Abstract
In the present study, a method for the synthesis of gelatin-stabilized copper oxide nanoparticles was developed. Synthesis was carried out by direct chemical precipitation. Copper sulfate, ...chloride, and acetate were used as precursors for the copper oxide synthesis. Gelatin was used as a stabilizer. It was found that the formation of monophase copper oxide II only occurred when copper acetate was used as a precursor. Our results showed that particles of the smallest diameter are formed in an aqueous medium (18 ± 6 nm), and those of th largest diameter—in an isobutanol medium (370 ± 131 nm). According to the photon correlation spectroscopy data, copper oxide nanoparticles synthesized in an aqueous medium were highly stable and had a monomodal size distribution with an average hydrodynamic radius of 61 nm. The study of the pH effect on the colloidal stability of copper oxide nanoparticles showed that the sample was stable in the pH range of 6.8 to 11.98. A possible mechanism for the pH influence on the stability of copper oxide nanoparticles is described. The effect of the ionic strength of the solution on the stability of the CuO nanoparticles sol was also studied, and the results showed that Ca
2+
ions had the greatest effect on the sample stability. IR spectroscopy showed that the interaction of CuO nanoparticles with gelatin occurred through the hydroxyl group. It was found that CuO nanoparticles stabilized with gelatin have a fungicidal activity at concentration equivalent 2.5 · 10
−3
mol/L and as a material for food nanopackaging can provide an increase in the shelf life of products on the example of strawberries and tomatoes. We investigated the possibility of using methylcellulose films modified with CuO nanoparticles for packaging and storage of hard cheese “Holland”. The distribution of CuO nanoparticles in the methylcellulose film was uniform. We found that methylcellulose films modified with CuO nanoparticles inhibited the growth and development of QMAFAM, coliforms, yeast and mold in experimental cheese sa mples. Our research has shown that during the cheese storage in thermostat at 35 ± 1 °C for 7 days, CuO nanoparticles migrated to the product from the film. Nevertheless, it is worth noting that the maximum change in the concentration of copper in the experimental samples was only 0.12 µg/mg, which is not a toxic concentration. In general, the small value of migration of CuO nanoparticles confirms the high stability of the developed preparation. Our results indicated that the CuO nanoparticles stabilized with gelatin have a high potential for use in food packaging – both as an independent nanofilm and as part of other packaging materials.
We present a metagenomic study of Lake Baikal (East Siberia). Two samples obtained from the water column under the ice cover (5 and 20 m deep) in March 2016 have been deep sequenced and the reads ...assembled to generate metagenome-assembled genomes (MAGs) that are representative of the microbes living in this special environment. Compared with freshwater bodies studied around the world, Lake Baikal had an unusually high fraction of
Other groups, such as
and
, were in proportions similar to those found in other lakes. The genomes (and probably cells) tended to be small, presumably reflecting the extremely oligotrophic and cold prevalent conditions. Baikal microbes are novel lineages recruiting very little from other water bodies and are distantly related to other freshwater microbes. Despite their novelty, they showed the closest relationship to genomes discovered by similar approaches from other freshwater lakes and reservoirs. Some of them were particularly similar to MAGs from the Baltic Sea, which, although it is brackish, connected to the ocean, and much more eutrophic, has similar climatological conditions. Many of the microbes contained rhodopsin genes, indicating that, in spite of the decreased light penetration allowed by the thick ice/snow cover, photoheterotrophy could be widespread in the water column, either because enough light penetrates or because the microbes are already adapted to the summer ice-less conditions. We have found a freshwater SAR11 subtype I/II representative showing striking synteny with
strains, as well as a phage infecting the widespread freshwater bacterium
Despite the increasing number of metagenomic studies on different freshwater bodies, there is still a missing component in oligotrophic cold lakes suffering from long seasonal frozen cycles. Here, we describe microbial genomes from metagenomic assemblies that appear in the upper water column of Lake Baikal, the largest and deepest freshwater body on Earth. This lake is frozen from January to May, which generates conditions that include an inverted temperature gradient (colder up), decrease in light penetration due to ice, and, especially, snow cover, and oligotrophic conditions more similar to the open-ocean and high-altitude lakes than to other freshwater or brackish systems. As could be expected, most reconstructed genomes are novel lineages distantly related to others in cold environments, like the Baltic Sea and other freshwater lakes. Among them, there was a broad set of streamlined microbes with small genomes/intergenic spacers, including a new nonmarine
-like (subtype I/II) genome.
In this work, selenium nanoparticles (Se NPs) stabilized with cocamidopropyl betaine were synthesized for the first time. It was observed that Se NPs synthesized in excess of selenic acid had a ...negative charge with ζ-potential of -21.86 mV, and in excess of cocamidopropyl betaine-a positive charge with ξ = + 22.71 mV. The resulting Se NPs with positive and negative charges had a spherical shape with an average size of about 20-30 nm and 40-50 nm, respectively. According to the data of TEM, HAADF-TEM using EDS, IR spectroscopy and quantum chemical modeling, positively charged selenium nanoparticles have a cocamidopropylbetaine shell while the potential- forming layer of negatively charged selenium nanoparticles is formed by SeO
ions. The influence of various ions on the sol stability of Se NPs showed that SO
and PO
ions had an effect on the positive Se NPs, and Ba
and Fe
ions had an effect on negative Se NPs, which corresponded with the Schulze-Hardy rule. The mechanism of coagulating action of various ions on positive and negative Se NPs was also presented. Also, influence of the active acidity of the medium on the stability of Se NPs solutions was investigated. Positive and negative sols of Se NPs had high levels of stability in the considered range of active acidity of the medium in the range of 1.21-11.98. Stability of synthesized Se NPs stability has been confirmed in real system (liquid soap). An experiment with the addition of Se NPs stabilized with cocamidopropyl betaine to liquid soap showed that the particles of dispersed phases retain their initial distributions, which revealed the stability of synthesized Se NPs.
The сrack growth characteristics are investigated in situ in a scanning electron microscope column during the tension of the welded joints of two-phase (γ + δ) and single-phase (γ) 05Kh22AG16N8M ...steel containing 0.36 and 0.52 wt % N, respectively. A crack in the steel with 0.36% N and its welded joint is shown to form and develop at a low load and strain due to the existence of the σ phase in the steel structure and δ ferrite in the welded joint.
This paper presents the compressor blade algorithm for predicting the defect influence on the characteristics of the stage, axial compressor or GTU as a whole. The developed model is based on the use ...of Bezier curves, with the control point coordinates calculated using the main geometric parameters of the airfoil, which provides highly precise geometry of both the airfoil and the blade as a whole. The paper shows some results of verification of the developed method and the selected numerical model parameters, as well as the analysis of the defect influence on the airfoil flow conditions in order to demonstrate the capabilities of the algorithm. The main results of the study were summarized and recommendations for further research were developed.
The crack growth characteristics are investigated in situ in a scanning electron microscope column during the tension of nonmagnetic 04Kh18AG20 steel specimens with a overequilibrium nitrogen content ...(0.98 wt % N) and various vanadium contents. The character of crack nucleation and propagation in steel after quenching from 1200°С and after subsequent aging at 650°С for 5 h is shown to be the same. The critical shear crack size at the maximum load is 300 μm in vanadium-free 04Kh18AG20 steel and 120 μm in vanadium-bearing 04Kh18AG20F steel. Corrosion-resistant nickel and vanadium-free austenitic 04Kh18AG20 steel (0.98 wt % N) after quenching from 1200°C is recommended for heavy-duty nonmagnetic structures.
The composition of bacterial communities in Lake Baikal in different hydrological periods and at different depths (down to 1515 m) has been analyzed using pyrosequencing of the 16S rRNA gene V3 ...variable region. Most of the resulting 34 562 reads of the Bacteria domain have clustered into 1693 operational taxonomic units (OTUs) classified with the phyla Proteobacteria, Actinobacteria, Chloroflexi, Bacteroidetes, Firmicutes, Acidobacteria and Cyanobacteria. It has been found that their composition at the family level and relative contributions to bacterial communities distributed over the water column vary depending on hydrological period. The number of OTUs and the parameters of taxonomic richness (ACE, Chao1 indices) and diversity (Shannon and inverse Simpson index) reach the highest values in water layers. The composition of bacterial communities in these layers remains relatively constant, whereas that in surface layers differs between hydrological seasons. The dynamics of physicochemical conditions over the water column and their relative constancy in deep layers are decisive factors in shaping the pattern of bacterial communities in Lake Baikal.
In this article, we detailed description of changes in the taxonomic composition and quantitative ratio of different groups of microorganisms along the Lake Baikal water column.
Graphical Abstract Figure.
In this article, we detailed description of changes in the taxonomic composition and quantitative ratio of different groups of microorganisms along the Lake Baikal water column.
A method based on machine learning is proposed for assessing the condition of a gas turbine system for transporting natural gas. The initial data are archived gas-dynamic parameters recorded by the ...automatic control system. The initial data set is created by determining the power from the change in enthalpy of the natural gas before and beyond the pump. The software is written in Python. The Sci-kit library is used for the machine learning models. The quality of prediction is assessed in terms of the mean absolute error (%). The quality of prediction of the machine learning models is assessed with different parameter sets and sample sizes. Recommendations are made regarding the use of the models.