luminosity functions of samples selected using morphological proxies like the color or spectral energy distribution (e.g., CFRS, CADIS, or COMBO-17). The difference is due to the `blue', (UV)0<1.7(U-V)_0<1.7, E/S0 galaxies, which make up to 30\sim30% of the sample at all magnitudes and an increasing proportion of faint galaxies. We thereby demonstrate the need for {\it both morphological and structural information} to constrain the evolution of galaxies. We find that the `blue' E/S0 galaxies have the same average sizes and Sersic parameters as the `red', (UV)0>1.7(U-V)_0>1.7, E/S0 galaxies at brighter luminosities (MB<20.1M_B<-20.1), but are increasingly different at fainter magnitudes where `blue' galaxies are both smaller and have lower Sersic parameters. Fits of the colors to stellar population models suggest that most E/S0 galaxies have short star-formation time scales (τ<1\tau<1 Gyr), and that galaxies have formed at an increasing rate from z8z\sim8 until z2z\sim2 after which there has been a gradual decline.Comment: 39 pages, 21 figures, accepted in A

    Instantons and Killing spinors

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    We investigate instantons on manifolds with Killing spinors and their cones. Examples of manifolds with Killing spinors include nearly Kaehler 6-manifolds, nearly parallel G_2-manifolds in dimension 7, Sasaki-Einstein manifolds, and 3-Sasakian manifolds. We construct a connection on the tangent bundle over these manifolds which solves the instanton equation, and also show that the instanton equation implies the Yang-Mills equation, despite the presence of torsion. We then construct instantons on the cones over these manifolds, and lift them to solutions of heterotic supergravity. Amongst our solutions are new instantons on even-dimensional Euclidean spaces, as well as the well-known BPST, quaternionic and octonionic instantons.Comment: 40 pages, 2 figures v2: author email addresses and affiliations adde

    Spin-Glass State in CuGa2O4\rm CuGa_2O_4

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    Magnetic susceptibility, magnetization, specific heat and positive muon spin relaxation (\musr) measurements have been used to characterize the magnetic ground-state of the spinel compound CuGa2O4\rm CuGa_2O_4. We observe a spin-glass transition of the S=1/2 Cu2+\rm Cu^{2+} spins below Tf=2.5K\rm T_f=2.5K characterized by a cusp in the susceptibility curve which suppressed when a magnetic field is applied. We show that the magnetization of CuGa2O4\rm CuGa_2O_4 depends on the magnetic histo Well below Tf\rm T_f, the muon signal resembles the dynamical Kubo-Toyabe expression reflecting that the spin freezing process in CuGa2O4\rm CuGa_2O_4 results Gaussian distribution of the magnetic moments. By means of Monte-Carlo simulati we obtain the relevant exchange integrals between the Cu2+\rm Cu^{2+} spins in this compound.Comment: 6 pages, 16 figure

    The Fading Optical Counterpart of GRB~970228, Six Months and One Year Later

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    We report on observations of the fading optical counterpart of the gamma-ray burst GRB 970228, made with the Hubble Space Telescope STIS CCD approximately six months after outburst and with the HST/NICMOS and Keck/NIRC approximately one year after outburst. The unresolved counterpart is detected by STIS at V=28.0 +/- 0.25, consistent with a continued power-law decline with exponent -1.14 +/- 0.05. The counterpart is located within, but near the edge of, a faint extended source with diameter ~0."8 and integrated magnitude V=25.8 +/- 0.25. A reanalysis of HST and NTT observations performed shortly after the burst shows no evidence of proper motion of the point source or fading of the extended emission. Only the extended source is visible in the NICMOS images with a magnitude of H=23.3 +/- 0.1. The Keck observations find K = 22.8 +/- 0.3. Several distinct and independent means of deriving the foreground extinction in the direction of GRB 970228 all agree with A_V = 0.75 +/- 0.2. After adjusting for Galactic extinction, we find that the size of the observed extended emission is consistent with that of galaxies of comparable magnitude found in the Hubble Deep Field (HDF) and other deep HST images. Only 2% of the sky is covered by galaxies of similar or greater surface brightness; therefore the extended source is almost certainly the host galaxy. Additionally, we find that the extinction-corrected V - H and V - K colors of the host are as blue as any galaxy of comparable or brighter magnitude in the HDF. Taken in concert with recent observations of GRB 970508, GRB 971214, and GRB 980703 our work suggests that all four GRBs with spectroscopic identification or deep multicolor broad-band imaging of the host lie in rapidly star-forming galaxies.Comment: 24 pages, Latex, 4 PostScript figures, to appear in the May 10 issue of The Astrophysical Journal (Note: displayed abstract is abridged

    Spatiotemporal Variation in Avian Migration Phenology: Citizen Science Reveals Effects of Climate Change

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    A growing number of studies have documented shifts in avian migratory phenology in response to climate change, and yet there is a large amount of unexplained variation in the magnitude of those responses across species and geographic regions. We use a database of citizen science bird observations to explore spatiotemporal variation in mean arrival dates across an unprecedented geographic extent for 18 common species in North America over the past decade, relating arrival dates to mean minimum spring temperature. Across all species and geographic locations, species shifted arrival dates 0.8 days earlier for every °C of warming of spring temperature, but it was common for some species in some locations to shift as much as 3–6 days earlier per °C. Species that advanced arrival dates the earliest in response to warming were those that migrate more slowly, short distance migrants, and species with broader climatic niches. These three variables explained 63% of the interspecific variation in phenological response. We also identify a latitudinal gradient in the average strength of phenological response, with species shifting arrival earlier at southern latitudes than northern latitudes for the same degree of warming. This observation is consistent with the idea that species must be more phenologically sensitive in less seasonal environments to maintain the same degree of precision in phenological timing

    Smoke rings:towards a comprehensive tobacco free policy for the Olympic Games

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    Background The tobacco industry has long sought affiliation with major sporting events, including the Olympic Games, for marketing, advertising and promotion purposes. Since 1988, each Olympic Games has adopted a tobacco-free policy. Limited study of the effectiveness of the smoke-free policy has been undertaken to date, with none examining the tobacco industry's involvement with the Olympics or use of the Olympic brand. Methods and Findings A comparison of the contents of Olympic tobacco-free policies from 1988 to 2014 was carried out by searching the websites of the IOC and host NOCs. The specific tobacco control measures adopted for each Games were compiled and compared with measures recommended by the WHO Tobacco Free Sports Initiative and Article 13 of the Framework Convention on Tobacco Control (FCTC). This was supported by semi-structured interviews of key informants involved with the adoption of tobacco-free policies for selected games. To understand the industry's interests in the Olympics, the Legacy Tobacco Documents Library (http://legacy.library.ucsf.edu) was systematically searched between June 2013 and August 2014. Company websites, secondary sources and media reports were also searched to triangulate the above data sources. This paper finds that, while most direct associations between tobacco and the Olympics have been prohibited since 1988, a variety of indirect associations undermine the Olympic tobacco-free policy. This is due to variation in the scope of tobacco-free policies, limited jurisdiction and continued efforts by the industry to be associated with Olympic ideals. Conclusions The paper concludes that, compatible with the IOC's commitment to promoting healthy lifestyles, a comprehensive tobacco-free policy with standardized and binding measures should be adopted by the International Olympic Committee and all national Olympic committees
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