1,581 research outputs found

    Resolved Imaging of the HR 8799 Debris Disk with Herschel

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    We present Herschel far-infrared and submillimeter maps of the debris disk associated with the HR 8799 planetary system. We resolve the outer disk emission at 70, 100, 160 and 250 um and detect the disk at 350 and 500 um. A smooth model explains the observed disk emission well. We observe no obvious clumps or asymmetries associated with the trapping of planetesimals that is a potential consequence of planetary migration in the system. We estimate that the disk eccentricity must be <0.1. As in previous work by Su et al. (2009), we find a disk with three components: a warm inner component and two outer components, a planetesimal belt extending from 100 - 310 AU, with some flexibility (+/- 10 AU) on the inner edge, and the external halo which extends to ~2000 AU. We measure the disk inclination to be 26 +/- 3 deg from face-on at a position angle of 64 deg E of N, establishing that the disk is coplanar with the star and planets. The SED of the disk is well fit by blackbody grains whose semi-major axes lie within the planetesimal belt, suggesting an absence of small grains. The wavelength at which the spectrum steepens from blackbody, 47 +/- 30 um, however, is short compared to other A star debris disks, suggesting that there are atypically small grains likely populating the halo. The PACS longer wavelength data yield a lower disk color temperature than do MIPS data (24 and 70 um), implying two distinct halo dust grain populations.Comment: 13 pages, 8 figures (6 color), accepted for publication in the Astrophysical Journa

    A compact to revitalise large-scale irrigation systems using a leadership-partnership-ownership ‘theory of change’

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    In countries with transitional economies such as those found in South Asia, large-scale irrigation systems (LSIS) with a history of public ownership account for about 115 million ha (Mha) or approximately 45% of their total area under irrigation. In terms of the global area of irrigation (320 Mha) for all countries, LSIS are estimated at 130 Mha or 40% of irrigated land. These systems can potentially deliver significant local, regional and global benefits in terms of food, water and energy security, employment, economic growth and ecosystem services. For example, primary crop production is conservatively valued at about US$355 billion. However, efforts to enhance these benefits and reform the sector have been costly and outcomes have been underwhelming and short-lived. We propose the application of a 'theory of change' (ToC) as a foundation for promoting transformational change in large-scale irrigation centred upon a 'global irrigation compact' that promotes new forms of leadership, partnership and ownership (LPO). The compact argues that LSIS can change by switching away from the current channelling of aid finances controlled by government irrigation agencies. Instead it is for irrigators, closely partnered by private, public and NGO advisory and regulatory services, to develop strong leadership models and to find new compensatory partnerships with cities and other river basin neighbours. The paper summarises key assumptions for change in the LSIS sector including the need to initially test this change via a handful of volunteer systems. Our other key purpose is to demonstrate a ToC template by which large-scale irrigation policy can be better elaborated and discussed

    A comparison of Australian and European Union research performance profiles

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    "Governments worldwide face the challenge of how best to prioritise their international science and innovation (S&I) cooperation activities. This involves balancing the intrinsic benefits that may arise from international S&I cooperation with extrinsic considerations – diplomacy, trade, national security etc. The interplay of these intrinsic and extrinsic considerations means that complex and often ambiguous tradeoffs need to be addressed by policymakers. In some cases international S&I cooperation priorities will reflect extrinsic diplomatic and geopolitical goals. In other cases the objectives will relate more closely to balancing the costs, risks and benefits of particular bilateral and multilateral S&I cooperation opportunities. Given the limited financial resources available to support international S&I cooperation it is useful for policymakers to have access to appropriate decision-support tools and information. This should help to avoid wasteful resource allocations caused by a lack of access to relevant information.This paper seeks to contribute to the evolving policy framework in this area by considering ways of characterising and mapping international imbalances in research performance." - page 2Australian National Universit

    Proverbs and Work

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    Introduction to Proverbs About the Book of Proverbs What Do the Proverbs Have to Do With Work? The Valiant Woman (Proverbs 31:10-31) The Wise Worker is Trustworthy (Proverbs) A Trustworthy Worker is Faithful to His or Her Fiduciary Responsibilities (Proverbs) A Trustworthy Worker is Honest (Proverbs) The Wise Worker is Diligent (Proverbs) A Diligent Worker is Hard-working (Proverbs) A Diligent Worker Plans for the Long Term (Proverbs) A Diligent Worker Contributes to the Profitability of the Enterprise (Proverbs) A Diligent Worker Can Smile at the Future (Proverbs) The Wise Worker is Shrewd (Proverbs) The Wise Worker is Generous (Proverbs) The Wise Worker is Just (Proverbs) The Wise Worker Guards the Tongue (Proverbs) The Wise Worker is Modest (Proverbs) Conclusion to Proverbs Index by Chapter-Verse (Proverbs

    The hydrino and other unlikely states

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    We discuss the tightly bound (hydrino) solution of the Klein-Gordon equation for the Coulomb potential in 3 dimensions. We show that a similarly tightly bound state occurs for the Dirac equation in 2 dimensions. These states are unphysical since they disappear if the nuclear charge distribution is taken to have an arbitrarily small but non-zero radius.Comment: Submitted to Physics Letters

    Characteristics of seismic survey pulses and the ambient soundscape in Baffin Bay and Melville Bay, West Greenland

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    In 2012 a seismic survey campaign involving four vessels was conducted in Baffin Bay, West Greenland. Long-distance (150 km) pre-survey acoustic modeling was performed in accordance with regulatory requirements. Four acoustic recorders, three with hydrophones at 100, 200, and 400m depths, measured ambient and anthropogenic sound during the survey. Additional recordings without the surveys were made from September 2013 to September 2014. The results show that (1) the soundscape of Baffin Bay is typical for open ocean environments and Melville Bay's soundscape is dominated by glacial ice noise; (2) there are distinct multipath arrivals of seismic pulses 40 km from the array; (3) seismic sound levels vary little as a function of depth; (4) high fidelity pre-survey acoustic propagation modeling produced reliable results; (5) the daily SEL did not exceed regulatory thresholds and were different using Southall, Bowles, Ellison, Finneran, Gentry, Greene, Kastak, Ketten, Miller, Nachtigall, Richardson, Thomas, and Tyack [(2007) Aquat. Mamm. 33, 411-521] or NOAA weightings [National Marine Fisheries Service (2016). NOAA Technical Memorandum NMFS-OPR-55, p. 178]; (6) fluctuations of SPL with range were better described by additive models than linear regression; and (7) the survey increased the 1-min SPL by 28 dB, with most of the energy below 100 Hz; energy in the 16 000 Hz octave band was 20 dB above the ambient background 6 km from the source. (C) 2017 Acoustical Society of America

    Screw Compressors

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    Discussion GroupAPI Standard 619 for screw compressors Wet and dry Silencers for dry screw compressors Noise reduction methods Lubricants and lubricant carryover for flooded screw compressor Over-compression and under-compression Pulsation and vibration issue
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