428 research outputs found

    Library E-Book Platforms Are Broken: Let\u27s Fix Them

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    E-books promise users convenience and accessibility, but library e-book platforms contain so many barriers to use and access that patrons often turn away in frustration. In addition, aggregators’ e-book platforms often include intrusive, onerous digital rights management (DRM) restrictions. The traditional solution of DRM-free e-books are generally only available only in large and expensive publisher packages. One approach to solving these problems is an evidence-based selection of e-books program; it not only offers access to hundreds of DRM-free, unlimited simultaneous-user e-books that are integrated with similar e-journal content, but also includes an agreement that libraries will only purchase titles with the highest use

    On the combined effects of surface tension force calculation and interface advection on spurious currents within Volume of Fluid and Level Set frameworks

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    This paper deals with the comparison of Eulerian methods to take into account the capillary contribution in the vicinity of a fluid–fluid interface. Eulerian methods are well- known to produce additional vorticity close to the interface that leads to non-physical spurious currents. Numerical equilibrium between pressure gradient and capillary force for the static bubble test case within a VOF framework has been reached in [35] with the height-function technique [14,35]. However, once the bubble is translated in a uniform flow, spurious currents are maintained by slight errors induced by translation schemes. In this work, two main points are investigated: the ability of Volume of Fluid and Level Set methods to accurately calculate the curvature, and the magnitude of spurious currents due to errors in the calculation of the curvature after advection in both translating and rotating flows. The spurious currents source term is expressed from the vorticity equation and used to discuss and compare the methods. Simulations of gas–liquid Taylor flow at low capillary number show that the flow structure and the bubble velocity can be significantly affected by spurious currents

    Hydrodynamics of gas-liquid Taylor flow in rectangular microchannels

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    The effect of fluid properties and operating conditions on the generation of gas–liquid Taylor flow in microchannels has been investigated experimentally and numerically. Visualisation experiments and 2D numerical simulations have been performed to study bubble and slug lengths, liquid film hold-up and bubble velocities. The results show that the bubble and slug lengths increase as a function of the gas and liquid flow rate ratios. The bubble and slug lengths follow the model developed by Garstecki et al. (Lab chip 6:437-446, 2006) and van Steijn et al. (Chem Eng Sci 62:7505-7514, 2007), however, the model coefficients appear to be dependent on the liquid properties and flow conditions in some cases. The ratio of the bubble velocity to superficial two-phase velocity is close to unity, which confirms a thin liquid film under the assumption of a stagnant liquid film. Numerical simulations confirm the hypothesis of a stagnant liquid film and provide information on the thickness of the liquid film

    "Menage à trois": the presence/absence of thyme shapes the mutualistic interaction between the host plant [i]Medicago truncatula[/i] (Fabaceae) and its symbiotic bacterium [i]Sinorhizobium meliloti[/i]

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    UMR 1334 AGAP : Equipe DAVEM Diversité et adaptation de la vigne et des espèces méditerranéennesThe long-term maintenance of specialized mutualisms remains an evolutionary puzzle. Recent focus has been on factors governing the stability of these mutualisms, including sanctions by the host, partner choice, and coevolutionary constraint, that is, the genetic correlation (r(G)) between fitness of both partners. So far these studies have been typically carried out in a single environment. Here, we ask if the genetic correlation between fitness of the host plant Medicago truncatula (Fabaceae) and its bacterial symbiont Sinorhizobium meliloti is affected by the presence/absence of a monoterpene (carvacrol) leached into the soil by Thymus vulgaris-a common plant of the Mediterranean vegetation, often co-occuring with Medicago. We show that the presence of carvacrol in the soil dramatically affects fitness of the rhizobial partner and increases the magnitude of rG between plant and rhizobia fitness (r(G) = 0.02 +/- 0.05 vs. r(G) = 0.57 +/- 0.02). This finding emphasizes the importance of heterogeneity in the biotic environment for understanding the evolution of species interactions

    MAPing Collection Use: Using Massive Analysis Projects for Collections Analysis

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    From The Library Assessment Cookbook, edited by Aaron W. Dobbs (http://www.alastore.ala.org/detail.aspx?ID=12238, ISBN: 9780838988664), this recipe outlines the assessment of resources that are similar in size, scope, coverage, and typical user population. While this recipe was first used at an academic institution, it could be adapted for public, state, school, or special libraries

    Limits to Plasticity in Gray Wolf, Canis lupus, Pack Structure: Conservation Implications for Recovering Populations

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    We documented the dynamics of the Five Corners Pack (FCP) in east-central Minnesota and northwestern Wisconsin through the loss and replacement of four alpha-females over a four-year period. This pack remained intact and produced offspring during the period despite the annual loss of the alpha female. However, we observed a disintegration of the pack after four consecutive alpha females died, at least two of which were due to illegal killing by humans. Our observations generally support the hypothesis that “single-parent” wolf packs may be more prevalent in areas with low densities of wolves and high densities of ungulate prey. Our observations also highlight the need to assess the potential negative impacts of wolf removal on pack structure and persistence at local and regional scales
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