1,068 research outputs found

    Hydrogenic Transitions in Multiply Charged Fe and Ni Ions

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    Ten lines in the range 3880≦λ≦5666 Å in the beam-foil spectrum of iron have been identified with specific hydrogenic transitions in Fe iv-viii. The same transitions were observed from Ni and Ar beams. Deviations from the hydrogenic wavelengths are shown to be consistent with that expected from core polarization. The absence of these lines in astrophysical sources is discussed. A wavelength table is presented for identification of hydrogenic transitions to be expected in beam-foil spectra

    Blue flag with yellow tiger? Flags, authenticity and identity

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    The Flag of the Formosa Republic in the collection of the National Taiwan Museum is a national icon. It is a copy of one made in 1895 to mark the formation of a new Taiwanese republic; this replica, described in a contemporary newspaper account as an exact copy, was made in Japan in 1909. The painted flag was an intriguing puzzle. Instrumental analysis and a close study of the flag itself and of surviving historic photographs and records were used to try to establish whether what looked like later additions and repairs were actually part of the original construction. An international team of conservators and scientists from Taiwan, the UK, the USA and Germany carried out the investigation and the conservation treatment. Although dye analysis was inconclusive and it has not yet been possible to ascertain the original colour, it was felt that an addition in the upper right corner and some of the repairs could well be part of the original construction and these were left in situ though other repairs were removed. The paper lining was removed, revealing that the flag was painted on both sides. The fabric was cleaned using a vacuum suction table, while the paint surface was cleaned with swabs. The flag was supported using an adhesive treatment with Lascaux acrylic resin

    An Analysis of the Source of Competencies Acquired by Principals in the Omaha Public Schools

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    Questions are often asked about the extent and nature of qualifications needed to become an effective school principal. Are there certain personal qualifications which help a principal operate effectively and implement change within his or her school? A person looking toward possible future administrative duties, or a current school administrator is likely concerned with effective decision making and problem solving within a framework of expectations from superiors, subordinates, the public and government funding sources

    Irish GDP between the Famine and the First World War : Estimates Based on a Dynamic Factor Model

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    A major issue in Irish economic history is the lack of historical national accounts before the interwar period. This paper addresses the gap with new annual estimates of real GDP between 1842 and 1913 using an indirect estimation technique based on a set of macroeconomic variables and a dynamic factor model. Three major results emerge from the data. First, per capita growth was faster in this period than anywhere in Europe. Second, aggregate output contracted by more than a third during the Great Famine of the 1840s, but had recovered its level and closed the output gap by the end of the decade. Third, the volatility of the business cycle fell by nearly three quarters in the second half of the sample

    Surface-directed spinodal decomposition in the pseudobinary alloy (HfO_2)_x(SiO_2)_{1-x}

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    Hf silicate films (HfO_2)_{0.25}(SiO_2)_{0.75} with thicknesses in the range 4-20 nm were grown on silicon substrate by atomic layer deposition at 350 deg.C.The Hf distributions in as-grown and 800 deg.C annealed films were investigated by high resolution transmission electron microscopy (HRTEM), angle-resolved x-ray photoelectron spectroscopy (ARXPS) and medium energy ion scattering (MEIS). HRTEM images show a layered structure in films thinner than 8 nm. The ARXPS data also reveal a non-uniform distribution of Hf throughout the film depth. Diffusion of SiO_2 to the film surface after a longer time anneal was observed by MEIS. All these observations provide evidence for surface-directed spinodal decomposition in the pseudobinary (HfO_2)_x(SiO_2)_{1-x} alloy system.Comment: 1o figures, one tabl

    Hydraulic redistribution: limitations for plants in saline soils

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    Hydraulic redistribution (HR), the movement of water from wet to dry patches in the soil via roots, occurs in different ecosystems and plant species. By extension of the principle that HR is driven by gradients in soil water potential, HR has been proposed to occur for plants in saline soils. Despite the inherent spatial patchiness and salinity gradients in these soils, the lack of direct evidence of HR in response to osmotic gradients prompted us to ask the question: are there physical or physiological constraints to HR for plants in saline environments? We propose that build-up of ions in the root xylem sap and in the leaf apoplast, with the latter resulting in a large predawn disequilibrium of water potential in shoots compared with roots and soil, would both impede HR. We present a conceptual model that illustrates how processes in root systems in heterogeneous salinity with water potential gradients, even if equal to those in non-saline soils, will experience a dampened magnitude of water potential gradients in the soil–plant continuum, minimizing or preventing HR. Finally, we provide an outlook for understanding the relevance of HR for plants in saline environments by addressing key research questions on plant salinity toleranc

    Transpiration by trees on land with shallow water-tables: a survey of the literature suggests that transpiration is affected by soil texture

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    This chapter surveys the literature relating site conditions to wateruse by stands of trees growing above shallow watertables. Analysis of the data suggests that transpiration by stands of trees is affected by Epan, depth of the watertable, planting density and soil texture
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