The experiment Neutrino-4 started in 2014 with a detector model and continued with a full-scale detector in 2016–2021. In this article, we describe all the steps of the preparatory work on this ...experiment. We present all results of the Neutrino-4 experiment with increased statistical accuracy provided to date. The experimental setup is constructed to measure the flux and spectrum of the reactor antineutrinos as a function of distance to the center of the active zone of the SM-3 reactor (Dimitrovgrad, Russia) in the range of 6–12 meters. Using all the collected data, we performed a model-independent analysis to determine the oscillation parameters Δm214 and sin22θ14. The method of coherent summation of measurement results allows us to directly demonstrate the oscillation effect. We present the analysis of possible systematic errors and the MC model of the experiment, which considers the possibility of the effect manifestation at the present precision level. As a result of the analysis, we can conclude that at currently available statistical accuracy, we observe the oscillations at the 2.9 σ level with the parameters Δm214 = (7.3 ± 0.13st ± 1.16syst) eV2 = (7.3 ± 1.17) eV2 and sin22θ = 0.36 ± 0.12 stat(2.9σ). Monte Carlo based statistical analysis gave an estimation of the confidence level at 2.7σ. We plan to improve the currently working experimental setup and create a completely new setup in order to increase the accuracy of the experiment by 3 times. We also provide a brief analysis of the general experimental situation in the search for sterile neutrinos.
This review analyzes recent data on mechanisms of cerebral hypoxia and the protective methods of hypoxic and ischemic postconditioning, as well as their interrelationship with the key mechanisms ...responsible for neuroprotection and neuroplasticity. Upregulation of expression of antiapoptotic factors and neurotrophins and modulation of activity of several protein kinases and transcription factors such as hypoxia-inducible factor-1 (HIF-1) are considered as the most important aspects in the neuroprotective potential of postconditioning. The presented information indicates substantial transformative promise of the noninvasive techniques of hypoxic postconditioning as well as significant similarity between the adaptive pathways activated by various postconditioning methods, which are far from being fully understood.
The correspondence of the results obtained in the Neutrino-4 experiment with the results of the NEOS, DANSS, STEREO, and PROSPECT experiments at reactors, the MiniBooNE, LSND, and MicroBoone ...experiments at accelerators, and the IceCube and BEST experiments with a
51
Cr neutrino source is analyzed. The agreement between the results of the Neutrino-4 experiment, the BEST experiment, and the gallium anomaly on the mixing angle is discussed. The discrepancy between the results of the listed direct experiments with the results of the reactor anomaly, as well as with constraints from solar and cosmological data, is discussed. It is shown that the results of these direct experiments on the search for sterile neutrinos and the IceCube experiment do not contradict the Neutrino-4 experiment within the 3 + 1 neutrino model within 3σ contours of experimental errors. The sterile neutrino parameters from the Neutrino-4 and BEST experiments make it possible to estimate the sterile neutrino mass as
m
4
= (2.70 ± 0.22) eV and the effective mass of the electron neutrino as
= (0.86 ± 0.21) eV. The matrix of the absolute values of the 3 + 1 neutrino model mixing parameters and the mixing scheme are presented.
We report Neutrino-4 experiment results of measurements of reactor antineutrinos flux and spectrum dependence on the distance in range 6–12 m from the center of the reactor core. The fit of ...experimental dependence with the law 1/
L
2
, where
L
is the distance from the reactor center, gave satisfactory result with goodness of fit 81%. However, we discovered that the experimental neutrino spectrum is different from the calculated one. Using experimental spectrum, we performed the model independent analysis of restrictions on oscillation parameters Δ
m
14
2
and sin
2
2θ
14
. The results of this analysis exclude area of reactor and gallium anomaly at CL more than 99.7% (>3σ) for values Δ
m
14
2
< 3 eV
2
and sin
2
2θ
14
> 0.1. However, we observed an oscillation effect at CL 2.8σ in vicinity of Δ
m
14
2
Δ
m
14
2
≈ 7.3 eV
2
and sin
2
2θ
14
≈ 0.39. The method of coherent addition of results of measurements, which allows us to directly observe the effect of oscillations, is proposed. The analysis of that effect is presented. In general, it seems that the effect predicted in gallium and reactor experiments is being confirmed but at sufficiently large value of Δ
m
14
2
. Future prospects of the experiment are discussed.
In the present paper, we report polymer composites based on phenolic resin filled with hexagonal boron nitride; hot compression molding coupled with solution-based mixing were used to manufacture the ...composites. The paper presents experimental results on the physical and physicochemical properties of the obtained composites: thermal stability in air and argon, dielectric constant and dielectric loss tangent, active electrical resistance, thermal conductivity (mean and anisotropy), and mechanical strength. It is shown that the proposed technique of composite manufacturing, including the application of high-process pressures, makes it possible to obtain materials with high anisotropy of thermal conductivity, extremely high-filler content, and excellent dielectric properties, all of which are very important for prospective highly efficient lightweight heatsink elements for electronic devices. Experimental values of thermal conductivity and dielectric constant were analyzed using known mathematical models. Experimental values for thermal conductivities (up to 18.5 W·m−1·K−1) of composites at filler loadings of 65–85 vol.% are significantly higher than published data for bulk boron nitride/polymer composites.
New measurements of the flux and spectrum of reactor antineutrinos as functions of the distance from the center of the core of the SM-3 reactor (Dimitrovgrad, Russia) in the range of 6–12 m have been ...reported. Additional measurements have been performed. The amount of experimental data has been increased by almost a factor of 2. The model-independent analysis has been performed in order to determine the oscillation parameters
Δ
m
14
2
and sin
2
2θ
14
. The method of coherent addition of measurement results allows the direct demonstration of the effect of oscillations. The effect of oscillations is observed near the values
Δ
m
14
2
=
7.25
±
0.13
st
±
1.08
sys
and sin
2
2θ = 0.26 ± 0.08
stat
± 0.05
syst
. This result has been compared to the results of other experiments on the search for the sterile neutrino. The joint analysis of the Neutrino -4 experiment with the gallium and reactor anomalies gives the value sin
2
2θ
14
≈ 0.19 ± 0.04 (4.6σ). The results of the Neutrino-4 experiment have been compared to the results of the NEOS, DANSS, STEREO, and PROSPECT reactor experiments; MiniBooNE and LSND accelerator experiments; and IceCube experiment. According to the Neutrino-4 experiment (under the assumption that
m
4
2
≈
Δ
m
14
2
), the mass of the sterile neutrino is
m
4
= (2.68 ± 0.13) eV. The calculations with the estimates of the mixing angles from other experiments give the values
m
V
e
eff
=
(
0.58
±
0.09
)
eV
,
m
V
μ
eff
=
(
0.42
±
0.24
)
eV
, and
m
V
τ
eff
≤
0.65
eV
for the masses of the electron, muon, and tau neutrinos, respectively. The extended Pontecorvo—Maki—Nakagawa—Sakata matrix for the 3 + 1 model with one sterile neutrino is given.
Objective.
To study changes in the level of DNA methylation in rat neocortex and hippocampus cells on exposure to different hypobaric hypoxia regimes.
Materials and methods.
Studies were performed on ...24 adult male Wistar rats (180–200 g). Animals were subjected to hypobaric hypoxia in different regimes using a flow-type barochamber. Brain sections were used for immunohistochemical reactions for 5-methylcytidine in DNA. Changes in the total number of cells and their distribution into two classes based on the intensity of the immunohistochemical reaction for DNA 5-methylcytidine in neocortex and hippocampus were evaluated.
Results.
Presentation of severe harmful hypoxia (SHH) produced increases in the number of intensively immunopositive cells in the neocortex by 3 h after exposure. The prophylactic neuroprotective action of three (but not one) sessions of moderate hypobaric hypoxia (MHH) led to a reduction in the number of intensely immunopositive cells in the neocortex in response to subsequent SHH. No significant changes were seen in the hippocampus.
Conclusions.
Opposite changes were seen in the level of DNA methylation in the rat neocortex depending on the degree of hypobaric hypoxia: harmful SHH was linked with gene repression, while adaptogenic MHH produced gene activation.
New results of measurements of the dependences of the flux of reactor antineutrinos and their spectrum on the distance from the center of the core of the SM-3 reactor (Dimitrovgrad, Russia) in the ...range from 6 to 12 m are presented. Additional measurements were conducted. The volume of accumulated experimental data was increased nearly by a factor of two. A model-independent analysis was performed on the basis of all data in order to determine the oscillation parameters
and
. The method of a coherent summation of measurement results makes it possible to demonstrate directly the oscillation effect. We observed the oscillation effect at a level of three standard deviations (
) in the vicinities of parameters values of
eV
and
. Combining the results of the Neutrino-4 experiment with results for the gallium anomaly and for the reactor anomaly, we obtained the following value:
.
The expression of neurogenesis marker – NeuroD2 transcription factor – in the hippocampal dentate gyrus was studied in rats exposed to severe destructive hypoxia, a single or three episodes of ...moderate hypobaric hypoxia, preconditioned severe hypoxia, and severe hypoxia followed by 3 sessions of postconditioning by moderate hypobaric hypoxia. All the studied hypoxic exposure modes led to an increase of NeuroD2 level. Three-fold moderate hypoxia
per se
and in the preconditioning mode (followed by exposure to severe hypoxia) produced most pronounced up-regulatory effect on NeuroD2 expression. The results indicated that stimulation of neurogenesis processes seemed to be one of the aspects of the neuroprotective effect of three-fold preconditioning moderate hypoxia, but not of hypoxic postconditioning.
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