13,097 research outputs found

    The Mutual Orbit, Mass, and Density of Transneptunian Binary Gknhmdm (229762 2007 UK126)

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    We present high spatial resolution images of the binary transneptunian object Gkn'hmdm (229762 2007 UK126) obtained with the Hubble Space Telescope and with the Keck observatory on Mauna Kea to determine the orbit of G' hG' h, the much smaller and redder satellite. G' h orbits in a prograde sense, on a circular or near-circular orbit with a period of 11.3 days and a semimajor axis of 6000 km. Tidal evolution is expected to be slow, so it is likely that the system formed already in a low-eccentricity configuration, and possibly also with the orbit plane of the satellite in or close to the plane of Gkn'hmdm's equator. From the orbital parameters we can compute the system mass to be 1.4 10(exp 20) kg. Combined with estimates of the size of Gkn'hmdm from thermal observations and stellar occultations, we can estimate the bulk density as about 1 g cm(exp 3). This low density is indicative of an ice-rich composition, unless there is substantial internal porosity. We consider the hypothesis that the composition is not unusually ice-rich compared with larger TNOs and comet nuclei, and instead the porosity is high, suggesting that mid-sized objects in the 400 to 1000 km diameter range mark the transition between small, porous objects and larger objects that have collapsed their internal void space as a result of their much higher internal pressures and temperatures

    Crystal structure of the catalytic fragment of murine poly(ADP-ribose) polymerase-2.

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    Poly(ADP-ribose) polymerase-1 (PARP-1) has become an important pharmacological target in the treatment of cancer due to its cellular role as a 'DNA-strand break sensor', which leads in part to resistance to some existing chemo- and radiological treatments. Inhibitors have now been developed which prevent PARP-1 from synthesizing poly(ADP-ribose) in response to DNA-breaks and potentiate the cytotoxicity of DNA damaging agents. However, with the recent discoveries of PARP-2, which has a similar DNA-damage dependent catalytic activity, and additional members containing the 'PARP catalytic' signature, the isoform selectivity and resultant pharmacological effects of existing inhibitors are brought into question. We present here the crystal structure of the catalytic fragment of murine PARP-2, at 2.8 A resolution, and compare this to the catalytic fragment of PARP-1, with an emphasis on providing a possible framework for rational drug design in order to develop future isoform-specific inhibitors

    Climate readiness in smallholder agricultural systems: lessons learned from REDD+

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    The debate around the role that agriculture should play in mitigating climate change and sequestering greenhouse gases is politically complex and technically complicated. In many countries, and particularly in developing countries with a large smallholder population, the agricultural sector faces competing priorities, such as national food security goals, poverty alleviation, addressing natural resource degradation and adapting to the already visible effects of climate change. Many of these goals are closer to the immediate, short-term priorities of national decision-makers, relegating climate change mitigation to a secondary priority. It is therefore essential to implement mitigation strategies in concert with strategies that increase the resilience and increase the productivity of agricultural systems. Despite differences in the forestry and the agricultural sectors, experiences from the REDD+ process, and particularly its readiness phase, can offer useful lessons for an agricultural readiness process. The REDD+ readiness process created an overall coherent structure, framework and process of guiding countries towards developing the technical and institutional ability to integrate mitigation activities into their forestry sectors. An overview of the lessons learned from REDD+ Readiness, organized by objectives, governance, process, scope and finance, is provided in this working paper

    Inference for bounded parameters

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    The estimation of signal frequency count in the presence of background noise has had much discussion in the recent physics literature, and Mandelkern [1] brings the central issues to the statistical community, leading in turn to extensive discussion by statisticians. The primary focus however in [1] and the accompanying discussion is on the construction of a confidence interval. We argue that the likelihood function and pp-value function provide a comprehensive presentation of the information available from the model and the data. This is illustrated for Gaussian and Poisson models with lower bounds for the mean parameter

    Localizations at infinity and essential spectrum of quantum Hamiltonians: I. General theory

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    We isolate a large class of self-adjoint operators H whose essential spectrum is determined by their behavior at large x and we give a canonical representation of their essential spectrum in terms of spectra of limits at infinity of translations of H. The configuration space is an arbitrary abelian locally compact not compact group.Comment: 63 pages. This is the published version with several correction

    Evaluation of Euler Fluxes for Hypersonic Flow Computations

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76462/1/AIAA-33735-324.pd

    The Positional Anthropometric and Performance Profile of Elite Gaelic Football Players.

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    The aim of the current investigation was to evaluate the variation in the anthropometric and performance characteristics of elite Gaelic football players with respect of position. One hundred and forty-eight elite Gaelic footballers underwent anthropometric (height, body mass, sum of seven skinfolds, % adipose tissue) and performance [counter movement jump height (CMJ), CMJ peak power, CMJ relative peak power, squat jump height (SJ), SJ peak power, SJ relative peak power, 5-, 10- and 20 m sprint times and Yo-Yo Intermittent Recovery Test Level 2 (Yo-YoIRT2)] during 'the early in-season' phase. Data were split into five positional groups (full-back, half-back, midfield, half-forward and full-forward). Higher %AT was observed in full forwards when compared to the half backs (p = 0.001), midfielders (p = 0.035) and half forwards (p = 0.021). Full forwards had significantly greater SJ (p = 0.036) and CMJ (p = 0.013) when compared to the midfielders with no other positional differences observed. No significant variation in sprint times was observed across positions. When Yo-YoIRT2 was considered, full forwards and full backs completed significantly lower distances compared to the middle three positional lines of, half backs, midfielders and half forwards (p = 0.00). The current study is the first to provide normative data for anthropometric and performance values of elite Gaelic football players which in turn can be utilised by coaches to generate appropriate training regimes to maximise position specific preparation for competitive match-play
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