818 research outputs found

    The DEdicated MONitor of EXotransits (DEMONEX): Seven Transits of XO-4b

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    The DEdicated MONitor of EXotransits (DEMONEX) was a 20 inch robotic and automated telescope to monitor bright stars hosting transiting exoplanets to discover new planets and improve constraints on the properties of known transiting planetary systems. We present results for the misaligned hot Jupiter XO-4b containing 7 new transits from the DEMONEX telescope, including 3 full and 4 partial transits. We combine these data with archival light curves and archival radial velocity measurements to derive the host star mass M=1.2930.029+0.030MM_{*}=1.293_{-0.029}^{+0.030} M_\odot and radius R=1.5540.030+0.042RR_{*}=1.554_{-0.030}^{+0.042} R_\odot as well as the planet mass MP=1.6150.099+0.10MJM_{P}=1.615_{-0.099}^{+0.10} M_{\rm J} and radius RP=1.3170.029+0.040RJR_{P}=1.317_{-0.029}^{+0.040} R_{\rm J} and a refined ephemeris of P=4.1250687±0.0000024P=4.1250687\pm0.0000024 days and T0=2454758.18978±0.00024BJDTDBT_{0}=2454758.18978\pm0.00024 \rm {BJD_{TDB}}. We include archival Rossiter-McLaughlin measurements of XO-4 to infer the stellar spin-planetary orbit alignment λ=40.07.5+8.8\lambda=-40.0_{-7.5}^{+8.8} degrees. We test the effects of including various detrend parameters, theoretical and empirical mass-radius relations, and Rossiter-McLaughlin models. We infer that detrending against CCD position and time or airmass can improve data quality, but can have significant effects on the inferred values of many parameters --- most significantly RP/RR_{P}/R_{*} and the observed central transit times TCT_{C}. In the case of RP/RR_{P}/R_{*} we find that the systematic uncertainty due to detrending can be three times that of the quoted statistical uncertainties. The choice of mass-radius relation has little effect on our inferred values of the system parameters. The choice of Rossiter-McLaughlin models can have significant effects of the inferred values of vsinIv\sin{I_{*}} and the stellar spin-planet orbit angle λ\lambda.Comment: Submitted to ApJ, 13 pages, 12 figures For a short video summarizing this paper, please visit: https://youtu.be/imev65lxSf

    Scheduling MapReduce Jobs under Multi-Round Precedences

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    We consider non-preemptive scheduling of MapReduce jobs with multiple tasks in the practical scenario where each job requires several map-reduce rounds. We seek to minimize the average weighted completion time and consider scheduling on identical and unrelated parallel processors. For identical processors, we present LP-based O(1)-approximation algorithms. For unrelated processors, the approximation ratio naturally depends on the maximum number of rounds of any job. Since the number of rounds per job in typical MapReduce algorithms is a small constant, our scheduling algorithms achieve a small approximation ratio in practice. For the single-round case, we substantially improve on previously best known approximation guarantees for both identical and unrelated processors. Moreover, we conduct an experimental analysis and compare the performance of our algorithms against a fast heuristic and a lower bound on the optimal solution, thus demonstrating their promising practical performance

    Remembering Thomas Mann

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    Environmental Costs of Government-Sponsored Agrarian Settlements in Brazilian Amazonia

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    Brazil has presided over the most comprehensive agrarian reform frontier colonization program on Earth, in which ~1.2 million settlers have been translocated by successive governments since the 1970's, mostly into forested hinterlands of Brazilian Amazonia. These settlements encompass 5.3% of this ~5 million km2 region, but have contributed with 13.5% of all land conversion into agropastoral land uses. The Brazilian Federal Agrarian Agency (INCRA) has repeatedly claimed that deforestation in these areas largely predates the sanctioned arrival of new settlers. Here, we quantify rates of natural vegetation conversion across 1911 agrarian settlements allocated to 568 Amazonian counties and compare fire incidence and deforestation rates before and after the official occupation of settlements by migrant farmers. The timing and spatial distribution of deforestation and fires in our analysis provides irrefutable chronological and spatially explicit evidence of agropastoral conversion both inside and immediately outside agrarian settlements over the last decade. Deforestation rates are strongly related to local human population density and road access to regional markets. Agrarian settlements consistently accelerated rates of deforestation and fires, compared to neighboring areas outside settlements, but within the same counties. Relocated smallholders allocated to forest areas undoubtedly operate as pivotal agents of deforestation, and most of the forest clearance occurs in the aftermath of government-induced migration

    Principles of meiotic chromosome assembly revealed in S. cerevisiae

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    During meiotic prophase, chromosomes organise into a series of chromatin loops emanating from a proteinaceous axis, but the mechanisms of assembly remain unclear. Here we use Saccharomyces cerevisiae to explore how this elaborate three-dimensional chromosome organisation is linked to genomic sequence. As cells enter meiosis, we observe that strong cohesin-dependent grid-like Hi-C interaction patterns emerge, reminiscent of mammalian interphase organisation, but with distinct regulation. Meiotic patterns agree with simulations of loop extrusion with growth limited by barriers, in which a heterogeneous population of expanding loops develop along the chromosome. Importantly, CTCF, the factor that imposes similar features in mammalian interphase, is absent in S. cerevisiae, suggesting alternative mechanisms of barrier formation. While grid-like interactions emerge independently of meiotic chromosome synapsis, synapsis itself generates additional compaction that matures differentially according to telomere proximity and chromosome size. Collectively, our results elucidate fundamental principles of chromosome assembly and demonstrate the essential role of cohesin within this evolutionarily conserved process

    Ecological and Behavioural Correlates of Intracellular Buffering Capacity in the Muscles of Antarctic Fishes

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    Five species of antarctic fishes can be arranged in order of increasing anaerobic capacity of the white muscles for burst swimming: Rhigophila dearborni (Zoarcidae), icefish (Channichthyidae), Dissostichus mawsoni, Trematomus centronotus, and Pagothenia borchgrevinki (Nototheniidae). This order reflects in-creasing dependence on anaerobic work done during short bursts of speed during prey capture or predator avoidance. Buffer capacity (beta) for white muscle was lower than that of behaviourally equivalent fish from lower latitudes and beta is itself temperature-dependent

    2007 National Lawyer’s Convention The Federalist Society \u3cem\u3eand its\u3c/em\u3e Federalism and Separation of Powers Practice Groups \u3cem\u3epresent a panel debate on\u3c/em\u3e Federalism: Religion, Early America and the Fourteenth Amendment

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    Transcript of the Federalist Society and its Federalism and Separation of Powers Practice Groups panel debate at the 2007 National Lawyers Convention including panelists Dean John Eastman of Chapman University School of Law, Professor Marci Hamilton of the Benjamin N. Cardozo School of Law, and moderated by Hon. William H. Pryor Jr. of the U.S. Court of Appeals, Eleventh Circuit
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