The effect of the cell voltage and external conditions on the characteristics of protonic ceramic fuel cells is theoretically elucidated taking into account the non-uniform distribution of charge ...carriers along and across the oxide membrane with proton and hole conductivity. The interdependence of this distribution and gas phase composition along the cathode and anode gas channels is a fundamental feature of fuel cells based on proton-conducting oxides. To address this issue, a novel computational method is proposed to determine the current densities and effective characteristics of the fuel cells operating on wet hydrogen and oxygen. It is shown that the effective proton conductivity can either increase or decrease with increasing the cell voltage depending on the fuel and oxidant humidity. In contrast, the effective hole conductivity drastically increases with increasing the cell voltage for any realistic gas phase compositions, thereby reducing the proton transport number and faradaic efficiency. It is demonstrated that the fuel cell parameters (partial conductivities, transport numbers, EMF,
etc.
) can be noticeably different under open circuit and operating conditions. The established relationships between the cell voltage, parameters of the inlet gas phases and output characteristics can be used as a guide to enhance the performance of protonic ceramic fuel cells.
The effects of the cell voltage and external conditions on the characteristics of protonic ceramic fuel cell are theoretically elucidated.
Silver nanoparticles (NPs), widely used in the manufacture of various types of consumer products and for medical applications, belong to novel types of materials that pose potential risks to human ...health. The potential negative effects of the influence of these NPs on reproduction are insufficiently researched. A quantitative assessment of the transfer of metallic silver nanoparticles through the placenta and breast milk was carried out during an in vivo experiment. We used 34.9 ± 14.8 nm in size silver NPs that were stabilized by low-molecularweight polyvinylpyrrolidone and labeled with the (110m)Ag radioactive isotope using thermal neutron irradiation in a nuclear reactor. (110m)Ag-labeled NPs preparations were administered intragastrically via a gavage needle to pregnant (20(th) day of gestation) or lactating (14-16th day of lactation) female rats at a dose of 1.69-2.21 mg/kg of body weight upon conversion into silver. The accumulation of NPs in rat fetuses and infant rats consuming their mother's breast milk was evaluated using a low-background semiconductor gamma-ray spectrometer 24 and 48 hours following labeling, respectively. In all cases, we observed a penetration of the (110m)Ag-labeled NPs through the placenta and ther entry into the mother's milk in amounts exceeding by 100-1,000 times the sensitivity of the utilized analytical method. The average level of accumulation of NPs in fetuses was 0.085-0.147% of the administered dose, which was comparable to the accumulation of the label in the liver, blood, and muscle carcass of adult animals and exceeded the penetration of NPs across the hematoencephalic barrier into the brain of females by a factor of 10-100. In lactating females, the total accumulation of (110m)Ag-labeled NPs into the milk exceeded 1.94 ± 0.29% of the administered dose over a 48 h period of lactation; not less than 25% of this amount was absorbed into the gastrointestinal tract of infant rats. Thus, this was the first time experimental evidence of the transfer of NPs from mother to offspring through the placenta and breast milk was obtained.
•We studied the patterns of formation of residual stresses in copper oxide nanoparticles.•We studied the relationship of the residual stresses and the magnetization of nanoparticles.•We detect the ...magnetic behavior of CuO nanoparticles similar to other ferromagnetic nanoparticle systems.
The laws governing the formation of residual stresses in copper oxide nanoparticles in the process of their direct plasma-chemical synthesis in a low-pressure arc discharge plasma are studied. Correlation dependences of the residual stress and the magnetization of nanoparticles on the pressure of the gas mixture of 10% O2 + 90% Ar are presented. The problems associated with the bifurcation of the magnetization curves during cooling in zero (ZFC) and non-zero (FC) magnetic field, non-equilibrium behavior, relaxation of magnetization and magnetic viscosity of the obtained CuO nanoparticles are discussed.
The article discusses management techniques of reforming the management system of the housing and community amenities of the metropolis, associated with the use of innovative technologies. The idea ...is substantiated that the “blockchain” technology can significantly increase the quality of public services: reduce data processing time and decrease the number of requests for the necessary information. The purpose of the article is to substantiate the possibility of bringing the provision of housing and community amenities to a fundamentally new level, to increase public confidence in the work of state bodies. The authors pay the main attention in the work to the analysis of the openness and transparency of new technologies, as well as preservation guarantees of personal data in the provision of public services. The authors propose possible directions for the application and development of “blockchain” technology in the public sector, as well as a mechanism for the formation of special automated “smart rules” that can be used for the public sector. The authors’ proposal is to create normative legal or administrative acts not just in a machine-readable format, but as “smart rules” is of fundamental importance. The introduction of such an order significantly optimizes the automation of management, because new legislation will not require automation – it will initially be published in the form of directly performed by means of automation of data processing, which do not require human participation.
An approximate mathematical description of the processes of homogeneous nucleation and homogeneous evaporation (explosive boiling) of a metal target (Al) under the influence of ns laser radiation is ...proposed in the framework of the hydrodynamic model. Within the continuum approach, a multi-phase, multi-front hydrodynamic model and a computational algorithm are designed to simulate nanosecond laser ablation of the metal targets immersed in gaseous media. The proposed approach is intended for modeling and detailed analysis of the mechanisms of heterogeneous and homogeneous evaporation and their interaction with each other. It is shown that the proposed model and computational algorithm allow modeling of interrelated mechanisms of heterogeneous and homogeneous evaporation of metals, manifested in the form of pulsating explosive boiling. Modeling has shown that explosive evaporation in metals is due to the presence of a near-surface temperature maximum. It has been established that in nanosecond pulsed laser ablation, such exposure regimes can be implemented in which phase explosion is the main mechanism of material removal.
Magnetic iron nanoparticles (MNPs) encapsulated in a carbon shells and containing sulfo groups on the surface (Fe@C-SO
3
H) were synthesized. The aggregative stability of aqueous suspensions of the ...Fe@C-SO
3
H nanoparticles was studied in solutions of bovine serum albumin and calcium chloride and in phosphate-buffered saline, which simulate blood plasma. It is shown that the Fe@C-SO
3
H particles practically do not aggregate in the phosphate buffer saline for a long time (several days). On the contrary, MNPs encapsulated in a protein shells using ultrasonic treatment form aggregates up to 110–120 nm in size under these conditions. Suspensions of the Fe@C-SO
3
H particles are stable in aqueous solutions of calcium chloride in the range of the solid phase concentration between 0.05 and 0.10 g L
−1
. The results obtained indicate the possibility of using the functionalized Fe@C-SO
3
H nanoparticles
in vitro
experiments in biological media.
Humic acids (HAs) make up to 30–50% of the soil organic matter, which is the main reservoir of organic carbon in the biosphere. The common isolation protocol for HAs implies alkaline extraction from ...soils followed by acidification of the extract with HCl to pH 2. International Humic Substances Society (IHSS) recommends isolation of HAs in oxygen-free atmosphere (e.g., under nitrogen or inert gas purging) to prevent oxidative transformations of HAs during the extraction process. In the Russian school of soil science, extraction is usually conducted without the use of nitrogen. In the present work, we compared the physicochemical properties of HAs isolated from A1 horizons of soddy-podzolic soil (Retisol) and chernozem (Chernozem) by 0.1 M NaOH in the presence and absence of oxygen. The soils used in this study represented zonal types of southern taiga and steppe, respectively, and differed markedly with respect to humus formation conditions. The yield of humic substances (C
org
content in the extracts), their elemental composition, functional groups content, molecular-weight distributions (gel filtration on Sephadex G-75), paramagnetic properties, and absorption spectra in the visible, UV, and IR regions were studied. For both soils, no statistically significant differences were found in the quantitative yield, molecular weight distribution, absorption spectra in the visible, UV and IR regions between HAs isolated by alkaline extraction in the presence and absence of oxygen. At the same time, for the HAs extracted from the Retisol soil in the presence of oxygen, higher O : C ratios, higher contents of quinone and carboxyl groups, and significantly higher content of free radicals were observed. This was revealed with the use of elemental analysis, potentiometric titration,
1
H and
13
C NMR spectroscopy, and electron paramagnetic resonance spectroscopy. For the Chernozem HAs, these differences were not observed. The obtained results suggest that partial oxidation of the soil organic matter components takes place during alkaline extraction from the Retisol in the presence of oxygen. In the Chernozem, humification process is apparently accompanied by significant oxidative transformation of organic residues, so the presence of molecular oxygen does not cause further oxidation of HAs under alkaline conditions. Our results indicate that, for the isolation of HAs from the mineral horizons of Chernozems, the use of oxygen-free atmosphere is optional. In the case of Retisols, the use of oxygen-free atmosphere is desirable, especially if it is intended to study the reactions of HA oxidation upon, for example, enzymatic catalysis.
As the burnup increases, the requirements of nuclear and radiation safety for spent nuclear fuel (SNF) at the subsequent stages of operation grow. The analysis and estimation of the required cooling ...time of the spent fuel assemblies (SFAs) of the VVER-1200 reactor for transportation in various types of transport containers (TUK-13 and TUK-141O) are performed. The estimates are based on the analysis of residual energy release and gamma-radiation intensity of SNF depending on the cooling time for different burnups. The data on the absorbed dose rate of neutron and gamma radiation from SNF after 4 and 5 yr of cooling are presented.
We present information on ozone concentration in the surface air layer in the second half of 2020. Data were obtained at 13 stations located in different regions of Russia. We estimated the excess ...over hygienic standards of the Russian Federation, both in the second half of the year and throughout 2020. It is shown that the daily average maximum permissible concentration of ozone is regularly exceeded at all stations. There are cases of exceeding the one-time maximum permissible concentration.
The problem of the use of burnable absorbers (BAs) in VVER-type reactors is considered to reduce the volume of "liquid" regulation of excess reactivity margin for fuel burnup. As such, natural ...gadolinium and europium are considered in the form of Gd2O3 and Eu2O3, placed in integrated form with uranium fuel in fuel rods. The ratio of fuel rods with BAs and conventional fuel elements is 1:6. Variants of both the homogeneous location of the BAs and heterogeneous, including for the mixed use of these BAs were considered. The strong influence of the BAs composition and their location in the fuel elements on the dependence of the multiplication factor on fuel burnup is shown.
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