781 research outputs found

    Anisotropic Distribution of SDSS Satellite Galaxies: Planar (not Polar) Alignment

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    The distribution of satellite galaxies relative to isolated host galaxies in the Sloan Digital Sky Survey (SDSS) is investigated. Host-satellite systems are selected using three different methods, yielding samples of ~3300, ~1600, and \~950 satellites. In the plane of the sky, the distributions of all three samples show highly significant deviations from circular symmetry (> 99.99%, > 99.99%, and 99.79% confidence levels, respectively), and the degree of anisotropy is a strong function of the projected radius, r_p, at which the satellites are found. For r_p < 100 kpc, the SDSS satellites are aligned preferentially with the major axes of the hosts. This is in stark contrast to the Holmberg effect, in which satellites are aligned with the minor axes of host galaxies. The degree of anisotropy in the distribution of the SDSS satellites decreases with r_p and is consistent with an isotropic distribution at of order the 1-sigma level for 250 kpc < r_p < 500 kpc.Comment: ApJ Letters (in press); Discussion section substantially revised, SDSS DR3 included in the analysis, no significant changes to the result

    3/2 Firefighters are not enough

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    The firefighter problem is a monotone dynamic process in graphs that can be viewed as modeling the use of a limited supply of vaccinations to stop the spread of an epidemic. In more detail, a fire spreads through a graph, from burning vertices to their unprotected neighbors. In every round, a small amount of unburnt vertices can be protected by firefighters. How many firefighters per turn, on average, are needed to stop the fire from advancing? We prove tight lower and upper bounds on the amount of firefighters needed to control a fire in the Cartesian planar grid and in the strong planar grid, resolving two conjectures of Ng and Raff.Comment: 8 page

    The properties of highly luminous IRAS galaxies

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    From a complete sample of 154 galaxies identified with IRAS sources in a 304 sq deg area centered on the South Galactic Pole, a subsample of 58 galaxies with L sub IR/L sub B > 3 was chosen. Low resolution spectra were obtained for 30% of the subsample and redshifts and relative emission line intensities were derived. As a class these galaxies are very luminous with = 2.9 x 10 to the 11th power L sub 0 and (L sub IR) max = 1.3 x 10 to the 12th power L sub 0. CCD images and JHK photometry were obtained for many of the subsample. The galaxies are for the most part newly identified and are optically faint, with a majority showing evidence of a recent interaction. Radio continuum observations of all galaxies of the subsample were recently obtained at 20 cm VLA with about 75% being detected in a typical integration time of about 10 minutes

    Two new pulsating hot subdwarf stars from the Edinburgh-Cape survey

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    We report the discovery of very rapid pulsations in two hot subdwarf stars from the Edinburgh- Cape blue object survey. The short periods, small amplitudes and multiperiodicity establish these stars as members of the class of rapidly-pulsating sdB stars. The spectrograms of both stars, however, show relatively strong He II 4686 and they are therefore more properly classified as sdOB. The light curve of EC 01541?1409 is dominated by two strong (?1 per cent) variations with frequencies near 7114 and 7870 ?Hz (periods near 140.6 and 127.1 s), though at least five frequencies are present with amplitudes above about 0.002 mag. The light curve of EC 22221?3152 appears to be generated by at least 10 frequencies in the range 5670-11850 ?Hz (about 175-85 s) with amplitudes between about 0.01 and 0.001 mag, including the first overtone of the strongest variation. Somewhat surprisingly, this number of frequencies is detectable in observing runs as short as 3 h, probably due to the fact that the detected frequencies are well-separated.IS

    Adverse effects of routine bovine health treatments containing triclabendazole and synthetic pyrethroids on the abundance of dipteran larvae in bovine faeces

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    Macrocyclic lactone treatments for livestock can have detrimental effects on the arthropod populations in livestock faeces. For the last twenty years, avoidance of these products has been a standard recommendation on livestock farms that are managed for wildlife by the Royal Society for Protection of Birds (RSPB). However, the continued decline in the populations of birds (in particular the red-billed chough Pyrrhocorax pyrrhocorax) that are dependent on dung invertebrates on islands in the Inner Hebrides of Scotland prompted us to investigate the effects of livestock treatments that are commonly used on these islands. We conducted a replicated field plot study over two years to quantify the effects of livestock treatments containing copper, deltamethrin and triclabendazole on invertebrate density in pooled, artificial faecal pats on the island of Islay. We found that the density of arthropod larvae was significantly reduced by the triclabendazole and deltamethrin treatments in both years and by as much as 86% when the treatments were combined. Copper-containing boluses did not consistently affect abundance of arthropod larvae. These results suggest that veterinary treatment of livestock might contribute to a reduction in the food supply of chough

    Complexation of Cm(III) with the recombinant N-lobe of human serum transferrin studied by time-resolved laser fluorescence spectroscopy (TRLFS)

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    The complexation of Cm(III) with the recombinant N-lobe of human serum transferrin (hTf/2N) is investigated in the pH range from 4.0 to 11.0 using TRLFS. At pH [greater-than-or-equal] 7.4 a Cm(III) hTf/2N species is formed with Cm(III) bound at the Fe(III) binding site. The results are compared with Cm(III) transferrin interaction at the C-lobe and indicate the similarity of the coordination environment of the C- and N-terminal binding sites with four amino acid residues of the protein, two H2O molecules and three additional ligands (e.g. synergistic anions such as carbonate) in the first coordination sphere. Measurements at c(carbonate)tot = 0.23 mM (ambient carbonate concentration) and c(carbonate)tot = 25 mM (physiological carbonate concentration) show that an increase of the total carbonate concentration suppresses the formation of the Cm(III) hTf/2N species significantly. Additionally, the three Cm(III) carbonate species Cm(CO3)+, Cm(CO3)2- and Cm(CO3)33- are formed successively with increasing pH. In general, carbonate complexation is a competing reaction for both Cm(III) complexation with transferrin and hTf/2N but the effect is significantly higher for the half molecule. At c(carbonate)tot = 0.23 mM the complexation of Cm(III) with transferrin and hTf/2N starts at pH [greater-than-or-equal] 7.4. At physiological carbonate concentration the Cm(III) transferrin species II forms at pH [greater-than-or-equal] 7.0 whereas the Cm(III) hTf/2N species is not formed until pH > 10.0. Hence, our results reveal significant differences in the complexation behavior of the C-terminal site of transferrin and the recombinant N-lobe (hTf/2N) towards trivalent actinides

    The Edinburgh-Cape Blue Object Survey - III. Zone 2; galactic latitudes -30? > b > -40?

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    The Edinburgh–Cape Blue Object Survey seeks to identify point sources with an ultraviolet excess. Results for zone 2 of the survey are presented here, covering that part of the South Galactic Cap between 30◦ and 40◦ from the Galactic plane and south of about −12. ◦ 3 of declination. Edinburgh–Cape zone 2 comprises 66 UK Schmidt Telescope fields covering about 1730 deg2, in which we find some 892 blue objects, including 423 hot subdwarfs (∼47 per cent); 128 white dwarfs (∼14 per cent); 25 cataclysmic variables (∼3 per cent); 119 binaries (∼13 per cent), mostly composed of a hot subdwarf and a main-sequence F or G star; 66 horizontal branch stars (∼7 per cent) and 48 ‘star-like’ extragalactic objects (∼5 per cent). A further 362 stars observed in the survey, mainly low-metallicity F- and G-type stars, are also listed. Both low-dispersion spectroscopic classification and UBV photometry are presented for almost all of the hot objects and either spectroscopy or photometry (or both) for the cooler ones.Department of HE and Training approved lis

    Retinal Biomarker Discovery for Dementia in an Elderly Diabetic Population

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    Dementia is a devastating disease, and has severe implications on affected individuals, their family and wider society. A growing body of literature is studying the association of retinal microvasculature measurement with dementia. We present a pilot study testing the strength of groups of conventional (semantic) and texture-based (non-semantic) measurements extracted from retinal fundus camera images to classify patients with and without dementia. We performed a 500-trial bootstrap analysis with regularized logistic regression on a cohort of 1,742 elderly diabetic individuals (median age 72.2). Age was the strongest predictor for this elderly cohort. Semantic retinal measurements featured in up to 81% of the bootstrap trials, with arterial caliber and optic disk size chosen most often, suggesting that they do complement age when selected together in a classifier. Textural features were able to train classifiers that match the performance of age, suggesting they are potentially a rich source of information for dementia outcome classification

    Livestock management in red-billed chough feeding habitat in Great Britain and the Isle of Man

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    In Great Britain, red-billed chough (Pyrrhocorax pyrrhocorax) breed in discrete populations along the west coast: on Islay and Colonsay, in the Inner Hebrides of Scotland; on the Isle of Man; in Wales; and in Cornwall. Chough are dependent on pastures grazed by sheep or cattle, and their survival therefore depends on sympathetic management of grassland. The Scottish population is in decline, and all other populations are growing or stable. Sixty-three farmers in these regions whose farms were known to support feeding chough were asked questions about their farm management using a structured, questionnaire-based personal interview. Islay farms were significantly larger and had more grazing area, with the lowest stocking densities. Welsh farms had the least cropping area and the smallest number of cattle. Cornwall had the smallest number of sheep per farm. Welsh farms were more likely to not house cattle during winter. Liver fluke in sheep and ticks and tick-borne disease were a higher concern on Islay than other regions, and abortion in sheep was of highest concern on the Isle of Man. Islay farmers applied between 4× and 13× as many synthetic pyrethroid (SP) treatments to cattle per year than farmers at other regions, and the application rate of triclabendazole (TCBZ) to sheep was higher on Islay than other regions. The rate of application of other products, including macrocyclic lactones, did not differ among regions. The study described here shows clear differences in the farm grazing management, in the priority given to animal health problems and in the frequency of application of veterinary parasiticides among four regions that provide feeding habitat for chough in the United Kingdom. These differences suggest that the viability of chough populations might be favored by higher-intensity grazing and low rates of application of veterinary parasiticides of either the TCBZ or SP, or both classes of parasiticides
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