454 research outputs found

    SmartEmbed: A tool for clone and bug detection in smart contracts through structural code embedding

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    Ministry of Education, Singapore under its Academic Research Funding Tier 1authors' own version</p

    The mass and density of the dwarf planet (225088) 2007 OR10

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    The satellite of (225088) 2007 OR10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, eā‰ˆ\approx0.3, may be a consequence of an intrinsically eccentric orbit and slow tidal evolution, but may also be caused by the Kozai mechanism. Dynamical considerations also suggest that the moon is small, Deff_{eff} << 100 km. Based on the newly determined system mass of 1.75x1021^{21} kg, 2007 OR10 is the fifth most massive dwarf planet after Eris, Pluto, Haumea and Makemake. The newly determined orbit has also been considered as an additional option in our radiometric analysis, provided that the moon orbits in the equatorial plane of the primary. Assuming a spherical shape for the primary this approach provides a size of 1230Ā±\pm50 km, with a slight dependence on the satellite orbit orientation and primary rotation rate chosen, and a bulk density of 1.75Ā±\pm0.07 g cmāˆ’3^{-3} for the primary. A previous size estimate that assumed an equator-on configuration (1535āˆ’225+75^{+75}_{-225} km) would provide a density of 0.92āˆ’0.14+0.46^{+0.46}_{-0.14} g cmāˆ’3^{-3}, unexpectedly low for a 1000 km-sized dwarf planet.Comment: Accepted for publication in Icaru

    Supratentorial and spinal pediatric ependymomas display a hypermethylated phenotype which includes the loss of tumor suppressor genes involved in the control of cell growth and death

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    Epigenetic alterations, including methylation, have been shown to be an important mechanism of gene silencing in cancer. Ependymoma has been well characterized at the DNA copy number and mRNA expression levels. However little is known about DNA methylation changes. To gain a more global view of the methylation profile of ependymoma we conducted an array-based analysis. Our data demonstrated tumors to segregate according to their location in the CNS, which was associated with a difference in the global level of methylation. Supratentorial and spinal tumors displayed significantly more hypermethylated genes than posterior fossa tumors, similar to the ā€˜CpG island methylator phenotypeā€™ (CIMP) identified in glioma and colon carcinoma. This hypermethylated profile was associated with an increase in expression of genes encoding for proteins involved in methylating DNA, suggesting an underlying mechanism. An integrated analysis of methylation and mRNA expression array data allowed us to identify methylation-induced expression changes. Most notably genes involved in the control of cell growth and death and the immune system were identified, including members of the JNK pathway and PPARG. In conclusion, we have generated a global view of the methylation profile of ependymoma. The data suggests epigenetic silencing of tumor suppressor genes is an important mechanism in the pathogenesis of supratentorial and spinal, but not posterior fossa ependymomas. Hypermethylation correlated with a decrease in expression of a number of tumor suppressor genes and pathways that could be playing an important role in tumor pathogenesis

    Generating domain-specific visual language tools from abstract visual specification.

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    Domain-specific visual languages support high-level modeling for a wide range of application domains. However, building tools to support such languages is very challenging. We describe a set of key conceptual requirements for such tools and our approach to addressing these requirements, a set of visual language-based meta tools. These support definition of meta models, visual notations, views, modeling behaviors, design critics, and model transformations and provide a platform to realize target visual modeling tools.Extensions support collaborative work, human-centric tool interaction, and multi platform deployment. We illustrate application of the meta tool set on tools developed with our approach. We describe tool developer and cognitive evaluations of our platform and our exemplar tools, and summarize key future research directions

    Moderate D/H Ratios in Methane Ice on Eris and Makemake as Evidence of Hydrothermal or Metamorphic Processes in Their Interiors: Geochemical Analysis

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    Dwarf planets Eris and Makemake have surfaces bearing methane ice of unknown origin. D/H ratios were recently determined from James Webb Space Telescope (JWST) observations of Eris and Makemake (Grundy et al., submitted), giving us new clues to decipher the origin of methane. Here, we develop geochemical models to test if the origin of methane could be primordial, derived from CO2_2 or CO ("abiotic"), or sourced by organics ("thermogenic"). We find that primordial methane is inconsistent with the observational data, whereas both abiotic and thermogenic methane can have D/H ratios that overlap the observed ranges. This suggests that Eris and Makemake either never acquired a significant amount of methane during their formation, or their original inventories were removed and then replaced by a source of internally produced methane. Because producing abiotic or thermogenic methane likely requires temperatures in excess of ~150{\deg}C, we infer that Eris and Makemake have rocky cores that underwent substantial radiogenic heating. Their cores may still be warm/hot enough to produce methane. This heating could have driven hydrothermal circulation at the bottom of an ice-covered ocean to generate abiotic methane, and/or metamorphic reactions involving accreted organic matter could have occurred in response to heating in the deeper interior, generating thermogenic methane. Additional analyses of thermal evolution model results and predictions from modeling of D-H exchange in the solar nebula support our findings of elevated subsurface temperatures and a lack of primordial methane on Eris and Makemake. It remains an open question whether their D/H ratios may have evolved subsequent to methane outgassing. Recommendations are given for future activities to further test proposed scenarios of abiotic and thermogenic methane production on Eris and Makemake, and to explore these worlds up close.Comment: Submitted to Icarus, 29 pages, 5 figures, 1 tabl

    Ralph: A Visible/Infrared Imager for the New Horizons Pluto/Kuiper Belt Mission

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    The New Horizons instrument named Ralph is a visible/near infrared multi-spectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA's first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with IR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg), power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission.Comment: 18 pages, 15 figures, 4 tables; To appear in a special volume of Space Science Reviews on the New Horizons missio
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