310,419 research outputs found

    Template-based Ontology Evolution

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    Katedra kybernetik

    Gravitational Wave Chirp Search: Economization of PN Matched Filter Bank via Cardinal Interpolation

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    The final inspiral phase in the evolution of a compact binary consisting of black holes and/or neutron stars is among the most probable events that a network of ground-based interferometric gravitational wave detectors is likely to observe. Gravitational radiation emitted during this phase will have to be dug out of noise by matched-filtering (correlating) the detector output with a bank of several 10510^5 templates, making the computational resources required quite demanding, though not formidable. We propose an interpolation method for evaluating the correlation between template waveforms and the detector output and show that the method is effective in substantially reducing the number of templates required. Indeed, the number of templates needed could be a factor 4\sim 4 smaller than required by the usual approach, when the minimal overlap between the template bank and an arbitrary signal (the so-called {\it minimal match}) is 0.97. The method is amenable to easy implementation, and the various detector projects might benefit by adopting it to reduce the computational costs of inspiraling neutron star and black hole binary search.Comment: scheduled for publicatin on Phys. Rev. D 6

    Peculiarities in Velocity Dispersion and Surface Density Profiles of Star Clusters

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    Based on our recent work on tidal tails of star clusters (Kuepper et al. 2009) we investigate star clusters of a few 10^4 Msun by means of velocity dispersion profiles and surface density profiles. We use a comprehensive set of NN-body computations of star clusters on various orbits within a realistic tidal field to study the evolution of these profiles with time, and ongoing cluster dissolution From the velocity dispersion profiles we find that the population of potential escapers, i.e. energetically unbound stars inside the Jacobi radius, dominates clusters at radii above about 50% of the Jacobi radius. Beyond 70% of the Jacobi radius nearly all stars are energetically unbound. The velocity dispersion therefore significantly deviates from the predictions of simple equilibrium models in this regime. We furthermore argue that for this reason this part of a cluster cannot be used to detect a dark matter halo or deviations from Newtonian gravity. By fitting templates to the about 10^4 computed surface density profiles we estimate the accuracy which can be achieved in reconstructing the Jacobi radius of a cluster in this way. We find that the template of King (1962) works well for extended clusters on nearly circular orbits, but shows significant flaws in the case of eccentric cluster orbits. This we fix by extending this template with 3 more free parameters. Our template can reconstruct the tidal radius over all fitted ranges with an accuracy of about 10%, and is especially useful in the case of cluster data with a wide radial coverage and for clusters showing significant extra-tidal stellar populations. No other template that we have tried can yield comparable results over this range of cluster conditions. All templates fail to reconstruct tidal parameters of concentrated clusters, however. (abridged)Comment: 23 pages, 13 figures, accepted for publication in MNRA

    Strain evolution in GaN Nanowires: from free-surface objects to coalesced templates

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    Top-down fabricated GaN nanowires, 250 nm in diameter and with various heights, have been used to experimentally determine the evolution of strain along the vertical direction of 1-dimensional objects. X-ray diffraction and photoluminescence techniques have been used to obtain the strain profile inside the nanowires from their base to their top facet for both initial compressive and tensile strains. The relaxation behaviors derived from optical and structural characterizations perfectly match the numerical results of calculations based on a continuous media approach. By monitoring the elastic relaxation enabled by the lateral free-surfaces, the height from which the nanowires can be considered strain-free has been estimated. Based on this result, NWs sufficiently high to be strain-free have been coalesced to form a continuous GaN layer. X-ray diffraction, photoluminescence and cathodoluminescence clearly show that despite the initial strain-free nanowires template, the final GaN layer is strained

    Photometric redshifts from reconstructed QSO templates

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    From SDSS commissioning photometric and spectroscopic data, we investigate the utility of photometric redshift techniques to the task of estimating QSO redshifts. We consider empirical methods (e.g. nearest-neighbor searches and polynomial fitting), standard spectral template fitting and hybrid approaches (i.e. training spectral templates from spectroscopic and photometric observations of QSOs). We find that in all cases, due to the presence of strong emission-lines within the QSO spectra, the nearest-neighbor and template fitting methods are superior to the polynomial fitting approach. Applying a novel reconstruction technique, we can, from the SDSS multicolor photometry, reconstruct a statistical representation of the underlying SEDs of the SDSS QSOs. Although, the reconstructed templates are based on only broadband photometry the common emission lines present within the QSO spectra can be recovered in the resulting spectral energy distributions. The technique should be useful in searching for spectral differences among QSOs at a given redshift, in searching for spectral evolution of QSOs, in comparing photometric redshifts for objects beyond the SDSS spectroscopic sample with those in the well calibrated photometric redshifts for objects brighter than 20th magnitude and in searching for systematic and time variable effects in the SDSS broad band photometric and spectral photometric calibrations.Comment: 21 pages, 9 figures, LaTeX AASTeX, submitted to A

    A Unifying Scenario on the Origin and Evolution of Cellular and Viral Domains

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    The cellular theory on the nature of life has been one of the first major advancements in biology. Viruses, however, are the most abundant life forms, and their exclusion from mainstream biology and the Tree of Life (TOL) is a major paradox in biology. This article presents a broad, unifying scenario on the origin and evolution of cellular and viral domains that challenges the conventional views about the history of life and supports a TOL that includes viruses. Co-evolution of viruses and their host cells has led to some of the most remarkable developments and transitions in the evolution of life, including the origin of non-coding DNA as a genomic protective device against viral insertion damage. However, one of the major fundamental evolutionary developments driven by viruses was probably the origin of cellular domains - Bacteria, Archaea and Eukarya - from the Last Universal Common Ancestor (LUCA) lineage, by evolving anti-fusion mechanisms. Consistent with a novel fusion/fission model for the population mode of evolution of LUCA, this paper presents a “cell-like world” model for the origin of life. According to this model the evolution of coupled replication, transcription and translation system (RT&T) occurred within non-living cell-like compartments (CCs). In this model, the ancestral ribosome originated as template-based RNA synthesizing machinery. The origin of the cellular genome as a centralized unit for storage and replication of genetic information within the CCs facilitated the evolution of the ancestral ribosome into a powerful translation machinery - the modern ribosome. After several hundred millions of years of providing an enclosed environment and fusion/fission based exchanges necessary for the population mode of evolution of the basic metabolism and the RT&T, the CCs evolved into the first living entities on earth - the LUCA lineage. The paper concludes with a proposal for a TOL that integrates the co-evolution of cellular and viral domains. This is one of a series of three articles that present a unifying scenario on the origin and evolution of viral and cellular domains, including the origin of life, which has significant t bio-medical implications and could lead to a significant paradigm shift in biology

    CGIAR Excellence in Breeding Platform - Plan of Work and Budget 2020

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    At the end of 2019, all CGIAR centers had submitted improvement plans based on an EiB template and in close collaboration with EiB staff while – in a parallel process with breeding programs, funders and private sector representatives – a vision for breeding program modernization was developed and presented to CGIAR breeding leadership at the EiB Annual Meeting. This vision represents an evolution of EiB in the context of the Crops to End Hunger Initiative (CtEH) beyond the initial scope of providing tools, services and expert advice, and serves as a guide for Center leadership to drive changes with EiB support. In addition, EiB has taken the role of managing and disbursing funding, made available by Funders via CtEH to modernize breeding and enable CGIAR breeding programs to implement the vision provided by EiB
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