1,769 research outputs found

    Multi-scale environmental filters and niche partitioning govern the distributions of riparian vegetation guilds

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    Across landscapes, riparian plant communities assemble under varying levels of disturbance, environmental stress, and resource availability, leading to the development of distinct riparian life-history guilds over evolutionary timescales. Identifying the environmental filters that exert selective pressures on specific riparian vegetation guilds is a critical step in setting baseline expectations for how riparian vegetation may respond to environmental conditions anticipated under future global change scenarios. In this study, we ask: (1) What riparian plant guilds exist across the interior Columbia and upper Missouri River basins? (2) What environmental filters shape riparian guild distributions? (3) How does resource partitioning among guilds influence guild distributions and co-occurrence? Woody species composition was measured at 703 stream reaches and each species\u27 morphological and functional attributes were extracted from a database in four categories: (1) life form, (2) persistence and growth, (3) reproduction, and (4) resource use. We clustered species into guilds by morphological characteristics and attributes related to environmental tolerances, modeling these guilds\u27 distributions as a function of environmental filters-regional climate, watershed hydrogeomorphic characteristics, and stream channel form- and guild coexistence. We identified five guilds: (1) a tall, deeply rooted, long-lived, evergreen tree guild, (2) a xeric, disturbance tolerant shrub guild, (3) a hydrophytic, thicket-forming shrub guild, (4) a low-statured, shadetolerant, understory shrub guild, and (5) a flood tolerant, mesoriparian shrub guild. Guilds were most strongly discriminated by species\u27 rooting depth, canopy height and potential to resprout and grow following biomass-removing disturbance (e.g., flooding, fire). Hydro-climatic variables, including precipitation, watershed area, water table depth, and channel form attributes reflective of hydrologic regime, were predictors of guilds whose life history strategies had affinity or aversion to flooding, drought, and fluvial disturbance. Biotic interactions excluded guilds with divergent life history strategies and/or allowed for the co-occurrence of guilds that partition resources differently in the same environment. We conclude that the riparian guild framework provides insight into how disturbance and bioclimatic gradients shape riparian functional plant diversity across heterogeneous landscapes. Multiple environmental filters should be considered when the riparian response guild framework is to be used as a decisionsupport tool framework across large spatial extents. Copyright: © 2015 Hough-Snee et al

    Membrane staining and phospholipid tracking in Pseudomonas aeruginosa PAO1 using the phosphatidylcholine mimic propargyl-choline

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    The use of membrane-specific dyes for in vivo fluorescent microscopy is commonplace. However, most of these reagents are non-specific and cannot track specific lipid species movement, instead often acting as non-covalent lipid associated probes or requiring uptake of whole lipids and acyl tails into the membrane. This issue has been solved in eukaryotic cell biology by use of click-chemistry liable phospholipid headgroup pulse-labels. Here we describe a method for in vivo phospholipid labelling by fluorescent imaging in Pseudomonas aeruginosa using a phosphatidylcholine (PC) mimic, “propargyl-choline”(PCho). This click-chemistry liable headgroup mimic is visible by microscopy and allows the covalent labelling of lipids. Fluorescence of the cell membranes, visible in heterogenous patches, is dependent on PCho concentration and is localised in the membrane fraction of cells, demonstrating that it is suitable for membrane labelling and cell imaging

    Overcoming the Challenges Associated with Image-based Mapping of Small Bodies in Preparation for the OSIRIS-REx Mission to (101955) Bennu

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    The OSIRIS-REx Asteroid Sample Return Mission is the third mission in NASA's New Frontiers Program and is the first U.S. mission to return samples from an asteroid to Earth. The most important decision ahead of the OSIRIS-REx team is the selection of a prime sample-site on the surface of asteroid (101955) Bennu. Mission success hinges on identifying a site that is safe and has regolith that can readily be ingested by the spacecraft's sampling mechanism. To inform this mission-critical decision, the surface of Bennu is mapped using the OSIRIS-REx Camera Suite and the images are used to develop several foundational data products. Acquiring the necessary inputs to these data products requires observational strategies that are defined specifically to overcome the challenges associated with mapping a small irregular body. We present these strategies in the context of assessing candidate sample-sites at Bennu according to a framework of decisions regarding the relative safety, sampleability, and scientific value across the asteroid's surface. To create data products that aid these assessments, we describe the best practices developed by the OSIRIS-REx team for image-based mapping of irregular small bodies. We emphasize the importance of using 3D shape models and the ability to work in body-fixed rectangular coordinates when dealing with planetary surfaces that cannot be uniquely addressed by body-fixed latitude and longitude.Comment: 31 pages, 10 figures, 2 table

    A New Measurement of the 1S0 Neutron-Neutron Scattering Length using the Neutron-Proton Scattering Length as a Standard

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    The present paper reports high-accuracy cross-section data for the 2H(n,nnp) reaction in the neutron-proton (np) and neutron-neutron (nn) final-state-interaction (FSI) regions at an incident mean neutron energy of 13.0 MeV. These data were analyzed with rigorous three-nucleon calculations to determine the 1S0 np and nn scattering lengths, a_np and a_nn. Our results are a_nn = -18.7 +/- 0.6 fm and a_np = -23.5 +/- 0.8 fm. Since our value for a_np obtained from neutron-deuteron (nd) breakup agrees with that from free np scattering, we conclude that our investigation of the nn FSI done simultaneously and under identical conditions gives the correct value for a_nn. Our value for a_nn is in agreement with that obtained in pion-deuteron capture measurements but disagrees with values obtained from earlier nd breakup studies.Comment: 4 pages and 3 figure

    Dominion cartoon satire as trench culture narratives: complaints, endurance and stoicism

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    Although Dominion soldiers’ Great War field publications are relatively well known, the way troops created cartoon multi-panel formats in some of them has been neglected as a record of satirical social observation. Visual narrative humour provides a ‘bottom-up’ perspective for journalistic observations that in many cases capture the spirit of the army in terms of stoicism, buoyed by a culture of internal complaints. Troop concerns expressed in the early comic strips of Australians, Canadians, New Zealanders and British were similar. They shared a collective editorial purpose of morale boosting among the ranks through the use of everyday narratives that elevated the anti-heroism of the citizen soldier, portrayed as a transnational everyman in the service of empire. The regenerative value of disparagement humour provided a redefinition of courage as the very act of endurance on the Western Front

    Lethal Injection, Politics, and the Future of the Death Penalty

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    “Welcome and Keynote:” Stephen Bright, Harvey Karp Visiting Lecturer at Yale Law School, and President and Senior Counsel with the Southern Center for Human Rights. (9:00 a.m. - 9:45 a.m.) “The Death Penalty Today: Lethal Injection Issues:” Panel 1 featured Deborah W. Denno, Arthur A. McGivney Professor of Law at Fordham University School of Law; Joel Zivot, Assistant Professor of Anesthesiology and Surgery at Emory University School of Medicine, and Medical Director of the Cardiothoracic Intensive Care Unit at Emory University Hospital; Eric Berger, Associate Professor of Law at Nebraska College of Law; and Frank Green, Reporter for the Richmond Times-Dispatch. Jim Gibson, Associate Dean for Student Affairs and Professor of Law at the University of Richmond School of Law, served as moderator. (10:00 a.m. -11:30 a.m.) “The Shifting Politics of the Death Penalty:” Panel 2 featured Mark Earley, former Attorney General of Virginia; Richard B. Roper, Partner with Thompson & Knight LLP, Corinna Barrett Lain, Associate Dean for Faculty Development and Professor of Law at the University of Richmond School of Law; and Stephen Smith, Professor of Law at Notre Dame Law School. Henry L. Chambers, Professor of Law at the University of Richmond School of Law, served as moderator. (1:00 p.m. - 2:30 p.m.) “The Future of the Death Penalty:” Panel 3 featured John Douglass, Professor of Law at the University of Richmond School of Law; Brandon L. Garrett, Professor of Law at the University of Virginia School of Law; and Richard Dieter, Executive Director of the Death Penalty Information Center. Mary Kelly Tate, Professor of Law at the University of Richmond School of Law, served as moderator. (2:45 p.m. - 4:15 p.m.

    Understanding the evolution of the entrepreneurial university:The case of English Higher Education

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    There has been strong policy interest in universities becoming more entrepreneurial and engaging in knowledge exchange activities as part of an expanding third mission agenda. However, our understanding of the evolution and diversity of such activities is limited. Using longitudinal data from the Higher Education Business Community Interaction (HEBCI) Survey, this study examines the evolving configuration of universities' knowledge exchange activities and stakeholders by analysing distinctive clusters of English universities. We find an increasingly diverse profile of third mission activities across different types of universities: within old, more established universities, Russell Group universities increasingly focus on research‐oriented activities typically in partnership with large firms and non‐commercial organisations; while another group engages in a broad range of knowledge exchange activities with low specialisation over time. Newer, less research intensive, universities increasingly rely on activities such as consultancy and formation of spin‐offs. A decreased engagement with small and medium enterprises and a lower share of knowledge exchange activities at the regional level are observed across the time studied for all universities.JRC.B.4-Human Capital and Employmen
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