13,909 research outputs found

    Representations of Nature in Middle-earth (2016), edited by Martin Simonson

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    Book review of Representations of Nature in Middle-earth (2016), edited by Martin Simonso

    Path Planning for Cooperative Routing of Air-Ground Vehicles

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    We consider a cooperative vehicle routing problem for surveillance and reconnaissance missions with communication constraints between the vehicles. We propose a framework which involves a ground vehicle and an aerial vehicle; the vehicles travel cooperatively satisfying the communication limits, and visit a set of targets. We present a mixed integer linear programming (MILP) formulation and develop a branch-and-cut algorithm to solve the path planning problem for the ground and air vehicles. The effectiveness of the proposed approach is corroborated through extensive computational experiments on several randomly generated instances

    Remodeling by fibroblasts alters the rate-dependent mechanical properties of collagen

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    The ways that fibroblasts remodel their environment are central to wound healing, development of musculoskeletal tissues, and progression of pathologies such as fibrosis. However, the changes that fibroblasts make to the material around them and the mechanical consequences of these changes have proven difficult to quantify, especially in realistic, viscoelastic three-dimensional culture environments, leaving a critical need for quantitative data. Here, we observed the mechanisms and quantified the mechanical effects of fibroblast remodeling in engineered tissue constructs (ETCs) comprised of reconstituted rat tail (type I) collagen and human fibroblast cells. To study the effects of remodeling on tissue mechanics, stress-relaxation tests were performed on ETCs cultured for 24, 48, and 72 h. ETCs were treated with deoxycholate and tested again to assess the ECM response. Viscoelastic relaxation spectra were obtained using the generalized Maxwell model. Cells exhibited viscoelastic damping at two finite time constants over which the ECM showed little damping, approximately 0.2 s and 10-30 s. Different finite time constants in the range of 1-7000 s were attributed to ECM relaxation. Cells remodeled the ECM to produce a relaxation time constant on the order of 7000 s, and to merge relaxation finite time constants in the 0.5-2 s range into a single time content in the 1 s range. Results shed light on hierarchical deformation mechanisms in tissues, and on pathologies related to collagen relaxation such as diastolic dysfunction. Statement of Significance As fibroblasts proliferate within and remodel a tissue, they change the tissue mechanically. Quantifying these changes is critical for understanding wound healing and the development of pathologies such as cardiac fibrosis. Here, we characterize for the first time the spectrum of viscoelastic (rate-dependent) changes arising from the remodeling of reconstituted collagen by fibroblasts. The method also provides estimates of the viscoelastic spectra of fibroblasts within a three-dimensional culture environment. Results are of particular interest because of the ways that fibroblasts alter the mechanical response of collagen at loading frequencies associated with cardiac contraction in humans. © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

    Optimal Design of Hierarchical Ring Networks

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    Preliminary specification and design documentation for software components to achieve catallaxy in computational systems

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    This Report is about the preliminary specifications and design documentation for software components to achieve Catallaxy in computational systems. -- Die Arbeit beschreibt die Spezifikation und das Design von Softwarekomponenten, um das Konzept der Katallaxie in Grid Systemen umzusetzen. Eine Einführung ordnet das Konzept der Katallaxie in bestehende Grid Taxonomien ein und stellt grundlegende Komponenten vor. Anschließend werden diese Komponenten auf ihre Anwendbarkeit in bestehenden Application Layer Netzwerken untersucht.Grid Computing

    Hierarchical Network Design

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    Function-led design of multifunctional stimuli-responsive superhydrophobic surface based on hierarchical graphene-titania nanocoating

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    Multifunctional smart superhydrophobic surface with full-spectrum tunable wettability control is fabricated through the self-assembly of the graphene and titania nanofilm double-layer coating. Advanced microfluidic manipulative functions, including directional water transport, adhesion & spreading controls, droplet storage & transfer, and droplet sensing array, can be readily realized on this smart surface. An in-depth mechanism study regarding the underlying secrets of the tunable wettability and the UV-induced superhydrophilic conversion of anatase titania are also presented

    A Neocolonial Warp of Outmoded Hierarchies, Curricula and Disciplinary Technologies in Trinidad’s Educational System

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    I re-appropriate the image of a space-time warp and its notion of disorientation to argue that colonialism created a warp in Trinidad’s educational system. Through an analysis of school violence and the wider network of structural violence in which it is steeped, I focus on three outmoded aspects as evidence of this warp--hierarchies, curricula and disciplinary technologies--by using data (interviews, documents and observations) from a longitudinal case study at a secondary school in Trinidad. Colonialism was about exclusion, alienation, violence, control and order, and this functionalism persists today; I therefore contend that hierarchies, curricula and disciplinary technologies are all enforcers of these tenets of (neo)colonialism in Trinidad’s schools. I conclude with some nascent thoughts on a Systemic Restorative Praxis (SRP) model as a way of de-stabilizing the warp, by stitching together literature/approaches from systems thinking, restorative justice and Freirean notions of praxis. SRP implies that colonialism (and this modern-day warp) has rendered much psychic and material damage, and that any intervention to address structural violence has to be systemic and iterative in scope and process, include healing, be participatory, and foster an ethic of horizontalization in human relations
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