Optical and near-infrared photometry, optical spectroscopy, and soft X-ray and UV monitoring of the changing-look active galactic nucleus NGC 2617 show that it continues to have the appearance of a ...type-1 Seyfert galaxy. An optical light curve for 2010–2016 indicates that the change of type probably occurred between 2010 October and 2012 February and was not related to the brightening in 2013. In 2016, NGC 2617 brightened again to a level of activity close to that in 2013 April. We find variations in all passbands and in both the intensities and profiles of the broad Balmer lines. A new displaced emission peak has appeared in Hβ. X-ray variations are well correlated with UV–optical variability and possibly lead by ∼2–3 d. The K band lags the J band by about 21.5 ± 2.5 d and lags the combined B + J filters by ∼25 d. J lags B by about 3 d. This could be because J-band variability arises from the outer part of the accretion disc, while K-band variability comes from thermal re-emission by dust. We propose that spectral-type changes are a result of increasing central luminosity causing sublimation of the innermost dust in the hollow bi-conical outflow. We briefly discuss various other possible reasons that might explain the dramatic changes in NGC 2617.
On a culture of human peripheral blood lymphocytes, antimutagenic activity of a composition from extracts of green tea leaves and Caucasian persimmon fruits was established with a modification of the ...mutation process induced by chemical compounds producing an alkylating effect (nitrosomethylurea and sodium fluoride). A concentration dependence of the antimutagenic efficiency of the studied phytocomposite was shown. The highest antimutagenic efficiency was observed when a combination of green tea extract at a concentration of 0.01 μg/ml and persimmon fruit extract at a concentration of 0.001 μg/ml were used. Moreover, this combination was most effective against mutations induced by both nitrosomethylurea and sodium fluoride: the antimutagen efficiency factor was 0.53 and 0.55, respectively.
To date, Higgs boson production has been observed at the Large Hadron Collider (LHC) in four different channels. Associated Higgs boson production with a single top quark has not yet been observed. ...Study of this channel would make it possible to determine, for the first time, the complex phase of top-quark coupling to the Higgs boson. The possibility of discovering associated Higgs boson production with a single top quark is studied here by means of a Monte Carlo simulation. Criteria for signal selection and for the suppression of background events are proposed. It is shown that the set of data currently available from the LHC permits confirming or excluding a model in which the top-quark coupling to the Higgs boson has a sign opposite to that predicted by the Standard Model.
ABSTRACT
We present the results of photometric and spectroscopic monitoring campaigns of the changing look AGN NGC 2617 carried out from 2016 until 2022 and covering the wavelength range from the ...X-ray to the near-IR. The facilities included the telescopes of the SAI MSU, MASTER Global Robotic Net, the 2.3-m WIRO telescope, Swift, and others. We found significant variability at all wavelengths and, specifically, in the intensities and profiles of the broad Balmer lines. We measured time delays of ∼6 d (∼8 d) in the responses of the Hβ (Hα) line to continuum variations. We found the X-ray variations to correlate well with the UV and optical (with a small time delay of a few days for longer wavelengths). The K-band lagged the B band by 14 ± 4 d during the last three seasons, which is significantly shorter than the delays reported previously by the 2016 and 2017–2019 campaigns. Near-IR variability arises from two different emission regions: the outer part of the accretion disc and a more distant dust component. The HK-band variability is governed primarily by dust. The Balmer decrement of the broad-line components is inversely correlated with the UV flux. The change of the object’s type from Sy1 to Sy1.8 was recorded over a period of ∼8 yr. We interpret these changes as a combination of two factors: changes in the accretion rate and dust recovery along the line of sight.
ABSTRACT
We present optical photometric observations of SN 2018aoq from 2 to 100 d after explosion, and 7 spectra at epochs from 11 to 71 d. The light curves and spectra are typical for SNe II-P. As ...previously reported, SN 2018aoq appears to be of intermediate brightness between subluminous and normal SNe II-P. SN 2018aoq was discovered in Seyfert galaxy NGC 4151, for which the distance is uncertain. We utilized the expanding photosphere method using three sets of filter combinations and velocities derived from the absorption minima of Fe ii lines and obtained a distance of 20.0 ± 1.6 Mpc. The standard candle method applied to SN 2018aoq yields a distance of 16.6 ± 1.1 Mpc. Both values are consistent with the distance measurements for NGC 4151 based on geometric method.
Abstract A fuzzy system for setting the location of electromagnetic exciter of vibration-frequency density meter is presented, taking into account the possible nonlinearities of the object. This ...paper proposes a system and algorithm for tuning the location of electromagnetic exciter of vibration-frequency density meter using fuzzy set theory. The use of fuzzy control methods allowed us to obtain a system for tuning the location of the electromagnetic exciter of the vibration-frequency density meter without the use of cumbersome computational procedures characteristic of the classical control method.
In the framework of the density functional theory electronic band structure and density of states of LaxBa1-xMnO3 solid solutions containing different concentrations of La and Ba atoms, were studied ...using different exchange correlation functionals. Our calculation show that the band gap, which characterizes the properties of semiconductors, varies depending on the concentration of La and Ba atoms in the compounds. Using such a dependence, it is possible to make changes in physical properties depending on the concentration of cations.
Abstract
The article is devoted to the study of the influence of the flow velocity of the measured pity on the readings of the vibration-frequency density meter. For this purpose, the process of free ...proper transverse vibrations of a resonator made in the form of a homogeneous tube rigidly fixed at the ends, along which the fluid flow is organized, is investigated. A differential equation of the resonator’s own transverse oscillations is compiled, taking into account the elastic forces, inertia forces and friction forces acting on the resonator. At the same time, the Coriolis force is neglected, in view of the rigid fastening of the ends of the tube. Taking into account the fact that the resonator oscillations are supported by the self-oscillation system, the friction force is compensated by an external force and in the differential equation the friction force becomes zero. As a result of solving the differential equation, the dependence of the frequency of self-oscillations of the resonator on the flow velocity of the measured liquid is determined. Possible ways to reduce the influence of the fluid flow velocity are determined. The conclusion is made about the expediency of determining the limit value of the fluid flow rate when determining the operating conditions of the density meter.
The paper describes mechanical tests of a nanocomposite produced from the ferromagnetic shape memory Fe−Ni−Co−Ti alloy under uniaxial tension over a wide temperature range. The production of the ...nanocomposite was preceded by preliminary thermomechanical treatment (TMT), involving drawing, quenching, and ageing, for precipitation hardening. The TMT imparted high superelastic strain and shape memory effect to the nanocomposite. The preliminary TMT with strain ψ = = 7.4−22.5% aged at T = 650°C for 5−10 min was experimentally found to correspond to the optimal combination of the maximum superelastic strain and shape memory effect. This contributed to the phase and twinning plastic deformation of the nanocomposite over the test temperature range M
s
< T
test
< A
f
(where M
s
is the start temperature of forward martensitic transformation on cooling and A
f
is the finish temperature of reverse martensitic transformation on heating). A plateau with constant stress was found in the two-phase M
f
< T
test
< M
s
region on the tensile curve at drawing strain ψ = 22.5%. A significant increase in the preliminary strain (more than 40%) substantially stabilized the austenitic matrix, thus inhibiting the martensitic transformation and reducing reversible effects because the austenite grain size refines when the lattice defect density increases. The austenite grain size distribution was assessed versus the chosen TMT conditions. When the austenite grain size increased, the superelastic strain recovery became higher. The factors leading to greater superelasticity were analyzed within different phenomenological models. The TMT has a crucial role in the variation of structure and mechanical properties, in turn promoting inelastic effects at different temperatures.
The issues of the chemical homogeneity of films obtained by magnetron sputtering are considered, and the rate of profiling of nanoscale layers of some 3
d
metals is estimated. The objects of study ...are C/Cr, C/Co, and C/Co/Cr films synthesized by magnetron sputtering on polycrystalline silicon. Deposition is carried out on a VUP-5 installation. The chemical composition of the C/Cr and C/Co films is studied by Auger-electron spectroscopy using argon-ion etching with an energy of 1 keV. Analysis of the elemental composition over depth is carried out, and the dependences of the change in the concentration of chemical elements on the etching time are plotted. The profiling depth of the studied samples is determined by atomic-force microscopy. The average etching rates are obtained for a thin cobalt film and a multilayer C/Co/Cr system.
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