Search

Very-high Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observations 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 CTAO telescope type - the Large-Sized Telescope, that is currently under commission., PoS: Proceedings of Science, 395, ISSN:1824-8039, Proceedings of 37th International Cosmic Ray Conference (ICRC2021)

Multiwavelength light curves in long-term campaigns have shown that, for several blazars, the radio emission occurs with a significant delay w.r.t. to $\gamma$-ray band, with timescales ranging from weeks to years. Such observational evidence has been a matter of debate for years and usually is interpreted as a signature of the $\gamma$-ray emission originating upstream in the jet, with the emitting region becoming radio transparent at larger scales. In this paper, we show, by means of self-consistent numerical modelling, that the adiabatic expansion of relativistic blob can explain these delays. We use the JetSeT framework to reproduce the numerical modelling of the radiative/accelerative processes, reproducing the temporal evolution, from the initial flaring activity, and the subsequent expansion. We follow the spectral evolution and the light curves, investigating the relations among the observed parameters, rise, time, and decay time, identifying the link with the physical parameters. We find that, when adiabatic expansion is active, lags due to the shift of the synchrotron frequency occur, with an offset equal to the distance in time between the flaring onset and the beginning of the expansion, whilst the rising and decaying timescales depend on the velocity of the expansion and on time required to the source to exhibit a synchrotron self-absorption frequency. We derive an inter-band response function, and we investigate the effects of the competitions between radiative and adiabatic cooling timescales on the response. We apply the response function to long-term radio and $\gamma-$ray light curves of Mrk 421, Mrk 501 and 3C 273, finding a satisfactory agreement on the log-term behaviour, and we use a Monte Carlo Markov Chain approach, to estimate some physical relevant parameters. We discuss the applications to polarization measurements, and to jets collimation profile kinematics., Comment: 27 pages, 22 figures, accepted for publication in A&A. Reproducible analysis: https://github.com/andreatramacere/adiabatic_exp_radio_gamma_delay; corrections after language editor revision and layout update

The blazar Mrk 421 shows frequent, short flares in the TeV energy regime. Due to the fast nature of such episodes, we often fail to obtain sufficient simultaneous information about flux variations in several energy bands. To overcome this lack of multi-wavelength (MWL) coverage, especially for the pre- and post-flare periods, we have set up a monitoring program with the FACT telescope (TeV energies) and the Neil Gehrels Swift Observatory (X-rays). On 2019 June 9, Mrk 421 showed a TeV outburst reaching a flux level of more than two times the flux of the Crab Nebula at TeV energies. We acquired simultaneous data in the X-rays with additional observations by XMM-Newton and INTEGRAL. For the first time, we can study a TeV blazar in outburst taking advantage of highly sensitive X-ray data from XMM-Newton and INTEGRAL combined. Our dataset is complemented by pointed radio observations by Effelsberg at GHz frequencies. We present our first results, including the {\gamma}-ray and X-ray light curves, a timing analysis of the X-ray data obtained with XMM-Newton , as well as the radio spectra before, during and after the flare., Comment: 8 pages, 4 figures; Proceedings of the 37th International Cosmic Ray Conference (ICRC2021). 12-23 July, 2021. Berlin, Germany. Online at https://pos.sissa.it/395/

The article describes the work to improve the accuracy and efficiency of assessing technological risks in automation of technological processes using the developed methods and algorithms of combined assessing technological risks. The practical significance is confirmed by the acts of implementation. A methodology for assessing technological risks was developed based on combinations of standardized methods, a modified algorithm for managing technological risks with the ability to combining methods for assessing technological risks, developed an algorithm for analyzing technological risks in application to a specific organizational context.

Remote electronic voting is the most promising way to increase voter turnout. The use of Blockchain technology will guarantee complete security and protection against hacking, ensure the secrecy of the vote and openness of the procedure for the society.The structure of the Blockchain voting is as follows. The user needs to have a mobile-specific address space. The mobile device identifier is recorded on the Blockchain as a wallet address that is associated with that user's token. The token will be limited in time in which it can be used for voting. Sending a marker (token) to a specific candidate address will constitute a vote. Received votes are securely stored in the Blockchain, and the correctness of addressing a vote to a specific candidate can always be checked in real time. All data that goes into the Blockchain vote is sent to it thanks to a smart contract.The proposed method for constructing remote electronic voting will allow to reliably store obtained results in the Blockchain, increasing the cryptographic strength of the data and the transparency of the system, and, consequently, the confidence of users in it. Early receipt of the ballot will allow to participate in voting remotely, as a result, the turnout will increase.The considered structure of Blockchain voting will have prospects of use not only in the electoral system, but at general meetings of shareholders, meetings of LLC participants, meetings of the board of directors (supervisory board), committees, forums, conferences and other events where voting is necessary.

The SST-1M is a 4-m diameter mirror Davies-Cotton gamma-ray telescope. It has been designed to cover the energy range above ~ 500 GeV and to be part of an array of telescopes separated by ~ 150−200 m. Its innovative camera is featuring large area hexagonal silicon photo-multipliers as photon detectors and a fully digital trigger and readout system. Here, the strategy and the methods for its calibration are presented, together with the obtained results. In particular, the off and on-site calibration strategies are demonstrated on the first camera prototype. The performances of the camera in terms of charge and time resolution are described.

The requirements to modeling dynamic processes in automated systems and educational processes in universities are considered. It is shown that taking into account the dynamics and stochastic processes allows creating adequate models of control processes for the systems of a hierarchical level of direct digital control and higher levels. The problem of creating virtual laboratory stands is relevant both for full-time training, as well as for distance learning. The effectiveness of modeling virtual laboratory processes depends significantly on the selection of tools. In view of systemically related limitations, the selection of a mathematical apparatus is justified as a combination of two requirements: to describe the dynamic properties of an object, the convolution equation should be used; to analyze the properties of signals in dynamical systems, one should apply the theory of random processes.

Проблематика. Визначення області перфузії головного мозку є попереднім етапом перфузійного аналізу, який призначений для виключення пікселів, що не характеризують мозок, із зображень динамічно-сприйнятливої контрастної магнітно-резонансної (МР) томографії. Точність цього етапу вважається ключовим фактором у наданні правильних результатів перфузійного аналізу. Незважаючи на велику кількість алгоритмів сегментації мозку, не існує таких, які б точно і надійно працювали на Т2-зважених МР-зображеннях мозку людини з аномальною анатомією. Отже, порогова фільтрація, як і раніше, залишається тим способом, що широко використовується в сучасному програмному забезпеченні з перфузійного аналізу для визначення пікселів, які характеризують область перфузії головного мозку. Мета дослідження. Аналіз ефективності методів порогової фільтрації щодо визначення області перфузії головного мозку на T2-зважених МР-зображеннях мозку людини з аномальною анатомією. Методика реалізації. Розглянуто чотири алгоритми пошуку порога: глобальний пошук за методом Оцу, локальний пошук за методом Ніблака, пошук у ділянці анатомічного розташування мозку і пошук за методом перебору. Результатом роботи всіх алгоритмів було зображення із заміною нульовими значеннями пікселів фону (пікселів повітря і пікселів, що не характеризують мозок) і з оригінальними значеннями пікселів з області перфузії головного мозку. Аналіз проводили, порівнюючи перфузійні карти, що були отримані із зображень після застосування порогової фільтрації та з еталонних зображень (мануальне визначення ділянки мозку досвідченими рентгенологами). Для порівняння були використані одні й ті самі зображення динамічно-сприйнятливої контрастної МР-томографії головного мозку 12 пацієнтів із цереброваскулярними захворюваннями. Результати дослідження. Кореляційний аналіз Пірсона показав сильний позитивний (r був від 0,7123 до 0,8518, p < 0,01) і слабкий позитивний (r < 0,35, p < 0,01) взаємозв'язок у проведених експериментах із CBF, CBV, MTT і Tmax перфузійними картами відповідно. Лінійний регресійний аналіз показав, що перфузійні карти, які були отримані із зображень після застосування порогової фільтрації, схильні до помилок масштабу і зсуву в усіх проведених експериментах з урахуванням 95 %-ного довірчого інтервалу. Висновки. Результати експериментів показали, що поширене використання порогової фільтрації є неефективним способом визначення пікселів, які характеризують область перфузії головного мозку. Використання порогової фільтрації як інструменту з проведення сегментації мозку може призводити до неправильного визначення області перфузії, і, як наслідок, перфузійні карти будуть схильні до наявності артефактів і призведуть до помилково високої або помилково низької оцінки параметрів перфузії. Background. The brain perfusion ROI detection being a preliminary step, designed to exclude non-brain tissues from analyzed DSC perfusion MR images. Its accuracy is considered as the key factor for delivering correct results of perfusion data analysis. Despite the large variety of algorithms developed on brain tissues segmentation, there is no one that works reliably and robustly on T2-weighted MR images of a human head with abnormal brain anatomy. Therefore, thresholding method is still the state-of-the-art technique that is widely used as a way of managing pixels involved in brain perfusion ROI in modern software applications for perfusion data analysis. Objective. This paper presents the analysis of effectiveness of thresholding techniques in brain perfusion ROI detection on T2-weighted MR images of a human head with abnormal brain anatomy. Methods. Four threshold-based algorithms implementation are considered: according to Otsu method as global thresholding, according to Niblack method as local thresholding, thresholding in approximate anatomical brain location, and brute force thresholding. The result of all algorithms is images with pixels’ values changed to zero for background regions (air pixels and pixels that represent non-brain tissues) and original values for foreground regions (brain perfusion ROIs). The analysis is done using comparison of qualitative perfusion maps produced from thresholded images and from the reference ones (manual brain tissues delineation by experienced radiologists). The same DSC perfusion MR datasets of a human head with abnormal brain anatomy from 12 patients with cerebrovascular disease are used for comparison. Results. Pearson correlation analysis showed strong positive (r was ranged from 0.7123 to 0.8518, p < 0.01) and weak positive (r < 0.35, p < 0.01) relationship in case of conducted experiments with CBF, CBV, MTT and Tmax perfusion maps, respectively. Linear regression analysis showed at level of 95 % confidence interval that perfusion maps produced from thresholded images were subject to scale and offset errors in all conducted experiments. Conclusions. The experimental results showed that widely used thresholding methods are an ineffective way of managing pixels involved in brain perfusion ROI. Thresholding as brain segmentation tool can lead to poor placement of perfusion ROI and, as a result, produced perfusion maps will be subject to artifacts and can cause falsely high or falsely low perfusion parameter assessment. Проблематика. Определение области перфузии головного мозга является предварительным этапом перфузионного анализа, который предназначен для исключения не относящихся к мозгу пикселей из изображений динамично-восприимчивой контрастной магнитно-резонансной (МР) томографии. Точность этого этапа считается ключевым фактором в предоставлении правильных результатов перфузионного анализа. Несмотря на большое разнообразие алгоритмов сегментации мозга, не существует таких, которые бы точно и надежно работали на Т2-взвешенных МР-изображениях мозга человека с аномальной анатомией. Таким образом, пороговая фильтрация по-прежнему остается широко используемым способом определения пикселей, которые характеризуют область перфузии головного мозга, в современном программном обеспечении для проведения перфузионного анализа. Цель исследования. Анализ эффективности методов пороговой фильтрации в определении области перфузии головного мозга на Т2-взвешенных МР-изображениях мозга человека с аномальной анатомией. Методика реализации. Рассмотрены четыре алгоритма поиска порога: глобальный поиск методом Оцу, локальный поиск методом Ниблака, поиск в области анатомического расположения мозга и поиск методом перебора. Результатом всех алгоритмов являлось изображение с измененными на ноль значениями пикселей для фона (пиксели воздуха и пиксели, которые представляют ткани, не являющиеся мозгом) и оригинальными значениями для пикселей области перфузии головного мозга. Анализ проводился на основании сравнения перфузионных карт, полученных из отсегментированных пороговой фильтрацией изображений и из эталонных (мануальное определение области мозга опытными рентгенологами). Для сравнения были использованы одни и те же изображения динамично-восприимчивой контрастной МР-томографии головного мозга 12 пациентов с цереброваскулярными заболеваниями. Результаты исследования. Корреляционный анализ Пирсона показал сильную положительную (r был от 0,7123 до 0,8518, p < 0,01) и слабую положительную (r < 0,35, p < 0,01) взаимосвязь в случае проведенных экспериментов с CBF, CBV, MTT и Tmax перфузионными картами соответственно. Линейный регрессионный анализ показал, что перфузионные карты, которые были получены из отсегментированных пороговой фильтрацией изображений, подвержены ошибкам масштаба и смещения во всех проведенных экспериментах с учетом 95 %-ного доверительного интервала. Выводы. Результаты экспериментов показали, что широко используемые методы пороговой фильтрации являются неэффективным способом определения пикселей, которые характеризуют область перфузии головного мозга. Использование пороговой фильтрации как инструмента для проведения сегментации мозга может приводить к неправильному определению области перфузии, и, как следствие, перфузионные карты будут подвержены наличию артефактов и приведут к ошибочно высокой или ошибочно низкой оценке параметров перфузии.

The paper is dedicated to algorithms for accounting the variations of calculated indicators in ERP systems. These algorithms are being compared by computational complexity, and their advantages and disadvantages are highlighted.

The paper considers the question of using triggers for business processes controlling modules of ERP systems. A comparative analysis of approaches used by the most common ERP systems by controlling complexity and portability is done.

The First G-APD Cherenkov Telescope (FACT) has been monitoring Active Galactic Nuclei (AGN) for the past five years. The use of robust silicon photomultipliers (SiPMs) allows for a continuous, unbiased sampling even during bright-light conditions. This dataset promises insights into the core regions of AGN by investigating the periodicity of the sources. Periodic changes in the flux could indicate a binary nature of the supermassive black holes. A study using the Lomb-Scargle periodogram to find periodicity in monitored AGN is presented. Repeating patterns in the observation times, like moon periods and seasonal effects, affect the analysis by introducing spurious peaks into the periodogram. The zenith-dependence of the observed $\gamma$-ray rates further complicate the interpretation. Showing no variability at TeV energies, the $\gamma$-ray flux of the Crab Nebula is used to characterize this latter effect, before applying the Lomb-Scargle algorithm.

The foreseen implementations of the Small Size Telescopes (SST) in CTA will provide unique insights into the highest energy gamma rays offering fundamental means to discover and under- stand the sources populating the Galaxy and our local neighborhood. Aiming at such a goal, the SST-1M is one of the three different implementations that are being prototyped and tested for CTA. SST-1M is a Davies-Cotton single mirror telescope equipped with a unique camera technology based on SiPMs with demonstrated advantages over classical photomultipliers in terms of duty-cycle. In this contribution, we describe the telescope components, the camera, and the trigger and readout system. The results of the commissioning of the camera using a dedicated test setup are then presented. The performances of the camera first prototype in terms of expected trigger rates and trigger efficiencies for different night-sky background conditions are presented, and the camera response is compared to end-to-end simulations., Comment: All CTA contributions at arXiv:1709.03483

R. Moderskic,W. Bilnikk, J. Blockig, L. Bogacze, T. Bulikd , F. Cadouxa, A. Christova, M. Chruślinskad , M. Curylog, D. della Volpea, M. Dyrdag, Y. Favrea, A. Frankowskic, Ł. Grudnikg, M. Grudzinskad , M. Hellera, B. Idźkowskib, M. Jamrozyb, M. Janiakc, J. Kasperekk, K. Lalikk, E. Lyard f , E. Machg, D. Mandatm, A. Marszalekh,b, J. Michalowskig, T. Montarulia, A. Neronov f , J. Niemiecg, M. Ostrowskib, P. Paśkoh, M. Pechm, A. Porcelli∗a, E. Prandini f , E. Puescheln, P. Rajdak, M. Rameeza, P. Rozwadowskid , E. jr Schioppaa, P. Schovanekm, K. Sewerynh, K. Skowrong, V. Sliusari, M. Sowinskig, Ł. Stawarzb, M. Stodulskab, M. Stodulskig, S. Toscano f ,l, I. Troyano Pujadasa, R. Walter f , M. Wiȩcekk, A. Zagdanskib, K. Ziȩtarab, P. Żychowskig for the CTA Consortium† aDPNC – Universite de Geneve, Geneve, Switzerland bAstronomical Observatory, Jagiellonian University, Krakow, Poland cNicolaus Copernicus Astronomical Centre, Polish Academy of Sciences, Warsaw, Poland dAstronomical Observatory, University of Warsaw, Warsaw,Poland eDepartment of Information Technologies, Jagiellonian University, Krakow, Poland f ISDC, Observatoire de Geneve, Universite de Geneve, Versoix, Switzerland gInstytut Fizyki Jadrowej im. H. Niewodniczanskiego Polskiej Akademii Nauk, Krakow, Poland hCentrum Badan Kosmicznych Polskiej Akademii Nauk, Warsaw, Poland iAstronomical Observatory, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine kAGH University of Science and Technology, Krakow, Poland lVrije Universiteit Brussels, Brussels, Belgium mInstitute of Physics of the Czech Academy of Sciences, Prague, Czech Republic nUniversity College Dublin, Ireland

The single-mirror small-size telescope (SST-1M) is one of the three proposed designs for the small-size telescopes (SSTs) of the Cherenkov Telescope Array (CTA) project. The SST-1M will be equipped with a 4 m-diameter segmented mirror dish and an innovative fully digital camera based on silicon photo-multipliers (SiPMs). Since the SST sub-array will consist of up to 70 telescopes, the challenge is not only to build a telescope with excellent performance, but also to design it so that its components can be commissioned, assembled and tested by industry. In this paper we review the basic steps that led to the design concepts for the SST-1M camera and the ongoing realization of the first prototype, with focus on the innovative solutions adopted for the photodetector plane and the readout and trigger parts of the camera. In addition, we report on results of laboratory measurements on real scale elements that validate the camera design and show that it is capable of matching the CTA requirements of operating up to high-moon-light background conditions., 30 pages, 61 figures

The single mirror Small Size Telescope (SST-1M) project proposes a design among others for the smallest type of telescopes (SST), that will compose the south observatory of the Cherenkov Telescope Array (CTA). The SST camera collecting the Cherenkov light resulting from very high energy gamma-ray interactions in the atmosphere proposes to use Silicon PhotoMultipliers (SiPM). The SST-1M design has led to the use of unique pixel shape and size that required a dedicated development by the University of Geneva and Hamamatsu. An active surface of ~94 mm2 and a resulting total capacitance of ~3.4 nF combined with the stringent requirements of the CTA project on timing and charge resolution have led the University of Geneva to develop a custom preamplifier stage and slow-control system. The design and performance of the tailor made preamplifier stage and of the slow control electronics will be briefly described. The bias circuit of the sensor contains a resistor meant to prevent the sensor from drawing high current. However this resistor also introduces a voltage drop at the sensor input impacting the stability of its operation. A model has been developed in order to derive the parameters needed to account for it at the data analysis level. A solution based on the SST-1M front-end and digital readout is proposed to compensate for the voltage drop at the sensor cathode.

The next generation of Cherenkov telescope cameras feature Silicon Photo Multipliers (SiPM), which can guarantee excellent performance and allow for observation also under moonlight, increasing duty-cycle and therefore the physics reach. A 4 m-diameter Davies-Cotton prototype telescope with a 9-degree optical FoV and a 1296-pixel SiPM camera, has been designed to meet the requirements of the next generation of ground-based gamma-ray observatories at the highest energies. The large-scale production of the telescopes for array deployment has required the development of a fully automated calibration strategy which relies on a dedicated hardware, the Camera Test Setup (CTS). For each camera pixel, the CTS is equipped with two LEDs, one operated in pulsed mode to reproduce signal and one in continuous mode to reproduce night-sky background. In this contribution we will present the camera calibration strategy, from the laboratory measurement to the on-site monitoring with emphasis on the results obtained with the first camera prototype. In addition, key performances such as charge resolution, time resolution and trigger efficiencies and their degradation with increasing night-sky background level will be presented., PoS: Proceedings of Science, 358, ISSN:1824-8039, Proceedings of 36th International Cosmic Ray Conference (ICRC 2019)