663 research outputs found

    Late Holocene ice-flow reconfiguration in the Weddell Sea sector of West Antarctica

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    Here we report Late Holocene ice sheet and grounding-line changes to the Weddell Sea sector of West Antarctica. Internal radio-echo layering within the Bungenstock Ice Rise, which comprises very slow-flowing ice separating the fast-flowing Institute and Möller ice streams, reveals ice deformed by former enhanced flow, overlain by un-deformed ice. The ice-rise surface is traversed by surface lineations explicable as diffuse ice-flow generated stripes, which thus capture the direction of flow immediately prior to the creation of the ice rise. The arrangement of internal layers can be explained by adjustment to the flow path of the Institute Ice Stream, during either a phase of ice sheet retreat not longer than ∼4000 years ago or by wholesale expansion of the grounding-line from an already retreated situation not sooner than ∼400 years ago. Some combination of these events, involving uplift of the ice rise bed during ice stream retreat and reorganisation, is also possible. Whichever the case, the implication is that the ice sheet upstream of the Bungenstock Ice Rise, which currently grounds over a >1.5 km deep basin has been, and therefore may be, susceptible to significant change

    MRI-Diagnosed Tumour Deposits and EMVI Status Have Superior Prognostic Accuracy to Current Clinical TNM Staging in Rectal Cancer.

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    BACKGROUND DATA: MRI assessment of rectal cancer not only assesses tumour depth and surgical resectability but also extramural disease which affects prognosis. We have observed that non-nodal tumour nodules (tumour deposits; mrTDs) have a distinct MRI appearance compared to lymph node metastases (mrLNMs). OBJECTIVE: We aimed to assess whether mrTDs and mrLNMs have different prognostic implications and compare these to other known prognostic markers. METHODS: This was a retrospective cohort study of 233 patients undergoing resection for rectal cancer from January 2007-October 2015. Data were obtained from electronic records and MRIs blindly re-reported. Survival was determined using Kaplan-Meier method. Prognostic markers were evaluated using Cox regression and competing risks analysis. Inter-observer agreement for mrTD was measured using Cohen's Kappa. RESULTS: On multivariable analysis, baseline mrTD/mrEMVI (extramural venous invasion) status was the only significant MRI factor for adverse survival (HR 2.36 (1.54-3.61) for OS, 2.37 (1.47-3.80) for DFS (both p < 0.001), superseding T and N categories. mrLNMs were associated with good prognosis (HR 0.50 (0.31-0.80)p= 0.004 for OS, 0.60 (0.40-0.90)p = 0.014 for DFS). On multivariable analysis, mrTDs/mrEMVI were strongly associated with distant recurrence (HR 6.53 (2.52-16.91) p = < 0.001) whereas T and N category were not. In a subgroup analysis of post-treatment MRIs in post-chemoradiotherapy (CRT) patients, mrTD/mrEMVI status was again the only significant prognostic factor; furthermore those who showed a good treatment response had a prognosis similar to patients who were negative at baseline. Inter-observer agreement for detection of mrTDs was κ0.77 and κ0.83. CONCLUSION: Current MRI staging predicting T and N status does not adequately predict prognosis. Positive mrTD/mrEMVI status has greater prognostic accuracy and would be superior in determining treatment and follow-up protocols. CRT may be a highly effective treatment strategy in mrTD/mrEMVI positive patients

    A manifesto for linguistics in language teaching in the UK context

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    This document sets out a manifesto for how linguistics could be incorporated into language teaching in the UK context. It responds directly to published calls for change, and identifies challenges and opportunities as well as potential actions. A number of prominent stakeholders have already formally endorsed our manifesto (see list on the final page). We will be adding further endorsers to this list once confirmed

    A new bed elevation model for the Weddell Sea sector of the West Antarctic Ice Sheet

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    We present a new bed elevation digital elevation model (DEM), with a 1 km spatial resolution, for the Weddell Sea sector of the West Antarctic Ice Sheet. The DEM has a total area of ~125,000 km2 covering the Institute, Möller and Foundation ice streams and the Bungenstock ice rise. In comparison with the Bedmap2 product, our DEM includes several new aerogeophysical datasets acquired by the Center for Remote Sensing of Ice Sheets (CReSIS) through the NASA Operation IceBridge (OIB) program in 2012, 2014 and 2016. We also update bed elevation information from the single largest existing dataset in the region, collected by the British Antarctic Survey (BAS) Polarimetric Airborne Survey Instrument (PASIN) in 2010-11, as BEDMAP2 included only relatively crude ice thickness measurements determined in the field for quality control purposes. This have resulted in the deep parts of the topography not being visible in the fieldwork non-SAR processed radargrams. While the gross form of the new DEM is similar to Bedmap2, there are some notable differences. For example, the position and size of a deep trough (~ 2 km below sea level) between the ice sheet interior and the grounding line of Foundation ice stream has been redefined. From the revised DEM, we are able to better derive the expected routing of basal water at the ice-bed interface, and by comparison with that calculated using Bedmap2 we are able to assess regions where hydraulic flow is sensitive to change. Given the sensitivity of this sector of the ice sheet to ocean-induced melting at the grounding line, especially in light of improved definition of the Foundation ice stream trough, our revised DEM will be of value to ice-sheet modelling in efforts to quantify future glaciological changes in the region, and therefore the potential impact on global sea level. The new 1 km bed elevation product of the Weddell Sea sector, West Antarctica can be found in the http://doi.org/10.5281/zenodo.1035488

    Solving the woolly mammoth conundrum: amino acid 15N-enrichment suggests a distinct forage or habitat

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    Understanding woolly mammoth ecology is key to understanding Pleistocene community dynamics and evaluating the roles of human hunting and climate change in late Quaternary megafaunal extinctions. Previous isotopic studies of mammoths’ diet and physiology have been hampered by the ‘mammoth conundrum’: woolly mammoths have anomalously high collagen δ15N values, which are more similar to coeval carnivores than herbivores and which could imply a distinct diet and (or) habitat, or a physiological adaptation. We analyzed individual amino acids from collagen of adult woolly mammoths and coeval species and discovered greater  15N enrichment in source amino acids of woolly mammoths than in most other herbivores or carnivores. Woolly mammoths consumed an isotopically distinct food source, reflective of extreme aridity, dung fertilization and (or) plant selection. This dietary signal suggests that woolly mammoths occupied a distinct habitat or forage niche relative to other Pleistocene herbivores

    Tritium retention in W plasma-facing materials : Impact of the material structure and helium irradiation

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    This article has an erratum: DOI 10.1016/j.nme.2020.100729Plasma-facing materials for next generation fusion devices, like ITER and DEMO, will be submitted to intense fluxes of light elements, notably He and H isotopes (HI). Our study focuses on tritium (T) retention on a wide range of W samples: first, different types of W materials were investigated to distinguish the impact of the pristine original structure on the retention, from W-coated samples to ITER-grade pure W samples submitted to various annealing and manufacturing procedures, along with monocrystalline W for reference. Then, He and He-D irradiated W samples were studied to investigate the impact on He-damages such as nano-bubbles (exposures in LHD or PSI-2) on T retention. We exposed all the samples to tritium gas-loading using a gentle technique preventing any introduction of new damage in the material. Tritium desorption is measured by Liquid Scintillation counting (LSC) at ambient and high temperatures (800 degrees C). The remaining T inventory is then measured by sample full dissolution and LSC. Results on T inventory on He exposed samples highlighted that in all cases, tritium desorption as a gas (HT) increases significantly due to the formation of He damages. Up to 1.8 times more T can be trapped in the material through a competition of various mechanisms, but the major part of the inventory desorbs at room temperature, and so will most likely not take part to the long-term trapped inventory for safety and operational perspectives. Unfortunately, investigation of "as received" industrial W (used for the making of plasma-facing materials) highlighted a strong impact of the pre existing defects on T retention: up to 2.5 times more T is trapped in "as received W" compared to annealed and polish W, and desorbs only at 800 degrees C, meaning ideal W material studies may underestimate T inventory for tokamak relevant conditions.Peer reviewe

    Social interaction, noise and antibiotic-mediated switches in the intestinal microbiota

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    The intestinal microbiota plays important roles in digestion and resistance against entero-pathogens. As with other ecosystems, its species composition is resilient against small disturbances but strong perturbations such as antibiotics can affect the consortium dramatically. Antibiotic cessation does not necessarily restore pre-treatment conditions and disturbed microbiota are often susceptible to pathogen invasion. Here we propose a mathematical model to explain how antibiotic-mediated switches in the microbiota composition can result from simple social interactions between antibiotic-tolerant and antibiotic-sensitive bacterial groups. We build a two-species (e.g. two functional-groups) model and identify regions of domination by antibiotic-sensitive or antibiotic-tolerant bacteria, as well as a region of multistability where domination by either group is possible. Using a new framework that we derived from statistical physics, we calculate the duration of each microbiota composition state. This is shown to depend on the balance between random fluctuations in the bacterial densities and the strength of microbial interactions. The singular value decomposition of recent metagenomic data confirms our assumption of grouping microbes as antibiotic-tolerant or antibiotic-sensitive in response to a single antibiotic. Our methodology can be extended to multiple bacterial groups and thus it provides an ecological formalism to help interpret the present surge in microbiome data.Comment: 20 pages, 5 figures accepted for publication in Plos Comp Bio. Supplementary video and information availabl

    Retrieval of aerosol single scattering albedo at ultraviolet wavelengths at the T1 site during MILAGRO

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    Surface measurements of direct and diffuse voltages at UV wavelengths were made at the T1 site during the MILAGRO (Megacity Initiative: Local and Global Research Observations) field campaign in March 2006, using a multifilter rotating shadowband radiometer (UV-MFRSR). We used the MFRSR data, together with measurements from a co-located CIMEL Sun photometer at the site operating as part of the AERONET network, to deduce aerosol single scattering albedo (ω) at 368 and 332 nm for four cloud-free days during the study. Our retrievals suggest that T1 aerosols with aerosol extinction optical depth &amp;tau;&lt;sub&gt;368&lt;/sub&gt;&amp;gt;0.1 that are influenced by Mexico City emissions, blowing dust, and biomass burning, are characterized by low &amp;omega;&lt;sub&gt;368&lt;/sub&gt;=0.73–0.85 and &amp;omega;&lt;sub&gt;332&lt;/sub&gt;=0.70–0.86, with small or no spectral variation of ω between 368 and 332 nm. Our findings are consistent with other published estimates of ω for Mexico City aerosols, including those that suggest that the absorption attributable to these aerosols is enhanced at UV wavelengths relative to visible wavelengths. We also demonstrate, via sensitivity tests, the importance of accurate τ and surface albedo measurements in ω retrievals at UV wavelengths
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