3,679 research outputs found

    Palynological age constraint of Les Vilelles unit, Catalan Coastal Chain, Spain

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    The Les Vilelles unit is a detrital sequence exposes at the southwestern margin of the Catalonian Coastal Range, NE Spain, below the Carboniferous turbiditic series. Based on the palynological content, the age of this unit was initially assigned to the Middle-Late Devonian (Eifelian to Famennian). Additional radiolarian and connodont findings were considered to be Early-Middle Mississippian (Tournaisian to early Viséan). This age inconsistency and the broad time interval, especially of the first dating, produce some ambiguity in the regional interpretations of the Les Vilelles unit and the overlying Carboniferous sequence. A palynostratigraphic analysis conducted in a section representative of the Les Vilelles unit has provided an assemblage containing miospores, acritarchs, prasinophyta phycomata and chitinozoan that can be confidently assigned to a latest Frasnian interval, in contact with the Frasnian-Famennian boundary. This dating casts doubt on the radiolarian/connodont age assignment and considerably refines the Middle -Late Devonian age formerly established. This study also includes a systematic section with the description of three newly established miospore species:Dibolisporites coniugatum, Dibolisporites priorato and Rugospora spinosa

    Decuplet Baryon Structure from Lattice QCD

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    The electromagnetic properties of the SU(3)-flavor baryon decuplet are examined within a lattice simulation of quenched QCD. Electric charge radii, magnetic moments, and magnetic radii are extracted from the E0 and M1 form factors. Preliminary results for the E2 and M3 moments are presented giving the first model independent insight to the shape of the quark distribution in the baryon ground state. As in our octet baryon analysis, the lattice results give evidence of spin-dependent forces and mass effects in the electromagnetic properties. The quark charge distribution radii indicate these effects act in opposing directions. Some baryon dependence of the effective quark magnetic moments is seen. However, this dependence in decuplet baryons is more subtle than that for octet baryons. Of particular interest are the lattice predictions for the magnetic moments of Ω\Omega^- and Δ++\Delta^{++} for which new recent experimental measurements are available. The lattice prediction of the Δ++/p\Delta^{++}/p ratio appears larger than the experimental ratio, while the lattice prediction for the Ω/p\Omega^-/p magnetic moment ratio is in good agreement with the experimental ratio.Comment: RevTeX manuscript, 34 pages plus 21 figures (available upon request

    Estudio Mineralógico de los Sediementos de las Cuencas de WAGNER y CONSAG. Golfo de California (México)

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    Las cuencas de Wagner y de Consag se encuentran localizadas en la parte más septentrional del Golfo de California (GC). Con una profundidad máxima de 216 m, son las cuencas más someras del golfo y presentan una actividad gasohidrotermal submarina intensa (Canet et al., 2008)

    Do we understand the unquenched value of fB?

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    I review our qualitative understanding of the increase in the value of the B meson decay constant (fB), when dynamical fermions are included in lattice QCD calculations.Comment: 4 pages. Talk at UK Phenomenology Workshop on Heavy Flavour and CP Violation, Durham, 17 - 22 September 2000 (Minor typo fixed

    Low-Dimensional Long-Range Topological Charge Structure in the QCD Vacuum

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    While sign-coherent 4-dimensional structures cannot dominate topological charge fluctuations in the QCD vacuum at all scales due to reflection positivity, it is possible that enhanced coherence exists over extended space-time regions of lower dimension. Using the overlap Dirac operator to calculate topological charge density, we present evidence for such structure in pure-glue SU(3) lattice gauge theory. It is found that a typical equilibrium configuration is dominated by two oppositely-charged sign-coherent connected structures (``sheets'') covering about 80% of space-time. Each sheet is built from elementary 3-d cubes connected through 2-d faces, and approximates a low-dimensional curved manifold (or possibly a fractal structure) embedded in the 4-d space. At the heart of the sheet is a ``skeleton'' formed by about 18% of the most intense space-time points organized into a global long-range structure, involving connected parts spreading over maximal possible distances. We find that the skeleton is locally 1-dimensional and propose that its geometrical properties might be relevant for understanding the possible role of topological charge fluctuations in the physics of chiral symmetry breaking.Comment: 4 pages RevTeX, 4 figures; v2: 6 pages, 5 figures, more explanations provided, figure and references added, published versio

    Local Chirality of Low-Lying Dirac Eigenmodes and the Instanton Liquid Model

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    The reasons for using low-lying Dirac eigenmodes to probe the local structure of topological charge fluctuations in QCD are discussed, and it is pointed out that the qualitative double-peaked behavior of the local chiral orientation probability distribution in these modes is necessary, but not sufficient for dominance of instanton-like fluctuations. The results with overlap Dirac operator in Wilson gauge backgrounds at lattice spacings ranging from a~0.04 fm to a~0.12 fm are reported, and it is found that the size and density of local structures responsible for double-peaking of the distribution are in disagreement with the assumptions of the Instanton Liquid Model. More generally, our results suggest that vacuum fluctuations of topological charge are not effectively dominated by locally quantized (integer-valued) lumps in QCD.Comment: 29 pages, 13 figures; v2: minor improvements in presentation, results and conclusions unchanged, version to appear in PR

    The nutritive value of corn oil meal and feather protein

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    The proteins, as one of the primary groups of nutrients, have commanded the attention of research workers for many years. Experiments have demonstrated that various proteins differ greatly in nutritive value. Since a large part of the animal diet is generally compounded from protein feeds, which are usually high priced, it is important that this nutrient group be utilized as efficiently as possible. Corn oil meal is a corn milling by-product consisting of the corn germ after the oil has been extracted. It contains from 20 to 25 percent protein. Eleven large companies are now operating in the United States processing from 60,000,000 to 125,000,000 bushels of shelled corn each year. This means that from 65,000 to 130,000 tons of corn oil meal are available annually for livestock feeding

    Glueball Matrix Elements on Anisotropic Lattices

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    The glueball-to-vacuum matrix elements of local gluonic operators in scalar, tensor, and pseudoscalar channels are investigated numerically on several anisotropic lattices with the spatial lattice spacing in the range 0.1fm -- 0.2fm. These matrix elements are needed to predict the glueball branching ratios in J/ψJ/\psi radiative decays which will help to identify the glueball states in experiments. Two types of improved local gluonic operators are constructed for a self-consistent check, and the finite volume effects are also studied. The lattice spacing dependence of our results is very small and the continuum limits are reliably extrapolated.Comment: 3 pages, 3 figures, Lattice2003 (spectrum

    Bulletin No. 361 - How Much Barley for Turkeys

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    During recent years high energy turkey diets containing com as the sole source of ground grain have been fed extensively. Corn has been used as the grain part of the mash because of its high energy, low fiber qualities, and because its deficiencies in amino acids, vitamins, and minerals have been determined by research. Supplements to overcome these deficiencies have been added to high energy corn diets. Excellent results have been obtained when adequate supplementation of vitamins, amino acids, and minerals were made. In this area frequent inquiries are made as to the possibilities of substituting barley for part or all of the corn. These inquiries are undoubtedly made because barley is generally cheaper than corn. It is a product that is grown locally and yields are above other grains on local irrigated farms. Poley and Wilson found no appreciable differences in the rate of growth when turkeys received either corn, wheat, oats, or barley in growing rations. No soybean oil meal was fed as a protein concentrate in their feeding trials. However, since their investigation, new vitamins necessary for growth have been discovered. Alder found that barley could replace a large part of corn in the turkey diet. However, all barley diets were not included in his investigations. The objectives of this investigation were to study the effects of substituting ground barley for ground corn on a pound for pound basis in the turkey growing mash

    The local structure of topological charge fluctuations in QCD

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    We introduce the Dirac eigenmode filtering of topological charge density associated with Ginsparg-Wilson fermions as a tool to investigate the local structure of topological charge fluctuations in QCD. The resulting framework is used to demonstrate that the bulk of topological charge in QCD does not appear in the form of unit quantized lumps. This means that the mixing of "would-be" zeromodes associated with such lumps is probably not the prevalent microscopic mechanism for spontaneous chiral symmetry breaking in QCD. To characterize the coherent local behavior in topological charge density at low energy, we compute the charges contained in maximal coherent spheres enclosing non-overlapping peaks. We find a continuous distribution essentially ending at ~0.5. Finally, we study, for the first time, the overlap-operator topological-charge-density correlators and find consistency with non-positivity at nonzero physical distance. This represents a non-trivial check on the locality (in gauge paths) of the overlap Dirac operator for realistic gauge backgrounds.Comment: 3 pages, 4 figures, talk, Lattice2002(topology
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