11. Astroparticles at the High Energy Frontier: Results from the Pierre Auger ObservatoryMarko Zavrtanik, Danilo Zavrtanik, Serguei Vorobiov, Darko Veberič, Samo Stanič, Ahmed Saleh, Andrej Filipčič, Gonzalo Parente, 2014, objavljeni znanstveni prispevek na konferenci Najdeno v: ključnih besedah
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), UHECR energy spectrum, mass composition, anisotropies
Objavljeno: 20.06.2017; Ogledov: 3887; Prenosov: 0
 Polno besedilo (1,06 MB) |
12. Results from the Pierre Auger ObservatoryMarko Zavrtanik, Danilo Zavrtanik, Darko Veberič, Samo Stanič, Andrej Filipčič, Ivan De Mitri, 2015, objavljeni znanstveni prispevek na konferenci Najdeno v: ključnih besedah
Ključne besede: Pierre Auger Observatory, Ultra High Energy Cosmic Rays (UHECR), UHECR energy spectrum, UHECR mass composition
Objavljeno: 27.06.2017; Ogledov: 3205; Prenosov: 0
Polno besedilo (475,69 KB) |
13. Depth of maximum of air-shower profiles at the Pierre Auger Observatory: Measurements above 10^17.2 eV and Composition ImplicationsMarko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Jose Bellido, 2017, objavljeni znanstveni prispevek na konferenci Najdeno v: ključnih besedah
Ključne besede: Pierre Auger Observatory, depth of maximum of air-shower, mass composition
Objavljeno: 16.02.2018; Ogledov: 2396; Prenosov: 131
Polno besedilo (1,19 MB) |
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16. Mass composition of ultra-high energy cosmic rays at the Pierre Auger ObservatoryGašper Kukec Mezek, 2019, doktorska disertacija Opis: Cosmic rays with energies above 10^18 eV, usually referred to as ultra-high energy cosmic rays (UHECR), have been a mystery from the moment they have been discovered. Although we have now more information on their extragalactic origin, their direct sources still remain hidden due to deviations caused by galactic magnetic fields. Another mystery, apart from their production sites, is their nature. Their mass composition, still uncertain at these energies, would give us a better understanding on their production, acceleration, propagation and capacity to produce extensive air showers in the Earth's atmosphere. Mass composition studies of UHECR try to determine their nature from the difference in development of their extensive air showers.
In this work, observational parameters from the hybrid detection system of the Pierre Auger Observatory are used in a multivariate analysis to obtain the mass composition of UHECR. The multivariate analysis (MVA) approach combines a number of mass composition sensitive variables and tries to improve the separation between different UHECR particle masses. Simulated distributions of different primary particles are fitted to measured observable distributions in order to determine individual elemental fractions of the composition. When including observables from the surface detector, we find a discrepancy in the estimated mass composition between a mixed simulation sample and the Pierre Auger data. Our analysis results from the Pierre Auger data are to a great degree independent on hadronic interaction models. Although they differ at higher primary masses, the different models are more consistent, when combining fractions of oxygen and iron. Compared to previously published results, the systematic uncertainty from hadronic interaction models is roughly four times smaller. Our analysis reports a predominantly heavy composition of UHECR, with more than a 50% fraction of oxygen and iron at low energies. The composition is then becoming heavier with increasing energy, with a fraction of oxygen and iron above 80% at the highest energies.
Najdeno v: ključnih besedah
Ključne besede: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, machine learning, multivariate analysis
Objavljeno: 03.04.2019; Ogledov: 3786; Prenosov: 163
Polno besedilo (17,53 MB) |
17. Mass composition of cosmic rays with energies from 10^17.2 eV to 10^20 eV using surface and fluorescence detectors of the Pierre Auger ObservatoryGašper Kukec Mezek, 2018, objavljeni znanstveni prispevek na konferenci Opis: Ultra-high-energy cosmic rays (UHECRs) are highly energetic particles with EeV energies, exceeding the capabilities of man-made colliders. They hold information on extreme astrophysical processes that create them and the medium they traverse on their way towards Earth. However, their mass composition at such energies is still unclear, because data interpretation depends on our choice of high energy hadronic interaction models. With its hybrid detection method, the Pierre Auger Observatory has the possibility to detect extensive air showers with an array of surface water-Cherenkov stations (SD) and fluorescence telescopes (FD). We present recent mass composition results from the Pierre Auger Collaboration using observational parameters from SD and FD measurements. Using the full dataset of the Pierre Auger Observatory, implications on composition can be made for energies above 10^17.2 eV.
Najdeno v: ključnih besedah
Ključne besede: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, fluorescence telescopes, water-Cherenkov stations
Objavljeno: 24.05.2019; Ogledov: 2578; Prenosov: 100
Polno besedilo (573,00 KB) |
18. Stable carbon isotope analysis of selected halocarbons at parts per trillion concentration in an urban locationM Iqbal Mead, M Anwar H Khan, Ian D Bull, Iain R White, Graham Nickless, Dudley E Shallcross, 2008, izvirni znanstveni članek Opis: ∂13C values of a suite of halocarbons have been determined in an urban background site in Bristol, UK. A novel mobile preconcentration system, based on the use of multi-adsorbent sample tubes, has been developed for trapping relatively large-volume air samples in potentially remote areas. An Adsorption Desorption System-Gas Chromatography-Electron Capture Detector was used to measure the mixing ratios of the selected halocarbon species, while a Gas ChromatographyCombustionIsotope Ratio Mass Spectrometer was used to determine ∂13C values. For the species with strong local sources, the variation of isotope ratios has been observed over the experimental period. Some of the results reported in the present study differ from previously reported values and reasons for this are discussed. The reporting of different ∂13C values for selected halocarbons from different areas in the present study suggests that ∂13C values may be used to determine the relative magnitudes of anthropogenic and biogenic sources.
Najdeno v: ključnih besedah
Ključne besede: Adsorption Desorption System (ADS), Automated Thermal Desorber (ATD), Electron Capture Detector (ECD), Gas Chromatography (GC), Isotope Ratio Mass Spectrometry (IRMS)
Objavljeno: 18.07.2019; Ogledov: 2290; Prenosov: 0
Polno besedilo (227,35 KB) |
19. Increased sensitivity in proton transfer reaction mass spectrometry by incorporation of a radio frequency ion funnelAndrew M Ellis, Stephen Mullock, Fraser Reich, Paul S Monks, Iain R White, Robert S Blake, Shane Barber, 2012, izvirni znanstveni članek Opis: A drift tube capable of simultaneously functioning as an ion funnel is demonstrated in proton transfer reaction mass spectrometry (PTR-MS) for the first time. The ion funnel enables a much higher proportion of ions to exit the drift tube and enter the mass spectrometer than would otherwise be the case. An increase in the detection sensitivity for volatile organic compounds of between 1 and 2 orders of magnitude is delivered, as demonstrated using several compounds. Other aspects of analytical performance explored in this study include the effective E/N (ratio of electric field to number density of the gas) and dynamic range over which the drift tube is operated. The dual-purpose drift tube/ion funnel can be coupled to various types of mass spectrometers to increase the detection sensitivity and may therefore offer considerable benefits in PTR-MS work.
Najdeno v: ključnih besedah
Ključne besede: Analytical performance, Detection sensitivity, Drift tube, Dynamic range, Ion funnels, Proton-transfer reaction mass spectrometry, Volatile organic compounds
Objavljeno: 18.07.2019; Ogledov: 2136; Prenosov: 0
Polno besedilo (799,47 KB) |
20. Real-time multi-marker measurement of organic compounds in human breath: Towards fingerprinting breathIain R White, Kerry A Willis, Christopher Whyte, Rebecca Cordell, Robert S Blake, Andrew J Wardlaw, 2013, izvirni znanstveni članek Opis: The prospects for exploiting proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) in medical diagnostics are illustrated through a series of case studies. Measurements of acetone levels in the breath of 68 healthy people are presented along with a longitudinal study of a single person over a period of 1 month. The median acetone concentration across the population was 484 ppbV with a geometric standard deviation (GSD) of 1.6, whilst the average GSD during the single subject longtitudinal study was 1.5. An additional case study is presented which highlights the potential of PTR-ToF-MS in pharmacokinetic studies, based upon the analysis of online breath samples of a person following the consumption of ethanol. PTR-ToF-MS comes into its own when information across a wide mass range is required, particularly when such information must be gathered in a short time during a breathing cycle. To illustrate this property, multicomponent breath analysis in a small study of cystic fibrosis patients is detailed, which provides tentative evidence that online PTR-ToF-MS analysis of tidal breath can distinguish between active infection and non-infected patients.
Najdeno v: ključnih besedah
Ključne besede: Volatile Organic Compounds, breath, proton transfer reaction mass spectrometry, Cystic Fibrosis
Objavljeno: 22.07.2019; Ogledov: 2460; Prenosov: 0
Polno besedilo (1,37 MB) |
