7,868 research outputs found

    A taxonomic study of the genus Atheas Champion (Heteroptera: Tingidae)

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    The genus Atheas Champion is revised. A key to all 14 species cataloged in the genus is included. Species occurring in Mexico are redefined and illustrated. Descriptions of species not occurring in Mexico are also provided. Host plant information has been included, when available

    Archives Conservation Discussion Group 2011: Digitization and Its Effect on Conservation Treatment Decisions: How Has Wide-Spread Digitizing of Collections Changed Our Approach to Treatment?

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    In line with this year’s AIC theme: ETHOS, LOGOS, PATHOS: ethical principles and critical thinking in conservation, The Archives Conservation Discussion Group 2011 examined the impact of providing digital collections in museums and libraries, and their conservation implications. Presentations and a subsequent discussion covered topics such as: How conservators are balancing ethical concerns, especially as dictated by the AIC Code of Ethics, with increased demand from digital projects. How conservators are keeping pace with large-scale or fast-paced digitizing projects, while maintaining standards. And the impact of limiting access to original materials by providing digital surrogates and its effect on treatment decisions

    Reynolds number limits for jet propulsion: A numerical study of simplified jellyfish

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    The Scallop Theorem states that reciprocal methods of locomotion, such as jet propulsion or paddling, will not work in Stokes flow (Reynolds number = 0). In nature the effective limit of jet propulsion is still in the range where inertial forces are significant. It appears that almost all animals that use jet propulsion swim at Reynolds numbers (Re) of about 5 or more. Juvenile squid and octopods hatch from the egg already swimming in this inertial regime. The limitations of jet propulsion at intermediate Re is explored here using the immersed boundary method to solve the two-dimensional Navier Stokes equations coupled to the motion of a simplified jellyfish. The contraction and expansion kinematics are prescribed, but the forward and backward swimming motions of the idealized jellyfish are emergent properties determined by the resulting fluid dynamics. Simulations are performed for both an oblate bell shape using a paddling mode of swimming and a prolate bell shape using jet propulsion. Average forward velocities and work put into the system are calculated for Reynolds numbers between 1 and 320. The results show that forward velocities rapidly decay with decreasing Re for all bell shapes when Re < 10. Similarly, the work required to generate the pulsing motion increases significantly for Re < 10. When compared actual organisms, the swimming velocities and vortex separation patterns for the model prolate agree with those observed in Nemopsis bachei. The forward swimming velocities of the model oblate jellyfish after two pulse cycles are comparable to those reported for Aurelia aurita, but discrepancies are observed in the vortex dynamics between when the 2D model oblate jellyfish and the organism

    Leaf roll-up and aquaplaning in strong winds and floods

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    Flexible plants, fungi, and sessile animals are thought to reconfigure in the wind and water to reduce the drag forces that act upon them. In strong winds, for example, leaves roll up into cone shapes that reduce flutter and drag when compared to paper cut-outs with similar shapes and flexibility. During flash floods, herbaceous broad leaves aquaplane on the surface of the water which reduces drag. Simple mathematical models of a flexible beam immersed in a two-dimensional flow will also reconfigure in flow. What is less understood is how the mechanical properties of a two-dimensional leaf in a three-dimensional flow will passively allow roll up and aquaplaning. In this study, we film leaf roll-up and aquaplaning in tree and vine leaves in both strong winds and water flows

    Bifurcations in valveless pumping techniques from a coupled fluid-structure-electrophysiology model in heart development

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    We explore an embryonic heart model that couples electrophysiology and muscle-force generation to flow induced using a 2D2D fluid-structure interaction framework based on the immersed boundary method. The propagation of action potentials are coupled to muscular contraction and hence the overall pumping dynamics. In comparison to previous models, the electro-dynamical model does not use prescribed motion to initiate the pumping motion, but rather the pumping dynamics are fully coupled to an underlying electrophysiology model, governed by the FitzHugh-Nagumo equations. Perturbing the diffusion parameter in the FitzHugh-Nagumo model leads to a bifurcation in dynamics of action potential propagation. This bifurcation is able to capture a spectrum of different pumping regimes, with dynamic suction pumping and peristaltic-like pumping at the extremes. We find that more bulk flow is produced within the realm of peristaltic-like pumping.Comment: 11 pages, 13 figures. arXiv admin note: text overlap with arXiv:1610.0342

    Working Together Toward Better Health Outcomes

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    Healthcare organizations and community-based organizations (CBOs) that provide human services are partnering in shared pursuit of better health outcomes. The Partnership for Healthy Outcomes – Nonprofit Finance Fund (NFF), the Center for Health Care Strategies (CHCS), and the Alliance for Strong Families and Communities (Alliance), with support from the Robert Wood Johnson Foundation (RWJF) – set out to capture and analyze the lessons emerging in this dynamic space. Information from more than 200 partnerships serving all 50 US states provide important lessons from, and for, partnerships that hope to improve access to care, address health inequities, and make progress on social issues like food, education, and housing

    Binomial D-modules

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    We study quotients of the Weyl algebra by left ideals whose generators consist of an arbitrary Z^d-graded binomial ideal I along with Euler operators defined by the grading and a parameter in C^d. We determine the parameters for which these D-modules (i) are holonomic (equivalently, regular holonomic, when I is standard-graded); (ii) decompose as direct sums indexed by the primary components of I; and (iii) have holonomic rank greater than the generic rank. In each of these three cases, the parameters in question are precisely those outside of a certain explicitly described affine subspace arrangement in C^d. In the special case of Horn hypergeometric D-modules, when I is a lattice basis ideal, we furthermore compute the generic holonomic rank combinatorially and write down a basis of solutions in terms of associated A-hypergeometric functions. This study relies fundamentally on the explicit lattice point description of the primary components of an arbitrary binomial ideal in characteristic zero, which we derive in our companion article arxiv:0803.3846.Comment: This version is shorter than v2. The material on binomial primary decomposition has been split off and now appears in its own paper arxiv:0803.384

    "Financial Development and Economic Growth in Transition Economies: Empirical Evidence from the CEE and CIS Countries"

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    We examine the role of financial development in economic growth in the former Communist countries of Central and Eastern Europe and the Commonwealth of Independent States during the first two decades since the beginning of transition. These countries, which had undeveloped financial systems under Communism, provide an interesting test of the relationship between financial development and growth. We show that credit to the private sector had a positive effect on growth in these countries; however, high levels of inflation can render the positive effect of private credit insignificant. High interest rate spreads and reduced banking competition hampered economic growth.transition economies, CEE, CIS, financial sector development, economic growth, panel data

    CRRES: Combined Release and Radiation Effects Satellite Program Summary

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    The experiments that comprise the Combined Release and Radiation Effects Satellite Program (CRRES) (Apr. 1990 - Jul. 1992) are presented. The experiments are as follows: PEGSAT; El Coqui; the Kwajalein Campaign; and experiments G1 - G14
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