| 1. |
- Adrian-Martinez, S., et al.
(author)
-
A first search for coincident gravitational waves and high energy neutrinos using LIGO, Virgo and ANTARES data from 2007
- 2013
-
In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :6
-
Journal article (peer-reviewed)abstract
- We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.
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| 2. |
- Singh, B. P., et al.
(author)
-
Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
- 2015
-
In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:8
-
Journal article (peer-reviewed)abstract
- Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (pi N) TDAs from (p) over barp -> e(+)e(-)pi(0) reaction with the future PANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q(2), the amplitude of the signal channel (p) over barp -> e(+)e(-)pi(0) admits a QCD factorized description in terms of pi N TDAs and nucleon Distribution Amplitudes (DAs) in the forward aid backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring (p) over barp -> e(+)e(-)pi(0) with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. (p) over barp -> pi(+)pi(-)pi(0) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q(2) < 4.3 GeV2 and 5 < q(2) < 9 GeV2, respectively, with a neutral pion scattered in the forward or backward cone vertical bar cos theta(pi 0)vertical bar > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of 5 . 10(7) (1 . 10(7)) at low (high) q(2) for s = 5 GeV2, and of 1 . 10(8) (6 . 10(6)) at low (high) q(2) for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing pi N TDAs.
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| 3. |
- Singh, B., et al.
(author)
-
Feasibility study for the measurement of pi N transition distribution amplitudes at (P)over-barANDA in (P)over-barp -> J/psi pi(0)
- 2017
-
In: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 95:3
-
Journal article (peer-reviewed)abstract
- The exclusive charmonium production process in (P) over barp annihilation with an associated pi 0 meson (p) over barp -> J/psi pi(0) is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the J/psi -> e(+) e(-) decay channel with the AntiProton ANnihilation at DArmstadt ((P) over bar ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the (P) over barp -> pi(+)pi(-)pi(0) and (p) over barp -> J/psi pi(0)pi(0) reactions are performed with PANDAROOT, the simulation and analysis software framework of the (P) over bar ANDA experiment. It is shown that the measurement can be done at (P) over bar ANDA with significant constraining power under the assumption of an integrated luminosity attainable in four to five months of data taking at the maximum design luminosity.
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| 4. |
- Singh, B., et al.
(author)
-
Study of doubly strange systems using stored antiprotons
- 2016
-
In: Nuclear Physics A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 954, s. 323-340
-
Journal article (peer-reviewed)abstract
- Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the PANDA experiment at FAIR. For the first time, high resolution gamma-spectroscopy of doubly strange Lambda Lambda-hypernuclei will be performed, thus complementing measurements of ground state decays of Lambda Lambda-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Xi(-) -atoms will be feasible and even the production of Omega(-) -atoms will be within reach. The latter might open the door to the vertical bar S vertical bar = 3 world in strangeness nuclear physics, by the study of the hadronic Omega(-) -nucleus interaction. For the first time it will be possible to study the behavior of Xi(+) in nuclear systems under well controlled conditions.
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| 5. |
- Collaboration, The PANDA, et al.
(author)
-
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
- 2016
-
In: European Physical Journal A. - : Springer Publishing Company. - 1434-6001 .- 1434-601X. ; 52:10
-
Journal article (peer-reviewed)abstract
- Simulation results for future measurements of electromagnetic proton form factors at P ¯ ANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel p¯ p→ e+e- is studied on the basis of two different but consistent procedures. The suppression of the main background channel, i.e.p¯ p→ π+π-, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance.
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| 6. |
- Erni, W., et al.
(author)
-
Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
- 2013
-
In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
-
Journal article (peer-reviewed)abstract
- This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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| 7. |
- Petroff, E., et al.
(author)
-
A polarized fast radio burst at low Galactic latitude
- 2017
-
In: Monthly notices of the Royal Astronomical Society. - : Oxford Academic. - 0035-8711 .- 1365-2966. ; 469:4, s. 4465-4482
-
Journal article (peer-reviewed)abstract
- We report on the discovery of a new fast radio burst (FRB), FRB 150215, with the Parkes radio telescope on 2015 February 15. The burst was detected in real time with a dispersion measure (DM) of 1105.6 +/- 0.8 pc cm(-3), a pulse duration of 2.8(-0.5)(+1.2) ms, and a measured peak flux density assuming that the burst was at beam centre of 0.7(-0.1)(+0.2) Jy. The FRB originated at a Galactic longitude and latitude of 24.66 degrees, 5.28 degrees and 25 degrees away from the Galactic Center. The burst was found to be 43 +/- 5 per cent linearly polarized with a rotation measure (RM) in the range -9 < RM < 12 rad m(-2) (95 per cent confidence level), consistent with zero. The burst was followed up with 11 telescopes to search for radio, optical, X-ray, gamma-ray and neutrino emission. Neither transient nor variable emission was found to be associated with the burst and no repeat pulses have been observed in 17.25 h of observing. The sightline to the burst is close to the Galactic plane and the observed physical properties of FRB 150215 demonstrate the existence of sight lines of anomalously low RM for a given electron column density. The Galactic RM foreground may approach a null value due to magnetic field reversals along the line of sight, a decreased total electron column density from the Milky Way, or some combination of these effects. A lower Galactic DM contribution might explain why this burst was detectable whereas previous searches at low latitude have had lower detection rates than those out of the plane.
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| 8. |
- Feroci, M., et al.
(author)
-
The large observatory for x-ray timing
- 2014
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9780819496126
-
Conference paper (peer-reviewed)abstract
- The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final downselection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supranuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m2 effective area, 2-30 keV, 240 eV spectral resolution, 1° collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g. GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the status of the mission at the end of its Phase A study.
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| 9. |
- Adrian-Martinez, S., et al.
(author)
-
The First Combined Search For Neutrino Point-Sources In The Southern Hemisphere With The Antares And Icecube Neutrino Telescopes
- 2016
-
In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 823:1
-
Journal article (peer-reviewed)abstract
- We present the results of searches for point-like sources of neutrinos based on the first combined analysis of data from both the ANTARES and IceCube neutrino telescopes. The combination of both detectors, which differ in size and location, forms a window in the southern sky where the sensitivity to point sources improves by up to a factor of 2 compared with individual analyses. Using data recorded by ANTARES from 2007 to 2012, and by IceCube from 2008 to 2011, we search for sources of neutrino emission both across the southern sky and from a preselected list of candidate objects. No significant excess over background has been found in these searches, and flux upper limits for the candidate sources are presented for E-2.5 and E-2 power-law spectra with different energy cut-offs.
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| 10. |
- Abdellaoui, G., et al.
(author)
-
Meteor studies in the framework of the JEM-EUSO program
- 2017
-
In: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 143, s. 245-255
-
Journal article (peer-reviewed)abstract
- We summarize the state of the art of a program of UV observations from space of meteor phenomena, a secondary objective of the JEM-EUSO international collaboration. Our preliminary analysis indicates that JEM-EUSO, taking advantage of its large FOV and good sensitivity, should be able to detect meteors down to absolute magnitude close to 7. This means that JEM-EUSO should be able to record a statistically significant flux of meteors, including both sporadic ones, and events produced by different meteor streams. Being unaffected by adverse weather conditions, JEM-EUSO can also be a very important facility for the detection of bright meteors and fireballs, as these events can be detected even in conditions of very high sky background. In the case of bright events, moreover, exhibiting some persistence of the meteor train, preliminary simulations show that it should be possible to exploit the motion of the ISS itself and derive at least a rough 3D reconstruction of the meteor trajectory. Moreover, the observing strategy developed to detect meteors may also be applied to the detection of nuclearites, exotic particles whose existence has been suggested by some theoretical investigations. Nuclearites are expected to move at higher velocities than meteoroids, and to exhibit a wider range of possible trajectories, including particles moving upward after crossing the Earth. Some pilot studies, including the approved Mini-EUSO mission, a precursor of JEM-EUSO, are currently operational or in preparation. We are doing simulations to assess the performance of Mini-EUSO for meteor studies, while a few meteor events have been already detected using the ground-based facility EUSO-TA.
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| 11. |
- Feroci, M., et al.
(author)
-
LOFT - The large observatory for x-ray timing
- 2012
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. - 9780819491442 ; , s. 84432D-
-
Conference paper (peer-reviewed)abstract
- The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a collimated (<1 degree field of view) experiment operating in the energy range 2-50 keV, with a 10 m2 peak effective area and an energy resolution of 260 eV at 6 keV. The WFM will operate in the same energy range as the LAD, enabling simultaneous monitoring of a few-steradian wide field of view, with an angular resolution of <5 arcmin. The LAD and WFM experiments will allow us to investigate variability from submillisecond QPO's to yearlong transient outbursts. In this paper we report the current status of the project.
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| 12. |
- Abdellaoui, G., et al.
(author)
-
First observations of speed of light tracks by a fluorescence detector looking down on the atmosphere
- 2018
-
In: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221. ; 13
-
Journal article (peer-reviewed)abstract
- EUSO-Balloon is a pathfinder mission for the Extreme Universe Space Observatory onboard the Japanese Experiment Module (JEM-EUSO). It was launched on the moonless night of the 25(th) of August 2014 from Timmins, Canada. The flight ended successfully after maintaining the target altitude of 38 km for five hours. One part of the mission was a 2.5 hour underflight using a helicopter equipped with three UV light sources (LED, xenon flasher and laser) to perform an inflight calibration and examine the detectors capability to measure tracks moving at the speed of light. We describe the helicopter laser system and details of the underflight as well as how the laser tracks were recorded and found in the data. These are the first recorded laser tracks measured from a fluorescence detector looking down on the atmosphere. Finally, we present a first reconstruction of the direction of the laser tracks relative to the detector.
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| 13. |
- Feroci, M., et al.
(author)
-
The Large Observatory for X-ray Timing (LOFT)
- 2012
-
In: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 34:2, s. 415-444
-
Journal article (peer-reviewed)abstract
- High-time-resolution X-ray observations of compact objects provide direct access to strong-field gravity, to the equation of state of ultradense matter and to black hole masses and spins. A 10 m(2)-class instrument in combination with good spectral resolution is required to exploit the relevant diagnostics and answer two of the fundamental questions of the European Space Agency (ESA) Cosmic Vision Theme "Matter under extreme conditions", namely: does matter orbiting close to the event horizon follow the predictions of general relativity? What is the equation of state of matter in neutron stars? The Large Observatory For X-ray Timing (LOFT), selected by ESA as one of the four Cosmic Vision M3 candidate missions to undergo an assessment phase, will revolutionise the study of collapsed objects in our galaxy and of the brightest supermassive black holes in active galactic nuclei. Thanks to an innovative design and the development of large-area monolithic silicon drift detectors, the Large Area Detector (LAD) on board LOFT will achieve an effective area of similar to 12 m(2) (more than an order of magnitude larger than any spaceborne predecessor) in the 2-30 keV range (up to 50 keV in expanded mode), yet still fits a conventional platform and small/medium-class launcher. With this large area and a spectral resolution of < 260 eV, LOFT will yield unprecedented information on strongly curved spacetimes and matter under extreme conditions of pressure and magnetic field strength.
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| 14. |
-
Modulated High-Energy Gamma-Ray Emission from the Microquasar Cygnus X-3
- 2009
-
In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 326:5959, s. 1512-
-
Journal article (peer-reviewed)abstract
- Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets.
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| 15. |
- Nelson, G., et al.
(author)
-
QUAREP-LiMi: A community-driven initiative to establish guidelines for quality assessment and reproducibility for instruments and images in light microscopy
- 2021
-
In: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 284:1, s. 56-73
-
Journal article (peer-reviewed)abstract
- A modern day light microscope has evolved from a tool devoted to making primarily empirical observations to what is now a sophisticated , quantitative device that is an integral part of both physical and life science research. Nowadays, microscopes are found in nearly every experimental laboratory. However, despite their prevalent use in capturing and quantifying scientific phenomena, neither a thorough understanding of the principles underlying quantitative imaging techniques nor appropriate knowledge of how to calibrate, operate and maintain microscopes can be taken for granted. This is clearly demonstrated by the well-documented and widespread difficulties that are routinely encountered in evaluating acquired data and reproducing scientific experiments. Indeed, studies have shown that more than 70% of researchers have tried and failed to repeat another scientist's experiments, while more than half have even failed to reproduce their own experiments. One factor behind the reproducibility crisis of experiments published in scientific journals is the frequent underreporting of imaging methods caused by a lack of awareness and/or a lack of knowledge of the applied technique. Whereas quality control procedures for some methods used in biomedical research, such as genomics (e.g. DNA sequencing, RNA-seq) or cytometry, have been introduced (e.g. ENCODE), this issue has not been tackled for optical microscopy instrumentation and images. Although many calibration standards and protocols have been published, there is a lack of awareness and agreement on common standards and guidelines for quality assessment and reproducibility. In April 2020, the QUality Assessment and REProducibility for instruments and images in Light Microscopy (QUAREP-LiMi) initiative was formed. This initiative comprises imaging scientists from academia and industry who share a common interest in achieving a better understanding of the performance and limitations of microscopes and improved quality control (QC) in light microscopy. The ultimate goal of the QUAREP-LiMi initiative is to establish a set of common QC standards, guidelines, metadata models and tools, including detailed protocols, with the ultimate aim of improving reproducible advances in scientific research. This White Paper (1) summarizes the major obstacles identified in the field that motivated the launch of the QUAREP-LiMi initiative; (2) identifies the urgent need to address these obstacles in a grassroots manner, through a community of stakeholders including, researchers, imaging scientists, bioimage analysts, bioimage informatics developers, corporate partners, funding agencies, standards organizations, scientific publishers and observers of such; (3) outlines the current actions of the QUAREP-LiMi initiative and (4) proposes future steps that can be taken to improve the dissemination and acceptance of the proposed guidelines to manage QC. To summarize, the principal goal of the QUAREP-LiMi initiative is to improve the overall quality and reproducibility of light microscope image data by introducing broadly accepted standard practices and accurately captured image data metrics.
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| 16. |
- Greiner, J., et al.
(author)
-
GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy
- 2012
-
In: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 34:2, s. 551-582
-
Journal article (peer-reviewed)abstract
- We propose to perform a continuously scanning all-sky survey from 200 keV to 80 MeV achieving a sensitivity which is better by a factor of 40 or more compared to the previous missions in this energy range (COMPTEL, INTEGRAL; see Fig. 1). These gamma-ray observations will be complemented by observations in the soft X-ray and (near-)infrared region with the corresponding telescopes placed on a separate satellite. The Gamma-Ray Imaging, Polarimetry and Spectroscopy ("GRIPS") mission with its three instruments Gamma-Ray Monitor (GRM), X-Ray Monitor (XRM) and InfraRed Telescope (IRT) addresses fundamental questions in ESA's Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS has its focus on the evolving, violent Universe, exploring a unique energy window. We propose to investigate γ-ray bursts and blazars, the mechanisms behind supernova explosions, nucleosynthesis and spallation, the enigmatic origin of positrons in our Galaxy, and the nature of radiation processes and particle acceleration in extreme cosmic sources including pulsars and magnetars. The natural energy scale for these non-thermal processes is of the order of MeV. Although they can be partially and indirectly studied using other methods, only the proposed GRIPS measurements will provide direct access to their primary photons. GRIPS will be a driver for the study of transient sources in the era of neutrino and gravitational wave observatories such as IceCUBE and LISA, establishing a new type of diagnostics in relativistic and nuclear astrophysics. This will support extrapolations to investigate star formation, galaxy evolution, and black hole formation at high redshifts.
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| 17. |
- Egron, E., et al.
(author)
-
Single-dish and VLBI observations of Cygnus X-3 during the 2016 giant flare episode
- 2017
-
In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 471:3, s. 2703-2714
-
Journal article (peer-reviewed)abstract
- In 2016 September, the microquasar Cygnus X-3 underwent a giant radio flare, which was monitored for 6 d with the Medicina Radio Astronomical Station and the Sardinia Radio Telescope. Long observations were performed in order to follow the evolution of the flare on an hourly scale, covering six frequency ranges from 1.5 to 25.6 GHz. The radio emission reached a maximum of 13.2 +/- 0.7 Jy at 7.2 GHz and 10 +/- 1 Jy at 18.6 GHz. Rapid flux variations were observed at high radio frequencies at the peak of the flare, together with rapid evolution of the spectral index: a steepened from 0.3 to 0.6 (with S-nu alpha nu(-alpha)) within 5 h. This is the first time that such fast variations are observed, giving support to the evolution from optically thick to optically thin plasmons in expansion moving outward from the core. Based on the Italian network (Noto, Medicina and SRT) and extended to the European antennas (Torun, Yebes, Onsala), very long baseline interferometry (VLBI) observations were triggered at 22 GHz on five different occasions, four times prior to the giant flare, and once during its decay phase. Flux variations of 2 h duration were recorded during the first session. They correspond to a mini-flare that occurred close to the core 10 d before the onset of the giant flare. From the latest VLBI observation we infer that 4 d after the flare peak the jet emission was extended over 30 mas.
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| 18. |
- Baczko, A. K., et al.
(author)
-
A highly magnetized twin-jet base pinpoints a supermassive black hole
- 2016
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 593
-
Journal article (peer-reviewed)abstract
- Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 10(3) G to 10(4) G. We imaged the vicinity of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the magnetic field at 1 Schwarzschild radius to lie between 200 G and similar to 8.3 x 10(4) G consistent with Blandford & Znajek models.
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| 19. |
- Kantzas, D., et al.
(author)
-
A new lepto-hadronic model applied to the first simultaneous multiwavelength data set for Cygnus X-1
- 2020
-
In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:2, s. 2112-2126
-
Journal article (peer-reviewed)abstract
- Cygnus X-1 is the first Galactic source confirmed to host an accreting black hole. It has been detected across the entire electromagnetic spectrum from radio to GeV gamma-rays. The source's radio through mid-infrared radiation is thought to originate from the relativistic jets. The observed high degree of linear polarization in the MeV X-rays suggests that the relativistic jets dominate in this regime as well, whereas a hot accretion flow dominates the soft X-ray band. The origin of the GeV non-thermal emission is still debated, with both leptonic and hadronic scenarios deemed to be viable. In this work, we present results from a new semi-analytical, multizone jet model applied to the broad-band spectral energy distribution of Cygnus X-1 for both leptonic and hadronic scenarios. We try to break this degeneracy by fitting the first-ever high-quality, simultaneous multiwavelength data set obtained from the CHOCBOX campaign (Cygnus X-1 Hard state Observations of a Complete Binary Orbit in X-rays). Our model parametrizes dynamical properties, such as the jet velocity profile, the magnetic field, and the energy density. Moreover, the model combines these dynamical properties with a self-consistent radiative transfer calculation including secondary cascades, both of leptonic and hadronic origin. We conclude that sensitive TeV gamma-ray telescopes like Cherenkov Telescope Array (CTA) will definitively answer the question of whether hadronic processes occur inside the relativistic jets of Cygnus X-1.
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| 20. |
- Seitenzahl, I. R., et al.
(author)
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5.9-keV Mn K-shell X-ray luminosity from the decay of Fe-55 in Type Ia supernova models
- 2015
-
In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 447:2, s. 1484-1490
-
Journal article (peer-reviewed)abstract
- We show that the X-ray line flux of the Mn Ka line at 5.9 keV from the decay of Fe-55 is a promising diagnostic to distinguish between Type Ia supernova (SN Ia) explosion models. Using radiation transport calculations, we compute the line flux for two three-dimensional explosion models: a near-Chandrasekhar mass delayed detonation and a violent merger of two (1.1 and 0.9 M-circle dot) white dwarfs. Both models are based on solar metallicity zero-age main-sequence progenitors. Due to explosive nuclear burning at higher density, the delayed-detonation model synthesizes similar to 3.5 times more radioactive Fe-55 than the merger model. As a result, we find that the peak Mn K alpha line flux of the delayed-detonation model exceeds that of the merger model by a factor of similar to 4.5. Since in both models the 5.9-keV X-ray flux peaks five to six years after the explosion, a single measurement of the X-ray line emission at this time can place a constraint on the explosion physics that is complementary to those derived from earlier phase optical spectra or light curves. We perform detector simulations of current and future X-ray telescopes to investigate the possibilities of detecting the X-ray line at 5.9 keV. Of the currently existing telescopes, XMM-Newton/pn is the best instrument for close (less than or similar to 1-2 Mpc), non-background limited SNe Ia because of its large effective area. Due to its low instrumental background, Chandra/ACIS is currently the best choice for SNe Ia at distances above similar to 2 Mpc. For the delayed-detonation scenario, a line detection is feasible with Chandra up to similar to 3 Mpc for an exposure time of 10(6) s. We find that it should be possible with currently existing X-ray instruments (with exposure times less than or similar to 5 x 10(5) s) to detect both of our models at sufficiently high S/N to distinguish between them for hypothetical events within the Local Group. The prospects for detection will be better with future missions. For example, the proposed Athena/X-IFU instrument could detect our delayed-detonation model out to a distance of similar to 5 Mpc. This would make it possible to study future events occurring during its operational life at distances comparable to those of the recent supernovae SN 2011 fe (similar to 6.4 Mpc) and SN 2014J (similar to 3.5 Mpc).
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| 21. |
- Bender, R., et al.
(author)
-
Corrosion challenges towards a sustainable society
- 2022
-
In: Materials and corrosion - Werkstoffe und Korrosion. - : Wiley. - 0947-5117 .- 1521-4176. ; 73:11, s. 1730-1751
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Journal article (peer-reviewed)abstract
- A global transition towards more sustainable, affordable and reliable energy systems is being stimulated by the Paris Agreement and the United Nation's 2030 Agenda for Sustainable Development. This poses a challenge for the corrosion industry, as building climate-resilient energy systems and infrastructures brings with it a long-term direction, so as a result the long-term behaviour of structural materials (mainly metals and alloys) becomes a major prospect. With this in mind “Corrosion Challenges Towards a Sustainable Society” presents a series of cases showing the importance of corrosion protection of metals and alloys in the development of energy production to further understand the science of corrosion, and bring the need for research and the consequences of corrosion into public and political focus. This includes emphasis on the limitation of greenhouse gas emissions, on the lifetime of infrastructures, implants, cultural heritage artefacts, and a variety of other topics.
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| 22. |
- Maier, O., et al.
(author)
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ISLES 2015-A public evaluation benchmark for ischemic stroke lesion segmentation from multispectral MRI
- 2017
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In: Medical Image Analysis. - : Elsevier BV. - 1361-8415 .- 1361-8423. ; 35, s. 250-269
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Journal article (peer-reviewed)abstract
- Ischemic stroke is the most common cerebrovascular disease, and its diagnosis, treatment, and study relies on non-invasive imaging. Algorithms for stroke lesion segmentation from magnetic resonance imaging (MRI) volumes are intensely researched, but the reported results are largely incomparable due to different datasets and evaluation schemes. We approached this urgent problem of comparability with the Ischemic Stroke Lesion Segmentation (ISLES) challenge organized in conjunction with the MICCAI 2015 conference. In this paper we propose a common evaluation framework, describe the publicly available datasets, and present the results of the two sub-challenges: Sub-Acute Stroke Lesion Segmentation (SISS) and Stroke Perfusion Estimation (SPES). A total of 16 research groups participated with a wide range of state-of-the-art automatic segmentation algorithms. A thorough analysis of the obtained data enables a critical evaluation of the current state-of-the-art, recommendations for further developments, and the identification of remaining challenges. The segmentation of acute perfusion lesions addressed in SPES was found to be feasible. However, algorithms applied to sub-acute lesion segmentation in SISS still lack accuracy. Overall, no algorithmic characteristic of any method was found to perform superior to the others. Instead, the characteristics of stroke lesion appearances, their evolution, and the observed challenges should be studied in detail. The annotated ISLES image datasets continue to be publicly available through an online evaluation system to serve as an ongoing benchmarking resource (www.isles-challenge.org).
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| 23. |
- Neff, A, et al.
(author)
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The ESTMJS (European Society of Temporomandibular Joint Surgeons) Consensus and Evidence-Based Recommendations on Management of Condylar Dislocation
- 2021
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In: Journal of clinical medicine. - : MDPI AG. - 2077-0383. ; 10:21
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Journal article (peer-reviewed)abstract
- Although condylar dislocation is not uncommon, terminology, diagnostics, and treatment concepts vary considerably worldwide. This study aims to present a consensus recommendation based on systematically reviewed literature and approved by the European Society of TMJ Surgeons (ESTMJS). Based on the template of the evidence-based German guideline (register # 007-063) the ESTMJS members voted on 30 draft recommendations regarding terminology, diagnostics, and treatment initially via a blinded modified Delphi procedure. After unblinding, a discussion and voting followed, using a structured consensus process in 2019. An independent moderator documented and evaluated voting results and alterations from the original draft. Although the results of the preliminary voting were very heterogenous and differed significantly from the German S3 guideline (p < 0.0005), a strong consensus was achieved in the final voting on terminology, diagnostics, and treatment. In this voting, multiple alterations, including adding and discarding recommendations, led to 24 final recommendations on assessment and management of TMJ dislocation. To our knowledge, the ESTMJS condylar dislocation recommendations are the first both evidence and consensus-based international recommendations in the field of TMJ surgery. We recommend they form the basis for clinical practice guidelines for the management of dislocations of the mandibular condyle.
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| 31. |
- Balucinska-Church, M., et al.
(author)
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Dipping in Cygnus X-2 in a multi-wavelength campaign due to absorption of extended ADC emission
- 2011
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 530
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Journal article (peer-reviewed)abstract
- We report results of one-day simultaneous multiwavelength observations of Cygnus X-2 using XMM, Chandra, the European VLBI Network and the XMM Optical Monitor. During the observations, the source did not exhibit Z-track movement, but remained in the vicinity of the soft apex. It was in a radio quiescent/quiet state of 60 degrees these structures can still cover large parts of the extended ADC, without absorbing emission from the central neutral star.
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| 32. |
- Schulz, R., et al.
(author)
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Sub-milliarcsecond imaging of a bright flare and ejection event in the extragalactic jet 3C 111
- 2020
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 644:December 2020
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Journal article (peer-reviewed)abstract
- Context Flares in radio-loud active galactic nuclei are thought to be associated with the injection of fresh plasma into the compact jet base. Such flares are usually strongest and appear earlier at shorter radio wavelengths. Hence, very long baseline interferometry (VLBI) at millimeter(mm)-wavelengths is the best-suited technique for studying the earliest structural changes of compact jets associated with emission flares. Aims We study the morphological changes of the parsec-scale jet in the nearby (z = 0.049) γ-ray bright radio galaxy 3C 111 following a flare that developed into a major radio outburst in 2007. Methods We analyse three successive observations of 3C 111 at 86 GHz with the Global mm-VLBI Array (GMVA) between 2007 and 2008 which yield a very high angular resolution of ∼45 μas. In addition, we make use of single-dish radio flux density measurements from the F-GAMMA and POLAMI programmes, archival single-dish and VLBI data. Results We resolve the flare into multiple plasma components with a distinct morphology resembling a bend in an otherwise remarkably straight jet. The flare-associated features move with apparent velocities of ∼4.0c to ∼4.5c and can be traced also at lower frequencies in later epochs. Near the base of the jet, we find two bright features with high brightness temperatures up to ∼1011 K, which we associate with the core and a stationary feature in the jet. Conclusions The flare led to multiple new jet components indicative of a dynamic modulation during the ejection. We interpret the bend-like feature as a direct result of the outburst which makes it possible to trace the transverse structure of the jet. In this scenario, the components follow different paths in the jet stream consistent with expectations for a spine-sheath structure, which is not seen during intermediate levels of activity. The possibility of coordinated multiwavelength observations during a future bright radio flare in 3C 111 makes this source an excellent target for probing the radio-γ-ray connection.
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- Wilms, H., et al.
(author)
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Suppression of Map Kinases Inhibits Microglial Activation and Attenuates Neuronal Cell Death Induced by Alpha-Synuclein Protofibrils
- 2009
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In: International Journal of Immunopathology and Pharmacology. - 0394-6320. ; 22:4, s. 897-909
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Journal article (peer-reviewed)abstract
- alpha-Synuclein (alpha-Syn) accounts, as a major component of Lewy bodies (LB), for the filamentous deposits in many cases of neurodegenerative diseases. Yet, little is known about the molecular mechanisms of neuronal loss in these diseases. The correlation between alpha-Syn oligomerization/aggregation and pathologies raises the key question of which molecular form of alpha-Syn (i.e. monomeric alpha-Syn, protofibrils or mature fibrils) represents the damage-inducing culprit in the scenario of synucleinopathies. We show that human alpha-Syn protofibrils (PFs) are potent activators of parallel proinflammatory signalling pathways (p38 and ERK1/2 MAP kinases and NF-kappa B) in microglial cells in vitro. Furthermore, stereotactic injection of alpha-Syn PFs into the substantia nigra of adult rats leads to a profound activation of microglia and adjacent neuronal cell loss, which can be attenuated by the MAP kinase inhibitor semapimod. We propose that the neurodegenerative process of alpha-synucleinopathies involves microglial activation through alpha-Syn released or extruded from cells with pathogenic alpha-Syn metabolism. Compounds that inhibit the MAPK/NF-kappa B pathways might be a promising pharmacological strategy for the treatment of the inflammatory component of synucleinopathies including PD.
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