3,513 research outputs found

    Exploration of planetesimals by a tripartite tethered spacecraft

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    Asteroids and comets exert such a small gravitational force that it is not practical to survey them from orbit. One must instead continuously accelerate using maneuvering rockets to move around the surface. A space exploration craft in three parts connected by lightweight cables can survey asteroids and comets, and deploy landers, without requiring the large thrusters and the continuous depletion of fuel required by a single craft. The spacecraft is deployed by spinning up from a compact configuration using low thrust jets, and then maintain surveying orbit without any major expenditure of energy. The triangular tether arrangement is stable, but care must be taken in changing orbits and with deploying and recovering samples, as can be demonstrated with a simple simulation. Even 100 km long tethers occupy a low payload fraction

    In times of recession, a population that is worried and uninformed on economic matters may help to prolong the financial misery

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    In 2008, financial speculation on over-valued US housing stock was rife. When investors awoke to the extent of the debt, Lehman Brothers went bankrupt, credit evaporated and world economies began to shrink. The global financial crisis had begun. Richard Stephens examines the psychological effects of such bad news, and argues that the more people are worried about the economy, the less they spend, thus prolonging the recession. He suggests that part of the solution may be to encourage a citizenry that is better informed on economic matters and knowledgeable of their place in the recession economy

    Identification of putative methanol dehydrogenase (moxF) structural genes in methylotrophs and cloning of moxF genes from Methylococcus capsulatus bath and Methylomonas albus BG8

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    An open-reading-frame fragment of a Methylobacterium sp. strain AM1 gene (moxF) encoding a portion of the methanol dehydrogenase structural protein has been used as a hybridization probe to detect similar sequences in a variety of methylotrophic bacteria. This hybridization was used to isolate clones containing putative moxF genes from two obligate methanotrophic bacteria, Methylococcus capsulatus Bath and Methylomonas albus BG8. The identity of these genes was confirmed in two ways. A T7 expression vector was used to produce methanol dehydrogenase protein in Escherichia coli from the cloned genes, and in each case the protein was identified by immunoblotting with antiserum against the Methylomonas albus methanol dehydrogenase. In addition, a moxF mutant of Methylobacterium strain AM1 was complemented to a methanol-positive phenotype that partially restored methanol dehydrogenase activity, using broad-host-range plasmids containing the moxF genes from each methanotroph. The partial complementation of a moxF mutant in a facultative serine pathway methanol utilizer by moxF genes from type I and type X obligate methane utilizers suggests broad functional conservation of the methanol oxidation system among gram-negative methylotrophs

    Developing the infrastructure for patient review in academic journals

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    Peer review is a well-established part of academic publishing. Its function is to assess the quality of a manuscript before publication in a journal. Research involvement and Engagement is the world’s first co-produced journal dedicated to developing the evidence base of patient and public involvement and engagement in health and social care research. Alongside traditional academic peer review we also involve other key stakeholders, including patients, carers, the public, policy makers, funders and practitioners. Following a recent survey looking at the motivations and feedback from patient reviewers in academic journals, we consider the key findings, reflect on what we already do and based on the feedback from the survey, we outline plans for future development. These plans include including improving training and guidance for reviewers, changes to systems and workflows, acknowledging and engaging reviewers, and building a sense of community

    LES of an Inclined Jet into a Supersonic Turbulent Crossflow

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    This short article describes flow parameters, numerical method, and animations of the fluid dynamics video "LES of an Inclined Jet into a Supersonic Turbulent Crossflow" (http://ecommons.library.cornell.edu/bitstream/1813/14073/3/GFM-2009.mpg [high-resolution] and http://ecommons.library.cornell.edu/bitstream/1813/14073/2/GFM-2009-web.m1v [low-resolution] video). We performed large-eddy simulation with the sub-grid scale (LES-SGS) stretched-vortex model of momentum and scalar transport to study the gas-dynamics interactions of a helium inclined round jet into a supersonic (M=3.6M=3.6) turbulent (\Reth=13×103 =13\times10^3) air flow over a flat surface. The video shows the temporal development of Mach-number and magnitude of density-gradient in the mid-span plane, and isosurface of helium mass-fraction and \lam_2 (vortical structures). The identified vortical structures are sheets, tilted tubes, and discontinuous rings. The vortical structures are shown to be well correlated in space and time with helium mass-fraction isosurface (YHe=0.25Y_{\rm He}=0.25).Comment: 7 pages, 1 figure, 1 table, article describing fluid dynamics video submitted to Gallery of Fluid Motion, APS-DFD 200

    The Drought Monitor

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    There is a need for improved drought monitoring and assessment methods in the United States. Drought is the most costly natural disaster [Federal Emergency Management Agancy (FEMA 1995; Wilhite 2000)], but it is often neglected by developers of assessment and forecast products. Drought is more nebulous than other disasters and does not lend itself to traditional assessments or forecast methods. Its relatively slow onset and the complexity of its impacts are reasons for the new assessment methodology. Improvements in drought monitoring and forecasting techniques will allow for better preparation, lead to better management practices, and reduce the vulnerability of society to drought and its subsequent impacts. The Drought Monitor (additional information available online at http://drought.unl/edu/dm) was created with the goal of tracking and displaying the magnitude and spatial extent of drought and its impacts across the United States. The Drought Monitor is produced weekly and classifies drought severity into four major categories, with a fifth category threshold assigned to locations on a map are determined from a number of indicators, or tools, blended with subjective interpretation
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