11. Search for point sources of ultra-high-energy photons with the Telescope Array surface detectorR.U. Abbasi, Jon Paul Lundquist, 2020, izvirni znanstveni članek Opis: The surface detector (SD) of the Telescope Array (TA) experiment allows us to detect indirectly photons with energies of the order of 10^18 eV and higher, and to separate photons from the cosmic ray background. In this paper, we present the results of a blind search for point sources of ultra-high-energy (UHE) photons in the Northern sky using the TA SD data. The photon-induced extensive air showers are separated from the hadron-induced extensive air shower background by means of a multivariate classifier based upon 16 parameters that characterize the air shower events. No significant evidence for the photon point sources is found. The upper limits are set on the flux of photons from each particular direction in the sky within the TA field of view, according to the experiment’s angular resolution for photons. The average 95 per cent confidence level upper-limits for the point-source flux of photons with energies greater than 10^18, 10^18.5, 10^19, 10^19.5 and 10^20 eV are 0.094, 0.029, 0.010, 0.0073 and 0.0058 km−2yr−1, respectively. For energies higher than 10^18.5 eV, the photon point-source limits are set for the first time. Numerical results for each given direction in each energy range are provided as a supplement to this paper.
Ključne besede: methods: data analysis, cosmic rays, gamma-rays: general
Objavljeno v RUNG: 29.04.2020; Ogledov: 2609; Prenosov: 0
Gradivo ima več datotek! Več... |
12. Testing a Reported Correlation between Arrival Directions of Ultra-high-energy Cosmic Rays and a Flux Pattern from nearby Starburst Galaxies using Telescope Array DataR.U. Abbasi, Jon Paul Lundquist, 2018, izvirni znanstveni članek Opis: The Pierre Auger Collaboration (Auger) recently reported a correlation between the arrival directions of cosmic rays with energies above 39 EeV and the flux pattern of 23 nearby starburst galaxies (SBGs). In this Letter, we tested the same hypothesis using cosmic rays detected by the Telescope Array experiment (TA) in the 9-year period from May 2008 to May 2017. Unlike the Auger analysis, we did not optimize the parameter values but kept them fixed to the best-fit values found by Auger, namely 9.7% for the anisotropic fraction of cosmic rays assumed to originate from the SBGs in the list and 12.9◦ for the angular scale of the correlations. The energy threshold we adopted is 43 EeV, corresponding to 39 EeV in Auger when taking into account the energy-scale difference between two experiments. We find that the TA data is compatible with isotropy to within 1.1σ and with the Auger result to within 1.4σ, meaning that it is not capable to discriminate between these two hypotheses.
Ključne besede: astroparticle physics, cosmic rays, galaxies: starburst, methods: data analysis
Objavljeno v RUNG: 27.04.2020; Ogledov: 2862; Prenosov: 124
 Celotno besedilo (700,72 KB) |
13. Exploring element accumulation patterns of a metal excluder plant naturally colonizing a highly contaminated soilSara Pignattelli, Ilaria Colzi, Lorenzo Cecchi, Miluscia Arnetoli, Roberto Monnanni, Roberto Gabbrielli, Cristina Gonnelli, 2012, izvirni znanstveni članek Opis: This work investigates the element distribution in Silene paradoxa growing on the mine dump of Fenice Capanne (Tuscany, Italy). The accumulation of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in root apoplast and symplast and in shoot was assessed and compared to the levels of the same metals in the respective rizosphere soils, analyzing both the total and the phytoavailable fractions.
Levels of As, Cu, Fe, Pb and Zn, were above toxicity thresholds in both soil and shoot samples. Inter- and intra-element correlations were analyzed in plant and soil using different statistical methods. Soil total and phytoavailable metal concentration were shown not to be dominant in determining metal accumulation by the plant, since no significant positive correlation was found between metal concentration in soils and plants. Moreover, results indicated that S. paradoxa was able to cope with the studied multi-metal contaminated soil excluding the elements from its tissues and preferentially accumulating them into the root compartment, thus suggesting this species as possible good candidate for phytostabilization purposes.
Ključne besede: Metals, Mine dump, Phytostabilization, Silene paradoxa, Compositional data analysis
Objavljeno v RUNG: 20.04.2020; Ogledov: 2780; Prenosov: 0
Gradivo ima več datotek! Več... |
14. A multielement analysis of Cu induced changes in the mineral profilesof Cu sensitive and tolerant populations of Silene paradoxa L.Sara Pignattelli, Ilaria Colzi, Antonella Buccianti, Ilenia Cattani, Gian Maria Beone, Henk Schat, Cristina Gonnelli, 2013, izvirni znanstveni članek Opis: tThis work investigates the Cu induced changes in element profiles in contrasting ecotypes of Silene para-doxa L. A metallicolous copper tolerant population and a non-metallicolous sensitive population weregrown in hydroponics and exposed to different CuSO4treatments. Shoot and root concentrations of Ca,Cu, Fe, K, Mg, Mn, Mo, Na, P, S and Zn were evaluated through ICP-OES.Results indicated that increasing the environmental Cu concentration had a population dependenteffect on element profiles, shoot-to-root ratios and correlations among the elements. Generally, in thetolerant population Cu treatment induced a higher element accumulation in roots and had minimaleffects on the shoot element profile, thus resulting in a progressively decreasing shoot-to-root ratio foreach element. In the sensitive population element concentrations in root and shoot were much moreaffected and without a consistent trend. Copper treatment also affected the correlations between theelements, both in roots and shoots of the two populations, but more so in the sensitive population thanin the tolerant one. Thus, Cu exposure strongly disturbed element homeostasis in the sensitive population,but barely or not in the tolerant one, probably mainly due to a higher capacity to maintain proper rootfunctioning under Cu exposure in the latter. Differences in element profiles were also observed in theabsence of toxic Cu exposure. These differences may reflect divergent population-specific adaptations todifferential nutrient availability levels prevailing in the populations’ natural environments. There is noevidence of inherent side-effects of the Cu tolerance mechanism operating in the tolerant population.
Ključne besede: Mineral profile, Copper tolerance, Silene paradoxa, Compositional data analysis
Objavljeno v RUNG: 20.04.2020; Ogledov: 2817; Prenosov: 0
Gradivo ima več datotek! Več... |
15. A cellular network database for fingerprint positioning systemsDonatella Gubiani, Paolo Gallo, Andrea Viel, Andrea Dalla Torre, Angelo Montanari, 2019, objavljeni znanstveni prispevek na konferenci Opis: Besides being a fundamental infrastructure for communication, cellular networks are increasingly exploited for positioning via signal fingerprinting.
Here, we focus on cellular signal fingerprinting, where an accurate and comprehensive knowledge of the network is fundamental.
We propose an original multilevel database for cellular networks, which can be automatically updated with new fingerprint measurements and makes it possible to execute a number of meaningful analyses. In particular, it allows one to monitor the distribution of cellular networks over countries, to determine the density of cells in different areas, and to detect inconsistencies in fingerprint observations.
Ključne besede: Cellular network, Signal fingerprinting, Multilevel database, Data analysis
Objavljeno v RUNG: 17.09.2019; Ogledov: 3337; Prenosov: 0
Gradivo ima več datotek! Več... |
16. |
17. An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray SourcesA. Aab, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2018, izvirni znanstveni članek Ključne besede: astroparticle physics, cosmic rays, active galaxies, starburst galaxies, data analysis methods
Objavljeno v RUNG: 14.02.2018; Ogledov: 3448; Prenosov: 0
Gradivo ima več datotek! Več... |
18. Towards a Joint Analysis of Data from the IceCube Neutrino Telescope, the Pierre Auger Observatory and Telescope ArrayA. Christov, Andrej Filipčič, Ahmed Saleh, Samo Stanič, Darko Veberič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2016, objavljeni znanstveni prispevek na konferenci Ključne besede: ultra-high energy cosmic rays (UHECR), Pierre Auger Observatory, Telescope Array, very-high energy (VHE) neutrinos, IceCube Neutrino Telescope, joint data analysis
Objavljeno v RUNG: 08.11.2016; Ogledov: 5181; Prenosov: 0
Gradivo ima več datotek! Več... |
