ABSTRACT
We present the first sample of tidal disruption events (TDEs) discovered during the SRG all-sky survey. These 13 events were selected among X-ray transients detected in the 0° < l < 180° ...hemisphere by eROSITA during its second sky survey (2020 June 10 to December 14) and confirmed by optical follow-up observations. The most distant event occurred at z = 0.581. One TDE continued to brighten at least 6 months. The X-ray spectra are consistent with nearly critical accretion on to black holes of a few ×103 to $10^8\, \mathrm{ M}_\odot$, although supercritical accretion is possibly taking place. In two TDEs, a spectral hardening is observed 6 months after the discovery. Four TDEs showed an optical brightening apart from the X-ray outburst. The other nine TDEs demonstrate no optical activity. All 13 TDEs are optically faint, with Lg/LX < 0.3 (Lg and LX being the g band and 0.2–6 keV luminosity, respectively). We have constructed a TDE X-ray luminosity function, which can be fit by a power law with a slope of −0.6 ± 0.2, similar to the trend observed for optically selected TDEs. The total rate is estimated at (1.1 ± 0.5) × 10−5 TDEs per galaxy per year, an order of magnitude lower than inferred from optical studies. This suggests that X-ray bright events constitute a minority of TDEs, consistent with models predicting that X-rays can only be observed from directions close to the axis of a thick accretion disc formed from the stellar debris. Our TDE detection threshold can be lowered by a factor of ∼2, which should allow a detection of ∼700 TDEs by the end of the SRG survey.
The effect of annealing on the porous structure formed upon deformation of poly(ethylene terephthalate) (PET) in a physically active liquid medium has been studied by means of small-angle X-ray ...scattering. Isometric annealing of the crazed polymer at temperatures below
T
g
has been ccompanied by decrease in specific surface area of the fibrils connecting the walls of the crazes, the bulk porosity remaining unchanged. During PET annealing at temperatures exceeding
T
g
, reduction in the dispersion of the fibrillated material of crazes has been accompanied by decrease in the volume of microvoids, more pronounced at higher treatment temperature. The obtained results have been analyzed from the point of view of changes in the structure of crazes during annealing.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
ABSTRACT
We present the gMOSS (Galaxies of Medium-band One-meter Schmidt telescope Survey) catalogue of ∼19 000 galaxies in 20 filters (4 broad-band SDSS and 16 medium-band filters). We observed ...2.386 deg2 on the central part of the HS47.5-22 field with the 1-m Schmidt telescope of the Byurakan Astrophysical Observatory. The gMOSS is a complete flux-limited sample of galaxies with a threshold magnitude of r SDSS ≤ 22.5 AB. From photometric measurements with 16 medium-band filters and u SDSS, we get spectral energy distributions for each object in the field, which are used for further analysis. Galaxy classification and photometric redshift estimation based on spectral template matching with zebra software. The obtained redshift accuracy is σNMAD < 0.0043. Using the SED-fitting cigale code, we obtained the main properties of the stellar population of galaxies, such as rest-frame (u − r)res colour, stellar mass, extinction, and mass-weighted age with a precision of 0.16 ± 0.07 mag, 0.14 ± 0.04 dex, 0.27 ± 0.1 mag, and 0.08 ± 0.04 dex, respectively. Using a dust-corrected colour–mass diagram, we divided the full sample into populations of red and blue galaxies and considered the dependencies between stellar mass and age. Throughout cosmic time, red sequence galaxies remain older and more massive than blue cloud galaxies. The star formation history of a complete subsample of galaxies selected in the redshift range 0.05 ≤ z ≤ 0.015 with <$\mathrm{log} M \mathrm{\gt }_\mathrm{M_\odot }$>8.3 shows an increase in the SFRD up to z ∼ 3, under the results obtained in earlier studies.
Reversibility of structural rearrangements in a liquid liposomal membrane upon electrostatic adsorption/desorption of the cationic polymer (chitosan) has been studied. The polycation can be ...completely removed from the lipid membrane via addition of an excess of polyacrylic acid forming more stable electrostatic complex with chitosan. Removal of chitosan has resulted in complete recovery of the original lipid distributions in lateral and transmembrane directions as well as intervesicular lipid exchange.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This article is devoted to the classification of substandard lexical units of medical orientation in English and Russian from the point of their semantic significance. The study is based on the ...materials of the most authoritative English-speaking and Russian-speaking substandard lexicographic sources. The classification and standardization of medical terminology is currently receiving close attention both from the professional medical community and from the point of linguistic science. The classification of medical vocabulary and, in particular, medical terminology is presented in domestic and foreign scientific from a position of the morphological and syntactic structure and according to the methods of word formation. The problems of medical terminology are discussed in detail in the works of B. Dennis, A.I. Rudova, M.N. Chernyavsky and others, however, the studies conducted did not affect the vocabulary of the substandard level. In this regard, it is advisable to expand and supplement the proposed classifications taking into account the extensive language layer of non-standard vocabulary.
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•Porous structure prepared by environmental crazing accelerates the PLA degradation.•Average weight of crazed PLA decreases by 2 times after exposure to PBS at 37 °C for ...6 weeks.•Structural modification by crazing allows to control a location of intense degradation.•Dicalcium phosphate dihydrate accelerates PLA hydrolysis in the crazes.
Hydrolytic degradation of porous polylactide (PLA) films with various porosity and morphology has been thoroughly investigated. It has been found that the structural and mechanical modification of PLA films by the environmental crazing mechanism results in the formation of a porous structure, is accompanied by the change in molecular-weight characteristics of the polymer and affects the localization and rate of its hydrolytic degradation. After the films were exposed in phosphate-buffered saline solution at 37 °C for 6 weeks, their average molecular weights MW and MN decreased by 1.5–2 and 3–5 times respectively, while their dispersity ĐM increased to 4–5. For PLA films containing alternating porous crazes and nonporous bulk parts, the hydrolysis leads to the appearance of bimodal molecular-weight distribution (MWD) curves. The degradation of the polymer material localizes predominantly at the craze–bulk polymer interfaces, thereby leading to a rather rapid and significant decrease in the deformation and strength properties of the films, which eventually become brittle. For PLA films, that have completely passed to the fibrillar-porous structure during the hydrolytic degradation, the character of the MWD curves remains preserved, but they gradually widen and shift toward lower molecular weights. The destruction of similar samples occurs uniformly throughout the volume, and the changes in their structural and mechanical parameters are not so abrupt, and even after the hydrolysis for 6 weeks their strength remains at a level of 90 MPa. When the porous matrix of PLA is filled with calcium phosphate (up to 30 wt%), the degradation of the polymer material occurs predominantly in the crazes and hardly proceeds in the bulk parts. The approaches proposed using PLA as an example enable one to control the degradation processes in polymers by varying their structural and morphological characteristics and incorporating inorganic fillers, thus opening new ways to the creation of bioactive and biodegradable materials with predictable degradation times.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We present the gMOSS (Galaxies of Medium-band One-meter Schmidt telescope Survey) catalogue of ~19 000 galaxies in 20 filters (4 broad-band SDSS and 16 medium-band filters). We observed 2.386 deg2 on ...the central part of the HS47.5-22 field with the 1-m Schmidt telescope of the Byurakan Astrophysical Observatory. The gMOSS is a complete flux-limited sample of galaxies with a threshold magnitude of r SDSS ≤ 22.5 AB. From photometric measurements with 16 medium-band filters and u SDSS, we get spectral energy distributions for each object in the field, which are used for further analysis. Galaxy classification and photometric redshift estimation based on spectral template matching with zebra software. The obtained redshift accuracy is σNMAD < 0.0043. Using the SED-fitting cigale code, we obtained the main properties of the stellar population of galaxies, such as rest-frame (u - r)res colour, stellar mass, extinction, and mass-weighted age with a precision of 0.16 ± 0.07 mag, 0.14 ± 0.04 dex, 0.27 ± 0.1 mag, and 0.08 ± 0.04 dex, respectively. Using a dust-corrected colour–mass diagram, we divided the full sample into populations of red and blue galaxies and considered the dependencies between stellar mass and age. Throughout cosmic time, red sequence galaxies remain older and more massive than blue cloud galaxies. The star formation history of a complete subsample of galaxies selected in the redshift range 0.05 ≤ z ≤ 0.015 with <$\mathrm{log} M \mathrm{\gt }_\mathrm{M_\odot }$>8.3 shows an increase in the SFRD up to z ~ 3, under the results obtained in earlier studies.
Based on a medium-band photometric survey at the 1-m Schmidt telescope of the Byurakan Astrophysical Observatory, we have produced a complete sample of quasars to 22.5 mag in the HS47.5-22 field with ...an area of 2.38 deg
. We have classified the objects and produced the sample of quasars using broadband photometric data and the morphological classification from DECaLS (Dey et al. 2019), infrared photometry from WISE (Meisner et al. 2018), spectroscopy from SDSS (Pâris et al. 2018), ROSAT X-ray data (Molthagen et al. 1997), FIRST radio data (Becker et al. 1995), and data on the proper motions of objects from the Gaia survey (Brown et al. 2018). The sample contains 682 quasars for which we have determined the medium-band photometric redshifts, calculated the absolute magnitudes, and investigated the quasar space density distribution and luminosity function. As a result, we have obtained evidence for the absence of a significant reduction in the space density of quasars up to
.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We present the results of long-term photometric monitoring of two active galactic nuclei, 2MASX J08535955+7700543 (
) and VII Zw 244 (
), being investigated by the reverberation mapping method in ...medium-band filters. To estimate the size of the broad line region, we have analyzed the light curves with the JAVELIN code. The emission line widths have been measured using the spectroscopic data obtained at the 6-m BTA telescope of SAO RAS. We give our estimates of the supermassive black hole masses
,
, and
, respectively.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The influence of cold rolling on the mechanical characteristics of polypropylene saturated with particles consisting of three to five monolayers of graphene (the degree of filling of 0.2–3.5 wt %) is ...studied. The nanocomposites are obtained by in situ filling, i.e., synthesis of the polypropylene matrix on the particles, thus allowing more uniform distribution of the filler throughout the bulk of the matrices. The filling makes it possible to increase the Young modulus of the material. A certain fraction of particles assemble to form agglomerates, and another fraction of particles are uniformly distributed in the matrix. The agglomerates already lead to the embrittlement of unrolled polypropylene at a degree of filling of 0.2 wt %. Cold rolling suppresses the brittle behavior of the composite irrespective of the method of reduction of the particles of graphite oxide (chemical or thermal reduction). As a result of preliminary cold rolling, the elongation at break and strength of filled polypropylene sharply increase (depending on the degree of cold rolling and concentration of the filler, the elongation at break increases 50- to 100-fold, and the strength increases 1.5- to 2.0-fold). In the initial material, the agglomerates initiate the appearance of local fluidity microzones where rhombohedral microcracks fracturing the composite are conceived. No microzones appear at a degree of cold rolling Λ = 1.25, while no neck is observed either at Λ = 1.9. After cold rolling to a value of Λ = 1.25, pore formation upon further stretching disappears.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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