2,088 research outputs found

    Discussion of: A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?

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    Discussion of "A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?" by B.B. McShane and A.J. Wyner [arXiv:1104.4002]Comment: Published in at http://dx.doi.org/10.1214/10-AOAS398J the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Properties of high emittance materials

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    High emittance coating materials for beryllium, niobium-zirconium compounds, and stainless steel used in spacecraft radiator

    Regional and seasonal patterns of epipelagic fish assemblages from the central California Current

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    The coastal Pacific Ocean off northern and central California encompasses the strongest seasonal upwelling zone in the California Current ecosystem. Headlands and bays here generate complex circulation features and confer unusual oceanographic complexity. We sampled the coastal epipelagic fish community of this region with a surface trawl in the summer and fall of 2000–05 to assess patterns of spatial and temporal community structure. Fifty-three species of fish were captured in 218 hauls at 34 fixed stations, with clupeiform species dominating. To examine spatial patterns, samples were grouped by location relative to a prominent headland at Point Reyes and the resulting two regions, north coast and Gulf of the Farallones, were plotted by using nonmetric multidimensional scaling. Seasonal and interannual patterns were also examined, and representative species were identified for each distinct community. Seven oceanographic variables measured concurrently with trawling were plotted by principal components analysis and tested for correlation with biotic patterns. We found significant differences in community structure by region, year, and season, but no interaction among main effects. Significant differences in oceanographic conditions mirrored the biotic patterns, and a match between biotic and hydrographic structure was detected. Dissimilarity between assemblages was mostly the result of differences in abundance and frequency of occurrence of about twelve common species. Community patterns were best described by a subset of hydrographic variables, including water depth, distance from shore, and any one of several correlated variables associated with upwelling intensity. Rather than discrete communities with clear borders and distinct member species, we found gradients in community structure and identified stations with similar fish communities by region and by proximity to features such as the San Francisco Bay

    Study to establish cost predictions for the production of Redox chemicals

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    The chromium and iron chloride chemicals are significant first costs for NASA Redox energy storage systems. This study was performed to determine the lowest cost at which chromium and iron chlorides could be obtained for a complex of redox energy storage systems. In addition, since the solutions gradually become intermixed during the course of operation of Redox units, it was an objective to evaluate schemes for regeneration of the operating solutions. Three processes were evaluated for the production of chromium and iron chlorides. As a basis for the preliminary plant design and economic evaluation, it was assumed that the plant would produce about 25,000 tons of contained chromium as CrCl3 and an equivalent molar quantity of FeCl2. Preliminary plant designs, including materials and energy balances and sizing of major equipment, were prepared, and capital and operating costs were estimated

    Agonistic behavior, social dominance, and predator evasion of Oncorhynchus mykiss from lake and stream parents: an evaluation of lacustrine refuges as a conservation strategy for threatened or endangered salmonids

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    Thesis (M.S.) University of Alaska Fairbanks, 2004The possibility of lakes providing temporary natural refugia for endangered salmonid populations, creating an alternative to hatchery propagation, is the context for this research. To investigate this possibility resident trout (Oncorhynchus mykiss) derived from a population that had been sequestered in a lake for seventy years were compared to fish from their founding anadromous steelhead trout population as well as to hybrid crosses of the two populations. Comparisons were made in the areas of aggression, dominance and predator evasion. In aggression trials the lake-derived population chased more than stream-derived O. mykiss at two life stages, age-0 and age-1. Lake-derived fry and the lake x stream hybrid fry also chased more than the stream x lake hybrid fry. Fin conditions (dorsal and pectoral fin lengths, an index of aggression) did not differ significantly. In dominance acquisition the stream x lake hybrid were least frequently dominant of all the crosstypes, and stream-derived parr were less dominant than lake-derived parr. Avoidance of a Dolly Varden predator by fry showed that the stream x lake hybrids achieved the highest survival rates. Seventy years of sequestration in a lake may be adequate time for divergence in aggressive behavior, social dominance and predator evasion between lake-resident and stream, O. mykiss populations

    Dual-band Monopole Antenna with Stagger-tuned Arms for Broadbanding

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    The paper describes a dual-band miniaturized printed monopole for integration in modern wireless systems. The printed monopole is augmented with two arms, resonant at slightly different frequencies, providing a broadened response for the upper band. The achieved bandwidth for the high band is 36%. These antennas are proposed for the emerging dual-mode multi-band WLAN transceivers, which operate over a wide range of bands as dictated by national authorities. Measured and simulated data, including return loss, antenna gain and radiation patterns, are presented. The numerical method employed was the finite integration technique

    The Cauchy problems for Einstein metrics and parallel spinors

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    We show that in the analytic category, given a Riemannian metric gg on a hypersurface M⊂ZM\subset \Z and a symmetric tensor WW on MM, the metric gg can be locally extended to a Riemannian Einstein metric on ZZ with second fundamental form WW, provided that gg and WW satisfy the constraints on MM imposed by the contracted Codazzi equations. We use this fact to study the Cauchy problem for metrics with parallel spinors in the real analytic category and give an affirmative answer to a question raised in B\"ar, Gauduchon, Moroianu (2005). We also answer negatively the corresponding questions in the smooth category.Comment: 28 pages; final versio

    Generic metrics and the mass endomorphism on spin three-manifolds

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    Let (M,g)(M,g) be a closed Riemannian spin manifold. The constant term in the expansion of the Green function for the Dirac operator at a fixed point p∈Mp\in M is called the mass endomorphism in pp associated to the metric gg due to an analogy to the mass in the Yamabe problem. We show that the mass endomorphism of a generic metric on a three-dimensional spin manifold is nonzero. This implies a strict inequality which can be used to avoid bubbling-off phenomena in conformal spin geometry.Comment: 8 page

    Surgery and the spinorial tau-invariant

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    We associate to a compact spin manifold M a real-valued invariant \tau(M) by taking the supremum over all conformal classes over the infimum inside each conformal class of the first positive Dirac eigenvalue, normalized to volume 1. This invariant is a spinorial analogue of Schoen's σ\sigma-constant, also known as the smooth Yamabe number. We prove that if N is obtained from M by surgery of codimension at least 2, then τ(N)≄min⁥{τ(M),Λn}\tau(N) \geq \min\{\tau(M),\Lambda_n\} with Λn>0\Lambda_n>0. Various topological conclusions can be drawn, in particular that \tau is a spin-bordism invariant below Λn\Lambda_n. Below Λn\Lambda_n, the values of τ\tau cannot accumulate from above when varied over all manifolds of a fixed dimension.Comment: to appear in CPD
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