227,035 research outputs found

    The distribution of species range size: a stochastic process

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    The major role played by environmental factors in determining the geographical range sizes of species raises the possibility of describing their long-term dynamics in relatively simple terms, a goal which has hitherto proved elusive. Here we develop a stochastic differential equation to describe the dynamics of the range size of an individual species based on the relationship between abundance and range size, derive a limiting stationary probability model to quantify the stochastic nature of the range size for that species at steady state, and then generalize this model to the species-range size distribution for an assemblage. The model fits well to several empirical datasets of the geographical range sizes of species in taxonomic assemblages, and provides the simplest explanation of species-range size distributions to date

    Enroller: an experiment in aggregating resources

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    This chapter describes a collaborative project between e-scientists and humanists working to create an online repository of linguistic data sets and tools. Corpora, dictionaries, and a thesaurus are brought together to enable a new method of research. It combines our most advanced knowledge in both computing and linguistic research techniques

    The ground state and the long-time evolution in the CMC Einstein flow

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    Let (g,K)(k) be a CMC (vacuum) Einstein flow over a compact three-manifold M with non-positive Yamabe invariant (Y(M)). As noted by Fischer and Moncrief, the reduced volume V(k)=(-k/3)^{3}Vol_{g(k)}(M) is monotonically decreasing in the expanding direction and bounded below by V_{\inf}=(-1/6)Y(M))^{3/2}. Inspired by this fact we define the ground state of the manifold M as "the limit" of any sequence of CMC states {(g_{i},K_{i})} satisfying: i. k_{i}=-3, ii. V_{i} --> V_{inf}, iii. Q_{0}((g_{i},K_{i}))< L where Q_{0} is the Bel-Robinson energy and L is any arbitrary positive constant. We prove that (as a geometric state) the ground state is equivalent to the Thurston geometrization of M. Ground states classify naturally into three types. We provide examples for each class, including a new ground state (the Double Cusp) that we analyze in detail. Finally consider a long time and cosmologically normalized flow (\g,\K)(s)=((-k/3)^{2}g,(-k/3))K) where s=-ln(-k) is in [a,\infty). We prove that if E_{1}=E_{1}((\g,\K))< L (where E_{1}=Q_{0}+Q_{1}, is the sum of the zero and first order Bel-Robinson energies) the flow (\g,\K)(s) persistently geometrizes the three-manifold M and the geometrization is the ground state if V --> V_{inf}.Comment: 40 pages. This article is an improved version of the second part of the First Version of arXiv:0705.307

    Method for removing oxygen impurities from cesium Patent

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    Heated tungsten filter for removing oxygen impurities from cesiu

    Propellant acquisition device for use with a spinning toroidal tank

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    System consists of four radially disposed communication channels attached to propellant-retaining ring situated at bottom of toroidal tank. Ring-and-channel acquisition system design provides uniform propellant distribution within spinning tank during all mission phases

    Rethinking Assessment: Information Literacy Instruction and the ACRL Framework

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    Most information literacy instruction (ILI) done in academic libraries today is based on the ACRL’s Information Literacy Competency Standards for Higher Education, but with the replacement of these standards by the new Framework for Information Literacy for Higher Education, there is a need to re-evaluate current teaching strategies and instructional techniques so that they can better serve the Framework’s goals. This paper explores current trends in ILI instruction and in the area of assessment in particular, since ILI assessment provides an opportunity not only to evaluate teaching effectiveness but also to reinforce the learning goals of the new Framework itself. It proposes several ways that assessment strategies can be aligned with the goals of the Framework by using guided group discussion, online discussion platforms, and social media platforms, and proposes further avenues for research in the evaluation of such strategies

    Solenoid valve design has one moving part

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    Solenoid valve structure has only one moving part, a ball and spring assembly. This eliminates wear caused by sliding motion contact between stationary and moving parts or between moving parts

    Thrust bearing

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    A gas lubricated thrust bearing is described which employs relatively rigid inwardly cantilevered spokes carrying a relatively resilient annular member or annulus. This annulus acts as a beam on which are mounted bearing pads. The resilience of the beam mount causes the pads to accept the load and, with proper design, responds to a rotating thrust-transmitting collar by creating a gas film between the pads and the thrust collar. The bearing may be arranged for load equalization thereby avoiding the necessity of gimbal mounts or the like for the bearing. It may also be arranged to respond to rotation in one or both directions

    High speed hybrid bearing comprising a fluid bearing and a rolling bearing convected in series

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    A description is given of an antifriction bearing and a process by which its fatigue life may be extended. The method involves a rotating shaft supported by a fluid bearing and a rolling element bearing coupled in series. Each bearing turns at a fraction of the rotational speed of the shaft. The fluid bearing is preferably conical, thereby providing thrust and radial load support in a single bearing structure

    Soft, thermally conductive material

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    Silicon rubber filled with high percentage of silver-plated copper microspheres provides soft, thermally conductive seat for thermal switch. Material also could be used in thin sheet form to prevent corrosion between dissimilar metals while maintaining good thermal communication. It could be used as thermal gasketing
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