818 research outputs found
The DEdicated MONitor of EXotransits (DEMONEX): Seven Transits of XO-4b
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
and radius
as well as the planet mass
and radius
and a refined ephemeris of
days and . We include archival Rossiter-McLaughlin measurements of XO-4 to
infer the stellar spin-planetary orbit alignment
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 and the observed central transit times
. In the case of 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
and the stellar spin-planet orbit angle .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
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
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Scenario-led modelling of broadleaf forest expansion in Wales
Context
Significant changes in the composition and extent of the UK forest cover are likely to take place in the coming decades. Current policy targets an increase in forest area, for example the Welsh Government aims for forest expansion by 2030, and a purposeful shift from non-native conifers to broadleaved tree species, as identified by the UK Forestry Standard Guidelines on Biodiversity.
Objectives
Using the example of Wales, we aim to generate evidence-based projection of impact of contrasting policy scenarios on the state of forests in the near future, with the view of stimulating debate and aiding decisions concerning plausible outcomes of different policies.
Methods
We quantified changes in different land use and land cover (LULC) classes in Wales between 2007 and 2015 and used a Multi-layer perceptron-Markov chain ensemble modelling approach to project the state of Welsh forests in 2030 under the current and an alternate policy scenario.
Results
The current level of expansion and restoration of broadleaf forest in Wales is sufficient to deliver on existing policy goals. We also show effects of a more ambitious afforestation policy on the Welsh landscape. In a key finding, the highest intensity of broadleaf expansion is likely to shift from south-eastern to a more central areas of Wales.
Conclusion
The study identifies the key predictors of LULC change in Wales. High resolution future land cover simulation maps using these predictors offers an evidence-based tool for forest managers and government officials to test effects of existing and alternative policy scenarios
Environmental Costs of Government-Sponsored Agrarian Settlements in Brazilian Amazonia
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
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
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
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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