1,899 research outputs found

    Matrilines in Neolithic cattle from Orkney, Scotland reveals complex husbandry patterns of ancestry

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    mtDNA, isotopic and archaeozoological analyses of cattle teeth and bones from the Late Neolithic site of Links of Noltland, Orkney, Scotland revealed these animals followed similar grazing regimes but displayed diverse genetic origins and included one cattle skull that carried an aurochs (wild cattle) genetic haplotype. Morphometric analyses indicate the presence of some cattle larger than published dimensions of Neolithic domestic cattle. Several explanations for these finding are possible but may be the evidence of a complex pattern of domestic cattle introductions into Neolithic Orkney and interbreeding between domestic and wild cattle

    Some Structural and Thermal Characteristics of Snow Shelters

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    Reports investigations of dome-shaped shelters constructed in Alaska during winter 1955-56, some of loose, unconsolidated snow at the Arctic Aeromedical Laboratory, near Fairbanks, others of snow blocks on sea ice at Barter Island (70 08 N, 143 40 W). Pneumatic forms such as inflated weather balloons were useful, but not indispensable, in the loose snow type. Due to compaction, the density of the snow increased during construction from 0.22 gm/cu cm to 0.28 gm/cu cm and the hardness range from 8-80 gm/sq cm to 200-850 gm/sq cm Air temperatures in and outside both occupied and unoccupied shelters of this type (tabulated) demonstrate the efficacy of snow as an insulator and thermal advantages derived from ground heat. Inside temperature close to that at the ground surface, remained nearly constant (15-20 F) while outside temperatures ranged from -12 to -40 F Shelters were warmer during occupancy. In the snow-block shelters built on bare sea ice and on an 18 in deep drift, temperatures varied from 10-19 F at the top, 7-20 F in the center, and 7-18 F at the floor, while outside temperatures ranged from -2 to -5 F; thus subnivean warmth on sea ice can also be utilized. The temperature in a 2.5 ft deep trench in a drift, covered with a roof of horizontal snow blocks, was 20-24 F at the sleeping level 6 in above the floor

    Study of HST counterparts to Chandra X-ray sources in the Globular Cluster M71

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    We report on archival Hubble Space Telescope (HST) observations of the globular cluster M71 (NGC 6838). These observations, covering the core of the globular cluster, were performed by the Advanced Camera for Surveys (ACS) and the Wide Field Planetary Camera 2 (WFPC2). Inside the half-mass radius (r_h = 1.65') of M71, we find 33 candidate optical counterparts to 25 out of 29 Chandra X-ray sources while outside the half-mass radius, 6 possible optical counterparts to 4 X-ray sources are found. Based on the X-ray and optical properties of the identifications, we find 1 certain and 7 candidate cataclysmic variables (CVs). We also classify 2 and 12 X-ray sources as certain and potential chromospherically active binaries (ABs), respectively. The only star in the error circle of the known millisecond pulsar (MSP) is inconsistent with being the optical counterpart. The number of X-ray faint sources with L_x>4x10^{30} ergs/s (0.5-6.0 keV) found in M71 is higher than extrapolations from other clusters on the basis of either collision frequency or mass. Since the core density of M71 is relatively low, we suggest that those CVs and ABs are primordial in origin.Comment: 12 pages, 6 figures. Accepted for publication in Astronomy and Astrophysic

    Diving behavior of the Emperor Penguin, Aptenodytes forsteri

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    Superconductivity in Organic Compounds with Pseudo-Triangular Lattice

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    We study spin fluctuation (SF) mediated superconductivity (SC) in a half-filled square lattice Hubbard model with the transfer matrices -t between nearest neighbor sites and -t' between a half of next nearest neighbor sites neighboring along only one of the directions, considering application of this model to organic kappa-(BEDT-TTF)2X compounds. Varying the t'/t value from 0 to 1, one can interpolate between a square and an equilateral triangular lattice, the latter giving frustration to antiferromagnetically (AF) coupled spin systems. Within the fluctuation exchange (FLEX) approximation, we calculate chi(q,omega), Tc and the SC order parameter for various model parameter values and find that both AF and SC are suppressed as one approaches the frustration geometry or |(t'/t)-1| \to 0. The SC phase, however, extends beyond the AF phase boundary fairly close to t'/t=1 for realistic U/t values. The order parameter is of x2-y2-type for t'/t1.Comment: 4 pages, 5 eps figures, to appear in J. Phys. Soc. Jp

    Study of material homogeneity in the long fiber thermoset injection molding process by image texture analysis

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    To quantify the homogeneity of fiber dispersion in short fiber-reinforced polymer composites, a method for image texture analysis of 3-dimensional X-ray micro computed tomography (µCT) images is presented in this work. The adaption of the method to the specific requirements of the composite material is accomplished using a statistical region merging approach. Subsequently, the method is applied for evaluating the homogeneity of specimens from an intermediate step of the long fiber thermoset injection molding process as well as molded parts. This new injection molding process enables the manufacturing of parts with a flexible combination of short and long glass fibers. By using a newly developed screw element based on the Maddock mixing element design, the material homogeneity of parts molded in the long fiber injection molding process is improved

    The shape of the CMB lensing bispectrum

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    Lensing of the CMB generates a significant bispectrum, which should be detected by the Planck satellite at the 5-sigma level and is potentially a non-negligible source of bias for f_NL estimators of local non-Gaussianity. We extend current understanding of the lensing bispectrum in several directions: (1) we perform a non-perturbative calculation of the lensing bispectrum which is ~10% more accurate than previous, first-order calculations; (2) we demonstrate how to incorporate the signal variance of the lensing bispectrum into estimates of its amplitude, providing a good analytical explanation for previous Monte-Carlo results; and (3) we discover the existence of a significant lensing bispectrum in polarization, due to a previously-unnoticed correlation between the lensing potential and E-polarization as large as 30% at low multipoles. We use this improved understanding of the lensing bispectra to re-evaluate Fisher-matrix predictions, both for Planck and cosmic variance limited data. We confirm that the non-negligible lensing-induced bias for estimation of local non-Gaussianity should be robustly treatable, and will only inflate f_NL error bars by a few percent over predictions where lensing effects are completely ignored (but note that lensing must still be accounted for to obtain unbiased constraints). We also show that the detection significance for the lensing bispectrum itself is ultimately limited to 9 sigma by cosmic variance. The tools that we develop for non-perturbative calculation of the lensing bispectrum are directly relevant to other calculations, and we give an explicit construction of a simple non-perturbative quadratic estimator for the lensing potential and relate its cross-correlation power spectrum to the bispectrum. Our numerical codes are publicly available as part of CAMB and LensPix.Comment: 32 pages, 10 figures; minor changes to match JCAP-accepted version. CMB lensing and primordial local bispectrum codes available as part of CAMB (http://camb.info/
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