15,429 research outputs found

    Management of land for purposes of conservation and sustainable local development.

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    Michael Adams’ Biosphere Reserves lecture will serve as something of a “boot camp” for students interested in working in management of land for purposes of conservation and sustainable local development. In the lecture on the Biosphere Reserves will include historical aspects, issues of conservation across a range of ecosystems, sustainable development, and the associated “Logistics” pertaining to requirements of Biosphere Reserves (see below in next line); The Logistics include such issues as use of reserves for education, training, management, research, networking with agencies, outreach to surrounding communities; The important connections with local people, indigenous peoples in many instances, and the specific stakeholders relevant to specific reserves;Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    The Widom-Rowlinson Model on the Delaunay Graph

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    We establish phase transitions for continuum Delaunay multi-type particle systems (continuum Potts or Widom-Rowlinson models) with a repulsive interaction between particles of different types. Our interaction potential depends solely on the length of the Delaunay edges. We show that a phase transition occurs for sufficiently large activities and for sufficiently large potential parameter proving an old conjecture of Lebowitz and Lieb extended to the Delaunay structure. Our approach involves a Delaunay random-cluster representation analogous to the Fortuin-Kasteleyn representation of the Potts model. The phase transition manifests itself in the mixed site-bond percolation of the corresponding random-cluster model. Our proofs rely mainly on geometric properties of Delaunay tessellations in R2\mathbb{R}^2 and on recent studies [DDG12] of Gibbs measures for geometry-dependent interactions. The main tool is a uniform bound on the number of connected components in the Delaunay graph which provides a novel approach to Delaunay Widom Rowlinson models based on purely geometric arguments. The interaction potential ensures that shorter Delaunay edges are more likely to be open and thus offsets the possibility of having an unbounded number of connected components.Comment: 36 pages, 11 figure

    Phase transitions in Delaunay Potts models

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    We establish phase transitions for classes of continuum Delaunay multi-type particle systems (continuum Potts models) with infinite range repulsive interaction between particles of different type. In one class of the Delaunay Potts models studied the repulsive interaction is a triangle (multi-body) interaction whereas in the second class the interaction is between pairs (edges) of the Delaunay graph. The result for the edge model is an extension of finite range results in \cite{BBD04} for the Delaunay graph and in \cite{GH96} for continuum Potts models to an infinite range repulsion decaying with the edge length. This is a proof of an old conjecture of Lebowitz and Lieb. The repulsive triangle interactions have infinite range as well and depend on the underlying geometry and thus are a first step towards studying phase transitions for geometry-dependent multi-body systems. Our approach involves a Delaunay random-cluster representation analogous to the Fortuin-Kasteleyn representation of the Potts model. The phase transitions manifest themselves in the percolation of the corresponding random-cluster model. Our proofs rely on recent studies \cite{DDG12} of Gibbs measures for geometry-dependent interactions

    When Learning Counts: Rethinking Licenses for School Leaders

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    Recommends restructuring state licensing systems to focus on the skills and knowledge leaders need to improve learning, and better aligning licenses with the current job demands on principals

    On the Complexity and Performance of Parsing with Derivatives

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    Current algorithms for context-free parsing inflict a trade-off between ease of understanding, ease of implementation, theoretical complexity, and practical performance. No algorithm achieves all of these properties simultaneously. Might et al. (2011) introduced parsing with derivatives, which handles arbitrary context-free grammars while being both easy to understand and simple to implement. Despite much initial enthusiasm and a multitude of independent implementations, its worst-case complexity has never been proven to be better than exponential. In fact, high-level arguments claiming it is fundamentally exponential have been advanced and even accepted as part of the folklore. Performance ended up being sluggish in practice, and this sluggishness was taken as informal evidence of exponentiality. In this paper, we reexamine the performance of parsing with derivatives. We have discovered that it is not exponential but, in fact, cubic. Moreover, simple (though perhaps not obvious) modifications to the implementation by Might et al. (2011) lead to an implementation that is not only easy to understand but also highly performant in practice.Comment: 13 pages; 12 figures; implementation at http://bitbucket.org/ucombinator/parsing-with-derivatives/ ; published in PLDI '16, Proceedings of the 37th ACM SIGPLAN Conference on Programming Language Design and Implementation, June 13 - 17, 2016, Santa Barbara, CA, US

    Ultra Short Period Planets in K2: SuPerPiG Results for Campaigns 0-5

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    We have analyzed data from Campaigns 0-5 of the K2 mission and report 19 ultra-short-period candidate planets with orbital periods of less than 1 day (nine of which have not been previously reported). Planet candidates range in size from 0.7-16 Earth radii and in orbital period from 4.2 to 23.5 hours. One candidate (EPIC 203533312, Kp=12.5) is among the shortest-period planet candidates discovered to date (P=4.2 hours), and, if confirmed as a planet, must have a density of at least rho=8.9 g/cm^3 in order to not be tidally disrupted. Five candidates have nominal radius values in the sub-Jovian desert (R_P=3-11 R_E and P<=1.5 days) where theoretical models do not favor their long-term stability; the only confirmed planet in this range is in fact thought to be disintegrating (EPIC 201637175). In addition to the planet candidates, we report on four objects which may not be planetary, including one with intermittent transits (EPIC 211152484) and three initially promising candidates that are likely false positives based on characteristics of their light curves and on radial velocity follow-up. A list of 91 suspected eclipsing binaries identified at various stages in our vetting process is also provided. Based on an assessment of our survey's completeness, we estimate an occurrence rate for ultra-short period planets among K2 target stars that is about half that estimated from the Kepler sample, raising questions as to whether K2 systems are intrinsically different from Kepler systems, possibly as a result of their different galactic location.Comment: 13 pages, 8 figures, accepted to AJ on 2016 May 2

    Development and infection of lenticels and potato tybers during growth and storage

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    Imperial Users onl

    Building Civic Infrastructure: Implementing Community Partnership Grant Programmes in South Africa

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    This article examines recent efforts to establish Community Partnership Grant Programmes (CPG) in six South African communities. CPG programmes provide the financial and organizational infrastructure to support citizen-initiated neighbourhood projects
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