In TAIGA Observatory (Tunka Advanced Instrument for cosmic ray physics and Gamma-ray Astronomy) we are commissioning the first Imaging Atmospheric Cherenkov Telescope (IACT). The telescope has an ...alt-azimuth mount and 17-bit shaft encoder for each axis, stepper motors are used for axis control. For the pointing calibration of the telescope a CCD-camera is installed on the dish of the telescope and its position allows to capture simultaneously both the Cherenkov camera with LEDs and the sky with observed source. Since October 2017, the telescope has been operating in tracking mode. In this work the TAIGAIACT telescope pointing calibration approach and first results of the tracking operations are described.
Over the past few years, the TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma-ray Astronomy) observatory has been being deployed in the Tunka Valley, Republic of Buryatia. It is ...designed for studying gamma rays of energy above 30 TeV and performing searches for sources of galactic cosmic rays with energies in the vicinity of 1 PeV, which is an energy region around the classic knee in the cosmic-ray energy spectrum. The first phase of the observatory will be situated at a distance of about 50 km from Lake Baikal at the site of the Tunka-133 array. The TAIGA gamma observatory will include a network of 500 wide-angle (0.6 sr) Cherenkov detectors (TAIGA-HiSCORE array) and up to 16 atmospheric Cherenkov telescopes (ACT) designed for analyzing the EAS images (imaging atmospheric Cherenkov telescopes, or IACT) and positioned within an area of 5 km
2
. The observatory will also include muon detectors of total area 2000 m
2
distributed over an area of 1 km
2
. Within the next three years, it is planned to enhance the area of the TAIGA-HiSCORE array by a factor of four—from 0.25 km
2
to 1 km
2
; to supplement the existing IACT with two new ones; and to deploy new muon detectors with a total coverage of 200 m
2
. The structure of the new observatory is described along with the data analysis techniques used. The most interesting physical results are presented, and the research program for the future is discussed.
We present the current status of high-energy cosmic-ray physics and gamma-ray astronomy at the Tunka Astrophysical Center (AC). This complex is located in the Tunka Valley, about 50 km from Lake ...Baikal. Present efforts are focused on the construction of the first stage of the gamma-ray observatory TAIGA - the TAIGA prototype. TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) is designed for the study of gamma rays and charged cosmic rays in the energy range 1013 eV–1018 eV. The array includes a network of wide angle timing Cherenkov stations (TAIGA-HiSCORE), each with a FOV = 0.6 sr, plus up to 16 IACTs (FOV - 10∘× 10∘). This part covers an area of 5 km2. Additional muon detectors (TAIGA-Muon), with a total coverage of 2000 m2, are distributed over an area of 1 km2.
A brief comparative analysis of US and Chinese infrastructure projects is provided. The world-system approach, which sets the objective possibilities and limitations of the strategies of the United ...States and China as interconnected parts of the world economy and politics, was chosen as the methodological basis. The first part of this article describes the world-system approach, as well as the position of the People’s Republic of China in the modern system of international relations. The second part is devoted to the Chinese Belt and Road Initiative. The third part provides an analysis of counterinitiatives put forward by the United States.
We present the current status of high-energy cosmic-ray physics and gamma-ray astronomy at the Tunka Astrophysical Center (AC). This complex is located in the Tunka Valley, about 50 km from Lake ...Baikal. Present efforts are focused on the construction of the first stage of the gamma-ray observatory TAIGA - the TAIGA prototype. TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) is designed for the study of gamma rays and charged cosmic rays in the energy range 1013 eV–1018 eV. The array includes a network of wide angle timing Cherenkov stations (TAIGA-HiSCORE), each with a FOV = 0.6 sr, plus up to 16 IACTs (FOV - 10∘× 10∘). This part covers an area of 5 km2. Additional muon detectors (TAIGA-Muon), with a total coverage of 2000 m2, are distributed over an area of 1 km2.
The physics motivations and advantages of the new TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) detector are presented. TAIGA aims at gamma-ray astronomy at energies ...from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV. For the energy range 30 – 200 TeV the sensitivity of 10 km
2
area TAIGA array for the detection of local sources is expected to be 5 × 10
-14
erg cm
-2
sec
-1
for 300 h of observations. Reconstruction of the given EAS energy, incoming direction and its core position, based on the timing TAIGA-HiSCORE data, allows one to increase a distance between the IACTs up to 600-1000 m. The low investments together with the high sensitivity for energies ≥ 30-50 TeV make this pioneering technique very attractive for exploring the galactic PeVatrons and cosmic rays. At present the TAIGA first stage has been constructed in Tunka valley, 50 km West from the Lake Baikal. The first experimental results of the TAIGA first stage are presented.
Observations of gamma rays up to several 100 TeV are particularly important to spectrally resolve the cutoff regime of the long-sought Pevatrons, the cosmic-ray PeV accelerators. One component of the ...TAIGA hybrid detector is the TAIGA-HiSCORE timing array, which currently consists of 28 wide angle (0.6 sr) air Cherenkov timing stations distributed on an area of 0.25 km2. The HiSCORE concept is based on (non-imaging) air shower front sampling with Cherenkov light. First results are presented.
Radiation damage can occur due to the direct effect of radiation on DNA molecules, which accounts for 30–40% of lesions, or by the generation of free radicals that in turn damage DNA, which accounts ...for 60–70% 1. A comparative analysis of the induction and repair of DNA single-strand break (SSB) and double-strand break (DSB) in neuronal cells of mice (hippocampus and cerebellum) under γ-irradiation after intraperitoneal administration of 1-β-D-arabino-furanosylcytosine (AraC) and 1-β-D-arabino-furanosylcytosine/hydroxyurea (AraC/HU) combination in vivo was performed. DNA comet assay method was used to study the regularities in the formation of DNA SSB and DSB in cells from hippocampus and cerebellum of mice under the action of γ-radiation in vivo, under the influence of AraC and HU. It was found that for all types of cells used, there is a linear character in the yield of DNA lesions. It has been shown that the amount of DNA SSBs and DSBs formed during irradiation under the influence of AraC significantly increases. An additional increase in the yield of DNA SSBs and DSBs is observed under the combined action of AraC and HU.
Increasing the radiosensitivity of normal and tumor cells is one of the priority aims of modern radiobiology. The agents that modify the yield of DNA double-strand breaks (DSBs) which are lethal to ...cells are of particular interest. We have previously shown that under the influence of DNA repair inhibitor - arabinosid cytosine (AraC) the DNA DSBs yield on cells of various types increases under the action of ionizing radiation. The mechanism of this process is based on the long-term non-reparable DNA single-strand breaks (SSBs) conversion into enzymatic DSBs. The main aim of this research was to elucidate the molecular and cellular effects of the proton action on the murine melanoma B16 cells under the influence of AraC. It was found that the amount of DNA SSB and DSB significantly increases under the influence of AraC. This difference persists in the post-radiation period up to 9 days.
The modifying effect of 1-β-D-arabinofuranosylcytosine (AraC) and hydroxyurea (HU) on the formation frequency of DNA double-strand breaks (DSB) in human U87 glioblastoma and murine B16 melanoma cells ...after accelerated proton and nitrogen ion (
15
N) exposure has been studied. The DNA comet assay and immunocytochemistry methods were used to determine the dependences of the frequency of DNA DSB formation and kinetics of their repair in tumor cells upon irradiation with particles of a wide linear energy transfer (LET) range under normal conditions and in the presence of modifiers. The combination of AraC and HU has the strongest modifying effect on the DSB yield. Under the influence of radiomodifiers, the dose change factor is ~2. Under normal conditions, DSB repair proceeds with exponential kinetics. In the presence of modifiers, a certain increase in the DNA DSB yield is observed after 6 h of post-irradiation incubation, followed by a decrease after 24 h of observation. The strongest modifying effect of AraC on the formation of radiation-induced foci (RIF) in glioblastoma cells is observed for proton exposure compared with nitrogen ions. In the presence of AraC, 24 hours after proton irradiation the RIF yield was 2.3 times higher than after exposure without it. For nitrogen ions with LET = 81 keV/μm and 180 keV/μm, the RIF yield in glioblastoma cells in the presence of AraC increases by 1.7 and 1.5 times 24 hours after irradiation, respectively, compared with the control samples. Possible mechanisms of tumor cell response to exposure to radiations with different LET in the presence of radiomodifiers are discussed.
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