1,598 research outputs found

    Off-shell Currents and Color-Kinematics Duality

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    We elaborate on the color-kinematics duality for off-shell diagrams in gauge theories coupled to matter, by investigating the scattering process gg→ss,qqˉ,gggg\to ss, q\bar q, gg, and show that the Jacobi relations for the kinematic numerators of off-shell diagrams, built with Feynman rules in axial gauge, reduce to a color-kinematics violating term due to the contributions of sub-graphs only. Such anomaly vanishes when the four particles connected by the Jacobi relation are on their mass shell with vanishing squared momenta, being either external or cut particles, where the validity of the color-kinematics duality is recovered. We discuss the role of the off-shell decomposition in the direct construction of higher-multiplicity numerators satisfying color-kinematics identity in four as well as in dd dimensions, for the latter employing the Four Dimensional Formalism variant of the Four Dimensional Helicity scheme. We provide explicit examples for the QCD process gg→qqˉggg\to q\bar{q}g.Comment: Accepted version for publication in PLB. Manuscript extended: 19 pages, 15 figures; C/K duality for tree-level amplitudes in dimensional regularization added; references added; title modifie

    Adaptive Integrand Decomposition

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    We present a simplified variant of the integrand reduction algorithm for multiloop scattering amplitudes in d=4−2ϵd = 4 - 2\epsilon dimensions, which exploits the decomposition of the integration momenta in parallel and orthogonal subspaces, d=d∥+d⊥d=d_\parallel+d_\perp, where d∥d_\parallel is the dimension of the space spanned by the legs of the diagrams. We discuss the advantages of a lighter polynomial division algorithm and how the orthogonality relations for Gegenbauer polynomilas can be suitably used for carrying out the integration of the irreducible monomials, which eliminates spurious integrals. Applications to one- and two-loop integrals, for arbitrary kinematics, are discussed.Comment: Conference Proceedings, Loops and Legs in Quantum Field Theory, 24-29 April 2016, Leipzig, German

    The radial variation of HI velocity dispersions in dwarfs and spirals

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    Gas velocity dispersions provide important diagnostics of the forces counteracting gravity to prevent collapse of the gas. We use the 21 cm line of neutral atomic hydrogen (HI) to study HI velocity dispersion and HI phases as a function of galaxy morphology in 22 galaxies from The HI Nearby Galaxy Survey (THINGS). We stack individual HI velocity profiles and decompose them into broad and narrow Gaussian components. We study the HI velocity dispersion and the HI surface density, as a function of radius. For spirals, the velocity dispersions of the narrow and broad components decline with radius and their radial profiles are well described by an exponential function. For dwarfs, however, the profiles are much flatter. The single Gaussian dispersion profiles are, in general, flatter than those of the narrow and broad components. In most cases, the dispersion profiles in the outer disks do not drop as fast as the star formation profiles, derived in the literature. This indicates the importance of other energy sources in driving HI velocity dispersion in the outer disks. The radial surface density profiles of spirals and dwarfs are similar. The surface density profiles of the narrow component decline more steeply than those of the broad component, but not as steep as what was found previously for the molecular component. As a consequence, the surface density ratio between the narrow and broad components, an estimate of the mass ratio between cold HI and warm HI, tends to decrease with radius. On average, this ratio is lower in dwarfs than in spirals. This lack of a narrow, cold HI component in dwarfs may explain their low star formation activity.Comment: Accepted for publication in The Astronomical Journal, 13 pages, 10 figures, 4 table

    Banning Commercial Foresting: What are the Costs?

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    The Philippines' forest cover has suffered from massive denudation through the years due to uncontrolled and indiscriminate commercial logging. Because of this, calls for a total logging ban had been raised in various fora, including in the legislature where bills that consider the possibility of a ban are being studied. However, the possible economic costs of such ban as espoused in some studies has delayed the passage of these bills. This Policy Notes provides some economic costing based on computations that may help in firming up decisions regarding the proposed ban.forestry sector, environmental issues, environmental management

    Acerca de la Validez de los Exámenes de la Calidad y el Logro Educativos (Excale).

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    Este documento trata de la validación de una nueva generación de pruebas de aprovechamiento desarrollados por el Instituto Nacional para la Evaluación de la Educación conocidos como Exámenes de la Calidad y el Logro Educativos (Excale). En el documento se discuten consideraciones conceptuales acerca de su validez, se propone un marco conceptual basado en premisas, y un marco de referencia para el diseño de estudios de validez. El marco de referencia se basa en la idea de que casi toda la información que se colecta durante el desarrollo de una prueba es útil para su validación. Este marco considera tres aspectos fundamentales: 1) las etapas de desarrollo de una prueba a gran escala (diseño y elaboración, administración, calificación, análisis e interpretación y usos), 2) la evaluación de argumentos confirmatorios (en favor) y no-confirmatorios (en contra) y 3) la evidencia lógica y empírica (uso de metodología cuantitativa y cualitativa). De acuerdo con este marco de referencia, el documento finaliza con una propuesta de líneas de investigación para la validación de los Excale

    X-ray structure of the mature ectodomain of phogrin

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    Phogrin/IA-2β and ICA512/IA-2 are two paralogs receptor-type protein-tyrosine phosphatases (RPTP) that localize in secretory granules of various neuroendocrine cells. In pancreatic islet β-cells, they participate in the regulation of insulin secretion, ensuring proper granulogenesis, and β-cell proliferation. The role of their cytoplasmic tail has been partially unveiled, while that of their luminal region remains unclear. To advance the understanding of its structure-function relationship, the X-ray structure of the mature ectodomain of phogrin (ME phogrin) at pH 7.4 and 4.6 has been solved at 1.95- and 2.01-Å resolution, respectively. Similarly to the ME of ICA512, ME phogrin adopts a ferredoxin-like fold: a sheet of four antiparallel β-strands packed against two α-helices. Sequence conservation among vertebrates, plants and insects suggests that the structural similarity extends to all the receptor family. Crystallized ME phogrin is monomeric, in agreement with solution studies but in striking contrast with the behavior of homodimeric ME ICA512. The structural details that may cause the quaternary structure differences are analyzed. The results provide a basis for building models of the overall orientation and oligomerization state of the receptor in biological membranes

    Sex Pheromone of the Invasive Mealybug Citrus Pest, Delottococcus aberiae (Hemiptera: Pseudococcidae). A New Monoterpenoid with a Necrodane Skeleton

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    This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Agricultural and Food Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see [insert ACS Articles on Request author-directed link to Published Work, see http://pubs.acs.org/page/policy/articlesonrequest/index.html].[EN] Native to sub-Saharan Africa, Delottococcus aberiae De Lotto (Hemiptera: Pseudoccidae) is an invasive mealybug that has been recently reported in Europe, seriously damaging citrus production in eastern Spain. In this study, we isolated and determined the structure of the sex pheromone of D. aberiae, to provide a highly specific and effective lure for detecting, monitoring, and potentially controlling this pest. The volatile profile of D. aberiae virgin and mated females was studied by aeration and collection of effluvia in Porapak-Q The resulting extracts were analyzed by gas chromatography coupled to mass spectrometry (GC-MS), revealing a candidate compound specific of virgin females. GC-MS and nuclear magnetic resonance spectroscopy data evidenced a new compound, (4,5,5-trimethyl-3-methylenecyclopent-1-en-1-yl)methyl acetate, with an unusual beta-necrodol skeleton. This compound was synthesized and shown to be attractive to male D. aberiae in both laboratory and field experiments. A GC analysis using an enantioselective stationary phase and polarimetry analyses of the synthetic enantiomers showed the natural compound emitted by virgin females to be the - enantiomer.This work received funding from Universitat Politecnica de Valencia (postdoctoral contract for SV) and Conselleria de Agricultura, Medio Ambiente, Cambio Climaico y Desarrollo Rural (Generalitat Valenciana) under grant agreement (S8456000)Vacas, S.; Navarro Fuertes, I.; Marzo, J.; Navarro-Llopis, V.; Primo Millo, J. (2019). Sex Pheromone of the Invasive Mealybug Citrus Pest, Delottococcus aberiae (Hemiptera: Pseudococcidae). A New Monoterpenoid with a Necrodane Skeleton. Journal of Agricultural and Food Chemistry. 67(34):9441-9449. https://doi.org/10.1021/acs.jafc.9b01443S94419449673
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