Search

Objective: A number of previously synthesized fluorogenic arylidene-imidazolones, which predominantly stain the endoplasmic reticulum (ER) of living cells, were studied by time-resolved fluorescence microscopy. It was suggested that the use of fluorescence microscopy of this type can enhance the selectivity of ER staining. Methods: The lifetimes of arylidene-imidazolone compounds in set of solvents with different polarity were measured with time-correlated single photon counting spectroscopy. Live HeLa Kyoto cells were stained with studied dyes and analyzed with time-resolved fluorescence microscopy. Results and discussion: It was found that most of the studied compounds show bi- or triexponential fluorescence decay patterns in solutions. In live cell culture dye (I) showed a monoexponential decay pattern, while dyes (II–IV) were better fitted by a biexponential function. Dyes (I), (III), and (IV) stained both ER and adiposomes, while dye (II) stained only ER. Conclusions: It is shown that under FLIM conditions discriminative filtering of cellular organelles stained with studied fluorogenic dyes is possible and applicable if the difference of mean amplitude-weighted lifetime is more than 0.1 ns, thus increasing the selectivity of ER staining in live cells. [ABSTRACT FROM AUTHOR]

This study aims to determine how the use of virtual reality impacts physics students, their knowledge, and the quality of training. The study involved 116 students aged 17–19. The main purpose is to explore the effect that VR technology has on students' knowledge and motivation. As per usual, the students were divided into two research groups: experimental and control. Physics students (experimental group) used virtual reality in learning, while radiophysics students (control group) followed the standard educational program. The results obtained upon completion of the training have confirmed that VR technology can effectively improve learning quality and increase student motivation. [ABSTRACT FROM AUTHOR]

New C–N-bonded bisazoles were obtained by cine-substitution of 1,3-dinitro-1H-pyrazole-4-carbonitrile by the action of N-azoles. Their spectral characteristics were investigated using multinuclear NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The article presents the results of hydrochemical studies of waterbodies with varying degrees of development of anaerobic conditions (up to the appearance of meromixia with sulfide anoxia) in the Porya Guba Bay (Kandalaksha Bay, White Sea, Kandalaksha State Nature Reserve). It is shown that these waterbodies, which are at different stages of isolation from the sea, have a unique hydrological and hydrochemical structure, formed at a certain stage of their evolution. The vertical stratification of water, with the development of all phenomena accompanying stagnation, is more pronounced in the most distant parts of their water area from the sea, where elevated contents of hydrogen sulfide (up to 16.5 mg/L), phosphates, silicon, nitrite, and ammonium nitrogen are noted in bottom anaerobic water. However, the concentrations of all major ions are comparable to those in seawater and hardly chance at all vertically. Analysis of the distribution of the hydrochemical parameters of the distant reaches of Ozerki Lagoon made it possible to conclude that, due to changes that have occurred with this waterbody over the past 90 years, it can now most likely be classified as meromictic. [ABSTRACT FROM AUTHOR]

The relic Lake Mogilnoe, separated from the Barents Sea by a sand and pebble dam, is located in the high Arctic on the Kildin island (Murmansk region). This lake is a classic example of a meromictic basin of marine origin. The data obtained during the 2018 expedition showed changes in the hydrochemical regime of the lake that have occurred over the past 20 years. Sulfide concentration in the monimolimnion of the lake was as high as 140 mg/L. A tendency for salinization of the surface waters to 7 g/L has been noted. The Lake Mogilnoe is characterized by a discrepancy between the halocline and thermocline levels. The chemocline zone in the lake is below the halocline level. In a narrow oxygen-containing layer between 3 and 7.5 m, aerobic microflora of the marine type and marine fauna were present. The bacterial plate was formed at the boundary of the sulfide layer at ~8 m and mainly consisted of green sulfur bacteria (GSB). Brown-colored GSB species containing bacteriochlorophyll e were predominant. The previously formed concept of anaerobic phototrophic bacteria (APB) biodiversity based on morphological characteristics was modified using metagenomic data obtained by analyzing DNA from two samples of lake water in the chemocline zone, and was also supplemented by identifying new GSB species. Molecular diagnostic data confirmed the absolute dominance of the brackish species of GSB Chlorobium phaeovibrioides. This is the first isolation and identification of brown- and green-colored Prosthecochloris aestuarii morphotypes from Lake Mogilnoe, as well as of bacteriochlorophyll c-containing Prosthecochloris sp. The taxonomic position of Pelodyction phaem, which was constantly present in the Lake Mogilnoe, is discussed in detail. Despite the partial isolation of the ecosystem of Lake Mogilnoe from the Barents Sea, the main properties of the dominant GSB species and Prosthecochlori aestuarii turned out to be similar to those of the phylotypes living in lakes on the White Sea coast. [ABSTRACT FROM AUTHOR]

Neurodegenerative diseases are a growing global health problem with enormous consequences for individuals and society. The most common neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases, can be caused by both genetic factors (mutations) and epigenetic changes caused by the environment, in particular, oxidative stress. One of the factors contributing to the development of oxidative stress that has an important effect on the nervous system is vitamin K, which is involved in redox processes. However, its role in cells is ambiguous: accumulation of high concentrations of vitamin K increases the content of reactive oxygen species increases, while small amounts of vitamin K have a protective effect and activate the antioxidant defense systems. The main function of vitamin K is its involvement in the gamma carboxylation of the so-called Gla proteins. Some Gla proteins are expressed in the nervous system and participate in its development. Vitamin K deficiency can lead to a decrease or loss of function of Gla proteins in the nervous system. It is assumed that the level of vitamin K in the body is associated with specific changes involved in the development of dementia and cognitive abilities. Vitamin K also influences the sphingolipid profile in the brain, which also affects cognitive function. The role of vitamin K in the regulation of biochemical processes at the cellular and whole-organism levels has been studied insufficiently. Further research can lead to the discovery of new targets for vitamin K and development of personalized diets and therapies. [ABSTRACT FROM AUTHOR]

A comparative characteristic of the structure of planktonic community is given for different parts of a lowland reservoir (the Kuibyshev Reservoir, the Volga River). The level of the effect of plankton (and seston as a whole) of tributaries on the plankton and seston of the reservoir is shown, depending on their location in different morphometric (hydrological) zones and the discharge regime of water masses through the nearby dams. The contribution of the inflow in the upper part of the reservoir to the total carbon concentration in the receiving water body is higher (81 and 61% of the total organic carbon of plankton on weekends and weekdays, respectively) than in the lower part of the reservoir (4.4 and 1.5%). The effect of HPP operation on the variation amplitude of the total biomass of planktonic community and its structure in the near-dam part of the reservoir (the upper Pool of the dam) is evaluated. In the period of a decrease of water discharge and, accordingly, lower flow velocity, the total plankton biomass was maximal on weekends with a parallel increase in the proportion of cyanobacteria in its structure. [ABSTRACT FROM AUTHOR]

The composition and structure of the anoxygenic phototrophic bacterial (APB) community in the water column of meromictic Lake Bol'shie Khruslomeny during winter were investigated. The community developed at the depth of 4.25 m, and its activity in the ice-cover period was very low (6.2 µmol C L–1 day–1). The water in the zone of highest development of phototrophic bacteria was of an unusual lemon-yellow color, probably due to the production and accumulation of polysulfides. The near-bottom water was also of lemon-yellow color and was resistant to oxidation by the air oxygen. In the zone of peak APB development the content of BChl d from green-colored green sulfur bacteria was considerably higher than that of BChl e from brown-colored green sulfur bacteria: 77 and 23%, respectively. The cultures of green and purple sulfur bacteria were isolated from lake water, and their physiological and genetic characteristics were determined. Two strains of green sulfur bacteria (brown-colored BrKhr17 and green-colored GrKhr17) contained gas vacuoles in their cells. Phylogenetically they were most closely related to the green-colored strain Chlorobium phaeovibrioides DSM 265 and were identified as new strains of the species Chlorobium phaeovibrioides. [ABSTRACT FROM AUTHOR]

Drainage for forestry has created ~ 1 million km of artificial waterways in Sweden, making it one of the largest human-induced environmental disturbances in the country. These extensive modifications of both peatland and mineral soil dominated landscapes still carry largely unknown, but potentially enormous environmental legacy effects. However, the consequences of contemporary ditch management strategies, such as hydrological restoration via ditch blocking or enhancing forest drainage to promote biomass production via ditch cleaning, on water resources and greenhouse gas (GHG) fluxes are unclear. To close the gap between science and management, we have developed a unique field research platform to experimentally evaluate key environmental strategies for drained northern landscapes with the aim to avoid further environmental degeneration. The Trollberget Experimental Area (TEA) includes replicated and controlled treatments applied at the catchment scale based on a BACI approach (before-after and control-impact). The treatments represent the dominant ecosystem types impacted by ditching in Sweden and the boreal zone: (1) rewetting of a drained peatland, (2) ditch cleaning in productive upland forests and (3) leaving these ditches unmanaged. Here we describe the TEA platform, report initial results, suggest ways forward for how to best manage this historical large-scale alteration of the boreal landscape, as well as warn against applying these treatments broadly before more long-term results are reported. [ABSTRACT FROM AUTHOR]

The data obtained on the synthesis and search for biological activity among metal complexes based on 4-aryl-2-hydroxy-4-oxo-2-butenoic acid (hetero)arylamides were integrated. The data on the antimicrobial, anti-inflammatory, analgesic, hypoglycemic, antihypoxic, and immunotropic activities of the synthesized compounds were analyzed. The relationship between the chemical structure and biological activity of chelate complexes was discussed and some regular features were identified. Promising compounds for further research and development of new domestic pharmaceutical substances were found. [ABSTRACT FROM AUTHOR]

Abstract—The occurrence and distribution of fin whales and humpback whales along the route of the R/V Akademik Mstislav Keldysh in the Atlantic sector of Antarctica in January and February 2022 were studied. The features of the whales' distribution were considered depending on the depth of the water area, the abundance and age of krill, and the Chl-a concentration in the water. The highest occurrence of fin whales was found in the deep waters of the Powell Basin and the Orkney Trench, where the highest concentrations of adult krill were recorded. The highest occurrence of humpback whales was observed in shallow Bransfield Strait, where small and young krill predominated. The dependence of the occurrence of whales on the concentration of chlorophyll was not confirmed. [ABSTRACT FROM AUTHOR]

inorganic-polymer composites are widely used as radio-absorbing materials, the study of their properties is important from the point of view of improving technical characteristics. The results of the study of Nafion/thermoexpanded graphite and Nafion/carbon black composites by nuclear magnetic resonance and thermogravimetry are presented. The formation of new compounds at the contact boundaries of the components, leading to thermal stabilization of the composites, is shown. Differences between thermally expanded graphite and carbon black upon interaction with Nafion are discussed. [ABSTRACT FROM AUTHOR]

A technology for obtaining graphene by means of ultrasonic dispersion of thermally expanded graphite in the presence of a surface-active polymer Nation is presented. The technology makes it possible to obtain large amounts of low-layer (1–3 layers) graphene in a relatively short time. An approach to control the dispersion process based on UV spectroscopy of dispersions is described. A mechanism is proposed for the effect of a surface-active polymer on the production of low-layer graphene by ultrasonic dispersion. [ABSTRACT FROM AUTHOR]

Gas seep and fluid flows from the seabed are an environment-forming factor of the aquatic environment, mainly due to their influence on the dissolved gases in the water, including dissolved oxygen. During the summer seasons from 2019 to 2021 in the area of shallow water gas emission site off the southern coast of the Heracles Peninsula, series of vertical probing profiles were carried out to determine hydrological parameters of the water: dissolved oxygen concentration (O2), temperature (T), salinity (S), and flow velocity (U). The study area is an underwater ledge with faults in the form of three canyons composed of dense limestones, two of which contained bubble gas emissions. Significant variability in O2 was identified in canyons where gas emissions are observed: from 1 to 80% saturation in the bottom layer, in contrast to normoxia at the background sites. Hypoxia was observed in the bottom layer above the emission sites in the absence of turbulence at temperature stratification. The values S decreased with depth, and the maximum difference reached 0.4‰. The bubble gas was dominated by methane (68.5–75.5%), and the carbon isotope composition of the bubble methane gas varied from –67.9 to –59.8‰ VPDB in 2019 and 2020, respectively. This generally indicates that the CH4 is of predominantly microbial genesis, was formed under different conditions, and matured in various periods of research during the monitoring period. Bacterial mats (mostly sulfur-oxidizing bacteria) were found in the areas of gas emissions. [ABSTRACT FROM AUTHOR]

From 2019 to 2021, integrated studies of new shallow-water methane bubble gas seeps were carried out in the coastal zone near Cape Fiolent (Southwest Coast of Crimea). The studies included determination of the hydrocarbon and isotope composition of bubble gas, measurement of the methane and nutrient concentration in the water in the areas of gas seeps, estimation of the value of bubble flows, and measurement of the hydrophysical parameters over the seep sites compared to background areas. A seasonal type of Cape Fiolent methane seeps was noted, and the durations of its active gas emission phases differed in different years. The increased pore water silica concentration at the seep sites and their localization in the vicinity of freshwater slope springs may indicate its association with submarine freshwater discharge in the area. However, no significant desalination of either pore water or the bottom water layer above the seeps was recorded. Dissolved methane concentrations in pore water at seep sites were two orders of magnitude higher compared to the background areas, reaching 448 μmol/L. High values were also obtained for surface water directly above the bubble gas emission points (maximum 353 nmol/L). Multihour monitoring of the hydrophysical parameters above the active seeps showed a decrease in dissolved oxygen compared to the background sites. The maximum difference in O2 concentrations was 3 mg/L. The carbon isotope composition of bubble gas methane δ13C-CH4 (–62.84 to –38.27‰) and carbon dioxide δ13C-CO2 (–16.83 to –10.17‰) corresponded to a mixture of isotopically heavy gas and near-surface isotopically light gas of microbial origin. The question remains open: what are the reasons for the change in the summer active and cold season passive gas emission phases? [ABSTRACT FROM AUTHOR]

Abyssal peridotite outcrops compose vast areas of the ocean floor in the Atlantic, Indian, and Arctic Oceans, where they are an indispensable part of the oceanic crust section formed in the slow-spreading oceanic ridges (Mid-Atlantic Ridge, Southwest Indian Ridge, and Gakkel Ridge). The final stage in the evolution of abyssal peridotites in the oceanic crust is their carbonation, which they experience on the ocean floor surface or near it. The main goal of this study was to reconstruct the geochemical trends accompanying the carbonation of abyssal peridotites using MAR ultramafic rocks as an example and to identify the main factors that determine their geochemical and mineralogical differences. The composition variations of rock-forming minerals and their characteristic assemblages indicate that the initial stages of carbonation of abyssal peridotites occurred in crustal conditions simultaneously with the serpentinization of these rocks. The final stage in the crustal evolution of the abyssal peridotites is their exhumation on the ocean floor where they were brought up along the detachment faults. On the ocean floor, the abyssal peridotites in close association with gabbro form oceanic core complexes, and the degree of their carbonation sharply increases with time of their exposure on the ocean floor. The presented data made it possible to qualitatively reconstruct the sequence of events that determined the mineralogical and geochemical features of carbonatized abyssal peridotites of the MAR. [ABSTRACT FROM AUTHOR]

Abstract—This article considers the results of a comprehensive study of the Cretaceous–Eocene deposits of Central Crimea (Mount Ak-Kaya). The temperature and salinity of the formation of Maastrichtian and Eocene rocks were determined and they were correlated with a global climatic event (Early Eocene Climatic Optimum). The synchronicity of the formation of steeply dipping submeridional fractures and the Eocene basal horizon has been confirmed. The three major deformation stages (pre-Eocene, Eocene, and post-Eocene) were identified. It has been shown that the Eocene stage corresponded to the formation of paleoseismic dislocations during the main phase of tectonic activity in the Pontides (Eastern Turkey). [ABSTRACT FROM AUTHOR]

This article presents modern data on the chemical and gas compositions, as well as the contents of the stable isotopes of oxygen, hydrogen, carbon, and sulfur, in the natural mineral waters of the Essentuki field. A detailed study of the geological and hydrogeological features of the water circulation territory, their macro-component compositions, the contents of organic matter in the water, and the temperature conditions and values of δDSMOW, δ18ОSMOW, δ13СDIC, δ18ОDIC, δ34SVCDT, δ13CCO2, δ13CCH4, and δ15N revealed the genesis of the aqueous, gas, and salt components of the natural mineral waters of the Essentuki field. It was established that all natural mineral waters of the Essentuki field are infiltration meteoric waters. The heterogeneous component composition of the natural mineral waters circulating in various aquifers represents the features of the lithological composition of the water-bearing rocks, the degree of openness or closeness of faults, and the intensity of reactions in the water–rock–gas–organic matter system. [ABSTRACT FROM AUTHOR]

The extraction of scandium with tetraoctyldiglycolamide from solutions of mineral acids is studied, and the effect of the diluent on the distribution coefficients of scandium and a number of elements is determined. It is shown that the scandium extraction is most efficient from nitric-acid media. The optimal conditions are found for nitric-acid leaching of red mud for further concentration of scandium by extraction with tetraoctyldiglycolamide as an extractant. [ABSTRACT FROM AUTHOR]

The results of a comprehensive study of the boundaries of the Turonian–Coniacian in the Upper Cretaceous deposits of the Abinskii region of the Northwestern Caucasus, composed of rhythmically constructed carbonate strata of the hemipelagic type, are presented. Biostratigraphic analysis of foraminifera complexes made it possible to identify zones in the section that are comparable to those proposed for the Point of the Global Stratotype of the boundary of the Coniacian in Germany. On the basis of chemostratigraphic (isotope) studies, the levels of abiotic events traced in the section and other territories have been established. The Shapsug section, after further study, can be proposed as a possible Hypostratotype (Limitotype) of the Turonian–Coniacian boundary for the territory of the Russian Federation. [ABSTRACT FROM AUTHOR]

An important characteristic of a natural water body is the distribution of pigment composition of different groups of photosynthesizing organisms over depth and its variations in different seasons. Optical methods are widely used to monitor the concentrations of chlorophylls in algae or cyanobacteria in aqueous ecosystems, but they have very limited application in monitoring the bacteriochlorophyll (BChl) concentration in phototrophic bacteria. The paper describes comprehensively three new methods of quantitative analysis of the photosynthetic pigment of BChl d of green sulfur bacteria using spectral measurements in both initial samples of natural water (absorption spectra), and in pigment extracts in organic solvents (absorption and fluorescence spectra). A comparative analysis of the results from different methods is carried out using, as an example, natural water from the chemocline region in Lake Trekhtzvetnoe, one of the meromictic water bodies in the Kandalaksha Bay in the White Sea. Conclusions are drawn about the applicability conditions of different methods, their advantages and limitations. All three methods suggested have been proven to be efficient using, as an example, samples of natural water with BChl concentrations differing by orders of magnitude, from 5 to 5000 mg/m3. [ABSTRACT FROM AUTHOR]

Abstract—Homocysteine is a sulfur-containing amino acid formed from methionine and considered as a risk factor for a number of pathologies. An increase in the homocysteine level (hyperhomocysteinemia, HHcy) during pregnancy leads to various complications of pregnancy, fetal hypoxia and, consequently, development of early and delayed postnatal pathologies. One of the main mechanisms of homocysteine action is induction of oxidative stress. The aim of our study was to analyze oxidative modification of proteins and activity of proteases, as well as the level of oxidative stress in the brain tissue of rats with prenatal HHcy in the first week after birth. Experimental HHcy was induced in female rats by feeding them with elevated amounts of methionine for 3 weeks before, during, and after pregnancy. In the homogenates of brain tissue of offspring with prenatal HHcy a significant increase in spontaneous protein carbonylation was observed. This result indicates a decrease in the reserve-adaptive potential of brain cells and a decrease in the resistance of the tissue to the action of free radicals. In the brains of rats with prenatal HHcy, the activity of acidic and neutral proteases was higher compared to controls which could be a result of aggregation and fragmentation of protein molecules due to carbonylation of amino acid residues. Brain tissues of newborn rats with prenatal HHcy were also characterized by a high content of hydrogen peroxide, malondialdehyde as the marker of lipid peroxidation, and a decrease in the activity of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. Thus, the data obtained indicate a significant increase in the irreversible process of oxidative modification of proteins in the brain of newborn rats with prenatal HHcy due to oxidative stress. These processes contribute to the mechanisms of homocysteine neurotoxicity during the critical period of brain development in the early postnatal period, during which intensive neurogenesis, synaptogenesis, and formation of neural networks take place. [ABSTRACT FROM AUTHOR]

Phytoplankton of the stratified Kislo-Sladkoe Lake (White Sea coast) was studied using chlorophyll fluorescence methods in 2018. A layer of red water was observed with a chlorophyll a concentration of 1.7 µg/L at a depth of 3.3 m in the chemocline (at the aerobic and anaerobic zone interface). Cryptomonad algae (Rhodomonas sp.) were dominant in the layer; high functional activity of the photosynthetic apparatus was recorded in the algae based on the PIABS fluorescence parameter (high values of the quantum yield of the primary photochemical reaction in photosystem 2 (PS2) (FV/FM)); the proportion of active reaction centers (RCs) (RC/ABS); and the quantum yield of electron transport in PS2 (). The high functional activity of the photosynthetic apparatus of cryptomonad algae in the chemocline points toward their stability in the presence of hydrogen sulfide. By comparison, the phytoplankton in the surface water layer showed lower photosynthetic activity. Experiments with photoinhibition showed that the chemocline phytoplankton community is characterized by a greater reparative capacity after photooxidative stress despite the increased photosensitivity. It is proposed to employ chlorophyll fluorescence methods to study a state of phytoplankton in stratified meromictic water bodies. [ABSTRACT FROM AUTHOR]

The composition of microbial communities and the rates of microbial processes in the water column of a meromictic trough in the Biofilter Bay, Kandalaksha Bay, White Sea were investigated in September 2020 and March 2021. The chemocline zone was located at the depths from 8 to 9 m. Sulfide was present in the monimolimnion, its concentration at the bottom reaching 25‒38 mg L–1 (0.7‒1.1 mmol). Conditions of the redox zone favored development of both anaerobic anoxygenic phototrophs and aerobic sulfur-oxidizing chemoautotrophs. A pinkish-brown bacterial plate was formed in this zone. Sequencing of the 16S rRNA gene fragments revealed predominance of green sulfur bacteria (GSB) Chlorobium phaeovibrioides. Aerobic sulfur-oxidizing bacteria Sulfurimonas sp. were the second most abundant group. Plating of chemocline samples on selective media resulted in massive formation of brown-colored Chlorobi colonies, while green GSB colonies were few. Both morphotypes were identified as Chlorobium phaeovibrioides. At the time of our study, purple sulfur bacteria (PSB) did not form a bacterial plate in the redox zone, although few PSB colonies were revealed. The PSB isolate was identified as Thiocapsa rosea. Members of this species are able to switch from photosynthesis to aerobic chemosynthesis and may compete for sulfide with sulfur-oxidizing chemo-autotrophs. We suggest that due to its openness the Biofilter Bay meromictic trough may act as a source for the propagation of anoxygenic phototrophic bacteria in the Kandalaksha Bay. [ABSTRACT FROM AUTHOR]

In the deterministic formulation, two problems are considered related to the generation of admissible reference actions for the automatic control of an autonomous mobile robot in the problem of path following stabilization. The first problem is the restoration of the derivatives of the reference vector signal without its analytical description. This signal sets the realizable trajectory for the robot. An easy-to-tune dynamic differentiator with piecewise linear corrective actions is proposed to solve that problem. The differentiator is constructed as a copy of the virtual canonical model with unknown input and provides an estimation of derivatives of any required order with any given accuracy. The second problem is the smoothing of composite spatial trajectories. For solution, a dynamic generator is presented. It is constructed as a copy of the motion equations of a specific robot. A decomposition procedure for the synthesis of S-shaped smooth and bounded corrective actions of the generator is developed. In the generator, a reference non-smooth vector signal is used to describe the path of the robot in the first approximation. For tuning the generator, the constraints on the state variables and controls of a specific robot are taken into account. It produces smooth output signals, as well as their derivatives, realizable by a particular robot. These algorithms can be implemented both at the planning stage and in real time since they do not require large computational costs. Their effectiveness is verified by numerical simulation for the movement of the center of mass of an unmanned aerial vehicle. [ABSTRACT FROM AUTHOR]

The variation of surface area of platinum–carbon material of hydrogen fuel cell electrodes in the presence of structure-modifying carbon nanotubes under long-term electrochemical action is studied. The method of cyclic voltammetric curves is used to study the specific features of the variation of platinum nanoparticle surface area by the hydrogen desorption in the hydrogen region and the charging current of electrical double layer in the double-layer potential region. The results are obtained separately for the electrodes on the cathodic and anodic sides. [ABSTRACT FROM AUTHOR]

The results of integrated study of the Turonian–Coniacian sediments from the Abinsky district (Northwest Caucasus), which are represented by a rhythmic terrigenous-carbonate sequence, are discussed. The use of microfacial, X-ray diffraction, isotope, and micropaleontological analyses allowed us to reveal important changes in abiotic and biotic evolution during this interval. The peculiarities of carbonate sedimentation, as well as changes in the composition of foraminiferal assemblages, helped to establish fluctuations in the relative sea level, whereas isotopic studies assisted in defining climatic fluctuations. During the periods of accumulation of carbonate and clayey material, the area was occupied by a relatively deep-water open-sea basin with normal salinity. In the background of high temperatures, cooling pulses are also recorded within the studied interval. The position of the Turonian–Coniacian boundary in the section is revised. [ABSTRACT FROM AUTHOR]

An important element in the reconstruction of the geodynamic evolution of the lithosphere in the northwestern Pacific Ocean is the Stalemate Ridge, which is located immediately south of the Aleutian island arc and stretches from southeast to northwest parallel to the Aleutian trench. The collection of our rock samples included rocks dredged along the entire strike of the Stalemate Ridge during cruises 201 and 249 of the German R/V Sonne. This study was focused on peridotites, gabbroids, dolerites, and basalts that fully represent the petrographic diversity of igneous rocks composing segments of the Stalemate Ridge located within a length of 500 km along its strike. The synthesis of all preexisting and newly acquired data on the structure of the Stalemate Ridge and the composition of its rocks led us to the following conclusions of principal importance for developing an adequate geodynamic models for the formation of magmatic complexes and their sources in this area of the northwestern Pacific Ocean: (1) the mafic-ultramafic rock association of the northwestern segment of the Stalemate Ridge was formed at a convergent boundary of lithospheric plates; (2) depleted and enriched sources participated in the formation of magmatic complexes of the Stalemate Ridge; (3) in the area at 170o E within the Stalemate Ridge, a large fault zone occurs, with outcrops of ultramafic rocks found only northwest of this zone and absent southeast of it; and (4) throughout the whole strike of the Stalemate Ridge, magmatic rocks that have no genetic relations to the oceanic lithosphere are sporadically widespread. [ABSTRACT FROM AUTHOR]

We have tested platinum–carbon electrodes with mixed conductivity as parts of membrane electrode assemblies of fuel cells containing structure-modifying additives with different structural elements (carbon nanotubes with extended structural elements and graphene-like materials with nearly 2D planes). Mass-transport losses of molecular oxygen transfer in these electrodes have been investigated on the basis of data on the limiting current density obtained in the potentiodynamic and potentiostatic regimes. The pressure dependences of the current density have been plotted using various conditions of measurements. Limiting factors and oxygen transport mechanisms in the tested structures and the role of introduced modifiers have been determined. [ABSTRACT FROM AUTHOR]

The article presents data on the composition and abundance of algal flora in the coastal stratified Kislo-Sladkoe Lake (the Karelian coast of the White Sea) after its flushing with seawater in autumn. The seasonal dynamics and vertical structure of the phytoplankton were monitored from March 17 to October 3, 2019. We also studied ice flora on March 17 and April 1. The largest carbon biomass of ice algae (0.79 g C/m3) dominated by Nitzschia frigida was recorded in April. The integrated biomass of phytoplankton in the water column varied from 0.01 g C/m2 in March to 5.83 g C/m2 during spring bloom in late May (when it was dominated by Chaetoceros invisibilis) and remained at the level of 0.07 to 0.29 g C/m2 until October; heterotrophic forms replaced autotrophic algae during this period. A regression analysis has shown that the structure of the phytoplankton was influenced by length of daylight, water temperature, dissolved oxygen level, depth, pH, salinity, and illuminance. [ABSTRACT FROM AUTHOR]

Abstract—The mechanism of passive (independent of recipient cells) aseptic calcification of pericardial materials fixed with gluteraldehyde, which are used for the manufacture of bioprostheses of heart valves, has been studied; in addition, the dependence of the calcification intensity on the degree of damage to the structure and microarchitectonics of their extracellular matrix has been determined. The microrelief of the surface of the inner serous layer of the pericardium of experimental and control materials has been explored by scanning electron microscopy with the determination of the degree of delamination and the intensity of micro-injuries depending on the type of preimplantation treatment. To determine the propensity to aseptic calcinosis of fixed biomaterials with an intact and damaged extracellular matrix, a study of the degree of calcifylaxis of samples during their incubation under model conditions of normocalcemia in vitro has been carried out. A direct dependence of the intensity of calcification of fixed biomaterials on the degree of damage to their extracellular matrix has been shown. [ABSTRACT FROM AUTHOR]

By means of the disk-electrode method (stationary and rotating), regularities of changes in the mass-transport properties of composite electrodes containing platinum nanoparticles on carbon black, the addition of carbon material with different shapes of structural elements (three- and pseudo-one-dimensional carbon nanotubes with different length-to-diameter ratios), and the Nafion proton-conducting polymer were studied. The transport of molecular oxygen inside a porous electrode to the platinum surface has been studied. Mechanisms for changing the mass-transport properties of structurally modified electrodes during electrochemical action are proposed. [ABSTRACT FROM AUTHOR]

We consider the tracking problem under exogenous and parametric disturbances for nonlinear single-channel plants with mathematical model representable in a triangular input–output form. Within the framework of the block approach, we develop a decomposition procedure for nonlinear feedback synthesis that provides tracking of the target signal by the output variable with given accuracy in given time. We formalize a new type of sigmoid local feedbacks in the class of smooth everywhere bounded S-shaped functions that ensure invariance with respect to uncontrolled bounded disturbances not belonging to the control space without any assumptions about their smoothness. The results of numerical simulation of our algorithms for an inverted pendulum control system are presented. [ABSTRACT FROM AUTHOR]

Peculiarities of molecular oxygen transport in platinum–carbon electrodes exhibiting mixed conductivity and containing structure-modified admixtures with structural elements of various types (short and long carbon nanotubes with extended structural elements characterized by different length/diameter ratios and graphene-like materials with practically 2D planes) are studied by the methods of a rotating disk electrode. [ABSTRACT FROM AUTHOR]

Garden berries and grapes constitute an integral part of a healthy and functional diet. Reduction of post-harvest losses can maximize the shelf life of berry fruits, increasing their market value and promoting consumption. Among current storage techniques, the use of edible films is an emerging strategy for packaging and protecting the surface of small fruits. They provide the necessary barrier for berries against adverse external biotic or abiotic factors while supporting the necessary physiological processes such as moisture and gas exchange. Carbohydrate polymers are an important component of edible films. The desired mechanical strength as well as barrier properties are achieved by combining carbohydrate polymers with other bio-based compounds, such as lipids, proteins, and functional additives. Unlike plant polysaccharides, the studies and use of microbial extracellular polysaccharides (EPSs) remain scarce, especially for films and coatings of garden berries and grapes. This review summarizes the available data for currently used (xanthan, pullulan, gellan, dextran, bacterial cellulose) and prospective microbial EPSs (levan, curdlan, kefiran, bacterial alginate). Directions in future research to achieve more widespread, cost-effective, environmentally friendly production and applications of edible microbial EPS films are discussed. [ABSTRACT FROM AUTHOR]

Our research focuses on the formation of ice crystals and evaluating the structure of preserved frozen and freeze-dried strawberries. Strawberries were frozen in two ways. One-half of strawberries were frozen at − 30 °C under conditions of convective heat exchange. The other half of strawberries were frozen under the same conditions with an additional effect on the strawberries of micro-vibrations created in the air of the freezer according to a specific program. A digital frequency synthesizer that generates 250 W/m3 electromagnetic field rectangular pulse packets in the frequency bands of 2500–5000 kHz creates micro-vibrations. The microstructure of strawberries, the number of cells that have retained their structure and firmness were determined in frozen strawberries. The strawberries retained 25–30% of the cell structure of their total number during traditional freezing, and 65–70% of the cell structure when frozen under micro-vibration. The data of the penetration and shear stress showed that the strawberries frozen under micro-vibration conditions were 10–15% stronger. Then researched strawberries were vacuum freeze-dried. The primary drying temperature was 30 + 1 °C below zero and at the secondary drying the temperature was 38–40 °C. The microstructure and firmness of strawberries were researched in dried samples also. Freeze-dried strawberries frozen under micro-vibration had small and evenly distributed capillaries and their firmness was 8–10% higher than freeze-dried strawberries frozen by the traditional method. Thus, freezing strawberries with the additional effect of micro-vibration have a positive effect on the firmness of both frozen strawberries and freeze-dried strawberries. [ABSTRACT FROM AUTHOR]

Riparian forests are known as hot spots of nitrogen cycling in landscapes. Climate warming speeds up the cycle. Here we present results from a multi-annual high temporal-frequency study of soil, stem, and ecosystem (eddy covariance) fluxes of N2O from a typical riparian forest in Europe. Hot moments (extreme events of N2O emission) lasted a quarter of the study period but contributed more than half of soil fluxes. We demonstrate that high soil emissions of N2O do not escape the ecosystem but are processed in the canopy. Rapid water content change across intermediate soil moisture was a major determinant of elevated soil emissions in spring. The freeze-thaw period is another hot moment. However, according to the eddy covariance measurements, the riparian forest is a modest source of N2O. We propose photochemical reactions and dissolution in canopy-space water as reduction mechanisms. [ABSTRACT FROM AUTHOR]

Studies of Black Sea cetaceans were carried out in September 2018 (11 days, 799 km of the survey route) and June 2019 (12 days, 1174 km of the survey route). The research vessel followed a survey route off the Caucasian coast of the Black Sea from Anapa to Adler at a distance of up to 165 km from the coast. There were 103 sightings of cetaceans (548 individuals) in 2018 and 347 sightings (1280 individuals) in 2019. Three species were recorded: common dolphin, bottlenose dolphin, and harbor porpoise; their ratios were 78.1 : 20.8 : 1.1 in 2018 and 90.1 : 7.1 : 2.8 in 2019. Common dolphins were sighted everywhere; in June, they were encountered more frequently in the coastal water area; in September, in the open sea. This was probably preconditioned by the availability of prey. Bottlenose dolphins and harbor porpoises performed short-distance seasonal migrations and preferred to remain in local coastal habitats. [ABSTRACT FROM AUTHOR]

Based on the state observer theory of dynamic plants operating under uncertainty, we propose a method for reconstructing high-order derivatives of an online signal (for example, a reference action in a tracking system). The method requires neither numerical differentiation nor the presence of an analytical description of the signal. The dynamic differentiator is constructed as a replica of the virtual canonical model with an unknown but bounded input. The use of bounded correction actions and a special structure of the differentiator permit one to reduce the outliers of the resulting estimates at the beginning of a transient compared with a linear differentiator with high-gain coefficients. By way of application, we consider the problem of tracking a spatial trajectory by the center of mass of an unmanned aerial vehicle and present simulation results. [ABSTRACT FROM AUTHOR]

The results of studies of four coastal lakes with unique hydrological and hydrochemical structure at different stages of isolation from Kandalaksha Bay of the White Sea are reported for 2012–2019. All waterbodies are characterized by a permanent or seasonal stratified structure; as a result, bacterial sulfate reduction and hydrogen sulfide accumulation, toxic for aerobic life forms, become more active under anaerobic conditions. The highest amount of hydrogen sulfide was recorded in Lake Trekhtsvetnoe, which is at the meromictic stage of isolation. [ABSTRACT FROM AUTHOR]

In this article, we report on the study of the electrochemical characteristics of the electrode material of a proton exchange membrane (PEM) fuel cell containing carbon nanotubes (CNTs) as a functional additive in the oxygen reduction reaction. The data of appraisal by the methods of scanning and transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), differential thermal analysis, cyclic and direct voltammetry on a stationary and rotating disk electrode are given. The results showed that the material has a higher electrode activity in the presence of oxygen-modified carbon nanotubes, a higher half-wave potential of oxygen electroreduction (610 and 500 mV in the presence and absence of CNTs, respectively), showed a threefold higher density of the kinetic current of oxygen reduction, has a 2.5-fold higher density of exchange current in the oxygen reaction. This can be explained by the effect of oxygen-modified CNTs on the content of surface oxide (PtO); in the presence of CNTs, the PtO content is lower. [ABSTRACT FROM AUTHOR]

Communities of macrozoobenthos in the White Sea coastal water bodies that have partially or completely lost connection with the sea as a result of postglacial land uplift, are studied. As the degree of isolation from the sea increases, stable vertical stratification with a tendency to meromixis and gradual dilution of seawater provide the conditions for the formation of an unusual composition of macrofauna and succession, from a normal or slightly depleted marine biome to a completely freshwater ecosystem. Data collected in the years 2012–2017 present the macrozoobenthos community of five marine lagoons and four meromictic lakes in comparison with the marine communities of Kislaya Inlet, which connects the two water bodies studied, and with the freshwater lakes of the Kindo Peninsula. The typology of the water bodies was carried out according to the degree of isolation, taking into account the hydrological regime and differences in fauna lists. A naturally determined change in bottom communities occurs as the degree of isolation of the water body from the sea increases. In marine lagoons, regularly flooded by tides, there is a community of Macoma balthica (L. 1758)–Pontonema vulgare (Bastian 1865) Filipjev 1916, widespread in the marine littoral. In more isolated lagoon-type water bodies with a similar set of species, Mytilus edulis L. 1758 and Mya arenaria L. 1758 make up a significant share in biomass in addition to M. balthica. The populations of the gastropod mollusk Hydrobia ulvae (Pennant 1777) are much developed here. Even at this stage, the fauna comprises more littoral eurybionts (H. ulvae, M. balthica, M. arenaria, M. edulis, Arenicola marina (L. 1758), Tubificoides benedeni (d'Udekem 1855), chironomids, etc.) and less sublittoral stenohaline forms. At the next stage, H. ulvae dominates by biomass, and the share of the chironomid Chironomus gr. salinarius and oligochaete T. benedeni increases as well. Insects and their larvae (beetles, chironomids, and other dipterans) settle in shallow areas. In meromictic lakes, where a salt aerobic layer is preserved under the pycnocline, the fauna of the mixolimnion mainly comprises insect larvae, while only a few euryhaline forms remain from the marine fauna, namely, the amphipod Gammarus duebeni Lilljeborg 1852 and the chironomid Ch. gr. salinarius. At the stage of complete isolation from the sea, conditions are anaerobic below the pycnocline and, despite the suitable salinity, there is no marine fauna. In such water bodies, the benthos is represented exclusively by freshwater forms, mainly insects and mollusks. In completely freshwater bodies, chironomids make up the majority of the biomass; each lake has its own set of species, which changes from year to year. In the fresh water of Nizhnee Ershovskoe Lake, the population of G. duebeni remains in the part of the lake closest to the sea. The species diversity decreases as the water body is isolated from the sea; the maximum number of species was found in marine lagoons near Sonostrov Island (23–34 species); in Kislo-Sladkoe Lake, 10–15 species are found per survey. In Bol'shie Khruslomeny Lake, the aerobic part of the monimolimnion has a critical salinity and the species diversity is minimal (6–10 species). The number of species increases again after a stable fresh layer appears in the water body. The quantitative characteristics of the macrobenthos change in a similar way. The maximum abundance were noted in marine lagoons; in Kislo-Sladkoe Lake, the average abundance is significantly lower. In the meromictic water bodies with a fresh mixolimnion, the maxima of abundance and biomass are observed in the upper 0.5-m water layer, while in marine lagoons the maxima are located in the depth range of 1.0–2.5 m; in addition, in less isolated water bodies, the maximum biodiversity is observed in deeper layers than in more isolated ones. This layer is characterized by the highest content of dissolved oxygen, and often by supersaturation. The benthos abundance varies greatly in freshwater bodies. [ABSTRACT FROM AUTHOR]

The challenges facing the creation of brazed joints of 12Kh18N10T (AISI 321) austenitic stainless steel with high unbrazing temperatures for extreme working conditions in aerospace appliances are considered in this study. An amorphous-nanocrystalline nickel–based foil, Ni-7Cr-4.5Si-3.5Fe-2.6B, wt.%, is used for brazing the steel. Experiments on brazing regimes with various temperatures (1070–1160 °С) and times of exposition (15–80 min) are carried out. The formation of Ni-based solid solutions with different Cr, Fe, Mn, Si, and Ti contents in the brazed seam is detected for all brazing regimes. Using Thermo-Calc software, the liquidus temperature located in a range between 1268 and 1388 °С is calculated. To verify the calculated values, the unbrazing temperature is experimentally determined for specimens, with a composition of the solid solutions, formed in the center of the brazed seam during brazing at 1160 °С/15 min, 1070 °С/15, and 1160 °С/80 min. The experimental results deviate from values computed by Thermo-Calc by no more than 54 °С. The experimental samples obtained using the 1070 °C/40 min and 1100 °C/80 min regimes demonstrate high unbrazing temperatures equal to 1303 °C and > 1330 °C, respectively, which corresponds to the calculations with an accuracy of 2.5%. Taking into account the combination of properties (strength and unbrazing temperature), brazing regimes of heating to 1070–1100 °C and an exposure time for 15–40 min can be recommended for the production of high-strength joints with high unbrazing temperatures. [ABSTRACT FROM AUTHOR]

MODY is a group of genetically and clinically heterogeneous forms of diabetes characterized by autosomal dominant inheritance and is subdivided in 13 subtypes dependent on the gene involved. The subtype MODY9 is a very rare form caused by mutations in the gene encoding the PAX4 transcription factor which is engaged in differentiation of pancreatic beta-cells. PAX4 contains two DNA-binding domains—Paired and Homeo. Expression of the human PAX4 gene is tissue-specific. The alternatively spliced mRNA variants encode for protein isoforms which differ within their N- and C-terminal regions. In this study, the transcriptional activities of the human PAX4 variants, both known and new ones, were determined. The full-length PAX4 containing intact DNA-binding domains was found to have maximal activity in transient expression system of the firefly luciferase reporter gene under control of the insulin promoter in HEK293 cells. The transcriptional activity is significantly reduced in the variants lacking eight N-terminal amino acid residues and/or variants whose Homeo domain is truncated from the C-terminus. Similar data were obtained with the glucagon promoter reporter system. The aberrant PAX4 variants were shown to retain stability and nuclear localization. [ABSTRACT FROM AUTHOR]