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  • Pinkney, T., et al. (författare)
  • Relationship between method of anastomosis and anastomotic failure after right hemicolectomy and ileo-caecal resection : an international snapshot audit
  • 2017
  • Ingår i: Colorectal Disease. - WILEY. - 1462-8910 .- 1463-1318. ; 19:8, s. e296-e311
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Aim: The anastomosis technique used following right-sided colonic resection is widely variable and may affect patient outcome. This study aimed to assess the association between leak and anastomosis technique (stapled vs handsewn).</p><p>Method: This was a prospective, multicentre, international audit including patients undergoing elective or emergency right hemicolectomy or ileo-caecal resection operations over a 2-month period in early 2015. The primary outcome measure was the presence of anastomotic leak within 30 days of surgery, determined using a prespecified definition. Mixed effects logistic regression models were used to assess the association between leak and anastomosis method, adjusting for patient, disease and operative cofactors, with centre included as a random-effect variable.</p><p>Results: This study included 3208 patients, of whom 78.4% (n = 2515) underwent surgery for malignancy and 11.7% (n = 375) underwent surgery for Crohn's disease. An anastomosis was performed in 94.8% (n = 3041) of patients, which was handsewn in 38.9% (n = 1183) and stapled in 61.1% (n = 1858). Patients undergoing hand-sewn anastomosis were more likely to be emergency admissions (20.5% handsewn vs 12.9% stapled) and to undergo open surgery (54.7% handsewn vs 36.6% stapled). The overall anastomotic leak rate was 8.1% (245/3041), which was similar following handsewn (7.4%) and stapled (8.5%) techniques (P = 0.3). After adjustment for cofactors, the odds of a leak were higher for stapled anastomosis (adjusted OR = 1.43; 95% CI: 1.04-1.95; P = 0.03).</p><p>Conclusion: Despite being used in lower-risk patients, stapled anastomosis was associated with an increased anastomotic leak rate in this observational study. Further research is needed to define patient groups in whom a stapled anastomosis is safe.</p>
  • Coda, S., et al. (författare)
  • Physics research on the TCV tokamak facility: From conventional to alternative scenarios and beyond
  • 2019
  • Ingår i: Nuclear Fusion. - 0029-5515. ; 59:11
  • Tidskriftsartikel (refereegranskat)abstract
    • The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, to exploratory plasmas driven by theoretical insight, exploiting the device's unique shaping capabilities. Disruption avoidance by real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic and radiation triggers. Runaway generation with high-Z noble-gas injection and runaway dissipation by subsequent Ne or Ar injection were studied for model validation. The new 1 MW neutral beam injector has expanded the parameter range, now encompassing ELMy H-modes in an ITER-like shape and nearly non-inductive H-mode discharges sustained by electron cyclotron and neutral beam current drive. In the H-mode, the pedestal pressure increases modestly with nitrogen seeding while fueling moves the density pedestal outwards, but the plasma stored energy is largely uncorrelated to either seeding or fueling. High fueling at high triangularity is key to accessing the attractive small edge-localized mode (type-II) regime. Turbulence is reduced in the core at negative triangularity, consistent with increased confinement and in accord with global gyrokinetic simulations. The geodesic acoustic mode, possibly coupled with avalanche events, has been linked with particle flow to the wall in diverted plasmas. Detachment, scrape-off layer transport, and turbulence were studied in L- and H-modes in both standard and alternative configurations (snowflake, super-X, and beyond). The detachment process is caused by power 'starvation' reducing the ionization source, with volume recombination playing only a minor role. Partial detachment in the H-mode is obtained with impurity seeding and has shown little dependence on flux expansion in standard single-null geometry. In the attached L-mode phase, increasing the outer connection length reduces the in-out heat-flow asymmetry. A doublet plasma, featuring an internal X-point, was achieved successfully, and a transport barrier was observed in the mantle just outside the internal separatrix. In the near future variable-configuration baffles and possibly divertor pumping will be introduced to investigate the effect of divertor closure on exhaust and performance, and 3.5 MW ECRH and 1 MW neutral beam injection heating will be added.
  • Aartsen, M. G., et al. (författare)
  • The Detection Of A Sn Iin In Optical Follow-Up Observations Of Icecube Neutrino Events
  • 2015
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 811:1
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The IceCube neutrino observatory pursues a follow-up program selecting interesting neutrino events in real-time and issuing alerts for electromagnetic follow-up observations. In 2012 March, the most significant neutrino alert during the first three years of operation was issued by IceCube. In the follow-up observations performed by the Palomar Transient Factory (PTF), a Type IIn supernova (SN IIn) PTF12csy was found 0.degrees 2 away from the neutrino alert direction, with an error radius of 0.degrees 54. It has a redshift of z = 0.0684, corresponding to a luminosity distance of about 300 Mpc and the Pan-STARRS1 survey shows that its explosion time was at least 158 days (in host galaxy rest frame) before the neutrino alert, so that a causal connection is unlikely. The a posteriori significance of the chance detection of both the neutrinos and the SN at any epoch is 2.2 sigma within IceCube's 2011/12 data acquisition season. Also, a complementary neutrino analysis reveals no long-term signal over the course of one year. Therefore, we consider the SN detection coincidental and the neutrinos uncorrelated to the SN. However, the SN is unusual and interesting by itself: it is luminous and energetic, bearing strong resemblance to the SN IIn 2010jl, and shows signs of interaction of the SN ejecta with a dense circumstellar medium. High-energy neutrino emission is expected in models of diffusive shock acceleration, but at a low, non-detectable level for this specific SN. In this paper, we describe the SN PTF12csy and present both the neutrino and electromagnetic data, as well as their analysis.</p>
  • Aartsen, M. G., et al. (författare)
  • A Combined Maximum-Likelihood Analysis Of The High-Energy Astrophysical Neutrino Flux Measured With Icecube
  • 2015
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 809:1
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Evidence for an extraterrestrial flux of high-energy neutrinos has now been found in multiple searches with the IceCube detector. The first solid evidence was provided by a search for neutrino events with deposited energies greater than or similar to 30 TeV and interaction vertices inside the instrumented volume. Recent analyses suggest that the extraterrestrial flux extends to lower energies and is also visible with throughgoing, nu(mu)-induced tracks from the Northern Hemisphere. Here, we combine the results from six different IceCube searches for astrophysical neutrinos in a maximum-likelihood analysis. The combined event sample features high-statistics samples of shower-like and track-like events. The data are fit in up to three observables: energy, zenith angle, and event topology. Assuming the astrophysical neutrino flux to be isotropic and to consist of equal flavors at Earth, the all-flavor spectrum with neutrino energies between 25 TeV and 2.8 PeV is well described by an unbroken power law with best-fit spectral index -2.50 +/- 0.09 and a flux at 100 TeV of (6.7(-1.2)(+1.1)) x 10(-18) GeV-1 s(-1) sr(-1) cm(-2). Under the same assumptions, an unbroken power law with index -2 is disfavored with a significance of 3.8 sigma (p = 0.0066%) with respect to the best fit. This significance is reduced to 2.1 sigma (p = 1.7%) if instead we compare the best fit to a spectrum with index -2 that has an exponential cut-off at high energies. Allowing the electron-neutrino flux to deviate from the other two flavors, we find a nu(e) fraction of 0.18 +/- 0.11 at Earth. The sole production of electron neutrinos, which would be characteristic of neutron-decay-dominated sources, is rejected with a significance of 3.6 sigma ( p = 0.014%).</p>
  • Aartsen, M. G., et al. (författare)
  • Atmospheric and astrophysical neutrinos above 1 TeV interacting in IceCube
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 91:2, s. 022001
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The IceCube Neutrino Observatory was designed primarily to search for high-energy (TeV-PeV) neutLrinos produced in distant astrophysical objects. A search for. greater than or similar to 100 TeV neutrinos interacting inside the instrumented volume has recently provided evidence for an isotropic flux of such neutrinos. At lower energies, IceCube collects large numbers of neutrinos from the weak decays of mesons in cosmic-ray air showers. Here we present the results of a search for neutrino interactions inside IceCube's instrumented volume between 1 TeV and 1 PeV in 641 days of data taken from 2010-2012, lowering the energy threshold for neutrinos from the southern sky below 10 TeV for the first time, far below the threshold of the previous high-energy analysis. Astrophysical neutrinos remain the dominant component in the southern sky down to a deposited energy of 10 TeV. From these data we derive new constraints on the diffuse astrophysical neutrino spectrum, Phi(v) = 2.06(-0.3)(+0.4) x 10(-18) (E-v = 10(5) GeV)-2.46 +/- 0.12GeV-1 cm(-2) sr(-1) s(-1) for 25 TeV &lt; E-v &lt; 1.4 PeV, as well as the strongest upper limit yet on the flux of neutrinos from charmed-meson decay in the atmosphere, 1.52 times the benchmark theoretical prediction used in previous IceCube results at 90% confidence.</p>
  • Aartsen, M. G., et al. (författare)
  • Characterization of the atmospheric muon flux in IceCube
  • 2016
  • Ingår i: Astroparticle physics. - 0927-6505 .- 1873-2852. ; 78, s. 1-27
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Muons produced in atmospheric cosmic ray showers account for the by far dominant part of the event yield in large-volume underground particle detectors. The IceCube detector, with an instrumented volume of about a cubic kilometer, has the potential to conduct unique investigations on atmospheric muons by exploiting the large collection area and the possibility to track particles over a long distance. Through detailed reconstruction of energy deposition along the tracks, the characteristics of muon bundles can be quantified, and individual particles of exceptionally high energy identified. The data can then be used to constrain the cosmic ray primary flux and the contribution to atmospheric lepton fluxes from prompt decays of short-lived hadrons. In this paper, techniques for the extraction of physical measurements from atmospheric muon events are described and first results are presented. The multiplicity spectrum of TeV muons in cosmic ray air showers for primaries in the energy range from the knee to the ankle is derived and found to be consistent with recent results from surface detectors. The single muon energy spectrum is determined up to PeV energies and shows a clear indication for the emergence of a distinct spectral component from prompt decays of short-lived hadrons. The magnitude of the prompt flux, which should include a substantial contribution from light vector meson di-muon decays, is consistent with current theoretical predictions. The variety of measurements and high event statistics can also be exploited for the evaluation of systematic effects. In the course of this study, internal inconsistencies in the zenith angle distribution of events were found which indicate the presence of an unexplained effect outside the currently applied range of detector systematics. The underlying cause could be related to the hadronic interaction models used to describe muon production in air showers.</p>
  • Aartsen, M. G., et al. (författare)
  • Cosmic ray spectrum and composition from PeV to EeV using 3 years of data from IceTop and IceCube
  • 2019
  • Ingår i: Physical Review D : covering particles, fields, gravitation, and cosmology. - AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 100:8
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We report on measurements of the all-particle cosmic ray energy spectrum and composition in the PeV to EeV energy range using 3 years of data from the IceCube Neutrino Observatory. The IceTop detector measures cosmic ray induced air showers on the surface of the ice, from which the energy spectrum of cosmic rays is determined by making additional assumptions about the mass composition. A separate measurement is performed when IceTop data are analyzed in coincidence with the high-energy muon energy loss information from the deep in-ice IceCube detector. In this measurement, both the spectrum and the mass composition of the primary cosmic rays are simultaneously reconstructed using a neural network trained on observables from both detectors. The performance and relative advantages of these two distinct analyses are discussed, including the systematic uncertainties and the dependence on the hadronic interaction models, and both all-particle spectra as well as individual spectra for elemental groups are presented.</p>
  • Aartsen, M. G., et al. (författare)
  • Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 91:7
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a measurement of neutrino oscillations via atmospheric muon neutrino disappearance with three years of data of the completed IceCube neutrino detector. DeepCore, a region of denser IceCube instrumentation, enables the detection and reconstruction of atmospheric muon neutrinos between 10 and 100 GeV, where a strong disappearance signal is expected. The IceCube detector volume surrounding DeepCore is used as a veto region to suppress the atmospheric muon background. Neutrino events are selected where the detected Cherenkov photons of the secondary particles minimally scatter, and the neutrino energy and arrival direction are reconstructed. Both variables are used to obtain the neutrino oscillation parameters from the data, with the best fit given by Delta m(32)(2) = 2.72(-0.20)(+0.19) x 10(-3) eV(2) and sin(2)theta(23) = 0.53(-0.12)(+0.09) (normal mass ordering assumed). The results are compatible, and comparable in precision, to those of dedicated oscillation experiments.</p>
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