| 1. |
- Acharya, B. S., et al.
(författare)
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Introducing the CTA concept
- 2013
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Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
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| 2. |
- Abramowski, A., et al.
(författare)
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The 2010 very high energy gamma-RAY flare and 10 years of multi-wavelength observations of M 87
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 746:2, s. 151-
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Tidskriftsartikel (refereegranskat)abstract
- The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3-6) x 10(9) M-circle dot) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE gamma-ray emitter since 2006. The VHE gamma-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz Very Long Baseline Array, VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of tau(rise)(d) = (1.69 +/- 0.30) days and tau(decay)(d) = (0.611 +/- 0.080) days, respectively. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (similar to day), peak fluxes (Phi(>0.35 TeV) similar or equal to (1-3) x 10(-11) photons cm(-2) s(-1)), and VHE spectra. VLBA radio observations of 43 GHz of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken similar to 3 days after the peak of the VHE gamma-ray emission reveal an enhanced flux from the core (flux increased by factor similar to 2; variability timescale <2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M 87, spanning from radio to VHE and including data from Hubble Space Telescope, Liverpool Telescope, Very Large Array, and European VLBI Network, is used to further investigate the origin of the VHE gamma-ray emission. No unique, common MWL signature of the three VHE flares has been identified. In the outer kiloparsec jet region, in particular in HST-1, no enhanced MWL activity was detected in 2008 and 2010, disfavoring it as the origin of the VHE flares during these years. Shortly after two of the three flares (2008 and 2010), the X-ray core was observed to be at a higher flux level than its characteristic range (determined from more than 60 monitoring observations: 2002-2009). In 2005, the strong flux dominance of HST-1 could have suppressed the detection of such a feature. Published models for VHE gamma-ray emission from M 87 are reviewed in the light of the new data.
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| 3. |
- Acciari, V. A., et al.
(författare)
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Radio Imaging of the Very-High-Energy gamma-Ray Emission Region in the Central Engine of a Radio Galaxy
- 2009
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 325:5939, s. 444-448
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Tidskriftsartikel (refereegranskat)abstract
- The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.
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| 4. |
- Actis, M., et al.
(författare)
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Design concepts for the Cherenkov Telescope Array CTA : an advanced facility for ground-based high-energy gamma-ray astronomy
- 2011
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Ingår i: Experimental astronomy. - : Springer. - 0922-6435 .- 1572-9508. ; 32:3, s. 193-316
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Tidskriftsartikel (refereegranskat)abstract
- Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.
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| 5. |
- Aleksic, J., et al.
(författare)
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PG 1553+113 : FIVE YEARS OF OBSERVATIONS WITH MAGIC
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 748:1, s. 46-
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of five years (2005-2009) of MAGIC observations of the BL Lac object PG 1553+113 at very high energies (VHEs; E > 100 GeV). Power-law fits of the individual years are compatible with a steady mean photon index Gamma = 4.27 +/- 0.14. In the last three years of data, the flux level above 150 GeV shows a clear variability (probability of constant flux < 0.001%). The flux variations are modest, lying in the range from 4% to 11% of the Crab Nebula flux. Simultaneous optical data also show only modest variability that seems to be correlated with VHE gamma-ray variability. We also performed a temporal analysis of (all available) simultaneous Fermi/Large Area Telescope data of PG 1553+113 above 1 GeV, which reveals hints of variability in the 2008-2009 sample. Finally, we present a combination of the mean spectrum measured at VHEs with archival data available for other wavelengths. The mean spectral energy distribution can be modeled with a one-zone synchrotron self-Compton model, which gives the main physical parameters governing the VHE emission in the blazar jet.
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| 6. |
- Aleksic, J., et al.
(författare)
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Discovery of VHE gamma-rays from the blazar 1ES 1215+303 with the MAGIC telescopes and simultaneous multi-wavelength observations
- 2012
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 544, s. A142-
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Tidskriftsartikel (refereegranskat)abstract
- Context. We present the discovery of very high energy (VHE, E > 100 GeV) gamma-ray emission from the BL Lac object 1ES 1215+303 by the MAGIC telescopes and simultaneous multi-wavelength data in a broad energy range from radio to gamma-rays. Aims. We study the VHE gamma-ray emission from 1ES 1215+303 and its relation to the emissions in other wavelengths. Methods. Triggered by an optical outburst, MAGIC observed the source in 2011 January-February for 20.3 h. The target was monitored in the optical R-band by the KVA telescope that also performed optical polarization measurements. We triggered target of opportunity observations with the Swift satellite and obtained simultaneous and quasi-simultaneous data from the Fermi Large Area Telescope and from the Metsahovi radio telescope. We also present the analysis of older MAGIC data taken in 2010. Results. The MAGIC observations of 1ES 1215+303 carried out in 2011 January-February resulted in the first detection of the source at VHE with a statistical significance of 9.4 sigma. Simultaneously, the source was observed in a high optical and X-ray state. In 2010 the source was observed in a lower state in optical, X-ray, and VHE, while the GeV gamma-ray flux and the radio flux were comparable in 2010 and 2011. The spectral energy distribution obtained with the 2011 data can be modeled with a simple one zone SSC model, but it requires extreme values for the Doppler factor or the electron energy distribution.
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| 7. |
- Aleksic, J., et al.
(författare)
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DETECTION OF VERY HIGH ENERGY gamma-RAY EMISSION FROM THE PERSEUS CLUSTER HEAD-TAIL GALAXY IC 310 BY THE MAGIC TELESCOPES
- 2010
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Ingår i: The Astrophysical Journal Letters. - 2041-8205. ; 723:2, s. l207-L212
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Tidskriftsartikel (refereegranskat)abstract
- We report on the detection with the MAGIC telescopes of very high energy (VHE) gamma-rays from IC 310, a head-tail radio galaxy in the Perseus galaxy cluster, observed during the interval 2008 November to 2010 February. The Fermi satellite has also detected this galaxy. The source is detected by MAGIC at a high statistical significance of 7.6 sigma in 20.6 hr of stereo data. The observed spectral energy distribution is flat with a differential spectral index of -2.00 +/- 0.14. The mean flux above 300 GeV, between 2009 October and 2010 February, (3.1 +/- 0.5) x 10(-12) cm(-2) s(-1), corresponds to (2.5 +/- 0.4)% of Crab Nebula units. Only an upper limit, of 1.9% of Crab Nebula units above 300 GeV, was obtained with the 2008 data. This, together with strong hints (>3 sigma) of flares in the middle of 2009 October and November, implies that the emission is variable. The MAGIC results favor a scenario with the VHE emission originating from the inner jet close to the central engine. More complicated models than a simple one-zone synchrotron self-Compton (SSC) scenario, e. g., multi-zone SSC, external Compton, or hadronic, may be required to explain the very flat spectrum and its extension over more than three orders of magnitude in energy.
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| 8. |
- Aleksic, J., et al.
(författare)
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MAGIC reveals a complex morphology within the unidentified gamma-ray source HESS J1857+026
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 571
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Tidskriftsartikel (refereegranskat)abstract
- Aims. HESS J1857+026 is an extended TeV gamma-ray source that was discovered by H. E. S. S. as part of its Galactic plane survey. Given its broadband spectral energy distribution and its spatial coincidence with the young energetic pulsar PSR J1856+0245, the source has been put forward as a pulsar wind nebula (PWN) candidate. MAGIC has performed follow-up observations aimed at mapping the source down to energies approaching 100 GeV in order to better understand its complex morphology. Methods. HESS J1857+026 was observed by MAGIC in 2010, yielding 29 h of good quality stereoscopic data that allowed us to map the source region in two separate ranges of energy. Results. We detected very-high-energy gamma-ray emission from HESS J1857+026 with a significance of 12 sigma above 150 GeV. The differential energy spectrum between 100 GeV and 13 TeV is described well by a power law function dN/dE = N-0(E/1TeV)(-Gamma) with N-0 = (5.37 +/- 0.44(stat) +/- 1.5(sys)) X 10(-12) (TeV-1 cm(-2) s(-1)) and Gamma = 2.16 +/- 0.07(stat) +/- 0.15(sys), which bridges the gap between the GeV emission measured by Fermi-LAT and the multi-TeV emission measured by H.E.S.S.. In addition, we present a detailed analysis of the energy-dependent morphology of this region. We couple these results with archival multiwavelength data and outline evidence in favor of a two-source scenario, whereby one source is associated with a PWN, while the other could be linked with a molecular cloud complex containing an HII region and a possible gas cavity.
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| 9. |
- Jones, Benedict C, et al.
(författare)
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To which world regions does the valence-dominance model of social perception apply?
- 2021
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Ingår i: Nature Human Behaviour. - : Springer Science and Business Media LLC. - 2397-3374. ; 5:1, s. 159-169
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Tidskriftsartikel (refereegranskat)abstract
- Over the past 10 years, Oosterhof and Todorov's valence-dominance model has emerged as the most prominent account of how people evaluate faces on social dimensions. In this model, two dimensions (valence and dominance) underpin social judgements of faces. Because this model has primarily been developed and tested in Western regions, it is unclear whether these findings apply to other regions. We addressed this question by replicating Oosterhof and Todorov's methodology across 11 world regions, 41 countries and 11,570 participants. When we used Oosterhof and Todorov's original analysis strategy, the valence-dominance model generalized across regions. When we used an alternative methodology to allow for correlated dimensions, we observed much less generalization. Collectively, these results suggest that, while the valence-dominance model generalizes very well across regions when dimensions are forced to be orthogonal, regional differences are revealed when we use different extraction methods and correlate and rotate the dimension reduction solution. PROTOCOL REGISTRATION: The stage 1 protocol for this Registered Report was accepted in principle on 5 November 2018. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.7611443.v1 .
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| 10. |
- Bearden, IG, et al.
(författare)
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Deuteron and triton production with high energy sulphur and lead beams
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 23:2, s. 237-247
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Tidskriftsartikel (refereegranskat)abstract
- Proton and deuteron production has been observed in S+S and S+Pb collisions at 200 A-GeV and in Pb+Pb reactions at 158 A-GeV at the CERN SPS accelerator. For Pb+Pb triton production was also measured. The p and d spectra as well as the p and t spectra were observed in similar rapidity ranges and over similar ranges of transverse momenta per nucleon, making it possible to interpret the cross sections of the composite particles in terms of coalescence mechanisms. Volumes of homogeneity were extracted and compared to pion-pair HBT interferometry results. Special attention is given to the dependence on transverse mass, centrality and rapidity.
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| 11. |
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| 12. |
- Bearden, IG, et al.
(författare)
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Particle production in central Pb+Pb collisions at 158A GeV/c
- 2002
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 66:4
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Tidskriftsartikel (refereegranskat)abstract
- The NA44 experiment has measured single-particle inclusive spectra for charged pions, kaons, and protons as a function of transverse mass near midrapidity in 158A GeV/c Pb+Pb collisions. From the particle mass dependence of the observed m(T) distributions, we are able to deduce a value of about 120 MeV for the temperature at thermal freeze-out. From the observed ratios of the rapidity densities, we find values of the chemical potentials for light and strange quarks and a chemical freeze-out temperature of approximately 140 MeV.
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| 13. |
- Meskó, Norbert, et al.
(författare)
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Exploring Attitudes Toward “Sugar Relationships” Across 87 Countries : A Global Perspective on Exchanges of Resources for Sex and Companionship
-
Ingår i: Archives of Sexual Behavior. - 0004-0002.
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Tidskriftsartikel (refereegranskat)abstract
- The current study investigates attitudes toward one form of sex for resources: the so-called sugar relationships, which often involve exchanges of resources for sex and/or companionship. The present study examined associations among attitudes toward sugar relationships and relevant variables (e.g., sex, sociosexuality, gender inequality, parasitic exposure) in 69,924 participants across 87 countries. Two self-report measures of Acceptance of Sugar Relationships (ASR) developed for younger companion providers (ASR-YWMS) and older resource providers (ASR-OMWS) were translated into 37 languages. We tested cross-sex and cross-linguistic construct equivalence, cross-cultural invariance in sex differences, and the importance of the hypothetical predictors of ASR. Both measures showed adequate psychometric properties in all languages (except the Persian version of ASR-YWMS). Results partially supported our hypotheses and were consistent with previous theoretical considerations and empirical evidence on human mating. For example, at the individual level, sociosexual orientation, traditional gender roles, and pathogen prevalence were significant predictors of both ASR-YWMS and ASR-OMWS. At the country level, gender inequality and parasite stress positively predicted the ASR-YWMS. However, being a woman negatively predicted the ASR-OMWS, but positively predicted the ASR-YWMS. At country-level, ingroup favoritism and parasite stress positively predicted the ASR-OMWS. Furthermore, significant cross-subregional differences were found in the openness to sugar relationships (both ASR-YWMS and ASR-OMWS scores) across subregions. Finally, significant differences were found between ASR-YWMS and ASR-OMWS when compared in each subregion. The ASR-YWMS was significantly higher than the ASR-OMWS in all subregions, except for Northern Africa and Western Asia.
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| 14. |
- Xin, Huang, et al.
(författare)
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Impact of chronic obstructive pulmonary disease on prognosis after percutaneous coronary intervention and bypass surgery for left main coronary artery disease: An analysis from the EXCEL trial
- 2019
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Ingår i: European Journal of Cardio-thoracic Surgery. - : Oxford University Press (OUP). - 1010-7940 .- 1873-734X. ; 55:6, s. 1144-1151
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Tidskriftsartikel (refereegranskat)abstract
- Percutaneous coronary intervention (PCI) is often favoured over coronary artery bypass grafting (CABG) surgery for revascularization in patients with chronic obstructive pulmonary disease (COPD). We studied whether COPD affected clinical outcomes according to revascularization in the Evaluation of XIENCE Versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization (EXCEL) trial, in which PCI with everolimus-eluting stents was non-inferior to CABG for the treatment of patients with left main coronary artery disease and low or intermediate SYNTAX scores. Patients with a history of COPD were propensity score matched to those without COPD. Outcomes at 30 days and 3 years in both groups were compared in patients randomized to PCI versus CABG. RESULTS: COPD status was available for 1901 of 1905 randomized patients (99.8%), 148 of whom had COPD (7.8%). Propensity score matching yielded 135 patients with COPD and 675 patients without COPD. Patients with COPD had higher 3-year rates of the primary composite end point of death, myocardial infarction or stroke (31.7% vs 14.5%, P 0.0001), death (17.1% vs 7.5%, P = 0.0005) and myocardial infarction (18.3% vs 7.3%, P 0.0001), but not stroke (3.3% vs 2.9%, P = 0.84). There were no statistically significant interactions in the relative risks of PCI versus CABG for the primary composite end point in patients with and without COPD at 30 days [hazard ratio (HR) 0.39, 95% confidence interval (CI) 0.12 1.21 vs HR 0.55, 95% CI 0.29 1.06; Pinteraction = 0.61] or at 3 years (HR 0.85, 95% CI 0.46 1.56 vs HR 1.28, 95% CI 0.84 1.94; Pinteraction = 0.27). CONCLUSIONS: In the EXCEL trial, COPD was independently associated with poor prognosis after left main coronary artery disease revascularization. The relative risks of PCI versus CABG at 30 days and 3 years were consistent in patients with and without COPD..
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| 15. |
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| 16. |
- Fenimore, Paul W., et al.
(författare)
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Concepts and problems in protein dynamics
- 2013
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 424, s. 2-6
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Tidskriftsartikel (refereegranskat)abstract
- The function of proteins depends crucially on conformational motions. The characteristic times of these motions extend from sub-picosecond to seconds. No single experimental tool can cover the entire time range and provide all necessary parameters for a complete understanding. Moreover, without a solid understanding of the data evaluation it is easy to misinterpret the complex phenomena. Because protein motions are truly complex, the evaluation of the data even from such well-known techniques as neutron scattering (Magazu and Migliardo, 2011 [1]) and the Mossbauer effect (Chen and Yang, 2007 [2]) can lead to erroneous concepts and conclusions. We believe that notions such as the Lamb-Mossbauer relation, the protein dynamic transition, the protein glass transition, and the dynamic crossover are misleading or misapplied. To justify this statement we first briefly describe our view of dynamic proteins and then explain why we believe that these notions should be revised or abandoned. (C) 2013 Elsevier B.V. All rights reserved.
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| 17. |
- Gheorghiade, Mihai, et al.
(författare)
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Assessing and grading congestion in acute heart failure : a scientific statement from the acute heart failure committee of the heart failure association of the European Society of Cardiology and endorsed by the European Society of Intensive Care Medicine.
- 2010
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Ingår i: European Journal of Heart Failure. - : Wiley. - 1388-9842 .- 1879-0844. ; 12:5, s. 423-33
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Tidskriftsartikel (refereegranskat)abstract
- Patients with acute heart failure (AHF) require urgent in-hospital treatment for relief of symptoms. The main reason for hospitalization is congestion, rather than low cardiac output. Although congestion is associated with a poor prognosis, many patients are discharged with persistent signs and symptoms of congestion and/or a high left ventricular filling pressure. Available data suggest that a pre-discharge clinical assessment of congestion is often not performed, and even when it is performed, it is not done systematically because no method to assess congestion prior to discharge has been validated. Grading congestion would be helpful for initiating and following response to therapy. We have reviewed a variety of strategies to assess congestion which should be considered in the care of patients admitted with HF. We propose a combination of available measurements of congestion. Key elements in the measurement of congestion include bedside assessment, laboratory analysis, and dynamic manoeuvres. These strategies expand by suggesting a routine assessment of congestion and a pre-discharge scoring system. A point system is used to quantify the degree of congestion. This score offers a new instrument to direct both current and investigational therapies designed to optimize volume status during and after hospitalization. In conclusion, this document reviews the available methods of evaluating congestion, provides suggestions on how to properly perform these measurements, and proposes a method to quantify the amount of congestion present.
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| 18. |
- Holec, D., et al.
(författare)
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Macroscopic elastic properties of textured ZrN-AlN polycrystalline aggregates: From ab initio calculations to grainscale interactions
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 90:18, s. 184106-
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Tidskriftsartikel (refereegranskat)abstract
- Despite the fast development of computational material modeling, the theoretical description of macroscopic elastic properties of textured polycrystalline aggregates starting from basic principles remains a challenging task. In this study we use a supercell-based approach to obtain the elastic properties of a random solid solution cubic Zr1-x Al-x N system as a function of the metallic sublattice composition and texture descriptors. The employed special quasirandom structures are optimized not only with respect to short-range-order parameters, but also to make the three cubic directions [1 0 0], [0 1 0], and [0 0 1] as similar as possible. In this way, only a small spread of elastic constant tensor components is achieved and an optimum trade-off between modeling of chemical disorder and computational limits regarding the supercell size and calculational time is proposed. The single-crystal elastic constants are shown to vary smoothly with composition, yielding x approximate to 0.5 an alloy constitution with an almost isotropic response. Consequently, polycrystals with this composition are suggested to have Youngs modulus independent of the actual microstructure. This is indeed confirmed by explicit calculations of polycrystal elastic properties, both within the isotropic aggregate limit and with fiber textures with various orientations and sharpness. It turns out that for low AlN mole fractions, the spread of the possible Youngs modulus data caused by the texture variation can be larger than 100 GPa. Consequently, our discussion of Youngs modulus data of cubic Zr1-x Al-x N contains also the evaluation of the texture typical for thin films.
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| 19. |
- Jahn, Olga, et al.
(författare)
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Towards intense isolated attosecond pulses from relativistic surface high harmonics
- 2019
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Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 6:3, s. 280-287
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Tidskriftsartikel (refereegranskat)abstract
- Relativistic surface high harmonics have been considered a unique source for the generation of intense isolated attosecond pulses in the extreme ultra-violet and x-ray spectral ranges. Their practical realization, however, is still a challenging task and requires identification of optimum experimental conditions and parameters. Here, we present measurements and particle-in-cell simulations to determine the optimum values for the most important parameters. In particular, we investigate the dependence of harmonics efficiency, divergence, and beam quality on the pre-plasma scale length as well as identify the optimum conditions for generation of isolated attosecond pulses by measuring the dependence of the harmonics spectrum on the carrier - envelope phase of the driving infrared field. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 20. |
- Konečný, Michal, et al.
(författare)
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Enclosing the behavior of a hybrid automaton up to and beyond a Zeno point
- 2016
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Ingår i: Nonlinear Analysis. - London : Elsevier. - 1751-570X .- 1878-7460. ; 20, s. 1-20
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Tidskriftsartikel (refereegranskat)abstract
- Even simple hybrid automata like the classic bouncing ball can exhibit Zeno behavior. The existence of this type of behavior has so far forced a large class of simulators to either ignore some events or risk looping indefinitely. This in turn forces modelers to either insert ad-hoc restrictions to circumvent Zeno behavior or to abandon hybrid automata. To address this problem, we take a fresh look at event detection and localization. A key insight that emerges from this investigation is that an enclosure for a given time interval can be valid independent of the occurrence of a given event. Such an event can then even occur an unbounded number of times. This insight makes it possible to handle some types of Zeno behavior. If the post-Zeno state is defined explicitly in the given model of the hybrid automaton, the computed enclosure covers the corresponding trajectory that starts from the Zeno point through a restarted evolution. ©2015 The Authors. Published by Elsevier Ltd.
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| 21. |
- Kratz, David P., et al.
(författare)
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An inter-comparison of far-infrared line-by-line radiative transfer models
- 2005
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 90:3-4, s. 323-341
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Tidskriftsartikel (refereegranskat)abstract
- A considerable fraction (>40%) of the outgoing longwave radiation escapes from the Earth's atmosphere-surface system within a region of the spectrum known as the far-infrared (wave-numbers less than ). Dominated by the line and continuum spectral features of the pure rotation band of water vapor, the far-infrared has a strong influence upon the radiative balance of the troposphere, and hence upon the climate of the Earth. Despite the importance of the far-infrared contribution, however, very few spectrally resolved observations have been made of the atmosphere for wave-numbers less than . The National Aeronautics and Space Administration (NASA), under its Instrument Incubator Program (IIP), is currently developing technology that will enable routine, space-based spectral measurements of the far-infrared. As part of NASA's IIP, the Far-Infrared Spectroscopy of the Troposphere (FIRST) project is developing an instrument that will have the capability of measuring the spectrum over the range from 100 to at a resolution of . To properly analyze the data from the FIRST instrument, accurate radiative transfer models will be required. Unlike the mid-infrared, however, no inter-comparison of codes has been performed for the far-infrared. Thus, in parallel with the development of the FIRST instrument, an investigation has been undertaken to inter-compare radiative transfer models for potential use in the analysis of far-infrared measurements. The initial phase of this investigation has focused upon the inter-comparison of six distinct line-by-line models. The results from this study have demonstrated remarkably good agreement among the models, with differences being of order 0.5%, thereby providing a high measure of confidence in our ability to accurately compute spectral radiances in the far-infrared.
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| 22. |
- Ma, Guangjin, et al.
(författare)
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Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses
- 2015
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 22:3
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Tidskriftsartikel (refereegranskat)abstract
- We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.
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| 23. |
- Pironi, Loris, et al.
(författare)
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Characteristics of adult patients with chronic intestinal failure due to short bowel syndrome: An international multicenter survey
- 2021
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Ingår i: Clinical Nutrition ESPEN. - : Elsevier BV. - 2405-4577. ; 45, s. 433-441
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Tidskriftsartikel (refereegranskat)abstract
- Background and aims: The case-mix of patients with intestinal failure due to short bowel syndrome (SBS-IF) can differ among centres and may also be affected by the timeframe of data collection. Therefore, the ESPEN international multicenter cross-sectional survey was analyzed to compare the characteristics of SBS-IF cohorts collected within the same timeframe in different countries. Methods: The study included 1880 adult SBS-IF patients collected in 2015 by 65 centres from 22 countries. The demographic, nutritional, SBS type (end jejunostomy, SBS-J; jejuno-colic anastomosis, SBS-JC; jejunoileal anastomosis with an intact colon and ileocecal valve, SBS-JIC), underlying disease and intravenous supplementation (IVS) characteristics were analyzed. IVS was classified as fluid and electrolyte alone (FE) or parenteral nutrition admixture (PN). The mean daily IVS volume, calculated on a weekly basis, was categorized as <1, 1–2, 2–3 and >3 L/day. Results: In the entire group: 60.7% were females and SBS-J comprised 60% of cases, while mesenteric ischaemia (MI) and Crohn’ disease (CD) were the main underlying diseases. IVS dependency was longer than 3 years in around 50% of cases; IVS was infused ≥5 days/week in 75% and FE in 10% of cases. Within the SBS-IF cohort: CD was twice and thrice more frequent in SBS-J than SBS-JC and SBS-JIC, respectively, while MI was more frequent in SBS-JC and SBS-JIC. Within countries: SBS-J represented 75% or more of patients in UK and Denmark and 50-60% in the other countries, except Poland where SBS-JC prevailed. CD was the main underlying disease in UK, USA, Denmark and The Netherlands, while MI prevailed in France, Italy and Poland. Conclusions: SBS-IF type is primarily determined by the underlying disease, with significant variation between countries. These novel data will be useful for planning and managing both clinical activity and research studies on SBS.
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- Wang, Fei, 1988-
(författare)
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Properties of multilayered and multicomponent nitride alloys from first principles
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is a theoretical exploration of properties of multilayered and multicomponent nitride alloys, in particular their mixing thermodynamics and elastic behaviors. Systematic investigation of properties of a large class of materials, such as the multicomponent nitride solid solutions, is in line with the modern approach of high-throughput search of novel materials. In this thesis we benchmark and utilize simple but efficient methodological frameworks in predicting mixing thermodynamics, Young’s moduli distribution of multilayer alloys and the linear thermal expansion of quaternary nitride solid solutions.We demonstrate by accurate ab-initio calculations that Ti1−xAlxN solid solution is stabilized by interfacial effects if it is coherently sandwiched between TiN layers along (001). For TiN/AlN and ZrN/AlN multilayers we show higher thermodynamic stability with semicoherent interfaces than with isostructural coherent ones.Accurate 0 Kelvin elastic constants of cubic TixXyAl1−x−yN (X=Zr, Hf, Nb, V, Ta) solid solutions and their multilayers are derived and an analytic comparison of strengths and ductility are presented to reveal the potential of these materials in hard coating applications. The Young’s moduli variation of the bulk materials has provided a reliable descriptor to screen the Young’s moduli of coherent multilayers.The Debye model is used to reveal the high-temperature thermodynamics and spinodal decomposition of TixNbyAl1−x−yN. We show that though the effect of vibration is large on the mixing Gibbs free energy the local spinoal decomposition tendencies are not altered. A quasi-harmonic Debye model is benchmarked against results of molecular dynamics simulations in predicting the thermal expansion coefficients of TixXyAl1−x−yN (X=Zr, Hf, Nb, V, Ta).
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