Seasonal variations in primary production (PP) in the Kara Sea are underresearched. Previous studies only collected data during autumn or in late summer. However, the middle of summer is close to the ...beginning of the growing season, when PP can contribute significantly to annual water column integrated primary production (IPP). In addition, differences can be expected in the spatial and vertical distribution of phytoplankton communities in this period. This gap in midsummer data was addressed within the framework of a multidisciplinary research cruise by the R/V “Akademik Mstislav Keldysh” (from 15 July to 18 August 2016). High values of IPP (> 200 mgC m
−2
day
−1
) and surface chlorophyll
a
(Chl
a
) concentration (Chl
0
> 1 mg m
−3
) were associated with the Ob–Yenisey river plume, located in the central part of the Kara Sea. Beyond the influence of the plume, in the western and southwestern regions of the Kara Sea, well-pronounced subsurface chlorophyll maxima (SCM) were observed. In some cases, the Chl
a
concentration in SCM exceeded Chl
0
by two orders of magnitude. SCM were often accompanied by subsurface PP maxima (SPM). At stations where SCM was pronounced, IPP values reached 500–800 mgC m
−2
day
−1
, and > 30 % of IPP was accounted for by SPM-integrated PP. Thus, in the middle of summer in the Kara Sea, IPP was linked with the chlorophyll-specific phytoplankton biomass and depended on the strength of the SCM.
The first data on the content of organic compounds (OCs), i.e., C
org
, lipids, and hydrocarbons (aliphatic (AHCs) and polycyclic aromatic (PAHs)) in the suspended particulate matter of the surface ...waters and bottom sediments in the western Kara Sea and the Gulf of Ob during the period of seasonal ice melting (July 2019) are considered. The highest content of OCs and suspended particulate matter in surface waters was found in the Gulf of Ob: AHCs up to 325 μg/L, PAHs up to 15 ng/L, and suspended particulate matter up to 15.5 mg/L. In the sea basin, the AHC concentrations increased, on average, from 20 to 59 μg/L, which was associated with flooding. A sharp decrease in all OC components supplied by the river runoff is observed at the geochemical barrier between the Gulf of Ob and the Kara Sea. The production of hydrocarbons and intensification of navigation in the southern part of the Kara Sea affect the AHC and PAH composition. The decomposition of autochthonous suspended particulate matter including the suspended OCs during sedimentation leads to the absence of increasing concentrations of C
org
, AHCs, and PAHs in the bottom sediments, unlike those in the surface waters.
We present results of validating the algorithms used to estimate sea surface solar radiation at 400-700 nm, photosynthetically available radiation (PAR), from satellite ocean color data and an ...appropriate validation procedure when data are collected using a moving ship. The validation was performed using field measurements of PAR during a transit cruise from the Baltic to the White Sea during the summer of 2014. The PAR was measured at 10-minute intervals using a deck radiometer throughout the daylight hours. The satellite estimate of daily surface PAR with an acceptable error, on the scale of 1 day-10
km, is shown.
—
Reconnection of magnetic field lines represents a universal process of releasing the stored energy of the magnetic field and its transformation into the thermal energy of plasma and the energy of ...accelerated charged particles. The initialization and proceeding of the magnetic reconnection process are essentially related with the dynamics of a spatially localized region of strong plasma currents—the current sheet. The two most studied cosmic magnetoplasma systems containing current sheets are the tail region of the Earth’s magnetosphere and the regions with closely spaced, elongated magnetic field lines of opposite polarity in the solar corona (in particular, the rays of coronal streamers and the eruptive flares). However, whereas the main source of information for the Earth’s magnetosphere about the structure and dynamics of current sheets are numerous direct measurements of satellite missions, then, for the solar corona, some characteristics of the current sheet can be restored on the basis of remote observations of quasi-periodic oscillations. As a consequence, to clarify the possible mechanisms responsible for these oscillations, it seems relevant to compare the properties of oscillations of the current sheet of the Earth’s magnetosphere and current sheets of the solar corona. This work is devoted to such a comparative analysis; it contains a brief overview of the available information about the quasi-periodic dynamics of the magnetospheric current sheet and discusses the probable interpretation of this dynamics in terms and parameters of observations of quasi-periodic processes in current sheets of the solar corona.
—The research was carried out on cruise 79 of the R/V
Akademik Mstislav Keldysh
. The variability of the chlorophyll
a
specific light absorption coefficient of phytoplankton and the correlation ...coefficient for the fluorescence intensity and chlorophyll
a
concentration at various optical depths under ambient light intensity and after dark adaptation was studied. It was shown that in the absence of water stratification, there was no vertical variability in the chlorophyll
a
specific light absorption coefficient of phytoplankton. It was found that when measuring the intensity of chlorophyll
a
fluorescence with a submersible sensor, without preliminary dark adaptation, a decrease in the fluorescence intensity signal in the upper layer of water was observed, which was associated with the effect of light on the fluorescence quantum yield.
The distribution of primary production (PP), chlorophyll
a
concentration (Chl
a
), and size structure of the phytoplankton community were studied in the Kara Sea during the first-year ice retreat in ...late June 2021. The maximum value of water column PP (IPP) reached 1352 mgC m
–2
day
–1
. The ice-edge phytoplankton bloom was characterized by high averaged of IPP and Chl
a
integrated in the photosynthetic layer (Chl
phs
) values: 740 mgC m
–2
day
–1
and 81.40 mg m
–2
, respectively. The highest IPP values were observed at sites where Chl
a
was concentrated in the upper mixed layer or where the subsurface chlorophyll maximum coincided with the pycnocline. Over the area of phytoplankton bloom, the contribution of microphytoplankton (>20 µm) to the total IPP and Chl
phs
was 92 and 82%, respectively. Contribution of picophytoplankton (<3 µm) to the total PP increased along the depth until reaching the lower margin of layer of photosynthesis, from 3 to 70%, on average. No similar pattern has been observed for vertical distribution of Chl
a
. This pattern was evidenced by an increase in the chlorophyll specific carbon fixation rate (assimilation number) of picophytoplankton with depth under low insolation conditions.
It is shown that Ryngo 1-23, a dynamin activator, significantly enhances the uptake of nanoparticles (NPs) encapsulated by an amphiphilic polymer by glioma C6, Hela, and Ehrlich’s ascites carcinoma ...cells, but not by cells of the monocyte-macrophage series U-937, KG-1, and THP-1. At the same time, the dynamin inhibitor, dynasore, has little effect on the uptake of NPs by glioma C6 and Hela cells, but significantly inhibits the cellular uptake by U-937. Brefeldin A, an inhibitor of ADP-ribosylation factor 1, reduces the uptake of NPs by glioma C6 and Hela cells, but not U-937. Thus, mechanisms dependent on dynamin and ADP-ribosylation factor 1 are involved in the uptake of NPs by cells. The role of these mechanisms varies considerably in different cell types. Chemical modulators of endocytosis processes can be used to enhance the selectivity of the interaction of NPs with certain cell types.
Sorption of pertechnetate on pyrrhotite Fe
n
S
n
+1
(I) and stibnite Sb
2
S
3
(II) from distilled water was evaluated. The distribution coefficients were found to be 185 and 223 cm
3
/g, ...respectively. The XPS study of the chemical state of
99Tc
absorbed on the surface of pyrrhotite and stibnite from aqueous solution of potassium pertechnetate (KTcO
4
) was carried out. It was found that Tc(IV) ions are present mostly on the surface of the studied samples, their concentration was 5.7 times higher on the surface of pyrrhotite compared to that on the surface of stibnite. A 13% admixture of Tc(VII) ions on the surface of pyrrhotite was observed.
This article presents measurements of the piezoelectric modulus d11 of a single crystal of lanthanum gallium silicate (LGS, La3Ga5SiO14). The piezoelectric modulus was measured by X‐ray diffraction ...at angles close to backscattering. Experiments in such schemes are very sensitive to relative changes in the lattice constant in crystals caused by external influences (constant or alternating electric field, mechanical load, temperature change etc.). The development opportunity of the technique is shown, its applicability is evaluated and results of measurement of the LGS single‐crystal piezo modulus by the method of diffraction of synchrotron radiation at angles near π are discussed.
The diffraction response of a single crystal to an electric field is measured by X‐ray diffraction at angles close to π. Such schemes allow one to determine with high (∼10−5–10−6) accuracy the relative changes in the lattice constant.
Abiotic characteristics of the waters in the Bransfield Strait were studied in a section from the South Shetland Islands to the Antarctic Peninsula. The Bransfield Current was recorded northeastward ...flowing along the archipelago with a speed of 20–47 cm/s. It is marked by the water temperature and salinity in the core (2.7°C and 34.18%). The depth of the lower boundary of the euphotic layer varies from 40 m near the South Shetland Islands to 80 m on the shelf of the Antarctic Peninsula. The oxygen content and parameters of the carbonate system indicate the predominance of production over destructive processes in the surface layer of the central part of the Strait during the period under study. A countercurrent from the Weddell Sea was recorded on the shelf of the Antarctic Peninsula, which is distinguished by the oxygen saturation (90%) and silica content (74 µM). Four water masses were identified in the region under studied: Antarctic Surface Water, Circumpolar Deep Water, modified water of the north-western Weddell Sea shelf, and Bottom Bransfield Water.
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