31. Application of pattern spectra and convolutional neural networks to the analysis of simulated Cherenkov Telescope Array dataJann Aschersleben, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci Opis: The Cherenkov Telescope Array (CTA) will be the next generation gamma-ray observatory and will be the major global instrument for very-high-energy astronomy over the next decade, o˙ering 5 − 10 × better flux sensitivity than current generation gamma-ray telescopes. Each telescope will provide a snapshot of gamma-ray induced particle showers by capturing the induced Cherenkov emission at ground level. The simulation of such events provides images that can be used as training data for convolutional neural networks (CNNs) to determine the energy of the initial gamma rays. Compared to other state-of-the-art algorithms, analyses based on CNNs promise to further enhance the performance to be achieved by CTA.
Pattern spectra are commonly used tools for image classification and provide the distributions of the shapes and sizes of various objects comprising an image. The use of relatively shallow CNNs on pattern spectra would automatically select relevant combinations of features within an image, taking advantage of the 2D nature of pattern spectra. In this work, we generate pattern spectra from simulated gamma-ray events instead of using the raw images themselves in order to train our CNN for energy reconstruction. This is di˙erent from other relevant learning and feature selection methods that have been tried in the past. Thereby, we aim to obtain a significantly faster and less computationally intensive algorithm, with minimal loss of performance.
Ključne besede: Cherenkov Telescope Array, very-high-energy astronomy, convolutional neural networks
Objavljeno v RUNG: 18.09.2023; Ogledov: 52; Prenosov: 2
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32. Detection methods for the Cherenkov Telescope Array at very-short exposure timesAmbra Di Piano, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci Opis: The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for very-high-energy (VHE) gamma-ray astronomy, with the deployment of tens of highly sensitive and fast-reacting Cherenkov telescopes. It will cover a wide energy range (20 GeV - 300 TeV) with unprecedented sensitivity. To maximize the scientific return, the observatory will be provided with an online software system that will perform the first analysis of scientific data in real-time. This study investigates the precision and accuracy of available science tools and analysis techniques for the short-term detection of gamma-ray sources, in terms of sky localization, detection significance and, if significant detection is achieved, a first estimation of the integral photon flux. The scope is to evaluate the feasibility of the algorithms’ implementation in the real-time analysis of CTA. In this contribution we present a general overview of the methods and some of the results for the test case of the short-term detection of a gamma-ray burst afterglow, as the VHE counterpart of a gravitational wave event.
Ključne besede: very-high-energy gamma-rays, Cherenkov Telescope Array, gamma-ray astronomy
Objavljeno v RUNG: 18.09.2023; Ogledov: 51; Prenosov: 2
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33. Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centreChristopher Eckner, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci Opis: High-energy gamma rays are promising tools to constrain or reveal the nature of dark matter, in particular Weakly Interacting Massive Particles. Being well into its pre-construction phase, the Cherenkov Telescope Array (CTA) will soon probe the sky in the 20 GeV - 300 TeV energy range. Thanks to its improved energy and angular resolutions as well as significantly larger e˙ective area when compared to the current generation of Cherenkov telescopes, CTA is expected to probe heavier dark matter, with unprecedented sensitivity, reaching the thermal annihilation cross-section at 1 TeV.
This talk will summarise the planned dark matter search strategies with CTA, focusing on the signal from the Galactic centre. As observed with the Fermi LAT at lower energies, this region is rather complex and CTA will be the first ground-based observatory sensitive to the large scale di˙use astrophysical emission from that region. We report on the collaboration e˙ort to study the impact of such extended astrophysical backgrounds on the dark matter search, based on Fermi-LAT data in order to guide our observational strategies, taking into account various sources of systematic uncertainty.
Ključne besede: high-energy gamma rays, Cherenkov Telescope Array, dark matter, galactic centre
Objavljeno v RUNG: 18.09.2023; Ogledov: 55; Prenosov: 2
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34. Cherenkov Telescope Array: the World's largest VHE gamma-ray observatoryRoberta Zanin, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje) Opis: Very-High Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and obser-vations over the past decade have surprisingly revealed almost two hundred VHE emitters which appear to act as cosmic particle accelerators. These sources are an important component of the Universe, influencing the evolution of stars and galaxies. At the same time, they also act as a probe of physics in the most extreme environments known - such as in supernova explosions, and around or after the merging of black holes and neutron stars. However, the existing experiments have provided exciting glimpses, but often falling short of supplying the full answer. A deeper understanding of the TeV sky requires a significant improvement in sensitivity at TeV energies, a wider energy coverage from tens of GeV to hundreds of TeV and a much better angular and energy resolution with respect to the currently running facilities. The next generation gamma-ray observatory, the Cherenkov Telescope Array Observatory (CTAO), is the answer to this need. In this talk I will present this upcoming observatory from its design to the construction, and its potential science exploitation. CTAO will allow the entire astronomical community to explore a new discovery space that will likely lead to paradigm-changing breakthroughs. In particular, CTA has an unprecedented sensitivity to short (sub-minute) timescale phenomena, placing it as a key instrument in the future of multi-messenger and multi-wavelength time domain astronomy. I will conclude the talk presenting the first scientific results obtained by the LST-1, the prototype of one CTA telescope type - the Large Sized Telescope, that is currently under commission.
Ključne besede: Very-High Energy Gamma-rays, Cherenkov Telescope Array
Objavljeno v RUNG: 18.09.2023; Ogledov: 40; Prenosov: 2
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35. Functional Characterization of Saccharomyces Yeasts from Cider Produced in HardangerAhmad Hosseini, 2023, izvirni znanstveni članek Ključne besede: Saccharomyces, Hardanger, characterization, fermentation, cider, non-volatile compounds, volatile organic compounds, partial least squares (PLS) regression
Objavljeno v RUNG: 18.09.2023; Ogledov: 64; Prenosov: 2
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37. Infrared spectra in amorphous aluminaLuigi Giacomazzi, Nikita S Shcheblanov, Mikhail E Povarnitsyn, Yanbo Li, Andraž Mavrič, Barbara Zupančič, Jože Grdadolnik, Alfredo Pasquarello, zaključena znanstvena zbirka raziskovalnih podatkov Opis: We present a combined study based on experimental measurements of infrared (IR) dielectric function and first-principles calculations of IR spectra and vibrational density of states (VDOS) of amorphous alumina (am-Al₂O₃). In particular, we show that the main features of the imaginary part of the dielectric function ε₂(ω) at ~380 and 630 cm-¹ are related to the motions of threefold coordinated oxygen atoms, which are the vast majority of oxygen atoms in am-Al₂O₃. Our analysis (involving three model structures) provides an alternative point of view with respect to an earlier suggested assignment of the vibrational modes, which relates them to the stretching and bending vibrational modes of AlOₙ (n = 4, 5, and 6) polyhedra. Our assignment is based on the additive decomposition of the VDOS and ε₂(ω) spectra, which shows that: (i) the band at ~380 cm-¹ features oxygen motions occurring in a direction normal to the plane defined by the three nearest-neighbor aluminum atoms, i.e. out-of-plane motions of oxygen atoms; (ii) Al-O stretching vibrations (i.e. in-plane motions of oxygen atoms) appear at frequencies above ~500 cm-¹, which characterize the vibrational modes underlying the band at ~630 cm-¹.
Ključne besede: amorphous alumina, infrared spectra, first-principles calculations
Objavljeno v RUNG: 15.09.2023; Ogledov: 120; Prenosov: 3
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38. Source apportionment study on particulate air pollution in two high-altitude Bolivian cities: La Paz and El AltoValeria Mardoñez, Marco Pandolfi, Griša Močnik, Gaëlle Uzu, 2023, izvirni znanstveni članek Opis: La Paz and El Alto are two fast-growing, high-altitude Bolivian cities forming the second-largest metropolitan area in the country. Located between 3200 and 4050 m a.s.l. (above sea level), these cities are home to a burgeoning population of approximately 1.8 million residents. The air quality in this conurbation is heavily influenced by urbanization; however, there are no comprehensive studies evaluating the sources of air pollution and their health impacts. Despite their proximity, the substantial variation in altitude, topography, and socioeconomic activities between La Paz and El Alto result in distinct sources, dynamics, and transport of particulate matter (PM). In this investigation, PM10 samples were collected at two urban background stations located in La Paz and El Alto between April 2016 and June 2017. The samples were later analyzed for a wide range of chemical species including numerous source tracers (OC, EC, water-soluble ions, sugar anhydrides, sugar alcohols, trace metals, and molecular organic species). The United States Environmental Protection Agency (U.S. EPA) Positive Matrix Factorization (PMF v.5.0) receptor model was employed for the source apportionment of PM10. This is one of the first source apportionment studies in South America that incorporates an extensive suite of organic markers, including levoglucosan, polycyclic aromatic hydrocarbons (PAHs), hopanes, and alkanes, alongside inorganic species. The multisite PMF resolved 11 main sources of PM. The largest annual contribution to PM10 came from the following two major sources: the ensemble of the four vehicular emissions sources (exhaust and non-exhaust), accountable for 35 % and 25 % of the measured PM in La Paz and El Alto, respectively; and dust, which contributed 20 % and 32 % to the total PM mass. Secondary aerosols accounted for 22 % (24 %) in La Paz (El Alto). Agricultural smoke resulting from biomass burning in the Bolivian lowlands and neighboring countries contributed to 9 % (8 %) of the total PM10 mass annually, increasing to 17 % (13 %) between August–October. Primary biogenic emissions were responsible for 13 % (7 %) of the measured PM10 mass. Additionally, a profile associated with open waste burning occurring from May to August was identified. Although this source contributed only to 2 % (5 %) of the total PM10 mass, it constitutes the second largest source of PAHs, which are compounds potentially hazardous to human health. Our analysis additionally resolved two different traffic-related factors, a lubricant source (not frequently identified), and a non-exhaust emissions source. Overall, this study demonstrates that PM10 concentrations in La Paz and El Alto region are predominantly influenced by a limited number of local sources. In conclusion, to improve air quality in both cities, efforts should primarily focus on addressing dust, traffic emissions, open waste burning, and biomass burning.
Ključne besede: source apportionment, particular air pollution, high altitude, positive matrix factorization, PMF
Objavljeno v RUNG: 15.09.2023; Ogledov: 109; Prenosov: 2
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39. Bright blazar flares with CTAM. Cerruti, Saptashwa BHATTACHARYYA, Judit Pérez-Romero, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha ŽIVEC, 2023, objavljeni znanstveni prispevek na konferenci Opis: The TeV extragalactic sky is dominated by blazars, radio-loud active galactic nuclei with a
relativistic jet pointing towards the Earth. Blazars show variability that can be quite exceptional
both in terms of flux (orders of magnitude of brightening) and time (down to the minute timescale).
This bright flaring activity contains key information on the physics of particle acceleration and
photon production in the emitting region, as well as the structure and physical properties of the
jet itself. The TeV band is accessed from the ground by Cherenkov telescopes that image the
pair cascade triggered by the interaction of the gamma ray with the Earth’s atmosphere. The
Cherenkov Telescope Array (CTA) represents the upcoming generation of imaging atmospheric
Cherenkov telescopes, with a significantly higher sensitivity and larger energy coverage with
respect to current instruments. It will thus provide us with unprecedented statistics on blazar
light-curves and spectra. In this contribution we present the results from realistic simulations of
CTA observations of bright blazar flares, taking as input state-of-the-art numerical simulations of
blazar emission models and including all relevant observational constraints.
Ključne besede: active galactic nuclei (AGN), radio-loud AGN, blazars, blazar flares, cosmic particle acceleration, very-high-energy gamma-rays, Cherenkov Telescope Array
Objavljeno v RUNG: 15.09.2023; Ogledov: 99; Prenosov: 2
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40. Utilizing Structurally Disordered AlMg-Oxide Phase in Cu/ZnO Catalyst for Efficient CO2 Hydrogenation to MethanolAndraž Mavrič, Gregor Žerjav, Blaž Belec, Matevž Roškarič, Matjaž Finšgar, Albin Pintar, Matjaž Valant, 2023, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: carbon dioxide, methanol, catalysis
Objavljeno v RUNG: 15.09.2023; Ogledov: 100; Prenosov: 0
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