330 research outputs found

    Seismic imaging of the Alaska Subduction Zone: implications for slab geometry and volcanism

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    Alaska has been a site of subduction and terrane accretion since the mid‐Jurassic. The area features abundant seismicity, active volcanism, rapid uplift, and broad intraplate deformation, all associated with subduction of the Pacific plate beneath North America. The juxtaposition of a slab edge with subducted, overthickened crust of the Yakutat terrane beneath central Alaska is associated with many enigmatic volcanic features. The causes of the Denali Volcanic Gap, a 400‐km‐long zone of volcanic quiescence west of the slab edge, are debated. Furthermore, the Wrangell Volcanic Field, southeast of the volcanic gap, also has an unexplained relationship with subduction. To address these issues, we present a joint ambient noise, earthquake‐based surface wave, and P‐S receiver function tomography model of Alaska, along with a teleseismic S wave velocity model. We compare the crust and mantle structure between the volcanic and nonvolcanic regions, across the eastern edge of the slab and between models. Low crustal velocities correspond to sedimentary basins, and several terrane boundaries are marked by changes in Moho depth. The continental lithosphere directly beneath the Denali Volcanic Gap is thicker than in the adjacent volcanic region. We suggest that shallow subduction here has cooled the mantle wedge, allowing the formation of thick lithosphere by the prevention of hot asthenosphere from reaching depths where it can interact with fluids released from the slab and promote volcanism. There is no evidence for subducted material east of the edge of the Yakutat terrane, implying the Wrangell Volcanic Field formed directly above a slab edge

    The effect of refurbishment and trickle vents on airtightness: the case of a 1930s semi-detached house

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    As UK homes are insulated and draught proofed in an attempt to reduce wintertime heating demand they become more airtight. Any reduction in infiltration could have a detrimental effect on indoor air quality. Controllable background ventilation provided by trickle vents is one method of maintaining indoor air quality. A 1930s semi-detached 3-bedroom house was refurbished with double-glazed windows, trickle vents, doors and loft insulation. 167 blower door tests were carried out pre- and post-refurbishment between January and March 2017 to understand the repeatability of the test and quantify how trickle vents affect airtightness. The refurbishment reduced air leakage by 29% from 20.8 to 14.7m3/h/m2 at 50Pa (with all windows and trickle vents closed), but still in excess of the current UK regulations for new builds (10m3/h/m2 at 50Pa). Opening trickle vents provided limited additional ventilation, only increasing air change rate by 1.8m3/h/m2 with all vents open. The test was found to be repeatable with a standard error of 0.07m3/h/m2 at 50Pa with no relationship between the test result and wind speed or direction. The results lead to two important conclusions. Firstly, after refurbishing older homes of this type, infiltration rates are still well above recommendations for adequate indoor air quality. Secondly, the omission of trickle vents in older homes may not unduly diminish indoor air quality

    Foliar wheat diseases and cereal smuts and control of Pleiochaeta setosa in lupins.

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    Disease complexes in field screening trials. Glasshouse screening for resistance. Reinfection of barley loose smut. Barley loose smut – varietal susceptibility. Seed dressings for barley loose smut. Seed dressings for barley leaf stripe. Seed dressings for molybdenum application and fungicidal control of soil-borne flag smut. Chemical control of Pleiochaeta setosa in lupins. Effect of cereal stubble and seed dressing fungicide on brown leaf spot (P. setosa) in lupins. Stubble retention and Rovral for control of P. setosa in lupins. Fungicide sprays for control of P. setosa in lupins. Data summary for chemical trials

    Midwives\u27 use of best available evidence in practice: An integrative review

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    Aims and objectives: To synthesise international research that relates to midwives\u27 use of best available evidence in practice settings and identify key issues relating to the translation of latest evidence into everyday maternity care. Background: Midwifery is a research‐informed profession. However, a gap persists in the translation of best available evidence into practice settings, compromising gold standard maternity care and delaying the translation of new knowledge into everyday practice. Design: A five‐step integrative review approach, based on a series of articles published by the Joanna Briggs Institute (JBI) for conducting systematic reviews, was used to facilitate development of a search strategy, selection criteria and quality appraisal process, and the extraction and synthesis of data to inform an integrative review. Methods: The databases CINAHL, MEDLINE, Web of Science, Implementation Science Journal and Scopus were searched for relevant articles. The screening and quality appraisal process complied with the PRISMA 2009 checklist. Narrative analysis was used to develop sub‐categories and dimensions from the data, which were then synthesised to form two major categories that together answer the review question. Results: The six articles reviewed report on midwives\u27 use of best available evidence in Australia, the UK and Asia. Two major categories emerged that confirm that although midwifery values evidence‐based practice (EBP), evidence‐informed maternity care is not always employed in clinical settings. Additionally, closure of the evidence‐to‐practice gap in maternity care requires a multidimensional approach. Conclusion: Collaborative partnerships between midwives and researchers are necessary to initiate strategies that support midwives\u27 efforts to facilitate the timely movement of best available evidence into practice. Relevance to clinical practice: Understanding midwives\u27 use of best available evidence in practice will direct future efforts towards the development of mechanisms that facilitate the timely uptake of latest evidence by all maternity care providers working in clinical settings

    The exposed Mule Creek vent deposits record the structure of a volcanic conduit during a hybrid explosive–effusive eruption

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    Silicic volcanic eruptions commonly begin with the explosive ejection of pyroclastic material, before transitioning to gentler effusion-dominated activity. Well-exposed dissected silicic systems are scarce and poorly studied, hindering the advances in our understanding of the explosive–effusive transition needed to improve interpretations of volcanic unrest and hazard forecasting. The Mule Creek vent (New Mexico, USA) is a dissected silicic conduit that records the processes controlling conduit formation and evolution, and the role tuffisites (fractures filled with variably welded pyroclasts) play in conduit dynamics. Here, we use decimeter-scale photo-mapping of lithostratigraphic units and thin section analysis to differentiate and interpret three dominant emplacement styles during vent evolution. First, there was repeated deposition and erosion of pyroclastic material at the conduit walls, recorded by erosive surfaces in pyroclastic breccia and agglomerates at the conduit margins. Second, sub-vertical domains of dense melt-dominated magma were emplaced and preserved as glass-dominated vitrophyre and brecciated vitrophyre, with the textural hallmarks of assembly from welding of pyroclasts. Finally, the sub-horizontal fracturing of previously deposited lithologies produced laterally cross-cutting tuffisites. The vent deposits track the widening and then narrowing of the conduit through time and reflect progressive insulation and generally higher temperatures towards the conduit center as pyroclasts accumulate. Welding of pyroclastic fill and the formation of dense vitrophyres towards the conduit center lowers deposit porosity and effective wall permeability. This drives localized gas pressure increases and results in gas-driven fracturing, generating tuffisites, which act as transient outgassing pathways. The structure of the Mule Creek vent records an explosive–effusive transition, constraining the processes controlling conduit evolution and aiding our interpretation of volcanic unrest

    Additive sustainability footprint: Rationale and pilot evaluation of a tool for assessing the sustainable use of PVC additives

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    © 2019 The Authors. Journal of Vinyl and Additive Technology published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers. PVC compounds contain additives necessary for processing and stability, and to modify the plastic's properties. The Europe-wide VinylPlusŸ voluntary commitment includes a challenge to make progress toward sustainable use of additives. Additive Sustainability Footprint (ASF) was developed to assess sustainable use of additives across the whole societal life cycles of finished PVC articles, taking a risk-based approach rather than simplistic hazard assessment. ASF addresses impacts across six life cycle assessment (LCA) stages established by ISO Standard 14040, using the four System Conditions (sustainability principles) developed by The Natural Step (TNS) covering social as well as environmental factors. For each LCA stage/System Condition combination, seven generically similar questions cover negative impacts (many covered by existing tools and regulations) but also the additive's positive contributions to the sustainability of finished articles. Positive contributions include ethical sourcing, longevity of service life, low maintenance inputs, and recyclability. Answers to questions determine a score, which can be combined across the life cycle and with other additives. Testing on a generic EU PVC window profile supported ASF development and demonstrated applicability and potential benefits including use for sensitivity analysis of alternative additives from different geopolitical regions or from recycled as opposed to virgin sources. J. VINYL ADDIT. TECHNOL., 2019. © 2019 The Authors. Journal of Vinyl and Additive Technology published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers
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