Abstract
In this work, we use muon bundles, which are formed in extensive air showers and detected at the ground level, as a tool for searching for anisotropy in high-energy cosmic rays. Such choice ...is explained by the penetrating ability of muons that allows them to retain the direction of primary particles with good accuracy. In 2012–2022, we performed long-term muon-bundle detection with the coordinate-tracking detector DECOR, which is a part of the Experimental Complex NEVOD (MEPhI, Moscow). To search for cosmic-ray anisotropy, muon bundles arriving at zenith angles in the range from 15° to 75° in the local coordinate system are used. During the entire period of data taking, about 14 million of such events have been accumulated. In this paper, we describe some methods developed in the Experimental Complex NEVOD and implemented in our research, including: the method for compensating for the influence of meteorological conditions on the intensity of muon bundles at the Earth’s surface, the method for accounting for the design features of the detector and the inhomogeneity of the detection efficiency for different directions, as well as the method for estimating the primary energies of cosmic rays. Here we present the results of the search for the dipole anisotropy of cosmic rays with energies in the PeV region and also compare them with the results obtained at other scientific facilities.
We proposed a method for the simultaneous rapid determination of four protein cardiomarkers (C‑reactive protein, cystatin C, myoglobin, and D-dimer) in the blood plasma of patients with ...cardiopathologies. A change in the concentration of each of the proteins separately may indicate specific pathological processes in a human body, and a simultaneous increase in the concentration of all four markers indicates the possible development of acute cardiopathology. Rapid analysis is based on the immunomagnetic affinity separation of target proteins from blood samples using a fluorescent label for each protein under study. The proposed method is automated and optimized for determining physiological and pathological concentrations of target blood markers. An automatic bioanalytical platform is developed based on the proposed method; it enables the rapid determination of cardiomarkers in 17 µL of blood plasma within 14 min.
Plasminogen is a zymogenic form of plasmin, an enzyme that plays a fundamental role in the dissolution of fibrin clots as well as in many other physiological processes. For the first time, by the ...method of gas chromatography–mass spectrometry, post-translational modifications in the primary structure of plasminogen treated with physiologically relevant amounts of hydrogen peroxide were identified. It was found that methionine and tryptophan residues located in different structural regions of plasminogen served as targets of the oxidant. Plasminogen oxidation caused a dose-dependent effect in decreasing the fibrinogenolytic activity of plasmin evidenced by the formation of fibrinogen degradation products. The possible antioxidant role of methionines in the oxidative modification of plasminogen is discussed.
In this study, a method is developed for the simplified preparation of samples for analysis by high performance liquid chromatography and tandem mass spectrometry (HPLC–TMS) for further clinical ...diagnostic use, including the immunoprecipitation of fibrinogen on magnetic microparticles followed by the enzymatic hydrolysis of the protein. Development of an effective technique that would include the isolation of the target protein from the studied plasma sample or any other physiological fluid with the exclusion of a large number of process steps (for example, numerous stages of reprecipitation and various types of chromatography for the isolation of target proteins) and the use of aggressive conditions (for example, for the elution of proteins from carriers), as well as with a decrease in the total labor intensity and time of preparation of samples for analysis, is necessary for use in proteomic studies.
NEVOD-DECOR is the unique experiment where systematic studies of cosmic ray muon bundles in a wide range of zenith angles and, accordingly, the energies of primary cosmic rays are carried out. ...Impressive experimental material (more than 100 thousand events) has been accumulated over a long time period from May 2012 to December 2022. The earlier developed method of local muon density spectra allows us to compare experimental data on muon bundles with the results of the EAS muon component simulations. The analysis showed that the observed intensity of muon bundles at primary cosmic ray energies of about 1 EeV and higher can be compatible with the expectation (in frame of widely used hadronic interaction models) only under the assumption of an extremely heavy mass composition. It is consistent with data of several other experiments on investigations of air shower muon content, but contradicts the available measurements of the depth of the shower maximum in the atmosphere by means of fluorescent technique, which favor a light mass composition at these energies. This probably leads to the need to revise the existing hadronic interaction models.
The neutrino telescope IceCube is capable to reconstruct the energy spectrum of muons in very high energy region by means of measurements of muon-induced cascades. To compare with experimental data, ...the expected spectra of cascades were theoretically estimated. Calculations were performed for two variants of muon spectrum on the ice surface: a simple power-law energy spectrum with a differential slope index −3.7, and a composite spectrum combined of two power spectra with differential indexes −3.7 and −2.7. The differential spectra of cascades for different zenith angles and integral cascade spectra calculated for two variants of muon spectra are discussed.
Data of NEVOD-DECOR experiment on investigations of inclined cosmic ray muon bundles for a long time period (May 2012 - May 2020) are presented. Their comparison with the results of calculations ...based on simulations of extensive air shower hadron and muon components is carried out. The analysis showed that the observed intensity of muon bundles at primary particle energies of about 1018 eV and higher can be compatible with the expectation only under the assumption of an extremely heavy mass composition of cosmic rays. On the contrary, measurements of the depth of the shower maximum in the atmosphere in the experiments using air fluorescence technique, favour a light mass composition of primary cosmic rays at these energies.
Oxidation of fibrinogen with hypochlorite inhibited the fibrin network self-assembly even at the lowest concentration of the oxidant. The analysis of the results of protein electrophoresis at this ...hypochlorite concentration showed the absence of fragmentation of the protein and covalent cross-linking of its chains. The study of the areas responsible for the conversion of fibrinogen into fibrin by mass spectrometry showed that they are not subject to oxidative damage. However, we identified oxidized amino acid residues, which could affect the protofibril aggregation.
The damage to blood coagulation factor XIII (FXIII) at different stages of its enzymatic activation under the action of various physiological amounts of hypochlorite ion was studied. The results ...obtained by HPLC-MS/MS, SDS-PAGE, and colorimetry showed that, during the conversion of FXIII to FXIIIa, the vulnerability of FXIII to hypochlorite-induced oxidation increased. FXIII oxidized with 150 μM hypochlorite completely retained its enzymatic activity inherent to the intact protein, whereas FXIIIa treated with 50 μM hypochlorite showed sharply reduced enzymatic activity. It was shown that a number of methionine and cysteine residues on the catalytic subunit can perform antioxidant function; additionally, the regulatory subunits of FXIII-B contribute to the antioxidant protection of the catalytic center of the FXIII-A subunit, which, together with the tight packing of the tetrameric structure of the FXIII proenzyme, are the three factors that provide high protein resistance to the oxidizing agent.
Data on cosmic ray muon bundles accumulated at the NEVOD-DECOR complex over the period from May 2012 to December 2018 have been analyzed. Local muon density spectra at various zenith angles have been ...reconstructed and compared with CORSIKA-based simulations. At large zenith angles and high muon multiplicities corresponding to primary particle energies more than about 3 × 10
17
eV an excess of multi-muon events compared to simulations is clearly seen. Present data are compatible with the expectation for recent LHC-adjusted hadron interaction models only under assumption of extremely heavy (iron group nuclei) primary composition. The assumption of a heavy composition is however in contradiction with other EAS observables, such as maximum depth and its fluctuations.
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