16,639 research outputs found

    Egg-laying substrate selection for optimal camouflage by quail

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    Camouflage is conferred by background matching and disruption, which are both affected by microhabitat [1]. However, microhabitat selection that enhances camouflage has only been demonstrated in species with discrete phenotypic morphs [2 and 3]. For most animals, phenotypic variation is continuous [4 and 5]; here we explore whether such individuals can select microhabitats to best exploit camouflage. We use substrate selection in a ground-nesting bird (Japanese quail, Coturnix japonica). For such species, threat from visual predators is high [6] and egg appearance shows strong between-female variation [7]. In quail, variation in appearance is particularly obvious in the amount of dark maculation on the light-colored shell [8]. When given a choice, birds consistently selected laying substrates that made visual detection of their egg outline most challenging. However, the strategy for maximizing camouflage varied with the degree of egg maculation. Females laying heavily maculated eggs selected the substrate that more closely matched egg maculation color properties, leading to camouflage through disruptive coloration. For lightly maculated eggs, females chose a substrate that best matched their egg background coloration, suggesting background matching. Our results show that quail “know” their individual egg patterning and seek out a nest position that provides most effective camouflage for their individual phenotyp

    Quantitative infrared spectroscopy of minor constituents of the Earth's atmosphere

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    We obtain quantitative laboratory spectroscopic measurements of molecular constituents which are of importance in understanding the health of the Earth's atmosphere, and, in particular, emphasize those species which are important for understanding stratospheric kinetics or are used for long term monitoring of the stratosphere. Our measurements provide: (1) line and band intensity values which are needed to establish limits of detectability for as yet unobserved species and to quantify the abundance of those species which are observed; (2) line-positions, -half widths and pressure induced shifts are all needed for remote sensing techniques, and (3) data on the above basic molecular parameters at temperatures and pressures appropriate for the real atmosphere

    ECHO user's guide

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    There are no author-identified significant results in this report

    Compact steep-spectrum sources from the S4 sample

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    We present the results of 5-GHz observations with the VLA A-array of a sample of candidate Compact Steep Spectrum sources (CSSs) selected from the S4 survey. We also estimate the symmetry parameters of high-luminosity CSSs selected from different samples of radio sources, and compare these with the larger sources of similar luminosity to understand their evolution and the consistency of the CSSs with the unified scheme for radio galaxies and quasars. The majority of CSSs are likely to be young sources advancing outwards through a dense asymmetric environment. The radio properties of CSSs are found to be consistent with the unified scheme, in which the axes of the quasars are observed close to the line of sight, while radio galaxies are observed close to the plane of the sky.Comment: accepted for publication in mnras; 8 pages, figure 1 with 21 images, and two additional figures; 2 table

    Lymphoproliferative malignancies in association with endemic African Kaposi’s Sarcoma

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    A CAJM study on Lymphoproliferative malignancies observed at a teaching hospital in South Africa among black Africans.The association of classical Kaposi’s sarcoma with lymphoproliferative disorders is well known. However, far less is known about lymphoproliferative malignancies in endemic African Kaposi’s sarcoma. A review of 47 patients with the endemic type of Kaposi’s sarcoma treated at the Johannesburg Teaching Hospital Complex between 1980 and 1992 revealed four patients (8,5 pc) in whom Kaposi’s sarcoma was associated with a malignant lymphoma. Possible pathogenetic mechanisms are suggested and the current literature is reviewed

    Spectral/hp element methods: recent developments, applications, and perspectives

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    The spectral/hp element method combines the geometric flexibility of the classical h-type finite element technique with the desirable numerical properties of spectral methods, employing high-degree piecewise polynomial basis functions on coarse finite element-type meshes. The spatial approximation is based upon orthogonal polynomials, such as Legendre or Chebychev polynomials, modified to accommodate C0-continuous expansions. Computationally and theoretically, by increasing the polynomial order p, high-precision solutions and fast convergence can be obtained and, in particular, under certain regularity assumptions an exponential reduction in approximation error between numerical and exact solutions can be achieved. This method has now been applied in many simulation studies of both fundamental and practical engineering flows. This paper briefly describes the formulation of the spectral/hp element method and provides an overview of its application to computational fluid dynamics. In particular, it focuses on the use the spectral/hp element method in transitional flows and ocean engineering. Finally, some of the major challenges to be overcome in order to use the spectral/hp element method in more complex science and engineering applications are discussed
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