Development of the technology of stowing the developed space during mining

An analysis of the world experience in the development of potash deposits shows that the main problems arising during their development are a high level of mineral losses, an increased risk of flooding of mine workings as a result of water-proof layer discontinuance and the development of emergency water inflows in the mined-out spaces. Reduction of potash ore losses can be achieved by using a long-pillar mining system, but this method is limited by the peculiarities of the geological structure of the potash deposits and the need to preserve the continuity of the water-proof layer during its underworking. The safety of underworking of the water-proof layer can be improved by using the stowing of the developed longwall space. However, the question of the influence of the stowing on the height of the zone of water supply cracks development remains little-studied. The world experience of stowing the developed spaces in the development of layers with long pillars is analyzed and the technology of placing the stowing masses, which can solve these problems, is proposed. The considered technology and the proposed solutions are supported by laboratory tests of stowing materials and mathematical modeling of deformation zones in the overlying rocks

NANOSTRUCTURES (Cu,Zn)/h-BN FOR HETEROGENEOUS CATALYSIS

(Cu,Zn)/h-BN heterogeneous nanostructures were successfully synthesized by wet chem-istry reaction. Metal nanopartciles, 10-20 nm in dimension, were homogeneously distributed over the BN support. Nanocatalysts showed high catalytic activity in CO oxidation reaction.Работа выполнена при финансовой поддержке Российского Научного Фонда (соглашение № 20-79-10286)

Immobilization of Platelet-Rich Plasma onto COOH Plasma-Coated PCL Nanofibers Boost Viability and Proliferation of Human Mesenchymal Stem Cells

The scaffolds made of polycaprolactone (PCL) are actively employed in different areas of biology and medicine, especially in tissue engineering. However, the usage of unmodified PCL is significantly restricted by the hydrophobicity of its surface, due to the fact that its inert surface hinders the adhesion of cells and the cell interactions on PCL surface. In this work, the surface of PCL nanofibers is modified by Ar/CO2/C2H4 plasma depositing active COOH groups in the amount of 0.57 at % that were later used for the immobilization of platelet-rich plasma (PRP). The modification of PCL nanofibers significantly enhances the viability and proliferation (by hundred times) of human mesenchymal stem cells, and decreases apoptotic cell death to a normal level. According to X-ray photoelectron spectroscopy (XPS), after immobilization of PRP, up to 10.7 at % of nitrogen was incorporated into the nanofibers surface confirming the grafting of proteins. Active proliferation and sustaining the cell viability on nanofibers with immobilized PRP led to an average number of cells of 258+-12.9 and 364+-34.5 for nanofibers with ionic and covalent bonding of PRP, respectively. Hence, our new method for the modification of PCL nanofibers with PRP opens new possibilities for its application in tissue engineering

PT/H-BN NANOSTRUCTURES DEVELOPMENT FOR HETEROGENEOUS CATALYSIS

Pt/h-BN hybrid nanostructures were successfully synthesized by the impregnation method. Pt nanopartciles, 3-10 nm in size, were homogeneously distributed on over the BN support. Nanocatalysts showed high catalytic activity in CO oxidation, full conversion was achieved at 184 °С.Работа выполнена при финансовой поддержке Российского научного фонда (проект № 20-79-10286)

Different concepts for creating antibacterial yet biocompatible surfaces: Adding bactericidal element, grafting therapeutic agent through COOH plasma polymer and their combination

Antibacterial coatings have become a rapidly developing field of research, strongly stimulated by the increasing urgency of identifying alternatives to the traditional administration of antibiotics. Such coatings can be deposited onto implants and other medical devices and prevent the inflammations caused by hospital-acquired infections. Nevertheless, the design of antibacterial yet biocompatible and bioactive surfaces is a challenge that biological community has faced for many years but the "materials of dream" have not yet been developed. In this work, the biocompatible yet antibacterial multi-layered films were prepared by a combination of magnetron sputtering (TiCaPCON film), ion implantation (Ag-doped TiCaPCON film), plasma polymerization (COOH layer), and the final immobilization of gentamicin (GM) and heparin (Hepa) molecules. The layer chemistry was thoroughly investigated by means of FTIR and X-ray photoelectron spectroscopies. It was found that the immobilization of therapeutic components occurs throughout the entire thickness of the plasma-deposited COOH layer. The influence of each type of bactericide (Ag+ ions, GM, and Hepa) on antibacterial activity and cell proliferation was analyzed. Our films were cytocompatible and demonstrated superior bactericidal efficiency toward antibioticresistant bacterial E. coli K261 strain. Increased toxicity while using the combination of Ag nanoparticles and COOH plasma polymer is discussed

Hollow spherical and nanosheet-base BN nanoparticles as perspective additives to oil lubricants: Correlation between large-scale friction behavior and in situ TEM compression testing

In the present study we utilized h-BN nanoparticles (NPs) with different morphologies (hollow NPs with smooth surface (H-BNNPs), solid NPs with “pompon”-like or petalled structure (P-BNNPs), and globular NPs formed by numerous thin h-BN nanosheets (N-BNNPs)) as additives to PAO6 oil. Two sliding 100Cr6 surfaces were tested in the presence of PAO6+BNNP lubricants with 0.1% and 0.01% of BNNPs. The positive effect of BNNP additives increased along the row P-BNNPs → H-BNNPs → N-BNNPs. Utilization of N-BNNPs permitted to decrease noticeably the friction coefficient from 0.1 to 0.06 and reduce significantly the wear rate. In situ mechanical TEM tests were also performed to visualize and correlate the mechanical properties of individual h-BN NPs to their large-scale friction behavior.</p

Catalytic properties of the framework-structured zirconium-containing phosphates in ethanol conversion

Aliphatic alcohols C1–C4 can serve as raw material for the production of essential organic products, such as olefins, aldehydes, ketones and ethers. For the development of catalysts of alcohols’ conversion, the authors considered two families of framework phosphate compounds with significant chemical, thermal and phase stability: NaZr2(PO4)3 (NZP/NASICON) and Sc2(WO4)3 (SW). Variation in the composition of zirconium-containing NZP- and SW-complex phosphates allows one to vary the number and strength of Lewis acid centers and incorporate oxidative-reducing centers (such as d-transition metals) into the structure. The phosphates M0.5+xNixZr2 − x(PO4)3 (where M are Mn and Ca) were studied in the reactions of ethanol conversion. From the results of complex investigation, the compounds with M–Mn (x = 0, 0.3 and 0.5) were crystallized in the SW-type (monoclinic symmetry), while the phosphates with M–Ca (x = 0, 0.2 and 0.4) were characterized as the NZP-structured compounds (trigonal symmetry). The surface areas and pore volumes of synthesized catalysts varied, with different compositions, from 14 to 32 m2/g and 0.03 to 0.12 mL/g, respectively. From the catalytic experiments, the main direction of conversion on all the studied catalysts was ethanol dehydrogenization with acetaldehyde formation. The other conversion products—diethyl ether and ethylene—were produced with small yields. Based on the results obtained, the NZP-sample Ca0.5Zr2(PO4)3 can be considered as a selective catalyst for producing acetaldehyde at 400 °C with a yield of 55% from its theoretical amount. © 2021, The Author(s), under exclusive licence to Springer Nature B.V

Microwave response of two-dimensional electron rings

We report microwave absorption studies on rings containing two-dimensional electrons. The absorption is measured on single rings with different widths using an optical luminescence technique. The dispersion of the plasmon modes has been determined in the presence of a perpendicular magnetic field. The transformation of two-dimensional plasmons in the disk geometry into plasmons with one-dimensional character in a narrow ring is addressed. Experimental data are compared with theoretical estimates based on a self-consistent solution of the Poisson and hydrodynamic equations