Abstract
We report on Konus-WIND (KW) and Mikhail Pavlinsky Astronomical Roentgen Telescope – X-ray Concentrator (ART-XC) observations and analysis of a nearby GRB 221009A, the brightest
γ
-ray burst ...(GRB) detected by KW for >28 yr of observations. The prompt, pulsed phase of the burst emission lasts for ∼600 s and is followed by a steady power-law decay lasting for more than 25 ks. From the analysis of the KW and ART-XC light curves and the KW spectral data, we derive time-averaged spectral peak energy of the burst
E
p
≈ 2.6 MeV,
E
p
at the brightest emission peak ≈ 3.0 MeV, the total 20 keV–10 MeV energy fluence of ≈0.22 erg cm
−2
, and the peak energy flux in the same band of ≈0.031 erg cm
−2
s
−1
. The enormous observed fluence and peak flux imply, at redshift
z
= 0.151, huge values of isotropic energy release
E
iso
≈ 1.2 × 10
55
erg (or ≳6.5 solar rest mass) and isotropic peak luminosity
L
iso
≈ 3.4 × 10
54
erg s
−1
(64 ms scale), making GRB 221009A the most energetic and one of the most luminous bursts observed since the beginning of the GRB cosmological era in 1997. The isotropic energetics of the burst fit nicely both “Amati” and “Yonetoku” hardness–intensity correlations for >300 KW long GRBs, implying that GRB 221009A is most likely a very hard, super-energetic version of a “normal” long GRB.
We examine a sample of 2301 gamma-ray bursts, detected by Konus-Wind in the triggered mode between 1994 and 2017 and localized by the interplanetary network (IPN), for evidence of gravitational ...lensing. We utilize all the available gamma-ray burst (GRB) data: time histories, localizations, and energy spectra. We employ common IPN techniques to find and quantify similarities in the light curves of 2,646,150 burst pairs, and for the pairs with significant similarities, we examine their IPN localizations to determine whether they are consistent with a common origin. For pairs that are consistent, we derive and compare energy spectra, and compute a figure of merit that allows us to compare and rank burst pairs. We conduct both a blind search, between all possible burst pairs, and a targeted search, between pairs in which one burst has both a spectroscopic redshift and an identification of an intervening system, as measured by one or more lower spectroscopic redshifts. We identify six pairs in the blind search that could be taken as evidence for lensing, but none are compelling enough to claim a detection with good confidence. No candidates were detected in the targeted search. For our GRB sample, we set an upper limit to the optical depth to lensing of 0.0033, which is comparable to that of optical sources. We conclude that proposed scenarios in which a large fraction of the GRB population is lensed are extremely unlikely.
The work is devoted to analyzing the negative effects of digitalizing education and considering the possibilities for their prevention. The urgency of this problem under the current conditions of ...combating the novel-coronavirus-infection pandemic and moving a significant part of education and leisure to the virtual space is noted. A significant increase in the frequency of mental and physical maladjustment symptoms, a decrease in performance indicators and a deterioration of the biological-age parameters are recorded in participants in the experiment against the background of a deficit in physical activity and an increase in the duration of information consumption. The geroprotective effect of correcting the lifestyle of students with an emphasis on the use of such health-preserving elements of behavior as informational hygiene, strict compliance with recommendations for optimizing sleep, rest, motor and nutritional regimens, in terms of qualitative and quantitative indicators (with the exception of bad habits and excessive entertainment), is shown.
•A new method is developed quantitative phase control in soft ferrimagnetic materials.•The method is based on thermomagnetometric analysis of the samples in magnetic field.•This method compared to ...X-ray diffraction analysis is more precise.•The method was successfully tested on the LiTi and LiZn ferrites.
In this work, the method of quantitative ferrite phase control, which is based on thermomagnetometric analysis of the ferrite samples in magnetic field, was developed. The magneto-phase transitions in LiZn and LiTi ferrites with chemical formulas Li0.5(1x)Fe2.50.5xZnxO4 and Li0.5(1+x)Fe2.51.5xTixO4 were studied, and their phase compositions were analyzed by both the developed method and X-ray diffraction analysis. It was shown that the thermomagnetometry method compared to X-ray diffraction analysis allows to examine more precisely the magnetic phases in synthesized ferrites with inhomogeneous phase composition. However, a complex analysis, using both X-ray and thermomagnetometry methods, will be the most optimal in case of the formation of non-magnetic and poor magnetic phases.
Abstract
We present a database of solar flares registered by the Konus-Wind instrument during more than 27 yr of operation, from 1994 November to now (2022 June). The constantly updated database ...(hereafter KW-Sun) contains over 1000 events detected in the instrument’s triggered mode and is accessible online at
http://www.ioffe.ru/LEA/kwsun/
. For each flare, the database provides time-resolved energy spectra in energy range from ∼20 keV to ∼15 MeV in FITS format along with count-rate light curves in three wide-energy bands, G1 (∼20–80 keV), G2 (∼80–300 keV), and G3 (∼300–1200 keV), with high time resolution (down to 16 ms) in ASCII and IDL SAV formats. This article focuses on the instrument capabilities in the context of solar observations, the structure of the KW-Sun data, and their intended usage. The presented homogeneous data set obtained in the broad energy range with high temporal resolution during more than two full solar cycles is beneficial for both statistical and case studies as well as a source of context data for solar flare research.
Objective:
The purpose of this study was to find out the indicators of the distribution of plantar pressure in the two-legged stands with open and closed eyes in experienced rhythmic gymnasts.
...Materials and methods:
31 highly qualified gymnasts (candidates and masters of sports of Russia), age 18.5 ± 0.5 years, experience in rhythmic gymnastics 13.5 ± 1.5, performed three upright postures on the footscan ® podometric platform of RSscan: the main stand, a modified Romberg test with open and closed eyes. Postural control was assessed by quantifying the plantar pressure (P%) in relation to 4 zones of the right and left foot and the trajectory of the movement of the center of pressure (CP) over time intervals.
Results:
The results of the study showed the presence of a right-sided distribution of plantar pressure in two-legged stands in experienced gymnasts. The regulation of posture occurs mainly in the anterior-posterior direction, but has different strategies for managing balance. The sagittal-cross pattern determines the interaction of plantar pressure between the right and left feet in the basic pose. The Romberg test with open eyes (EO) and closed eyes (EC) characterizes sagittal-parallel and sagittal-asymmetric balance, respectively. We revealed an increase in the vibrations of the gymnast's body in the absence of visual information for only the first 12 seconds.
Conclusions:
We have identified a variety of combinations of two types of strategies while maintaining posture in simple poses. This indicates the ability of experienced gymnasts to fine-tune the postural stability, including in the absence of visual information.
Silicon nanoparticles (SiNPs) prepared by mechanical grinding of luminescent porous silicon were coated with a biopolymer (dextran) and investigated as a potential theranostic agent for bioimaging ...and sonodynamic therapy. Transmission electron microscopy, photoluminescence and Raman scattering measurements of dextran-coated SiNPs gave evidence of their enhanced stability in water. In vitro experiments confirmed the lower cytotoxicity of the dextran-coated NPs in comparison with uncoated ones, especially for high concentrations of about 2 mg ml
. Efficient uptake of the NPs by cancer cells was found using bioimaging in the optical transmittance and photoluminescence modes. Treatment of the cells with uptaken SiNPs by therapeutic ultrasound for 5-20 min resulted in a strong decrease in the number of living cells, while the total number of cells remained nearly unchanged. The obtained data indicate a 'mild' effect of the combined action of ultrasonic irradiation and SiNPs on cancer cells. The observed results reveal new opportunities for controlling the photoluminescent and sonosensitizing properties of silicon-based NPs for applications in the diagnostics and mild therapy of cancer.
It has been suggested that geomagnetic storms could be perceived by organisms via disruption of naturally occurring diurnal geomagnetic variation. This variation, in turn, is viewed by way of a ...zeitgeber for biological circadian rhythms. The biological effects of a geomagnetic storm, therefore, could depend on the local time of day when its main phase occurs. We have assessed calpain activity in tissues of roach (
Rutilus rutilus
) and great pond snail (
Limnaea stagnalis
) after exposure to a simulated geomagnetic storm, reproduced at different times of day, in order to evaluate this hypothesis. Significant decrease in calpain activity was observed in organisms exposed to the simulated geomagnetic storm whose main phase, and initial period of a recovery phase, did not coincide with the expected peak of diurnal geomagnetic variation. The results obtained are considered an experimental confirmation of the aforementioned hypothesis. Improvement of a correlative approach for the assessment of biological effects of geomagnetic activity can be achieved by considering information on the synchronization of geomagnetic storm’s main phase with diurnal geomagnetic variation.
The article is devoted to the development of two-layer composites with a fluoroplastic matrix and fiberglass reinforcing elements. The fluoroplastic matrix acts as a protective chemo- and ...heat-resistant coating, and the glass-fiber layer can make it possible to obtain n-layer composites of increased strength and rigidity. The paper shows options for combining glass fiber reinforcing fillers with fluoroplastic matrices, as well as methods for joining (combining) such composites into complex flat and cylindrical extended and high-volume structures. The work has both applied and scientific and technical significance associated with the development of the provisions of the theory of diffusion bonding (welding).
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