The content of metals, organochlorines, and C
org
in the bottom sediments of the coastal areas of the Kola Peninsula was studied. The grain size analysis of the bottom sediments was carried out. The ...toxic potential of the sediment elutriates for unicellular algae
Phaeodactylum tricornutum
and for larvae of brine shrimp
Artemia salina
was studied. The influence of the grain size, C
org
, and human activities on metals and organochlorines accumulation in the sediments was discussed. Correlations between the survival rate of
A. salina
larvae in the sediment elutriates and the content of pollutants, C
org
, and <0.063 mm fraction in the bottom sediments were calculated.
Bioassay is used to study bottom sediment ecotoxicity in the central and eastern parts of the Barents Sea. The effect of sediment elutriates on the growth of microalgae Phaedactylum tricornutum ...Bohlin and survival of brine shrimp Artemia salina L. larvae has been studied. As shown by scientific evidence, low and moderately toxic bottom sediments are present in the Eastern Basin, West Novaya Zemlya and South Novaya Zemlya troughs along with non-toxic bottom sediments, which may be indicative of accumulation of pollutants in these areas of the Barents Sea. Toxic bottom sediments have not been found in the sea areas adjacent to them. Reduced survival rate in sediment elutriates of low and moderate toxicity has been shown predominantly by A. salina larvae. Only one sediment elutriate from the South Novaya Zemlya trough has had a slight toxic effect on Ph. tricornutum. The amount of fine-grained fraction (> 0.063 mm) in bottom sediments classified as low and moderately toxic is 24.8-66.8 % and do not differ from its amount found in bottom sediments classified as non-toxic - 27.8-76.9 %. The findings obtained are consistent with published chemical analysis data according to which the Eastern Basin, West Novaya Zemlya and South Novaya Zemlya troughs are included in the Barents Sea areas having highest amounts of a number of pollutants in bottom sediments.
Abstract
Galactic sites of acceleration of cosmic rays to energies of order 10
15
eV and higher, dubbed PeVatrons, reveal themselves by recently discovered gamma radiation of energies above 100 TeV. ...However, joint gamma-ray and neutrino production, which marks unambiguously cosmic-ray interactions with ambient matter and radiation, was not observed until now. In 2020 November, the IceCube neutrino observatory reported an ∼150 TeV neutrino event from the direction of one of the most promising Galactic PeVatrons, the Cygnus Cocoon. Here we report on the observation of a 3.1
σ
(post-trial) excess of atmospheric air showers from the same direction, observed by the Carpet–2 experiment and consistent with a few months flare in photons above 300 TeV, in temporal coincidence with the neutrino event. The fluence of the gamma-ray flare is of the same order as that expected from the neutrino observation, assuming the standard mechanism of neutrino production. This is the first evidence for the joint production of high-energy neutrinos and gamma-rays in a Galactic source.
.
The stability of the electroosmotic flow of electrolyte-dielectric viscous liquids under the influence of the DC and AC electric fields along with the external pressure gradient is studied ...theoretically. Liquids are bounded by two infinite parallel plates. The lower wall bordering the electrolyte is assumed to be a charged surface, and the upper wall is electrically isolated. The charge at the lower boundary is assumed to be immobile, while the surface charge at the free surface is assumed to be mobile. In this paper, we study the micro- and nanosized liquid layers. The mathematical model is described by a nonlinear system of the Nernst-Planck-Poisson-Stokes partial differential equations with the appropriate boundary conditions on the solid surface, the electrolyte/dielectric interface, and on the upper wall. The pressure gradient is highly important for the stability of the flow. For the DC case, the external pressure could either stabilize and destabilize the flow depending on the relative directions of the electroosmotic flow and the pressure-driven flow. For the AC case, the dependence on the value of the external pressure is not monotonous for different wave numbers of perturbations, but, as a rule, the external pressure destabilizes the flow. As the frequency of the electric field increases, the one-dimensional solution of the problem becomes stable.
Graphical abstract
The Carpet-3 experiment for investigation of gamma radiation with energy above 100 TeV is currently being prepared at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian ...Academy of Science. At present the plastic scintillation counters with a total continuous area of 410 m
are installed in the muon detector (MD) underground tunnel, and they are totally equipped with electronics. The counters’ gains and thresholds have been adjusted. Fifteen modules of shower detectors are placed on the surface of the MD absorber. Ten of them contain 9 standard plastic counters with an area of 1 m
each. Also 24 modules without counters are arranged on the territory of the array. These modules will accomplish a surface part of the Carpet-3 array. The preliminary estimates show that the new array will have the best sensitivity to the flux of primary gamma rays with energy in region 100 TeV
1 PeV. The increased area of the surface part of the array gives a possibility to increase the area of location of the shower axis, thereby increasing the statistics of detected events and decreasing the energy threshold for primary cosmic radiation. The Carpet-3 experiment will start data taking at the end of 2021.
Large-scale monitoring of anthropogenic marine litter in the Barents Sea was carried out in 2012–2018. The marine litter composition was estimated by recording by-catch from pelagic and bottom ...trawling. Litter on the sea surface (floating litter) was also taken into account during visual observations. The contents of 949 pelagic and 1477 bottom trawls were analyzed. Marine litter was recorded in 256 pelagic and 571 bottom trawl catches and in 454 cases during visual observations. Litter was sorted into plastic, wood, metal, rubber, textiles, paper, and glass. The occurrence of plastic prevailed in all litter records. It covered 71% of marine litter observed on the surface, 97% in pelagic trawls, and 78% in bottom trawls. Fishery litter prevailed in plastic litter (about 65% of its weight). Wood was recorded in 19% of surface litter observations
,
1% in pelagic trawls and 13% in bottom ones. Metal, rubber, paper, textiles, and glass were occasionally observed; however, their weight (except glass) could be very large. Thus, metal and wood prevailed by weight on the bottom (45 and 36.8%, respectively). Wood prevailed in pelagic layers, being 73% of the total litter weight. The volume of plastic and wood prevailed on the sea surface (50 and 47%, respectively). The average density of all types of litter on the sea bottom was about 7.9 kg/km
2
. Some significant differences in the litter composition were recorded between the southwestern and northeastern areas of the Barents Sea.
The Baksan Neutrino Observatory setups are currently performing search for neutrino and ultra-high-energy gamma-ray counterparts of the events on the Gamma-ray Coordinates Network. The Gamma-ray ...Coordinates Network is a system for distributing alerts from gamma-ray bursts, transients. Muon neutrinos and antineutrinos with energies above 1 GeV are registered with the Baksan Underground Scintillation Telescope. Ultra-high-energy gamma rays are registered with the ‘‘Carpet-2’’ setup. Registration of events and analysis of alerts occurs in near-real time. Alerts from Swift BAT, Fermi-GBM, Fermi-LAT, INTEGRAL, IceCube, HAWC are used. This work presents the description of the alert processing program and preliminary results.
Brain ischemia is a complex of damaging factors, which include oxygen and glucose deprivation, as well as the possibility of repeated lesions during tissue reperfusion. Thrombin, a key serine ...protease of hemostasis, can be detected in the parenchyma of the brain in ischemic and hemorrhagic strokes, where it enters directly from the bloodstream through the damaged blood-brain barrier (BBB). In this study, the effect of thrombin on the state of glial brain cells under conditions of oxygen-glucose deprivation and subsequent normoxia (ischemia/reperfusion model) was evaluated. It was found that thrombin at low concentrations (10 nM) has a protective effect on rat astrocytes during ischemia/reperfusion. Pre-incubation of astrocytes with the protease at a low concentration caused an increase in cell survival under these conditions, while an increase in concentration (50 nM) reduced its protective effect. It was found that thrombin at both concentrations did not affect the proliferation of astrocytes induced by ischemia/reperfusion. It has been shown that oxygen-glucose deprivation led to the redistribution of actin filaments in astrocytes from the near membrane space to the region of the cell nucleus. Thrombin at high concentration potentiated the effect of oxygen-glucose deprivation on the actin cytoskeleton of astrocytes. Thus, thrombin is an endogenous regulatory molecule for brain astrocytes, and its effect under oxygen-glucose deprivation and subsequent reperfusion is dose-dependent.
Isotropic diffuse gamma-ray flux in the PeV energy band is an important tool for multimessenger tests of models of the origin of high-energy astrophysical neutrinos and for new-physics searches. So ...far, this flux has not yet been observed. Carpet-2 is an air-shower experiment capable of detecting astrophysical gamma rays with energies above 0.1 PeV. Here we report the upper limits on the isotropic gamma-ray flux from Carpet-2 data obtained in 1999–2011 and 2018–2022. These results, obtained with the new statistical method based on the shape of the muon-number distribution, summarize Carpet-2 observations as the upgraded installation, Carpet-3, starts its operation.
PDF
