259 research outputs found

    Interplay of Dirac nodes and Volkov-Pankratov surface states in compressively strained HgTe

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    Preceded by the discovery of topological insulators, Dirac and Weyl semimetals have become a pivotal direction of research in contemporary condensed matter physics. While easily accessible from a theoretical viewpoint, these topological semimetals pose a serious challenge in terms of experimental synthesis and analysis to allow for their unambiguous identification. In this work, we report on detailed transport experiments on compressively strained HgTe. Due to the superior sample quality in comparison to other topological semimetallic materials, this enables us to resolve the interplay of topological surface states and semimetallic bulk states to an unprecedented degree of precision and complexity. As our gate design allows us to precisely tune the Fermi level at the Weyl and Dirac points, we identify a magnetotransport regime dominated by Weyl/Dirac bulk state conduction for small carrier densities and by topological surface state conduction for larger carrier densities. As such, similar to topological insulators, HgTe provides the archetypical reference for the experimental investigation of topological semimetals.Comment: 8 pages, 7 figures, accepted in PRX, added kp calculation and supplementar

    Feasibility of the Manchester Acute Coronary Syndromes (MACS) decision rule to safely reduce unnecessary hospital admissions: a pilot randomised controlled trial

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    Background Observational studies suggest that the Manchester Acute Coronary Syndromes (MACS) decision rule can effectively rule out' and rule in' acute coronary syndromes (ACS) following a single blood test. In a pilot randomised controlled trial, we aimed to determine whether a large trial is feasible. Methods Patients presenting to two EDs with suspected cardiac chest pain were randomised to receive care guided by the MACS decision rule (intervention group) or standard care (controls). The primary efficacy outcome was a successful discharge from the ED, defined as a decision to discharge within 4 hours of arrival providing that the patient did not have a missed acute myocardial infarction (AMI) or develop a major adverse cardiac event (MACE: death, AMI or coronary revascularisation) within 30 days. Feasibility outcomes included recruitment and attrition rates. Results In total, 138 patients were included between October 2013 and October 2014, of whom 131 (95%) were randomised (66 to intervention and 65 controls). Nine (7%) patients had prevalent AMI and six (5%) had incident MACE within 30 days. All 131 patients completed 30-day follow-up and were included in the final analysis with no missing data for the primary analyses. Compared with standard care, a significantly greater proportion of patients whose care was guided by the MACS rule were successfully discharged within 4 hours (26% vs 8%, adjusted OR 5.45, 95% CI 1.73 to 17.11, p=0.004). No patients in either group who were discharged within 4 hours had a diagnosis of AMI or incident MACE within 30 days (0.0%, 95% CI 0% to 20.0% in the intervention group). Conclusions In this pilot trial, use of the MACS rule led to a significant increase in safe discharges from the ED but a larger, fully powered trial remains necessary. Our findings seem to support the feasibility of that trial. Trial registration number ISRCTN 86818215. Research Ethics Committee reference 13/NW/0081. UKCRN registration ID 14334

    Recital Christa Ludwig

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    Programa de mà del recital dut a terme per Christa Ludwig i Charles Spencer el 30 de novembre del 1991 i on es van intepretar les següents peçes: Geheimnis, Im Abendrot, Auf der Donau, Sehnsucht, Der Lindenbaum i Der Musensohn de Schubert ; Ich gign mit Lust, Rheinlegendchen, Das irrdische Leben, Ich bin der Welt abhanden gedommen i Um Mitternacht de Gustav Mahler ; Freudvoll und leidvoll, Du bist wie eine Blume i Die drei Zigeuner, de Franz Liszt ; Dein blaues Auge, An eine Äolsharfe, St¨ndchen i Immer leiser wird mein Schlummer, de Johannes Brahms ; Du meines Herzens Krönelein, Begegnung, Die Nacht, Ruhe, meine Seele i Morgen, de Richard Straus

    Beyond the Ultra-deep Frontier Fields And Legacy Observations (BUFFALO): a high-resolution strong + weak-lensing view of Abell 370

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    The HST treasury program BUFFALO provides extended wide-field imaging of the six Hubble Frontier Fields galaxy clusters. Here we present the combined strong and weak-lensing analysis of Abell 370, a massive cluster at z=0.375. From the reconstructed total projected mass distribution in the 6arcmin x 6arcmin BUFFALO field-of-view, we obtain the distribution of massive substructures outside the cluster core and report the presence of a total of seven candidates, each with mass 5×1013M\sim 5 \times 10^{13}M_{\odot}. Combining the total mass distribution derived from lensing with multi-wavelength data, we evaluate the physical significance of each candidate substructure, and conclude that 5 out of the 7 substructure candidates seem reliable, and that the mass distribution in Abell 370 is extended along the North-West and South-East directions. While this finding is in general agreement with previous studies, our detailed spatial reconstruction provides new insights into the complex mass distribution at large cluster-centric radius. We explore the impact of the extended mass reconstruction on the model of the cluster core and in particular, we attempt to physically explain the presence of an important external shear component, necessary to obtain a low root-mean-square separation between the model-predicted and observed positions of the multiple images in the cluster core. The substructures can only account for up to half the amplitude of the external shear, suggesting that more effort is needed to fully replace it by more physically motivated mass components. We provide public access to all the lensing data used as well as the different lens models.Comment: 29 pages, 17 figures, 3 table

    Cardiorespiratory fitness, adiposity and incident asthma in adults

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    Available large-scale prospective studies on adiposity and asthma used body mass index as an indicator of adiposity. Studies involving more accurate measures of adiposity, such as body fat percentage (BF%), are needed to confirm or contrast body mass index - related results. Cardiorepiratory fitness is a strong predictor of morbidity and mortality, and the available literature suggests that moderate-high cardiorespiratory fitness reduces many of the health hazards associated with obesity. The present study aimed: 1) to examine whether cardiorespiratory fitness and/or BF% are associated with subsequent acquisition of asthma in adults; and 2) to test the hypothesis that a high cardiorespiratory fitness level can reduce the risk of incident asthma in individuals with excess adiposity

    BUFFALO/Flashlights: Constraints on the abundance of lensed supergiant stars in the Spock galaxy at redshift 1

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    In this work, we present a constraint on the abundance of supergiant (SG) stars at redshift z ≈ 1, based on recent observations of astrongly lensed arc at this redshift. First we derived a free-form model of MACS J0416.1-2403 using data from the Beyond Ultradeep Frontier Fields and Legacy Observations (BUFFALO) program. The new lens model is based on 72 multiply lensed galaxies thatproduce 214 multiple images, making it the largest sample of spectroscopically confirmed lensed galaxies on this cluster. The largercoverage in BUFFALO allowed us to measure the shear up to the outskirts of the cluster, and extend the range of lensing constraintsup to ∼1 Mpc from the central region, providing a mass estimate up to this radius. As an application, we make predictions for thenumber of high-redshift multiply lensed galaxies detected in future observations with the James Webb Space Telescope (JWST).Then we focus on a previously known lensed galaxy at z = 1.0054, nicknamed Spock, which contains four previously reportedtransients. We interpret these transients as microcaustic crossings of SG stars and explain how we computed the probability of suchevents. Based on simplifications regarding the stellar evolution, we find that microlensing (by stars in the intracluster medium) ofSG stars at z = 1.0054 can fully explain these events. The inferred abundance of SG stars is consistent with either (1) a numberdensity of stars with bolometric luminosities beyond the Humphreys-Davidson (HD) limit (Lmax ≈ 6 × 105 L for red stars), whichis below ∼400 stars kpc−2, or (2) the absence of stars beyond the HD limit but with a SG number density of ∼9000 kpc−2 for starswith luminosities between 105 L and 6 × 105 L. This is equivalent to one SG star per 10 × 10 pc2. Finally, we make predictions forfuture observations with JWST’s NIRcam. We find that in observations made with the F200W filter that reach 29 mag AB, if cool red SG stars exist at z ≈ 1 beyond the HD limit, they should be easily detected in this arc

    BUFFALO/Flashlights: Constraints on the abundance of lensed supergiant stars in the Spock galaxy at redshift 1

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    We present a constraint on the abundance of supergiant (SG) stars at redshift z approx. 1, based on recent observations of a strongly lensed arc at this redshift. First we derive a free-form model of MACS J0416.1-2403 using data from the BUFFALO program. The new lens model is based on 72 multiply lensed galaxies that produce 214 multiple images, making it the largest sample of spectroscopically confirmed lensed galaxies on this cluster. The larger coverage in BUFFALO allows us to measure the shear up to the outskirts of the cluster, and extend the range of lensing constraints up to ~ 1 Mpc from the central region, providing a mass estimate up to this radius. As an application, we make predictions for the number of high-redshift multiply-lensed galaxies detected in future observations with JWST. Then we focus on a previously known lensed galaxy at z=1.0054, nicknamed Spock, which contains four previously reported transients. We interpret these transients as microcaustic crossings of SG stars and compute the probability of such events. Based on simplifications regarding the stellar evolution, we find that microlensing (by stars in the intracluster medium) of SG stars at z=1.0054 can fully explain these events. The inferred abundance of SG stars is consistent with either (1) a number density of stars with bolometric luminosities beyond the Humphreys-Davidson (HD) limit (L ~ 6×105L6\times10^5 L_{\odot}) that is below 400 stars per sq. kpc, or (2) the absence of stars beyond the HD limit but with a SG number density of ~ 9000 per sq. kpc for stars with luminosities between 10510^5 and 6×1056\times10^5. This is equivalent to one SG star per 10x10 pc2^2. We finally make predictions for future observations with JWST's NIRcam. We find that in observations made with the F200W filter that reach 29 mag AB, if cool red SG stars exist at z~1 beyond the HD limit, they should be easily detected in this arcComment: 24 pages & 18 figure
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