Surface elevation change and mass balance of Icelandic ice caps derived from swath mode CryoSat-2 altimetry

We apply swath processing to CryoSat-2 interferometric mode data acquired over the Icelandic ice caps to generate maps of rates of surface elevation change at 0.5 km postings. This high-resolution mapping reveals complex surface elevation changes in the region, related to climate, ice dynamics, and subglacial geothermal and magmatic processes. We estimate rates of volume and mass change independently for the six major Icelandic ice caps, 90% of Iceland's permanent ice cover, for five glaciological years between October 2010 and September 2015. Annual mass balance is highly variable; during the 2014/2015 glaciological year, the Vatnajökull ice cap (~70% of the glaciated area) experienced positive mass balance for the first time since 1992/1993. Our results indicate that between glaciological years 2010/2011and 2014/2015 Icelandic ice caps have lost 5.8 ± 0.7 Gt a−1 on average, ~40% less than the preceding 15 years, contributing 0.016 ± 0.002 mm a−1 to sea level rise

The Jet and the Supernova in GRB990712

The optical light curve of the afterglow following the gamma-ray burst GRB990712 is re-examined. Recently published polarization measurements of that source require a collimated outflow geometry that in turn predicts a break in the light curve. We show that the V-band light curve is consistent with such a break and that the post-break light curve evolution is dominated by a supernova contribution

Melt movement through the Icelandic crust.

We use both seismology and geobarometry to investigate the movement of melt through the volcanic crust of Iceland. We have captured melt in the act of moving within or through a series of sills ranging from the upper mantle to the shallow crust by the clusters of small earthquakes it produces as it forces its way upward. The melt is injected not just beneath the central volcanoes, but also at discrete locations along the rift zones and above the centre of the underlying mantle plume. We suggest that the high strain rates required to produce seismicity at depths of 10-25 km in a normally ductile part of the Icelandic crust are linked to the exsolution of carbon dioxide from the basaltic melts. The seismicity and geobarometry provide complementary information on the way that the melt moves through the crust, stalling and fractionating, and often freezing in one or more melt lenses on its way upwards: the seismicity shows what is happening instantaneously today, while the geobarometry gives constraints averaged over longer time scales on the depths of residence in the crust of melts prior to their eruption. This article is part of the Theo Murphy meeting issue 'Magma reservoir architecture and dynamics'

Why compatibilist intuitions are not mistaken: a reply to Feltz and Millan

In the past decade, a number of empirical researchers have suggested that laypeople have compatibilist intuitions. In a recent paper, Feltz and Millan (2015) have challenged this conclusion by claiming that most laypeople are only compatibilists in appearance and are in fact willing to attribute free will to people no matter what. As evidence for this claim, they have shown that an important proportion of laypeople still attribute free will to agents in fatalistic universes. In this paper, we first argue that Feltz and Millan’s error-theory rests on a conceptual confusion: it is perfectly acceptable for a certain brand of compatibilist to judge free will and fatalism to be compatible, as long as fatalism does not prevent agents from being the source of their actions. We then present the results of two studies showing that laypeople’s intuitions are best understood as following a certain brand of source compatibilism rather than a “free-will-no-matter-what” strategy

Upper limit on spontaneous supercurrents in Sr2_2RuO4_4

It is widely believed that the perovskite Sr$_2$RuO$_4$ is an unconventional superconductor with broken time reversal symmetry. It has been predicted that superconductors with broken time reversal symmetry should have spontaneously generated supercurrents at edges and domain walls. We have done careful imaging of the magnetic fields above Sr$_2$RuO$_4$ single crystals using scanning Hall bar and SQUID microscopies, and see no evidence for such spontaneously generated supercurrents. We use the results from our magnetic imaging to place upper limits on the spontaneously generated supercurrents at edges and domain walls as a function of domain size. For a single domain, this upper limit is below the predicted signal by two orders of magnitude. We speculate on the causes and implications of the lack of large spontaneous supercurrents in this very interesting superconducting system.Comment: 9 page

HST/STIS Imaging of the Host Galaxy of GRB980425/SN1998bw

We present HST/STIS observations of ESO 184-G82, the host galaxy of the gamma-ray burst GRB 980425 associated with the peculiar Type Ic supernova SN1998bw. ESO 184-G82 is found to be an actively star forming SBc sub-luminous galaxy. We detect an object consistent with being a point source within the astrometric uncertainty of 0.018 arcseconds of the position of the supernova. The object is located inside a star-forming region and is at least one magnitude brighter than expected for the supernova based on a simple radioactive decay model. This implies either a significant flattening of the light curve or a contribution from an underlying star cluster.Comment: 12 pages, 2 figures, AASTeX v5.02 accepted for publication in ApJ Letter

Computation of Lyapunov functions for systems with multiple attractors

We present a novel method to compute Lyapunov functions for continuous-time systems with multiple local attractors. In the proposed method one first computes an outer approximation of the local attractors using a graphtheoretic approach. Then a candidate Lyapunov function is computed using a Massera-like construction adapted to multiple local attractors. In the final step this candidate Lyapunov function is interpolated over the simplices of a simplicial complex and, by checking certain inequalities at the vertices of the complex, we can identify the region in which the Lyapunov function is decreasing along system trajectories. The resulting Lyapunov function gives information on the qualitative behavior of the dynamics, including lower bounds on the basins of attraction of the individual local attractors. We develop the theory in detail and present numerical examples demonstrating the applicability of our method

Acute lower gastrointestinal bleeding : A population-based five-year follow-up study

Publisher Copyright: © Author(s) 2019.Background: Data on the natural history of acute lower gastrointestinal bleeding (ALGIB) are lacking. We evaluated five-year bleeding risk and mortality in ALGIB patients and controls. Furthermore, we aimed to find predictors of rebleeding. Methods: This was a population-based retrospective case-control study conducted at the National University Hospital of Iceland, and included every individual who underwent endoscopy in 2010–2011. ALGIB was defined as rectal bleeding leading to hospitalisation or occurring in a hospitalised patient. Controls were randomly selected from those who underwent endoscopy in the same time period but who did not have GIB, and were matched for sex and age. Patients were followed up five years after index bleeding. Rebleeding was defined as ALGIB >14 days after index bleeding. Results: In total, 2294 patients underwent 2602 colonoscopies in 2010–2011. Of those, 319 (14%) had ALGIB. The mean age for cases and controls was 64 and 65 years (±19.3–20.7), respectively, and females accounted for 51–52% of the study population. For ALGIB patients, the five-year risk of a bleeding was 20% (95% confidence interval (CI) 15–24%) compared to 3% (95% CI 1–5%) in controls (log rank < 0.0001; co-morbidity-adjusted hazard ratio (HR) 6.9 (95% CI 3.4–14)). Only 37% of bleeders had the same cause of index bleeding and rebleeding. In ALGIB patients, age and inflammatory bowel disease (IBD) were predictors of rebleeding, with odds ratios per 10 years of 1.3 (95% CI 1.1–1.6) and 4.3 (95% CI 1.5–12), respectively. Bleeders did not have a higher risk of five-year mortality compared to controls (HR = 1.2; 95% CI 0.87–1.6). Conclusions: One fifth of ALGIB patients had rebleeding during follow-up. Age and IBD were independent predictors of rebleeding. ALGIB was not associated with lower five-year survival.Peer reviewe

The bright optical flash from GRB 060117

We present a discovery and observation of an extraordinarily bright prompt optical emission of the GRB 060117 obtained by a wide-field camera atop the robotic telescope FRAM of the Pierre Auger Observatory from 2 to 10 minutes after the GRB. We found rapid average temporal flux decay of alpha = -1.7 +- 0.1 and a peak brightness R = 10.1 mag. Later observations by other instruments set a strong limit on the optical and radio transient fluxes, unveiling an unexpectedly rapid further decay. We present an interpretation featuring a relatively steep electron-distribution parameter p ~ 3.0 and providing a straightforward solution for the overall fast decay of this optical transient as a transition between reverse and forward shock.Comment: Accepted to A&A, 4 pages, corected few typos pointed out by X.F. W