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The Baksan Experiment on Sterile Transitions (BEST) probes the gallium anomaly and its possible connections to oscillations between active and sterile neutrinos. Based on the Gallium-Germanium Neutrino Telescope (GGNT) technology of the SAGE experiment, BEST employs two zones of liquid Ga target to explore neutrino oscillations on the meter scale. Oscillations on this short scale could produce deficits in the $^{71}$Ge production rates within the two zones, as well as a possible rate difference between the zones. From July 5th to October 13th 2019, the two-zone target was exposed to a primarily monoenergetic, 3.4-MCi $^{51}$Cr neutrino source 10 times for a total of 20 independent $^{71}$Ge extractions from the two Ga targets. The $^{71}$Ge production rates from the neutrino source were measured from July 2019 to March 2020. At the end of these measurements, the counters were filled with $^{71}$Ge doped gas and calibrated during November 2020. In this paper, results from the BEST sterile neutrino oscillation experiment are presented in details. The ratio of the measured $^{71}$Ge production rates to the predicted rates for the inner and the outer target volumes are calculated from the known neutrino capture cross section. Comparable deficits in the measured ratios relative to predicted values are found for both zones, with the $4 \sigma$ deviations from unity consistent with the previously reported gallium anomaly. If interpreted in the context of neutrino oscillations, the deficits give best fit oscillation parameters of $\Delta m^2=3.3^{+\infty}_{-2.3}$ eV$^2$ and sin$^2 2\theta=0.42^{+0.15}_{-0.17}$, consistent with $\nu_e \rightarrow \nu_s$ oscillations governed by a surprisingly large mixing angle.

The Baksan Experiment on Sterile Transitions (BEST) was designed to investigate the deficit of electron neutrinos, $\nu_{e}$, observed in previous gallium-based radiochemical measurements with high-intensity neutrino sources, commonly referred to as the \textit{gallium anomaly}, which could be interpreted as evidence for oscillations between $\nu_e$ and sterile neutrino ($\nu_s$) states. A 3.414-MCi \nuc{51}{Cr} $\nu_e$ source was placed at the center of two nested Ga volumes and measurements were made of the production of \nuc{71}{Ge} through the charged current reaction, \nuc{71}{Ga}($\nu_e$,e$^-$)\nuc{71}{Ge}, at two average distances. The measured production rates for the inner and the outer targets respectively are ($54.9^{+2.5}_{-2.4}(\mbox{stat})\pm1.4 (\mbox{syst})$) and ($55.6^{+2.7}_{-2.6}(\mbox{stat})\pm1.4 (\mbox{syst})$) atoms of \nuc{71}{Ge}/d. The ratio ($R$) of the measured rate of \nuc{71}{Ge} production at each distance to the expected rate from the known cross section and experimental efficiencies are $R_{in}=0.79\pm0.05$ and $R_{out}= 0.77\pm0.05$. The ratio of the outer to the inner result is 0.97$\pm$0.07, which is consistent with unity within uncertainty. The rates at each distance were found to be similar, but 20-24\% lower than expected, thus reaffirming the anomaly. These results are consistent with $\nu_e \rightarrow \nu_s$ oscillations with a relatively large $\Delta m^2$ ($>$0.5 eV$^2$) and mixing sin$^2 2\theta$ ($\approx$0.4)., Comment: Paper updated to final version

The possibility of employing a 65Zn source in the gallium experiment BEST-2 with the aim of constraining the region of allowed oscillation parameters is examined. The source activity required for the BEST-2 experiment is calculated, and the size of the source and its effect on the results of oscillation measurements are discussed along with the possibilities for producing such a source. Various schemes for implementing respective measurements are considered.

The paper describes the capabilities of the three experiments on the search for oscillations on a short baseline—BEST, SOX, and DANSS. It is shown that only the first two experiments have the capabilities for localization of the oscillation parameters.

Counting characteristics of the system for recording rare events of the 71Ge decay in the radiochemical gallium Baksan Experiment on Sterile Transitions (BEST) are presented. Events are recorded simultaneously along eight counting channels in the energy range 0.3–16 keV, which include 71Ge decays in the region of L and K peaks with a total efficiency of up to 75%. The data analysis is based on the recording of the full shape of the leading edge of the charge pulses using a digital oscilloscope.

A method of determining the activity of intensive distributed -sources on the measurement of the continuous spectrum of radiation, for example the internal bremsstrahlung, is developed. The recurrent formula for reconstructing of a continuous spectrum, registered in a Ge detector, at distorting it in the detector. The method of precise measurements of the spectrum of 51Cr internal bremsstrahlung using two point sources of low activity is described.

New counting system for 71Ge decays rare events registration is developed for realization of the BEST experiment to search for sterile neutrinos. Description of the system, its technical and counting data are presented in the article. Comparison with already existing counting system for SAGE is given also.

The activity of the 51Cr source in the BEST experiment searching for sterile neutrinos is planned to be determined by measuring the spectrum of internal bremsstrahlung. The measurements of activity and the spectrum of internal bremsstrahlung of point low-activity 51Cr sources with Ge semiconductor detectors are discussed. The accuracy and errors of this measurement method are examined.

The possibility of the BEST experiment on electron neutrino disappearance with intense artificial sources of electron neutrino 51Cr is considered. BEST has the great potential to search for transitions of active neutrinos to sterile states with Δm2 ∼ 1 eV2 and to set the limits on short baseline electron neutrino disappearance oscillation parameters. The possibility of the further constraints the oscillation parameters region with using 65Zn source is discussed.

The interpretation of a signal produced by the mtDNA cytb gene as a molecular marker in phylogenetic and population-genetic research can be complicated by the cumulative influence of parallel mutations, i.e., by the entropy of nucleotide sequences that impede differentiation among the effects of the hybridization, natural polymorphisms, and artifacts imposed by pseudo-genes. We analyzed possible limitations in the use of the mtDNA cytb gene as a molecular marker by the example of the Apodemus genus. For this purpose, the entropy of nucleotide sequences was calculated and the probable tracts of gene conversion were sought in samples of various Apodemus species from Tibet, Korea, the southern part of the Russian Primorye, and Western Europe. Many haplotypes were identified as containing tracts of gene conversion. A high level of nucleotide sequence variability was found in species from the Tibetian Plateau, particularly, in A. draco, presumably due to the influence exercised by the low-effective size of populations on the rate of point mutation accumulation and also the role of cytochrome b in the adaptation to unfavorable environment. The effects of hypervariability in the cytb nucleotide sequences of some samplings resulting in the entropy growth, imitating gene conversion when compared to other species of the genus were analyzed. Furthermore, the examples of possible pseudo-gene interference among the published cytb sequences are provided. It is suggested that the strategy in the use of the mtDNA cytb gene in population genetics and phylogenetics should be adapted to the degree of gene variability. The emphasis is placed on the necessity of close control over sequencing data at all stages of their analysis.

The SAGE experiment, which measures the flux of solar neutrinos, contains approximately 50 tonnes of liquid gallium metal. Low-energy neutrinos interact with the isotope Ga 71 in the Ga and convert it into Ge 71 at a rate of approximately one atom per day. In each measurement of the solar neutrinos about 210 μg of a stable Ge isotope in a Ga matrix is added to the Ga and the mixture is stirred to homogeneity. After a 30-day exposure of the gallium to solar neutrinos, any germanium is chemically extracted from the gallium. The Ge is converted into the gas germane and the number of Ge 71 atoms that it contains is measured in a proportional counter. After 6 months of counting, the Ge is removed from the counter, dissolved in an aqueous solution, and the isotopic content of Ge in this solution is measured by ICP-MS. The efficiency of extraction of Ge from the Ga is calculated from the measured mass and isotopic content of added and extracted Ge. In 75 recent exposures of the Ga to solar neutrinos the average Ge extraction efficiency was 97.7 ± 1.1%. This uncertainty in extraction efficiency is much less than the 3.3% uncertainty obtained by measurements of Ge mass alone, i.e., without isotopic analysis.

A technique for the measurement of activities of intense β sources by measuring the continuous gamma-radiation (internal bremsstrahlung) spectra is developed. A method for reconstructing the spectrum recorded by a germanium semiconductor detector is described. A method for the absolute measurement of the internal bremsstrahlung spectrum of 51Cr is presented.

A method for measuring the activity of high-intensity radioactive sources via registration of innerbremsstrahlung spectra was developed. Equations that connect the spectrum shape to the activity of different parts of a source and to the γ activity of background impurities were obtained. A technique was developed that allows unambiguous elimination of the detector influence on spectral measurements. A procedure for modeling the passage of γ radiation through the source substance and protection is described, and the calculation of the germanium-detector response functions, which was performed with the Monte Carlo method using the Geant4 package, is presented. The developed method can be used for independent measurements of the activity of neutrino sources of the 51Cr and 37Ar type as an alternative to calorimetric measurements.

The proposal for an experiment on a 2-zone gallium target of a solar Galliumgermanium neutrino telescope at the Baksan neutrino observatory of the INR RAS with a 65Zn source for short baseline neutrino oscillations search is considered. The possibilities of determining the parameters of oscillations, the necessary characteristics of the neutrino source, the possibility of its production and its use are described. The expected results of measurements with a 65Zn source are compared with the results expected in the experiment BEST with the 51Cr source.

The potential of the SAGE and BOREXINO experiments with 51Cr artificial neutrino sources for searches for and determination of parameters of short-baseline oscillations.

Using parameters of molecular variability, calculated on the basis of comparison of mitochondrial DNA (mtDNA) control region sequences, no differentiation between samples of spawning herring from different regions of Sea of Okhotsk was found (p > 0.05). The absence of differentiation can be attributed to a permanent gene flow between schools, and it is possible to establish the value of the flow of migrants (Nm) only indirectly. Analysis of total molecular variability (global AMOVA) demonstrated that, when combining all studied samples or when pairwise uniting them, the intersample component accounts for approximately 0.1–0.2% of polymorphism with a high level of significance (p > 0.1); it can be considered a consequence of the influence of intense migrations. When estimating the minimal portion of migrants, it was determined that their amount is 3.6–9.5% per year by locality.

Mathematical simulation has been used to analyze how the sample size affects the accuracy of the estimation of molecular variation in a population. The sample size was varied from 1/200 to 1/4 of the total size of the simulated population. The possible effect of the length of the nucleotide sequences compared has also been estimated; it was varied from 500 to 15 000 bp. A tendency towards underestimation of the mean nucleotide diversity (π) by about 25% of the expected value has been found. The sample size and/or the length of the nucleotide sequence used have been shown to affect more the scatter of the π values than the accuracy of its measurement (the proportion of correct estimates of π is about 14%). The assumption is made that the sample size affects the probability of accepting a false null hypothesis in analysis of the demographic history of a species.

The differentiation of local herring populations from the Sea of Japan and the southern Sea of Okhotsk was assessed on the basis of mtDNA (mitochondrial DNA) control region variability. Three samplings of sea herring and one sampling of lake herring were studied. The genetic analysis showed a significant (P 0.05). AMOVA analysis revealed that only 4.11% of the variability was attributed to the interpopulation component, while variability within populations was 95.89%. It is suggested that the reason for the weak differentiation of local sea herring populations may be an intensive gene flow.

In April 2004, a neutrino source was produced by irradiating a 330-kg piece of pressed calcium oxide at the fast-neutron reactor BN-600 (Zarechny, Russia) for six months. The 37Ar isotope was obtained via the (n, α) reaction on 40Ca, and 37Ar was extracted from an aqueous solution of nitric acid in which the solid target was dissolved. After that, 37Ar was purified and sealed into a capsule. This source was used to measure the neutrino-capture rate in metalic gallium for neutrinos from 37Ar decay, which have an energy close to that of the main line of solar 7Be neutrinos (863 keV). The target of the SAGE Gallium-Germanium Neutrino Telescope was irradiated by using this source at the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences). The source activity was measured by several methods during its production, in the course of irradiation, and after its completion. The weighted mean of the activity for six measurements was 409 ± 2 kCi at the beginning of irradiation of the gallium target (04:00 Moscow time, 30.04.2004). The scatter in the activity values obtained by different methods does not exceed 5%.

The activity of an artificial neutrino source based on 37Ar was measured by a specially developed method of directly counting 37Ar decays in a proportional counter. This source was used to irradiate the target of the SAGE radiochemical gallium—germanium neutrino telescope at the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences, Moscow), whereupon the measurements were performed at the Institute of Reactor Materials (Zarechny, Sverdlovsk oblast, Russia). The method used to prepare gaseous samples for measurements in proportional counters and the counting procedure are described. The measured activity of the 37Ar neutrino source is 405.1 ± 3.7 kCi (corrected for decays that occurred within the period between the instant of activity measurement and the commencement of the irradiation of Ga target at 04:00 Moscow time, 30.04.2004).

A design of an artificial neutrino source with an activity of 400 kCi and a technology for filling it with 37Ar are described. The compliance of this source to Russian and international safety standards is confirmed by the test results.

A method for measuring the detector counting rates of up to 106 s−1 with an accuracy better than 1% using a digital oscilloscope is described. An example of measuring the counting rate of 37Ar decays in proportional counters is considered.

Combined analysis of the data of 92 runs of SAGE during the 12-year period January 1990 through December 2001 gives a capture rate of solar neutrinos with energy more than 233 keV of 70.9 −5.2 +5.3 (stat.) −3.2 +3.7 (syst.) SNU. This represents only 55% of the predicted standard solar model rate of ∼130 SNU. The results of individual runs as well as the results of combined analysis of all runs during yearly, monthly, and bimonthly periods are presented. No compelling evidence for temporal variations is observed. By an analysis of the SAGE results combined with those from all other solar neutrino experiments, we make the first estimate of the electron neutrino pp flux that reaches the Earth to be (4.6 ± 1.2) x 10 10 /(cm 2 s). Assuming that neutrinos oscillate to active flavors the pp neutrino flux emitted in the solar fusion reaction is approximately (7.6 ± 2.0) x 10 10 /(cm 2 s), in agreement with the standard solar model calculation of (5.95 ± 0.06) x 10 10 /(cm 2 s).

The effect of external γ radiation on the process of counting 71Ge decays in the proportional counters of the SAGE experiment measuring the solar-neutrino flux is considered. The systematic uncertainty in the SAGE result due to radon decays inside the air volume surrounding the counters is estimated. The background counting rate in the proportional counters that is caused by γ radiation from the enclosing shield is also determined.

We used Bayesian statistics to investigate the demographic history of the walleye pollock in the sea of Okhotks based on polymorphisms of sequences of the Nd2 and Cytb mitochondrial genes. We determined the average age for the Most Recent Common Ancestor (MRCA) as 44.1 ± 2 and 52.6 1.3 thousand years, respectively, for Nd2 and Cytb. These findings suggest that demographic expansion of the Okhotsk Sea pollock began 10-12 thousand years ago, which coincides with the period of global changes in the sea level during the Late Pleistocene-Early Holocene eras.

The solar neutrino capture rate measured by the Russian-American Gallium Experiment on a metallic gallium target SAGE during the time from January 1990 through December 2000 is 77.0 −6.2 −3.0 +6.2 +3.5 SNU, where the uncertainties are statistical and systematic, respectively. The experimental procedures and data analysis are presented.

We present measurements of the solar neutrino capture rate on metallic gallium in the Soviet-American gallium experiment (SAGE) over a period of slightly more than half the 22-year solar cycle. A combined analysis of 92 runs over the twelve-year period from January 1990 until December 2001 yields a capture rate of 70.8 −5.2 +5.3 (stat) −3.2 +3.7 (sys) SNU for solar neutrinos with energies above 0.233 MeV. This value is slightly more than half the rate predicted by the standard solar model, 130 SNU. We present the results of new runs since April 1998 and analyze all runs combined by years, months, and bimonthly periods beginning in 1990. A simple analysis of the SAGE results together with the results of other solar neutrino experiments gives an estimate of (4.6±1.2)× 1010 neutrinos cm−2 s−1 for the flux of the electron pp neutrinos that reach the Earth without changing their flavor. The flux of the pp neutrinos produced in thermonuclear reactions in the Sun is estimated to be (7.6 ± 2.0) × 1010 neutrinos cm−2 s−1, in agreement with the value of (5.95±0.06)×1010 neutrinos cm−2 s−1 predicted by the standard solar model.

Data on a direct determination of systematic uncertainties caused by the background production of germanium isotopes in the radiochemical SAGE experiment measuring the solar-neutrino flux are analyzed. The result obtained for the rate of 68Ge production is 6.5(1±1.0) times greater than the expected one; the rate of 69Ge production does not exceed preliminary estimates. The above result for 68Ge corresponds to the systematic uncertainty that is caused by the interaction of cosmic-ray muons and which is equal to 5.8% (4.5 SNU) at a solar-neutrino-capture rate of 77.0 SNU. An experiment is proposed that would test the effect of cosmic-ray muon influence on the SAGE systematic uncertainty and which would be performed at the location of the underground scintillation telescope facilities of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences).

A method for estimating the systematic uncertainty associated with radon in the SAGE experiment1) aimed at observing the solar-neutrino flux is described. For the gallium target used in this experiment, the systematic uncertainty in the measured neutrino-capture rate of 75 SNU2) is below 0.3 SNU.

The parameters of the gas mixture for the proportional counters have been optimized using calibrations with 55Fe and Cd-Se sources. As a result, the accuracy in determining the energy region of 71Ge decays detected in the SAGE experiment with the aim of measuring the solar neutrino flux has been improved.

The genetic parameters of donor and artificial populations of Siberian salmon (Oncorhynchus keta) have been analyzed. The parameters were obtained Wvith the use of different molecular markers as well as mathematic modeling based on experimental data. The difference between results is explained by the different resolving power of individual markers and/or stochastic effects. It is assumed that these factors together with temporal differentiation of spawning salmonid populations and the stable interpopulation gene flow constrain resolution of methods based on the use of molecular markers and designated for the analysis of differentiation of salmonid populations.

The structure of glass opacified with phosphor is investigated as a function of its thermal prehistory using the positron annihilation method, x-ray phase, and electron microscope analysis. Structural differences are identified, which depend on the wall thickness of articles and the temperature conditions of annealing. It is proposed to use this method for a quick test of the homogeneity and the degree of annealing of opaque glasses.

The solar-neutrino-capture rate measured by the Russian-American Gallium Experiment on metallic gallium during the period from January 1990 to December 1997 is (67.2 −7.0−3.0 +7.2+3.5 ) SNU, where the uncertainties are statistical and systematic, respectively. This result represents a 7σ depression in the neutrino flux in relation to the predicted standard-solar-model rates. The experimental procedures used and data analysis are presented.

The neutrino capture rate measured by the Russian-American Gallium Experiment is well below that predicted by solar models. To check the response of this experiment to low-energy neutrinos, a 517 kCi source of 51Cr was produced by irradiating 512.7 g of 92.4%-enriched 50Cr in a high-flux fast neutron reactor. This source, which mainly emits monoenergetic 747-keV neutrinos, was placed at the center of a 13.1 tonne target of liquid gallium and the cross section for the production of 71Ge by the inverse beta decay reaction was measured to be (5.55 +/- 0.60 (stat.) +/- 0.32 (syst.)) x 10^(-45) cm^2. The ratio of this cross section to the theoretical cross section of Bahcall for this reaction is 0.95 +/- 0.12 (exp.) +/- 0.03 (theor.) and to the cross section of Haxton is 0.87 +/- 0.11 (exp.) +/- 0.09 (theor.). This good agreement between prediction and observation implies that the overall experimental efficiency for the solar neutrino measurements is correctly determined and provides considerable evidence for the reliability of the solar neutrino measurement., 20 pages including figures in two column format

The antiradical activity of aqueous ethanol extracts from some edible plants and berries of the Okhotsk Sea northern coastal region was assessed using the method of bleaching (quenching) of stable free radicals of N,N-diphenyl-N′-picrylhydrazyl. Some of the obtained extract showed significantly higher activity as compared to that of the available commercial preparation from dried bilberry fruit. The high activity was retained even after high-temperature drying of the initial material, which makes it possible to use such a drying stage in the technology of products subject to long-term storage.

An intense source of 37Ar was produced by the (n, α) reaction on 40Ca by irradiating calcium oxide in the fast neutron breeder reactor at Zarechny, Russia. The 37Ar was released from the solid target, sealed into a small source, and was used to irradiate 13 tonnes of gallium metal in the Russian-American gallium solar neutrino experiment SAGE. The initial source strength was 409 ± 2 kCi. The measured production rate of 71Ge on gallium metal was 11.0+1.0−0.9 (stat) ± 0.6 (syst.) atoms per day, which is 0.79+0.09−0.10 of the theoretically calculated production rate.

Eleven samples of Pacific herring from the four seas of Eurasia (Sea of Japan, Sea of Okhotsk, Bering Sea, and White Sea), and one sample of Atlantic herring were analyzed. Complete and partial sequences of the mtDNA control region with the sizes up to 1071 bp were used. To verify the haplogroups identified, additional sequencing of the cytochrome oxidase I gene was performed. It was demonstrated that Pacific herring from the seas of Eurasia belonged to one mitochondrial haplogroup. The gene flow between the localities from different parts of the Far Eastern sea basins was about 11% per locality, per generation, which led to constant leveling of herring intraspecific differentiation. The data presented gave no reasons for subdivision of the herring populations in accordance to ecological characters (lacustrine and marine). Analysis of global molecular variance (global AMOVA) demonstrated that in Asian water basins, more than 98% of molecular polymorphism was found within the samples at the low level of significance (p0.05).

Mathematical simulation has been used to analyze how the sample size affects the accuracy of the estimation of molecular variation in a population. The sample size was varied from 1/200 to 1/4 of the total size of the simulated population. The possible effect of the length of the nucleotide sequences compared has also been estimated; it was varied from 500 to 15 000 bp. A tendency towards underestimation of the mean nucleotide diversity (pi) by about 25% of the expected value has been found. The sample size and/or the length of the nucleotide sequence used have been shown to affect more the scatter of the pi values than the accuracy of its measurement (the proportion of correct estimates of pi is about 14%). The assumption is made that the sample size affects the probability of accepting a false null hypothesis in analysis of the demographic history of a species.

Various remote sensing measures, particularly monitoring, in support of the planning and operation of reclamation systems are described. Particular emphasis is placed on monitoring the condition of irrigated and drained lands, determination of soil moisture content in areas of excess or deficient water, ascertaining depth and mineralization of ground water, the effective construction and management of irrigation systems, general environmental protection and resource conservation functions, and inputs into the formulation of planning guidelines. Translated by Edward Torrey, Alexandria, VA 22308 from: Aerokosmicheskiye metody v pochvovedenii i ikh ispol'zovaniye v sel'skom khozyaystve: sbornik nauchnykh trudov [Remote Sensing Methods in Soil Science and Their Utilization in Agriculture: A Collection of Scientific Works]. Moscow: Nauka, 1990, pp. 77-81.