| 1. |
- Abdallah, Jalal, et al.
(författare)
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Study of energy response and resolution of the ATLAS Tile Calorimeter to hadrons of energies from 16 to 30 GeV
- 2021
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:6
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Tidskriftsartikel (refereegranskat)abstract
- Three spare modules of the ATLAS Tile Calorimeter were exposed to test beams from the Super Proton Synchrotron accelerator at CERN in 2017. The detector’s measurements of the energy response and resolution to positive pions and kaons, and protons with energies ranging from 16 to 30 GeV are reported. The results have uncertainties of a few percent. They were compared to the predictions of the Geant4-based simulation program used in ATLAS to estimate the response of the detector to proton-proton events at the Large Hadron Collider. The determinations obtained using experimental and simulated data agree within the uncertainties.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- Hildebrand, Robert, 1967-
(författare)
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Countermeasures against railway ground and track vibrations
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Railway track and ground vibrations are considered, with anemphasis on methods of mitigation ("countermeasures"), forapplication to wayside disturbance problems.Original field measurements from two sites in Sweden, aswell as borrowed measurements from Norway, provide vibrationresults at many points on the track, on and underneath theground surface, for a variety of trains, both with and withoutcountermeasures in-place.Infinite periodic system theory is the basis of track-onlyand track-ground interaction models presented. The repeatingelement includes the sleeper, pad-fastener, rail, and either alocally-reacting ballast or a continuous ballast-soilwaveguide. The track-only model is even refined for nonlinearand high-frequency cases. The models are suitable for studyingcountermeasures in the track, or in the foundation(soil-stabilization). This latter countermeasure is shown to beeffective at low frequencies (of geotechnical interest), butsometimes counterproductive at audible frequencies (disturbanceproblems).An analytical model for hard seismic screens is alsopresented, to complement the treatment of ground vibrationcountermeasures; this is based on physical approximations whichare favored by "high" (i.e, audible)frequencies and softsoils. Notably, experimentally observed resonant behavior isexplained.Keywords:ground vibration, vibration screen, trackvibration, railway vibration
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| 5. |
- Hildebrand, Robert
(författare)
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Effect of soil stabilization on audible band railway ground vibration
- 2004
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261 .- 1879-341X. ; 24:5, s. 411-424
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Tidskriftsartikel (refereegranskat)abstract
- Although railway-generated ground vibrations usually have greater energy levels at lower frequencies, vibrations in the audible range above 20 Hz can nevertheless be relevant for secondary noise problems in buildings. One countermeasure is soil stabilization under the track embankment. While effective at low frequencies, a potential side effect is amplification in some audible bands. Presented here are both experimental and theoretical assessments of the countermeasure in the audible bands. The main innovation is the treatment of an infinite periodic track-ground system, using a transfer matrix approach with a repeating element including the rail, pad, sleeper, and an underlying half-space (ballast and soil). Excitation in this band is attributed to rail and wheel roughness. The model makes successful predictions when the half-space properties are allowed to be frequency-dependent such that the dispersion of the surface wave matches that in the actual layered earth (including ballast and underlying soil layers). The field measurements are also unique in that both before and after evaluation of the countermeasure was possible.
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| 6. |
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| 8. |
- Streng, Michael, et al.
(författare)
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Clarification of the systematic position of two calcareous dinoflagellate taxa belonging to the genus Calciodinellum (Dinophyceae, Peridiniales)
- 2006
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Ingår i: Micropaleontology. - : Micropaleontological Foundation MicroPress Europe. - 0026-2803 .- 1937-2795. ; 52:2, s. 189-192
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Tidskriftsartikel (refereegranskat)abstract
- In an attempt to tidy up some previously published nomenclaturalinconsistencies in their index of fossil dinoflagellates, Fensome and Williams (2004)inadvertently proposed transfers to two taxa that are not consistentwith the current understanding of calcareous dinoflagellates.They proposed the transfers of Sphaerodinella? tuberosa formaelongata Hildebrand-Habel, Willems and Versteegh 1999 to Pernambugiaas Pernambugia tuberosa forma elongata, and Sphaerodinella?tuberosa forma variospinosa Hildebrand-Habel, Willems and Versteegh 1999to Pernambugia as Pernambugia tuberosa forma variospinosa. Inorder to clarify the systematics of these taxa and bring thetaxonomy into line with current concepts, we herein proposethe new combinations Calciodinellum elongatum and Calciodinellumlevantinum forma variospinosum.
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| 9. |
- Wallin, Hans Petter, et al.
(författare)
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Sound and vibration
- 2010. - 2., rev. uppl.
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Bok (övrigt vetenskapligt/konstnärligt)
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