| 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. |
- 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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| 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. |
- Ajello, M., et al.
(författare)
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FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE SUPERNOVA REMNANT G8.7-0.1
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 744:1, s. 80-
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 +/- 0.6 (stat) +/- 1.2 (sys) GeV, and photon indices of 2.10 +/- 0.06 (stat) +/- 0.10 (sys) below the break and 2.70 +/- 0.12 (stat) +/- 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of pi(0)s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.
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| 5. |
- Koettgen, Anna, et al.
(författare)
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Genome-wide association analyses identify 18 new loci associated with serum urate concentrations
- 2013
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 45:2, s. 145-154
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Tidskriftsartikel (refereegranskat)abstract
- Elevated serum urate concentrations can cause gout, a prevalent and painful inflammatory arthritis. By combining data from >140,000 individuals of European ancestry within the Global Urate Genetics Consortium (GUGC), we identified and replicated 28 genome-wide significant loci in association with serum urate concentrations (18 new regions in or near TRIM46, INHBB, SEMBT1, TMEM171, VEGFA, BAZ1B, PRKAG2, STC1, HNF4G, A1CF, ATXN2, UBE2Q2, IGF1R, NFAT5, MAF, HLF, ACVR1B-ACVRL1 and B3GNT4). Associations for many of the loci were of similar magnitude in individuals of non-European ancestry. We further characterized these loci for associations with gout, transcript expression and the fractional excretion of urate. Network analyses implicate the inhibins-activins signaling pathways and glucose metabolism in systemic urate control. New candidate genes for serum urate concentration highlight the importance of metabolic control of urate production and excretion, which may have implications for the treatment and prevention of gout.
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| 6. |
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| 7. |
- Luo, Y. -W, et al.
(författare)
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Database of diazotrophs in global ocean : abundance, biomass and nitrogen fixation rates
- 2012
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 4:1, s. 47-73
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Tidskriftsartikel (refereegranskat)abstract
- Marine N-2 fixing microorganisms, termed di-azotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen ( N-2) to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR assays targeting the nifH genes) and N-2 fixation rates. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N-2 fixation rate in the global ocean is estimated to be 62 (52-73) Tg Nyr(-1) and the pelagic diazotrophic biomass in the global ocean is estimated to be 2.1 (1.4-3.1) Tg C from cell counts and to 89 (43-150) Tg C from nifH- based abundances. Reporting the arithmetic mean and one standard error instead, these three global estimates are 140 +/- 9.2 Tg Nyr(-1), 18 +/- 1.8 Tg C and 590 +/- 70 Tg C, respectively. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about +/- 70 %. It was recently established that the most commonly applied method used to measure N-2 fixation has underestimated the true rates. As a result, one can expect that future rate measurements will shift the mean N-2 fixation rate upward and may result in significantly higher estimates for the global N-2 fixation. The evolving database can nevertheless be used to study spatial and temporal distributions and variations of marine N-2 fixation, to validate geochemical estimates and to parameterize and validate biogeochemical models, keeping in mind that future rate measurements may rise in the future.
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| 8. |
- Ellinor, Patrick T., et al.
(författare)
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Meta-analysis identifies six new susceptibility loci for atrial fibrillation
- 2012
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 44:6, s. 88-670
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Tidskriftsartikel (refereegranskat)abstract
- Atrial fibrillation is a highly prevalent arrhythmia and a major risk factor for stroke, heart failure and death(1). We conducted a genome-wide association study (GWAS) in individuals of European ancestry, including 6,707 with and 52,426 without atrial fibrillation. Six new atrial fibrillation susceptibility loci were identified and replicated in an additional sample of individuals of European ancestry, including 5,381 subjects with and 10,030 subjects without atrial fibrillation (P < 5 x 10(-8)). Four of the loci identified in Europeans were further replicated in silico in a GWAS of Japanese individuals, including 843 individuals with and 3,350 individuals without atrial fibrillation. The identified loci implicate candidate genes that encode transcription factors related to cardiopulmonary development, cardiac-expressed ion channels and cell signaling molecules.
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| 9. |
- Takechi, M., et al.
(författare)
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Interaction cross sections for Ne isotopes towards the island of inversion and halo structures of 29Ne and 31Ne
- 2012
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Ingår i: Physics Letters B. - Elsevier : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:3-€“4, s. 357-361
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Tidskriftsartikel (refereegranskat)abstract
- Interaction cross sections (σI) for Ne isotopes from the stability line to the vicinity of the neutron dripline have been measured at around 240 MeV/nucleon using BigRIPS at RIBF, RIKEN. The σI for 27–32Ne in every case exceed the systematic mass-number dependence of σI for stable nuclei, which can be explained by considering the nuclear deformation. In particular the σI for 29Ne and 31Ne are significantly greater than those of their neighboring nuclides. These enhancements of σI for 29Ne and 31Ne cannot be explained by a single-particle model calculation under the assumption that the valence neutron of 29Ne (31Ne) occupies the 0d3/2 (0f7/2 ) orbital, as expected from the standard spherical shell ordering. The present data suggest an s dominant halo structure of 29Ne and s- or p-orbital halo in 31Ne.
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| 10. |
- Fukuda, M., et al.
(författare)
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Reaction cross section studies at NIRS and RIBF
- 2010
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Ingår i: American Institute of Physics Conference Series. - American Institute of Physics : AIP. ; , s. 270-273
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Konferensbidrag (refereegranskat)abstract
- Reaction cross sections for stable nuclei at intermediate energies have been measured precisely and systematically. The data have been found to be reproduced nicely by the optical‐limit approximation of Glauber theory modified to include the nucleon multiple scattering effect and the Fermi‐motion effect. Applying this prescription, the nucleon density distribution of 17Ne has been studied. The surface structure of 8B and 11Be has been also studied using this prescription and hydrogen targets. Using the RIBF that has just started application to studies of exotic nuclei, neutron‐rich Ne isotopes around the Island of Inversion have been investigated through measurements of their interaction cross sections.
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