Natural and Exact Sciences

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  • Item
    Statistical Estimation for Stationary Models with Tapered Data
    (Armenian Academy of Sciences, 2021) M. S. Ginovyan ; A. A. Sahakyan
    In this paper, we survey some recent results on parametric and nonparametric statistical estimation about the spectrum of stationary models with tapered data, as well as, a question concerning robustness of inferences, carried out on a linear stationary process contaminated by a small trend. We also discuss some questions concerning tapered Toeplitz matrices and operators, central limit theorems for tapered Toeplitz type quadratic functionals, and tapered Fejer-type ´ singular integrals. These are the main tools for obtaining the corres ponding results, and also are of interest in themselves. The processes considered will be discrete- time and continuous-time Gaussian, linear or Levy-driven linear processes with memory.
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    Molecular-genetic identification of Darevskia unisexualis × D. valentini triploid hybrids from sympatric populations of Armenia
    (Pleiades Publishing, 2021) A. E. Girnyk ; A. A. Vergun ; M. S. Arakelyan ; A. P. Ryskov
    Seven putative triploid hybrid Darevskia lizards were genotyped on the basis of the Du215 microsatellite locus. The alleles at this locus were identified and sequenced in these individuals. We found that five out of seven individuals are triploid hybrids of Darevskia unisexualis × D. valentini, each containing two alleles of the D. unisexualis parthenospecies and one allele of D. valentini. The other two individuals were heterozygous at this locus and contained alleles only of the bisexual species D. valentini.
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    Electron–hole interaction in cylindrical quantum dots
    (Elsevier, 2022) Vram Mughnetsya ; Ashot Movsisyan ; Albert Kirakosyan
    The Coulomb interaction of electron and hole in a cylindrical quantum dot in the frame of the first perturbation theory and the effective mass approximation is studied. The analogue of Brus’s equation for Coulomb interaction of electron–hole pair in a spherical quantum dot is obtained for a cylindrical nanocrystal and an expression for the energy band gap shift is derived, which can be used for explaining of some experimental results obtained for MoS and 3C-SiC nanocrystals.
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    Control of String Vibrations by Displacement of One End with the Other End Fixed, Given the Deflection Form at an Intermediate Moment of Time
    (MDPI AG, 2022) Vanya Barseghyan ; Svetlana Solodusha
    We consider a boundary control problem for the equation of string vibration with given initial and final conditions, given the deflection form at an intermediate moment of time. The control is carried out by displacement of one end with the other end fixed. The problem is reduced to the problem of a distributed action control with zero boundary conditions. We propose a constructive approach to constructing a boundary control action by the separation of variables and methods of the theory of control of finite-dimensional systems. The approach is applied to given functions. A computational experiment was carried out with the construction of the corresponding graphs and their comparative analysis. They confirm the obtained results.
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    Spectroscopic analysis of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol binding to blood plasma albumin
    (Springer-Verlag Wien, 2022) Karine R. Grigoryan ; Hasmik A. Shilajyan ; Ashkhen Zatikyan ; Iskuhi Aleksanyan ; Lilit Hambardzumyan
    Binding of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol (C1), a biologically active substance, to bovine blood plasma albumin (BSA) at 293, 298, and 303 K was studied using fluorescence (steady state, synchronous, excitation/emission matrix) and FT-IR spectroscopy methods. The experimental results showed that C1 causes fluorescence quenching of BSA through both static and dynamic quenching mechanisms. The thermodynamic parameters, enthalpy and entropy change, for the static quenching were calculated to be − 35.73 kJ mol−1 and − 35.34 J mol−1 K−1, which indicated that hydrogen bonding and van der Waals interactions were the predominant intermolecular forces regulating C1–BSA interactions. Distance between donor and acceptor (2.14, 2.26, and 2.30 nm) depending on the temperature, obtained from intrinsic Förster resonance energy transfer calculations, revealed the static quenching mechanism of BSA fluorescence in 0–3.0 × 10−5 mol/dm3 concentration range of C1. The micro-environmental and conformational changes in BSA structure, established by synchronous, excitation/emission matrices and FT-IR spectra showed the changes in the BSA secondary structure.
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    Methods for determining shear resistance by a system of cracks and old slip surfaces with the purpose to evaluate the stability of landslides
    (IOP Publishing Ltd., 2022) S G Hayroyan ; H S Hayroyan
    On slopes, landslide displacements mainly occur along bedding boundaries, lithogenetic and tectonic fractures, as well as along existing ancient slip surfaces, which are the weak zones and potential slip surfaces for new landslides. According to experimental studies to determine the shear resistance by the standard and double cut test methods: a) without wetting the sliding surface, and b) by the wetting the sliding surface, we can conclude: when double- cutting the clay soils of a solid, semi-solid and tightplastic consistency, the cohesion is mainly reduced, but the internal friction factor is slightly changed. Double-cut tests of soft-plastic and flow-plastic clay soils have shown the cohesion and the internal friction factors are being changed insignificantly. At the same time, taking into account the fact that under the condition τ > σ tan ϕ the soft-plastic and flowing-plastic clay soils undergo viscous-plastic deformations, we come to the following conclusion. When developing the anti-landslide measures, independent of the consistency of the soils forming the slope, the τf = σ tan ϕ component should be taken as the slip resistance index in the formula for calculating the slip resistance taking into account the condition Cc + Σw = 0.
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    FTIR ATR SPECTRAL AND THEORETICAL VIBRATIONAL STUDIES OF URACIL IN DIMETHYLSULFOXIDE OR DIETHYLSULFOXIDE SOLUTIONS
    (Pleiades Publishing, 2022) A.L. Zatikyan ; Sh.A. Markarian
    In this work the solutions of uracil in pure dimethylsulfoxide (DMSO) and diethylsulfoxide (DESO) have been studied by both FTIR ATR spectroscopy and quantum-chemical calculations. The remarkable changes were observed in the C=O, N–H (1745-1630 cm–1) and in S=O stretching region (1100-970 cm–1). The changes of the aforementioned frequencies are explained by the destruction of self-associates of sulfoxides in the presence of uracil and formation of uracil/DMSO (DESO) complexes via hydrogen-bond of the uracil N–H group with the S=O group of sulfoxides. Structural, energetic and vibrational characteristics for the hydrogen-bonded molecular complex of uracil/DMSO (DESO) in the gas phase and in solution have been studied by DFT and ab initio MO theory. It revealed, that the uracil/DMSO complex is more compact compared with uracil/DESO complex due to additional hydrogen bonds via C=O group of uracil and –CH group of DMSO. The observed wavenumbers are in good agreement with calculated wavenumbers.
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    Heatwaves in Southern Armenia in the context of climate change
    (Elsevier, 2022) Tatevik Safarya ; Hrachuhi Galstya ; Babak Shiri
    The quantitative and qualitative evaluations of long-term trends and spatial distribution of heatwaves (HW) are carried out in Southern Armenia (Syunik province). For this purpose, the daily average maximum air temperature data (Tmax) from four meteorological stations (Sisian, Goris, Kapan, and Meghri) are studied for the 1936–2019 period. The HW catchment algorithm and a new concept of HW (which is called potential HWs [PHWs]) are developed. The presence of trends and their significance for different HW measures are assessed utilizing linear and exponential trends, Sen's slope, and Mann– Kendall (MK) trend test. The results show that HWs become increasingly frequent and intense. Moreover, they have extended duration, as they emerge earlier and fade later in Syunik province. Significant variation trends of HW are observed (e.g., the frequency of HWs increased up to five times), especially after the 1990s in southern and central parts of the province. Contrary to this, relatively weaker or no trends occurred in the northern parts. Our methodological approach successfully determines the HW measures' trends in the province based on the relief features and altitude differences. The outcomes highlight their notable impact on the progression of HW. Overall, this study provides significant insights into understanding HW's variations and their transformation in the mountainous areas.
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    Tidal disruption effects near black holes and Lambda-gravity
    (Springer, 2022-08-26) A.Stepanian ; V.Gurzadya ; Sh.Khlghatyan
    The tidal disruption of stars in the vicinity of massive black holes is discussed in the context of Λ-gravity. The latter provides an explanation to the Hubble tension as a possible consequence of two Hubble flows, the local and global ones. The bunch of notions that play role for the considered tidal effect are obtained, along with the rate of the disrupted stars. The role of pulsars is emphasized due to their ability to penetrate up to the horizon of the massive black hole as for them the tidal radius can reach the horizon. Tidal disruption mechanism also can lead to segregation of stars by their mean density versus the distance from the black hole, the denser stars surviving at shorter distances. The interplay of the central gravity field and the repulsive Λ-term increase with radius, and its certain observational consequences are discussed.