8,885 research outputs found

    Exploratory Pollen Analysis of Hargrove Lake, Davy Crockett National Forest Houston County, Texas

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    The objectives of this exploratory pollen analysis of selected samples from a sediment core taken at Hargrove Lake, Davy Crockett National Forest, Houston County, Texas, are to ascertain the quality of pollen preservation in the lake bottom matrix and to evaluate the potential of the pollen spectra deposited in the lake for providing information about former environmental conditions on Davy Crockett National Forest. Hargrove Lake is a natural lake in the floodplain of the Neches River in Houston County, Texas. The Hargrove Lake site (41H0150) lies a short distance to the west. The lake is presently is surrounded by a 10m wide stand of buttonbush (Cephalanthus). These plants are three m tall and have two to ten em diameter trunks. A woodland dominated by water oaks (Quercus nigra) and sweetgum (Liquidambar styraciflua) lies beyond the button bush. These trees are 30 to 40 m tall, and the woodland canopy is 90 to 98 percent closed. The lake is normally about 50 m wide by 200 m long, giving it a normal surface area of approximately 2.5 hectares. The mean depth of the lake at high water is about 90 em. Bedrock marl underlies the area, and the lake retains water during even the most severe droughts. It should provide a continuous pollen deposition record

    Diffractive X-ray Telescopes

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    Diffractive X-ray telescopes using zone plates, phase Fresnel lenses, or related optical elements have the potential to provide astronomers with true imaging capability with resolution several orders of magnitude better than available in any other waveband. Lenses that would be relatively easy to fabricate could have an angular resolution of the order of micro-arc-seconds or even better, that would allow, for example, imaging of the distorted space- time in the immediate vicinity of the super-massive black holes in the center of active galaxies What then is precluding their immediate adoption? Extremely long focal lengths, very limited bandwidth, and difficulty stabilizing the image are the main problems. The history, and status of the development of such lenses is reviewed here and the prospects for managing the challenges that they present are discussed.Comment: 46 pages, 15 figures, invited review paper to be published in a special issue on "X-Ray Focusing: Techniques and Applications" of the online journal "X-Ray Optics & Instrumentation

    Regenerative Cu/La zeolite supported desulfurizing sorbents

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    Efficient, regenerable sorbents for removal of H2S from fluid hydrocarbons such as diesel fuel at moderate condition comprise a porous, high surface area aluminosilicate support, suitably a synthetic zeolite, and most preferably a zeolite having a free lattice opening of at least 6 Angstroms containing from 0.1 to 0.5 moles of copper ions, lanthanum ions or their mixtures. The sorbent removes sulfur from the hydrocarbon fuel in high efficiency and can be repetitively regenerated without loss of activity

    Global Climate Change and Catholic Responsibility: Facts and Faith Response

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    Citation: Braun G, Hellwig MK, Byrnes WM (2007) Global Climate Change and Catholic Responsibility: Facts and Faith Response. Journal of Catholic Social Thought 4(2): 373-401. Abstract: The scientific evidence is now overwhelming that human activity is causing the Earth’s atmosphere to grow hotter, which is leading to global climate change. If current rates of greenhouse gas (GHG) emissions continue, it is predicted that there will be dramatic changes, including flooding, more intense heat waves and storms, and an increase in disease. Indigenous peoples and the poor will be most severely affected, as will Earth’s wild animals and plants, a quarter of which could become extinct in fifty years. We urgently need to switch to renewable (non-GHG emitting) energy sources, and try to live in a simpler, more sustainable way. In this article, a renewable energy expert, a biochemist, and a theologian have come together to describe the situation in which we find ourselves, and present ideas for a solution that incorporates Catholic social teaching

    IS LEONTIEF'S PARADOX APPLICABLE TO U.S. AGRICULTURAL TRADE?

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    The labor and capital intensities of U.S. agricultural trade during 1973, 1974, and 1976 are examined through an input-output model. The empirical results indicate that U.S. agricultural exports tend to be more capital intensive while agricultural imports are more labor intensive, a result counter to Leontief's paradox.International Relations/Trade,

    Portable random number generators

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    Computers are deterministic devices, and a computer-generated random number is a contradiction in terms. As a result, computer-generated pseudorandom numbers are fraught with peril for the unwary. We summarize much that is known about the most well-known pseudorandom number generators: congruential generators. We also provide machine-independent programs to implement the generators in any language that has 32-bit signed integers-for example C, C++, and FORTRAN. Based on an extensive search, we provide parameter values better than those previously available.Programming (Mathematics) ; Computers
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