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  • 2015-2019  (391)
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  • 2015-2019  (391)
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  • 1
    Online-Ressource
    Online-Ressource
    Drosophila Muller F Elements Maintain a Distinct Set of Genomic Properties Over 40 Million Years of Evolution
    Oxford University Press (OUP) ; 2015
    In:  G3 Genes|Genomes|Genetics Vol. 5, No. 5 ( 2015-05-01), p. 719-740
    Details
    In: G3 Genes|Genomes|Genetics, Oxford University Press (OUP), Vol. 5, No. 5 ( 2015-05-01), p. 719-740
    Kurzfassung: The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu.
    Materialart: Online-Ressource
    ISSN: 2160-1836
    URL: Article
    DOI: 10.1534/g3.114.015966
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2015
    ZDB Id: 2629978-1
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    Overview of the JET preparation for deuterium–tritium operation with the ITER like-wall
    IOP Publishing ; 2019
    In:  Nuclear Fusion Vol. 59, No. 11 ( 2019-11-01), p. 112021-
    Details
    In: Nuclear Fusion, IOP Publishing, Vol. 59, No. 11 ( 2019-11-01), p. 112021-
    Kurzfassung: For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des . 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D–T mixtures since 1997 and the first ever D–T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D–T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D–T preparation. This intense preparation includes the review of the physics basis for the D–T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D–T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfvèn eigenmode antennas, neutral gauges, radiation hard imaging systems…) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D–T campaign provides an incomparable source of information and a basis for the future D–T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
    Materialart: Online-Ressource
    ISSN: 0029-5515 , 1741-4326
    URL: Article
    DOI: 10.1088/1741-4326/ab2276
    Sprache: Unbekannt
    Verlag: IOP Publishing
    Publikationsdatum: 2019
    ZDB Id: 2037980-8
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    Multi-messenger Observations of a Binary Neutron Star Merger
    American Astronomical Society ; 2017
    In:  The Astrophysical Journal Vol. 848, No. 2 ( 2017-10-16), p. L12-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 848, No. 2 ( 2017-10-16), p. L12-
    Materialart: Online-Ressource
    ISSN: 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/aa91c9
    Sprache: Unbekannt
    Verlag: American Astronomical Society
    Publikationsdatum: 2017
    ZDB Id: 2207648-7
    ZDB Id: 2006858-X
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    Overview of the JET results in support to ITER
    IOP Publishing ; 2017
    In:  Nuclear Fusion Vol. 57, No. 10 ( 2017-10-01), p. 102001-
    Details
    In: Nuclear Fusion, IOP Publishing, Vol. 57, No. 10 ( 2017-10-01), p. 102001-
    Materialart: Online-Ressource
    ISSN: 0029-5515 , 1741-4326
    URL: Article
    DOI: 10.1088/1741-4326/aa5e28
    Sprache: Unbekannt
    Verlag: IOP Publishing
    Publikationsdatum: 2017
    ZDB Id: 2037980-8
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 5
    Online-Ressource
    Online-Ressource
    Gamma-ray blazar spectra with H.E.S.S. II mono analysis: The case of PKS 2155−304 and PG 1553+113
    EDP Sciences ; 2017
    In:  Astronomy & Astrophysics Vol. 600 ( 2017-4), p. A89-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 600 ( 2017-4), p. A89-
    Kurzfassung: Context. The addition of a 28 m Cherenkov telescope (CT5) to the H.E.S.S. array extended the experiment’s sensitivityto lower energies. The lowest energy threshold is obtained using monoscopic analysis of data taken with CT5, providing access to gamma-ray energies below 100 GeV for small zenith angle observations. Such an extension of the instrument’s energy range is particularly beneficial for studies of active galactic nuclei with soft spectra, as expected for those at a redshift ≥0.5. The high-frequency peaked BL Lac objects PKS 2155−304 ( z = 0.116) and PG 1553+113 (0.43 〈 z 〈 0.58) are among the brightest objects in the gamma-ray sky, both showing clear signatures of gamma-ray absorption at E 〉 100 GeV interpreted as being due to interactions with the extragalactic background light (EBL). Aims. The aims of this work are twofold: to demonstrate the monoscopic analysis of CT5 data with a low energy threshold, and to obtain accurate measurements of the spectral energy distributions (SED) of PKS 2155−304 and PG 1553+113 near their SED peaks at energies ≈100 GeV. Methods. Multiple observational campaigns of PKS 2155−304 and PG 1553+113 were conducted during 2013 and 2014 using the full H.E.S.S. II instrument (CT1–5). A monoscopic analysis of the data taken with the new CT5 telescope was developed along with an investigation into the systematic uncertainties on the spectral parameters which are derived from this analysis. Results. Using the data from CT5, the energy spectra of PKS 2155−304 and PG 1553+113 were reconstructed down to conservative threshold energies of 80 GeV for PKS 2155−304 , which transits near zenith, and 110 GeV for the more northern PG 1553+113 . The measured spectra, well fitted in both cases by a log-parabola spectral model (with a 5.0 σ statistical preference for non-zero curvature for PKS 2155−304 and 4.5 σ for PG 1553+113 ), were found consistent with spectra derived from contemporaneous Fermi -LAT data, indicating a sharp break in the observed spectra of both sources at E ≈ 100 GeV. When corrected for EBL absorption, the intrinsic H.E.S.S. II mono and Fermi -LAT spectrum of PKS 2155−304 was found to show significant curvature. For PG 1553+113 , however, no significant detection of curvature in the intrinsic spectrum could be found within statistical and systematic uncertainties.
    Materialart: Online-Ressource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201629427
    RVK:
    UA 1000
    RVK:
    US 1090
    Sprache: Englisch
    Verlag: EDP Sciences
    Publikationsdatum: 2017
    ZDB Id: 1458466-9
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Online-Ressource
    Online-Ressource
    A polarized fast radio burst at low Galactic latitude
    Oxford University Press (OUP) ; 2017
    In:  Monthly Notices of the Royal Astronomical Society ( 2017-05-09)
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), ( 2017-05-09)
    Materialart: Online-Ressource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stx1098
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2017
    ZDB Id: 2016084-7
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Online-Ressource
    Online-Ressource
    Constraints on particle acceleration in SS433/W50 from MAGIC and H.E.S.S. observations
    EDP Sciences ; 2018
    In:  Astronomy & Astrophysics Vol. 612 ( 2018-4), p. A14-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 612 ( 2018-4), p. A14-
    Kurzfassung: Context. The large jet kinetic power and non-thermal processes occurring in the microquasar SS 433 make this source a good candidate for a very high-energy (VHE) gamma-ray emitter. Gamma-ray fluxes above the sensitivity limits of current Cherenkov telescopes have been predicted for both the central X-ray binary system and the interaction regions of SS 433 jets with the surrounding W50 nebula. Non-thermal emission at lower energies has been previously reported, indicating that efficient particle acceleration is taking place in the system. Aim. We explore the capability of SS 433 to emit VHE gamma rays during periods in which the expected flux attenuation due to periodic eclipses ( P orb ~ 13.1 days) and precession of the circumstellar disk ( P pre ~ 162 days) periodically covering the central binary system is expected to be at its minimum. The eastern and western SS 433/W50 interaction regions are also examined using the whole data set available. We aim to constrain some theoretical models previously developed for this system with our observations. Methods. We made use of dedicated observations from the Major Atmospheric Gamma Imaging Cherenkov telescopes (MAGIC) and High Energy Spectroscopic System (H.E.S.S.) of SS 433 taken from 2006 to 2011. These observation were combined for the first time and accounted for a total effective observation time of 16.5 h, which were scheduled considering the expected phases of minimum absorption of the putative VHE emission. Gamma-ray attenuation does not affect the jet/medium interaction regions. In this case, the analysis of a larger data set amounting to ~40–80 h, depending on the region, was employed. Results. No evidence of VHE gamma-ray emission either from the central binary system or from the eastern/western interaction regions was found. Upper limits were computed for the combined data set. Differential fluxes from the central system are found to be ≲ 10 −12 –10 −13 TeV −1 cm −2 s −1 in an energy interval ranging from ~few × 100 GeV to ~few TeV. Integral flux limits down to ~ 10 −12 –10 −13 ph cm −2 s −1 and ~ 10 −13 –10 −14 ph cm −2 s −1 are obtainedat 300 and 800 GeV, respectively. Our results are used to place constraints on the particle acceleration fraction at the inner jetregions and on the physics of the jet/medium interactions. Conclusions. Our findings suggest that the fraction of the jet kinetic power that is transferred to relativistic protons must be relatively small in SS 433, q p ≤ 2.5 × 10 −5 , to explain the lack of TeV and neutrino emission from the central system. At the SS 433/W50 interface, the presence of magnetic fields ≳10 μ G is derived assuming a synchrotron origin for the observed X-ray emission. This also implies the presence of high-energy electrons with E e − up to 50 TeV, preventing an efficient production of gamma-ray fluxes in these interaction regions.
    Materialart: Online-Ressource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201731169
    RVK:
    UA 1000
    RVK:
    US 1090
    Sprache: Englisch
    Verlag: EDP Sciences
    Publikationsdatum: 2018
    ZDB Id: 1458466-9
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 8
    Online-Ressource
    Online-Ressource
    VHE γ-ray discovery and multi-wavelength study of the blazar 1ES 2322-409
    Oxford University Press (OUP) ; 2018
    In:  Monthly Notices of the Royal Astronomical Society ( 2018-10-05)
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), ( 2018-10-05)
    Materialart: Online-Ressource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/sty2686
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2018
    ZDB Id: 2016084-7
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 9
    Online-Ressource
    Online-Ressource
    The starburst galaxy NGC 253 revisited by H.E.S.S. and Fermi -LAT
    EDP Sciences ; 2018
    In:  Astronomy & Astrophysics Vol. 617 ( 2018-09), p. A73-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 617 ( 2018-09), p. A73-
    Kurzfassung: Context. NGC 253 is one of only two starburst galaxies found to emit γ -rays from hundreds of MeV to multi-TeV energies. Accurate measurements of the very-high-energy (VHE; E 〉 100 GeV) and high-energy (HE; E 〉 60 MeV) spectra are crucial to study the underlying particle accelerators, probe the dominant emission mechanism(s) and to study cosmic-ray interaction and transport. Aims. The measurement of the VHE γ -ray emission of NGC 253 published in 2012 by H.E.S.S. was limited by large systematic uncertainties. Here, the most up to date measurement of the γ -ray spectrum of NGC 253 is investigated in both HE and VHE γ -rays. Assuming a hadronic origin of the γ -ray emission, the measurement uncertainties are propagated into the interpretation of the accelerated particle population. Methods. The data of H.E.S.S. observations are reanalysed using an updated calibration and analysis chain. The improved Fermi –LAT analysis employs more than 8 yr of data processed using pass 8. The cosmic-ray particle population is evaluated from the combined HE–VHE γ -ray spectrum using NAIMA in the optically thin case. Results. The VHE γ -ray energy spectrum is best fit by a power-law distribution with a flux normalisation of (1.34 ± 0.14 stat ± 0.27 sys ) × 10 −13 cm −2 s −1 TeV 1 at 1 TeV – about 40% above, but compatible with the value obtained in Abramowski et al. (2012). The spectral index Γ = 2.39 ± 0.14 stat ± 0.25 sys is slightly softer than but consistent with the previous measurement within systematic errors. In the Fermi energy range an integral flux of F ( E 〉 60 MeV) = (1.56 ± 0.28 stat ± 0.15 sys ) × 10 −8 cm −2 s −1 is obtained. At energies above ∼3 GeV the HE spectrum is consistent with a power-law ranging into the VHE part of the spectrum measured by H.E.S.S. with an overall spectral index Γ = 2.22 ± 0.06 stat . Conclusions. Two scenarios for the starburst nucleus are tested, in which the gas in the starburst nucleus acts as either a thin or a thick target for hadronic cosmic rays accelerated by the individual sources in the nucleus. In these two models, the level to which NGC 253 acts as a calorimeter is estimated to a range of f cal = 0.1 to 1 while accounting for the measurement uncertainties. The presented spectrum is likely to remain the most accurate measurements until the Cherenkov Telescope Array (CTA) has collected a substantial set of data towards NGC 253.
    Materialart: Online-Ressource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201833202
    RVK:
    UA 1000
    RVK:
    US 1090
    Sprache: Englisch
    Verlag: EDP Sciences
    Publikationsdatum: 2018
    ZDB Id: 1458466-9
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 10
    Online-Ressource
    Online-Ressource
    Deeper H.E.S.S. observations of Vela Junior (RX J0852.0−4622): Morphology studies and resolved spectroscopy
    EDP Sciences ; 2018
    In:  Astronomy & Astrophysics Vol. 612 ( 2018-4), p. A7-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 612 ( 2018-4), p. A7-
    Kurzfassung: Aims. We study γ -ray emission from the shell-type supernova remnant (SNR) RX J0852.0−4622 to better characterize its spectral properties and its distribution over the SNR. Methods. The analysis of an extended High Energy Spectroscopic System (H.E.S.S.) data set at very high energies ( E 〉 100 GeV) permits detailed studies, as well as spatially resolved spectroscopy, of the morphology and spectrum of the whole RX J0852.0−4622 region. The H.E.S.S. data are combined with archival data from other wavebands and interpreted in the framework of leptonic and hadronic models. The joint Fermi -LAT-H.E.S.S. spectrum allows the direct determination of the spectral characteristics of the parent particle population in leptonic and hadronic scenarios using only GeV-TeV data. Results. An updated analysis of the H.E.S.S. data shows that the spectrum of the entire SNR connects smoothly to the high-energy spectrum measured by Fermi -LAT. The increased data set makes it possible to demonstrate that the H.E.S.S. spectrum deviates significantly from a power law and is well described by both a curved power law and a power law with an exponential cutoff at an energy of E cut = (6.7 ± 1.2 stat ± 1.2 syst ) TeV. The joint Fermi -LAT-H.E.S.S. spectrum allows the unambiguous identification of the spectral shape as a power law with an exponential cutoff. No significant evidence is found for a variation of the spectral parameters across the SNR, suggesting similar conditions of particle acceleration across the remnant. A simple modeling using one particle population to model the SNR emission demonstrates that both leptonic and hadronic emission scenarios remain plausible. It is also shown that at least a part of the shell emission is likely due to the presence of a pulsar wind nebula around PSR J0855−4644.
    Materialart: Online-Ressource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201630002
    RVK:
    UA 1000
    RVK:
    US 1090
    Sprache: Englisch
    Verlag: EDP Sciences
    Publikationsdatum: 2018
    ZDB Id: 1458466-9
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
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