ABSTRACT
Plain bearings, renowned for their versatility and simplicity, are extensively utilized in engineering design across various industries involving moving parts. Lubrication is vital to the functioning of these bearings, yet their usage is inhibited under dynamic load conditions, or at elevated or reduced temperatures due to this dependency on lubrication. This study introduces an innovative method to significantly mitigate friction and wear in plain bearings operating without lubrication. The plain bearings were constructed from steel-bronze pairs, where the steel shafts were alloyed with bismuth oxide via short-pulse laser treatment. MnO2 was utilized as a carrier to incorporate the bismuth oxide into the surface layers of the steel. Insights from transmission electron microscopy and X-ray photoelectron spectroscopy revealed a highly non-equilibrium state of matter, unattainable through conventional engineering methods. The tribological performance of the modified steel disks was assessed via a block-on-ring sliding test, demonstrating superior wear and friction performance without lubrication, as well as an ultra-low coefficient of friction. Remarkably, the modified friction pairs remained functional after 200 km of linear sliding at a load of 250 N (12.5 MPa) and a sliding speed of 9 m/s. To substantiate the technique's viability, we tested the performance of an internal combustion engine turbocharger fitted with a modified steel shaft. The turbocharger's performance validated the long-term effectiveness of the steel-bronze coupling operating without lubrication at 75,000 rpm. The simplicity and resilience of this technique for modifying steel-bronze pairs offer a ground-breaking and promising approach for a wide range of applications.
ABSTRACT
Equiatomic medium-entropy alloy (MEA) FeNiCr-B4C (0, 1, and 3 wt.% B4C) coatings were deposited onto an AISI 1040 steel substrate using pulsed laser cladding. Based on an SEM microstructural analysis, it was found that the cross-sections of all the obtained specimens were characterized by an average coating thickness of 400 ± 20 µm, a sufficiently narrow (100 ± 20 µm) "coating-substrate" transition zone, and the presence of a small number of defects, including cracks and pores. An XRD analysis showed that the formed coatings consisted of a single face-centered cubic (FCC) γ-phase and the space group Fm-3m, regardless of the B4C content. However, additional TEM analysis of the FeNiCr coating with 3 wt.% B4C revealed a two-phase FCC structure consisting of grains (FCC-1 phase, Fm-3m) up to 1 µm in size and banded interlayers (FCC-2 phase, Fm-3m) between the grains. The grains were clean with a low density of dislocations. Raman spectroscopy confirmed the presence of B4C carbides inside the FeNiCr (1 and 3 wt.% B4C) coatings, as evidenced by detected peaks corresponding to amorphous carbon and peaks indicating the stretching of C-B-C chains. The mechanical characterization of the FeNiCr-B4C coatings specified that additions of 1 and 3 wt.% B4C resulted in a notable increase in microhardness of 16% and 38%, respectively, with a slight decrease in ductility of 4% and 10%, respectively, compared to the B4C-free FeNiCr coating. Thus, the B4C addition can be considered a promising method for strengthening laser-cladded MEA FeNiCr-B4C coatings.
ABSTRACT
The communication reports a new stereoselective method for the synthesis of a natural acetylenic alcohol, lembehyne B. The key stage of the process uses new cross-cyclomagnesiation reaction of aliphatic and oxygenated 1,2-dienes with Grignard reagents in the presence of a catalytic amount of Cp2TiCl2. A study of the cytotoxic properties of lembehyne B on tumor cell lines using flow cytometry demonstrated that this is a selective inducer of early apoptosis of the Jurkat, HL-60 and K562 cell cultures and hypodiploid (sub-G1) sub-population inducer in cell cycle studies for all cell lines used.
Subject(s)
Alcohols/pharmacology , Alkynes/pharmacology , Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Fatty Alcohols/pharmacology , Alcohols/chemical synthesis , Alcohols/chemistry , Alkynes/chemical synthesis , Alkynes/chemistry , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Cell Cycle/drug effects , Cell Proliferation/drug effects , Cell Survival/drug effects , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Fatty Alcohols/chemical synthesis , Fatty Alcohols/chemistry , Humans , Molecular Structure , Structure-Activity Relationship , Tumor Cells, CulturedABSTRACT
Two approaches to stereoselective synthesis of steroid 5Z,9Z-dienoic acids were developed, the first one being based on the cross-cyclomagnesiation of 2-(hepta-5,6-dien-1-yloxy)tetrahydro-2H-pyran and 1,2-diene cholesterol derivatives on treatment with EtMgBr catalyzed by Cp2TiCl2, while the other involving the synthesis of esters of hydroxy steroids with (5Z,9Z)-tetradeca-5,9-dienedioic acid, prepared in two steps using homo-cyclomagnesiation of 2-(hepta-5,6-dien-1-yloxy)tetrahydro-2H-pyran as the key step. High inhibitory activity of the synthesized acids against human topoisomerase I (hTop1) was found.
Subject(s)
DNA Topoisomerases, Type I/chemistry , Steroids , Topoisomerase I Inhibitors , Humans , Steroids/chemical synthesis , Steroids/chemistry , Topoisomerase I Inhibitors/chemical synthesis , Topoisomerase I Inhibitors/chemistryABSTRACT
(5Z,9Z)-11-Phenylundeca-5,9-dienoic acid was stereoselectively synthesized, based on original cross-cyclomagnesiation of 2-(hepta-5,6-dien-1-yloxy)tetrahydro-2H-pyran and buta-2,3-dien-1-ylbenzene with EtMgBr in the presence of the Cp2TiCl2 catalyst giving 2,5-dialkylydenemagnesacyclopentane in 86% yield. The acid hydrolysis of the product and Jones oxidation of the resulting 2-{[(5Z,9Z)-11-phenylundeca-5,9-dien-1-yl]oxy}tetrahydro-2Ð-pyran afforded (5Z,9Z)-11-phenylundeca-5,9-dienoic acid in an overall yield of 75%. A high inhibitory activity of the synthesized acid with respect to human topoisomerase I (hTop1) and II (hTop2α) was detected. Resorting to the data of molecular docking, a mechanism of inhibition was proposed.
Subject(s)
DNA-Binding Proteins/antagonists & inhibitors , Drug Design , Fatty Acids, Unsaturated/chemical synthesis , Fatty Acids, Unsaturated/pharmacology , Topoisomerase I Inhibitors/chemical synthesis , Topoisomerase I Inhibitors/pharmacology , Topoisomerase II Inhibitors/chemical synthesis , Topoisomerase II Inhibitors/pharmacology , Antigens, Neoplasm/chemistry , Antigens, Neoplasm/metabolism , Binding Sites , Catalytic Domain , DNA Topoisomerases, Type I/chemistry , DNA Topoisomerases, Type I/metabolism , DNA Topoisomerases, Type II/chemistry , DNA Topoisomerases, Type II/metabolism , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/metabolism , Fatty Acids, Unsaturated/metabolism , Humans , Molecular Docking Simulation , Protein Binding , Protein Conformation , Structure-Activity Relationship , Topoisomerase I Inhibitors/metabolism , Topoisomerase II Inhibitors/metabolismABSTRACT
(5Z,9Z)-11-Phenylundeca-5,9-dienoic acid was stereoselectively synthesized, based on original cross-cyclomagnesiation of 2-(hepta-5,6-dien-1-yloxy)tetrahydro-2H-pyran and buta-2,3-dien-1-ylbenzene with EtMgBr in the presence of Cp2TiCl2 catalyst giving 2,5-dialkylidenemagnesacyclopentane in 86% yield. The acid hydrolysis of the product and the Jones oxidation of the resulting 2-{[(5Z,9Z)-11-phenylundeca-5,9-dien-1-yl]oxy}tetrahydro-2Ð-pyran afforded (5Z,9Z)-11-phenylundeca-5,9-dienoic acid in an overall yield of 75%. A high inhibitory activity of the synthesized acid with respect to human topoisomerase I (hTop1) and II (hTop2α) was determined.
Subject(s)
DNA Topoisomerases, Type I/metabolism , DNA-Binding Proteins/antagonists & inhibitors , Fatty Acids, Unsaturated/chemical synthesis , Fatty Acids, Unsaturated/pharmacology , Topoisomerase I Inhibitors/chemical synthesis , Topoisomerase I Inhibitors/pharmacology , Antigens, Neoplasm/genetics , Antigens, Neoplasm/metabolism , Computer Simulation , DNA Topoisomerases, Type II/genetics , DNA Topoisomerases, Type II/metabolism , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Fatty Acids, Unsaturated/chemistry , Gene Expression Regulation, Enzymologic , Humans , Models, Chemical , Models, Molecular , Molecular Structure , Topoisomerase I Inhibitors/chemistryABSTRACT
An original, effective approach to the synthesis of natural and synthetic 5Z,9Z-dienoic acids in high yields (61-67%) and with high selectivity (>98%) was developed. The approach is based on the use of the new intermolecular catalytic cross cyclomagnesiation of terminal aliphatic and oxygenated 1,2-dienes upon treatment with Grignard reagents in the presence of the Cp2TiCl2 catalyst. High activity of (5Z,9Z)-5,9-eicosadienoic acid as a human topoisomerase I inhibitor at concentrations above 0.1 µM was elucidated.
