5,484 research outputs found

    Basic and regional characteristics of streamflow in the Upper Colorado River Basin: interim report

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    CER70-71GBE-HJMSS6.December 1970.Includes bibliographical reference (pages 23-24).Prepared for: Bureau of Reclamation, Division of Atmospheric Water Resources Management, Denver, Colorado, Project Skywater.This report describes the first phase of a research project concerned with two somewhat related subjects: 1. The study of the flow regimen of the rivers in the Upper Colorado River Basin and their relation to differences in geology, geomorphology, latitude, longitude, and physiographic parameters. 2. The application of such relations to the selection of hydrologically suitable basins for precipitation management. In this report, only general results about the flow characteristics of the streams in the Upper Colorado River Basin are presented. The determination of the streamflow characteristics was obtained from monthly flow data as published by the U.S. Geological Survey and corrected for diversions and regulations. Corrected records, stored on magnetic tape, for 707 stations were used in the study. From the monthly flow data mean yearly hydrographs have been computed for all stations. These hydrographs are expressed as specific yield in units of inches, cfs/sq. mi and liters per second per km2. The hydrographs are drawn on regular (linear), semi-logarithmic and double logarithmic scales. Monthly duration curves and mean yearly graphs of monthly coefficients of variation are also presented. This report contains a brief description of the methodology for the calculations, samples of computer output, tables of the calculated values and samples of various kinds of graphs which present in a concise and appealing visual way the characteristics of each gaging station. Maps with the results for the Colorado River Basin Project Area, a Bureau of Reclamation program of precipitation management in the San Juan Mountains area of Colorado, are given. A second report to be published later will contain an interpretation of the results and the implications for precipitation management.Under contract no. 14-06-D-6597

    Extrapolations of Lattice Meson Form Factors

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    We use chiral perturbation theory to study the extrapolations necessary to make physical predictions from lattice QCD data for the electromagnetic form factors of pseudoscalar mesons. We focus on the quark mass, momentum, lattice spacing, and volume dependence and apply our results to simulations employing mixed actions of Ginsparg-Wilson valence quarks and staggered sea quarks. To determine charge radii at quark masses on the lattices currently used, we find that all extrapolations except the one to infinite volume make significant contributions to the systematic error.Comment: 14pp, discussion and Ref. added for disconnected diagram

    Scaling of Crack Surfaces and Implications on Fracture Mechanics

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    The scaling laws describing the roughness development of crack surfaces are incorporated into the Griffith criterion. We show that, in the case of a Family-Vicsek scaling, the energy balance leads to a purely elastic brittle behavior. On the contrary, it appears that an anomalous scaling reflects a R-curve behavior associated to a size effect of the critical resistance to crack growth in agreement with the fracture process of heterogeneous brittle materials exhibiting a microcracking damage.Comment: Revtex, 4 pages, 3 figures, accepted for publication in Physical Review Letter

    Lie Superalgebras and the Multiplet Structure of the Genetic Code II: Branching Schemes

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    Continuing our attempt to explain the degeneracy of the genetic code using basic classical Lie superalgebras, we present the branching schemes for the typical codon representations (typical 64-dimensional irreducible representations) of basic classical Lie superalgebras and find three schemes that do reproduce the degeneracies of the standard code, based on the orthosymplectic algebra osp(5|2) and differing only in details of the symmetry breaking pattern during the last step.Comment: 34 pages, 9 tables, LaTe

    GeneRax: A Tool for Species-Tree-Aware Maximum Likelihood-Based Gene Family Tree Inference under Gene Duplication, Transfer, and Loss

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    Inferring phylogenetic trees for individual homologous gene families is difficult because alignments are often too short, and thus contain insufficient signal, while substitution models inevitably fail to capture the complexity of the evolutionary processes. To overcome these challenges, species-tree-aware methods also leverage information from a putative species tree. However, only few methods are available that implement a full likelihood framework or account for horizontal gene transfers. Furthermore, these methods often require expensive data preprocessing (e.g., computing bootstrap trees) and rely on approximations and heuristics that limit the degree of tree space exploration. Here, we present GeneRax, the first maximum likelihood species-tree-aware phylogenetic inference software. It simultaneously accounts for substitutions at the sequence level as well as gene level events, such as duplication, transfer, and loss relying on established maximum likelihood optimization algorithms. GeneRax can infer rooted phylogenetic trees for multiple gene families, directly from the per-gene sequence alignments and a rooted, yet undated, species tree. We show that compared with competing tools, on simulated data GeneRax infers trees that are the closest to the true tree in 90% of the simulations in terms of relative Robinson–Foulds distance. On empirical data sets, GeneRax is the fastest among all tested methods when starting from aligned sequences, and it infers trees with the highest likelihood score, based on our model. GeneRax completed tree inferences and reconciliations for 1,099 Cyanobacteria families in 8 min on 512 CPU cores. Thus, its parallelization scheme enables large-scale analyses. GeneRax is available under GNU GPL at https://github.com/BenoitMorel/GeneRax (last accessed June 17, 2020)
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