Otoliths are organs used by fish for hearing and keeping balance. They consist of biogenic crystals of hydroxyapatite and do not contain any living cells. Upon exposure to ionizing radiation, otolith ...hydroxyapatite accumulates radiation-induced stable CO
2
−
radicals whose amount is proportional to absorbed dose. In electron paramagnetic resonance (EPR) dosimetry, carbonate ions are registered and, hence, the total accumulated dose in the fish otolith can be quantified. Therefore, otoliths can be used as individual fish dosimeters to support radiobiological and radioecological studies. An important aspect of otolith-based EPR dosimetry on fish from contaminated water bodies is the potential presence of bone-seeking
90
Sr. Consequently, cumulative absorbed doses measured with EPR in otoliths may reflect the superposition of internal exposure to
90
Sr/
90
Y and external exposure due to radionuclides circulating in soft tissue of the fish as well as due to environmental contamination. The objective of the present study was to develop a method that allows for an assessment of the contribution of
90
Sr to the total dose in otolith. The method has been tested using otoliths from seven fish taken from reservoirs located in the Southern Urals contaminated with radionuclides including
90
Sr. It has been shown that dose to otoliths is largely determined by
90
Sr in the hydroxyapatite. The internal dose component can be calculated using activity concentration-to-dose conversion factors, which vary slightly in the range of 2.0–2.8 × 10
–3
Gy year
−1
per Bq g
−1
depending on fish species and age. Internal doses to fish from water bodies with different levels of
90
Sr contamination were calculated in the range from 2 mGy to ~ 200 Gy. External dose contribution was derived for two fish only to be about 100 and 40 Gy. It is concluded that EPR dosimetry on fish otoliths is a promising tool when external exposure prevails or is comparable to internal exposure due to
90
Sr.
Al – 11% Si hypoeutectic alloy and Al – 20% Si hypereutectic alloy are studied after two-stage modification of the surface, which combines electroerosion alloying and subsequent irradiation with a ...pulsed electron beam. The structure of the surface layer is determined after two variants of two-stage treatment. The two-stage treatment of alloy Al – 11% Si yields a multi-element multiphase layer with a thickness of about 80 μm and a submicro-nanocrystalline structure. The surface of alloy Al – 20% Si acquires two layers (a surface one and an intermediate one) differing in the structure from the silumin. The surface layer contains many phases and is up to 1 μm thick. The transition layer with a thickness of up to 40 μm is formed from rapid-crystallization cells produced by the high-rate cooling of the fused layer of alloy Al – 20% Si. The cells are separated by thin sublayers composed of chiefly silicon nanosize particles.
We present K
s-band light curves for 299 Cepheids in the Small Magellanic Cloud (SMC) of which 288 are new discoveries that we have identified using multi-epoch near-infrared photometry obtained by ...the VISTA survey of the Magellanic Clouds system (VMC). The new Cepheids have periods in the range from 0.34 to 9.1 d and cover the magnitude interval 12.9 ≤ 〈K
s〉 ≤ 17.6 mag. Our method was developed using variable stars previously identified by the optical microlensing survey OGLE. We focus on searching new Cepheids in external regions of the SMC for which complete VMC K
s-band observations are available and no comprehensive identification of different types of variable stars from other surveys exists yet.
We developed a new test system to detect the omicron variant of SARS-CoV-2 using allele-specific reverse transcription PCR and estimated the frequency of its detection in patients living in the ...Novosibirsk Region. Clinical samples were divided into 3 groups: samples collected from December 1 to December 30, 2021 (group 1;
n
=66), from December 30, 2021 to January 10, 2022 (group 2;
n
=20), and from January 11 to January 22, 2022 (group 3;
n
=101). Based on the identification of 5 mutations specific to SARS-CoV-2 (B.1.1.529), two systems of oligonucleotide primers and probes were developed for detecting this coronavirus genotype in clinical samples. Limit of detection (LOD
95
) was 4×10
3
genome equivalents per 1 ml of clinical sample for the first test system and 2×10
3
for the for the second test system. The omicron variant of SARS-CoV-2 was absent in group 1 of studied samples, but was detected in 20% (4/20) of group 2 samples and 88% of group 2 samples collected within less than 2 weeks of January 2022. Using developed test system, we showed that in less than 2 weeks the omicron variant has become dominant in patients, which confirms previously published data on its exceptional contagiousness.
Layers accumulated in the pre-industrial period were selected using dated bottom sediment cores. They determine the mercury concentrations that are the geochemical background for the selected water ...basins. The variability of the mercury concentrations in the sediments of the inner shelf is low (20–30 μg/kg) and can be used as a basis for ecological assessment during the economic development of the Arctic regions.
•The article describes a phase transition at the intermediate and concluding stages.•The “tail” of the distribution function at the intermediate stage is derived.•This “tail” is used as the initial ...condition at the stage of Ostwald ripening.
A theoretical description of the intermediate stage of the phase transformation process, passing into the Ostwald ripening stage, is presented. First, we consider the intermediate stage of nucleation and growth of crystals in the supercooled melts or supersaturated solutions with allowance for fluctuations in their growth rates. The evolutionary behavior of the particle-size distribution function and the metastability degree is described analytically for the Meirs kinetic mechanism. The asymptotic solution for the “tail” of the particle-size distribution function is deduced in the form of the power-dependent function. This distribution function is used as the initial condition for the concluding stage where Ostwald ripening occurs. On this basis, the concluding stage of Ostwald ripening is analytically described. Namely, the maximum of the distribution function is lower and shifted to the left in comparison with the Lifshitz-Slyozov (LS) asymptotic solution. In addition, the distribution function obtained has a “tail” on the right of the LS blocking point. The theory is in good agreement with experimental data.
•A theory of bulk crystallization in the moving two-phase region is developed.•The saddle-point technique is used to find an approximate analytical solution.•The particle-size distribution function ...and metastability degree are found.
The paper deals with the process of directional steady-state crystallization in the presence of a metastable phase transition region, where nucleation and crystal growth occur. A new analytical solution describing such a nonlinear heat and mass transfer phase transformation process is constructed on the basis of the saddle-point method for a Laplace-type integral. The crystal-size distribution function, supercooling and solid fraction in a moving metastable two-phase region are found analytically.
A 60 mW output power has been achieved in mid‐UV (λ = 270 nm) spontaneous sources with electron‐beam pulse‐scanning pumping, fabricated from AlGaN MQW heterostructures grown by PA MBE on c‐Al2O3 ...substrates. Under the CW pumping at much lower excitation power density the mid‐UV sources demonstrate a 4.7 mW output power. In that regime the power efficiency of the structures is about 0.24%, while their internal quantum efficiency is estimated to be as high as 50%.
We report the discovery of an L dwarf companion to the A3V star β Circini. VVV J151721.49−585131.5, or β Cir B, was identified in a proper motion and parallax catalogue of the VISTA Variables in the ...Vía Láctea survey as having near-infrared luminosity and colour indicative of an early L dwarf, and a proper motion and parallax consistent with that of β Cir. The projected separation of ∼3.6 arcmin corresponds to 6656 au, which is unusually wide. The most recent published estimate of the age of the primary combined with our own estimate based on newer isochrones yields an age of 370–500 Myr. The system therefore serves as a useful benchmark at an age greater than that of the Pleiades brown dwarfs and most other young L dwarf benchmarks. We have obtained a medium resolution echelle spectrum of the companion which indicates a spectral type of L1.0 ± 0.5 and lacks the typical signatures of low-surface gravity seen in younger brown dwarfs. This suggests that signs of low-surface gravity disappear from the spectra of early L dwarfs by an age of ∼370–500 Myr, as expected from theoretical isochrones. The mass of β Cir B is estimated from the BHAC15 isochrones as 0.056 ± 0.007 M⊙.
Operation of a model of a compact neutron source that can be used to calibrate dark-matter and electron-antineutrino detectors and to determine their response functions is demonstrated. The ...calibration neutron source in question is a combination of the
Cf radionuclide, which undergoes spontaneous fission, producing neutrons, and an original silicon semiconductor detector. The latter provides a time reference for the neutron-emission instant by recording signals from fission fragments.
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