146 research outputs found

    Towards Efficient Viscous Modeling Based on Cartesian Methods for Automated Flow Simulation

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    The advanced Computational Fluid Dynamics (CFD) techniques that address the current limitations of Cartesian-based Navier-Stokes CFD schemes are explored in current investigation. Three promising methods of implementing improved wall boundary conditions are applied: (1) the enhanced diamond path stencil approach, (2) the reformulated extended extrapolation boundary condition, and (3) the ghost cell method. Several initial testing cases have been conducted with all these three boundary conditions, including the flow past a circular cylinder, flow past a flat plate at different inclined angles and flow past an AGARD RAE2822 airfoil. All the results show the effectiveness of these boundary conditions in resolving both laminar and turbulent boundary layer. Among all these methods, the extended extrapolation boundary condition attains the better results than the other two methods

    An Observed Correlation Between Thermal and Non-Thermal Emission in Gamma-Ray Bursts

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    Recent observations by the FermiFermi Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some Gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal γ\gamma-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, EpE_{\rm p} and kTkT, of these two components are correlated via the relation EpTαE_{\rm p} \propto T^{\alpha} which varies from GRB to GRB. We present an interpretation in which the value of index α\alpha indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data

    The Fermi GBM Gamma-Ray Burst Spectral Catalog: Four Years Of Data

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    In this catalog we present the updated set of spectral analyses of GRBs detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first four years of operation. It contains two types of spectra, time-integrated spectral fits and spectral fits at the brightest time bin, from 943 triggered GRBs. Four different spectral models were fitted to the data, resulting in a compendium of more than 7500 spectra. The analysis was performed similarly, but not identically to Goldstein et al. 2012. All 487 GRBs from the first two years have been re-fitted using the same methodology as that of the 456 GRBs in years three and four. We describe, in detail, our procedure and criteria for the analysis, and present the results in the form of parameter distributions both for the observer-frame and rest-frame quantities. The data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center (HEASARC).Comment: Accepted for publication in ApJ

    The 3rd Fermi GBM Gamma-Ray Burst Catalog: The First Six Years

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    Since its launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has triggered and located on average approximately two gamma-ray bursts (GRB) every three days. Here we present the third of a series of catalogs of GRBs detected by GBM, extending the second catalog by two more years, through the middle of July 2014. The resulting list includes 1405 triggers identified as GRBs. The intention of the GBM GRB catalog is to provide information to the community on the most important observables of the GBM detected GRBs. For each GRB the location and main characteristics of the prompt emission, the duration, peak flux and fluence are derived. The latter two quantities are calculated for the 50-300~keV energy band, where the maximum energy release of GRBs in the instrument reference system is observed, and also for a broader energy band from 10-1000 keV, exploiting the full energy range of GBM's low-energy NaI(Tl) detectors. Using statistical methods to assess clustering, we find that the hardness and duration of GRBs are better fitted by a two-component model with short-hard and long-soft bursts, than by a model with three components. Furthermore, information is provided on the settings and modifications of the triggering criteria and exceptional operational conditions during years five and six in the mission. This third catalog is an official product of the Fermi GBM science team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center (HEASARC).Comment: 225 pages, 13 figures and 8 tables. Accepted for publication in Astrophysical Journal Supplement 201

    Identification and Characterization of Full-Length cDNAs in Channel Catfish (Ictalurus punctatus) and Blue Catfish (Ictalurus furcatus)

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    Background: Genome annotation projects, gene functional studies, and phylogenetic analyses for a given organism all greatly benefit from access to a validated full-length cDNA resource. While increasingly common in model species, fulllength cDNA resources in aquaculture species are scarce. Methodology and Principal Findings: Through in silico analysis of catfish (Ictalurus spp.) ESTs, a total of 10,037 channel catfish and 7,382 blue catfish cDNA clones were identified as potentially encoding full-length cDNAs. Of this set, a total of 1,169 channel catfish and 933 blue catfish full-length cDNA clones were selected for re-sequencing to provide additional coverage and ensure sequence accuracy. A total of 1,745 unique gene transcripts were identified from the full-length cDNA set, including 1,064 gene transcripts from channel catfish and 681gene transcripts from blue catfish, with 416 transcripts shared between the two closely related species. Full-length sequence characteristics (ortholog conservation, UTR length, Kozak sequence, and conserved motifs) of the channel and blue catfish were examined in detail. Comparison of gene ontology composition between full-length cDNAs and all catfish ESTs revealed that the full-length cDNA set is representative of the gene diversity encoded in the catfish transcriptome. Conclusions: This study describes the first catfish full-length cDNA set constructed from several cDNA libraries. The catfish full-length cDNA sequences, and data gleaned from sequence characteristics analysis, will be a valuable resource fo

    Measuring luteinising hormone pulsatility with a robotic aptamer-enabled electrochemical reader

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    Assessment of luteinising hormone pulsatility is important in the diagnosis of reproductive disorders. Here the authors develop a DNA aptamer-based electrochemical analysis integrated into a robotic platform for high-throughput and sensitive analysis

    Sonochemically Fabricated Microelectrode Arrays for Use as Sensing Platforms

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    The development, manufacture, modification and subsequent utilisation of sonochemically-formed microelectrode arrays is described for a range of applications. Initial fabrication of the sensing platform utilises ultrasonic ablation of electrochemically insulating polymers deposited upon conductive carbon substrates, forming an array of up to 70,000 microelectrode pores cm−2. Electrochemical and optical analyses using these arrays, their enhanced signal response and stir-independence area are all discussed. The growth of conducting polymeric “mushroom” protrusion arrays with entrapped biological entities, thereby forming biosensors is detailed. The simplicity and inexpensiveness of this approach, lending itself ideally to mass fabrication coupled with unrivalled sensitivity and stir independence makes commercial viability of this process a reality. Application of microelectrode arrays as functional components within sensors include devices for detection of chlorine, glucose, ethanol and pesticides. Immunosensors based on microelectrode arrays are described within this monograph for antigens associated with prostate cancer and transient ischemic attacks (strokes)
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