Investigation of the Tribological Properties of Two Different Layered Sodium Silicates Utilized as Solid Lubrication Additives in Lithium Grease

Layered sodium silicates β-Na₂Si₂O₅ and kanemite were synthesized via facile methods under mild conditions. The tribological properties of β-Na₂Si₂O₅ and kanemite utilized as additives in lithium grease were evaluated with a four-ball tester under different experimental conditions. The maximum nonseizure load value of 5.0 wt % β-Na₂Si₂O₅ grease jumped from 353 N (the base grease) to 1568 N. However, 5.0 wt % MoS₂ grease could only reach 617 N under the same conditions. The SEM and EDS results confirm that a protective film mainly composed of sodium silicates was formed on the worn surface during the friction process. The structural stability of β-Na₂Si₂O₅ and kanemite after the wear test was studied by XRD. It was found that a loss of interlamellar water causes the layer structure of kanemite to collapse during a long-duration wear test. The layered structure of β-Na₂Si₂O₅ is stable, and its tribological properties are better than those of kanemite

Aromatic Residues Regulating Electron Relay Ability of S‑Containing Amino Acids by Formations of S∴π Multicenter Three-Electron Bonds in Proteins

The ab initio calculations predict that the side chains of four aromatic amino acids (Phe, His, Tyr, and Trp residues) may promote methionine and cystine residues to participate in the protein electron hole transport by the formation of special multicenter, three-electron bonds (S∴π) between the S-atoms and the aromatic rings. The formations of S∴π bonds can efficiently lower the local ionization energies, which drive the electron hole moving to the close side chains of S-containing and aromatic residues in proteins. Additionally, the proper binding energies for the S∴π bonds imply that the self-movement of proteins can dissociate these three-electron bonds and promote electron hole relay

Potent Relay Stations for Electron Transfer in Proteins: π∴π Three-Electron Bonds

The paper is of relevance to weak interactions between two parallel rings of close aromatic amino acids, which may participate in electron hole transport in proteins. The ab initio calculations reveal the possibility for the formation of the π∴π three-electron bond between two parallel aromatic rings, facilitating electron hole transport in proteins as the effective relay stations. The relay functionality of these special structures comes from their lower local ionization energies and proper binding energies, which vary with the different aromatic amino acids and the arrangements of the same aromatic rings according to the local microsurroundings in proteins

DataSheet1_Mechanical upside of PAO mainstream fixations: co-simulation based on early postoperative gait characteristics of DDH patients.ZIP

Purpose: To investigate the early postoperative gait characteristics of patients who underwent periacetabular osteotomy (PAO) and predict the biomechanical performance of two commonly used PAO fixation methods: iliac screw (IS) and transverse screw (TS).Methods: A total of 12 patients with unilateral developmental dysplasia of the hip (DDH) (mean age 27.81 ± 4.64 years, 42% male) that were scheduled to undergo PAO surgery were included in this study. Their preoperative CT images and pre- and postoperative gait data were used to create subject-specific musculoskeletal models and complete the inverse dynamics analysis (IDA). Two patients with typical gait characteristics were selected using clustering analysis, and their IDA data were incorporated into finite element (FE) models of IS and TS fixations. Failure simulation was performed by applying iterative steps with increasing gait load to predict yield load. Stress results and yield loads were calculated for each FE model at different phases of the gait cycle.Results: Postoperative gait showed improvement compared to preoperative gait but remained inferior to that of healthy individuals. Postoperative gait was characterized by a lower hip range of motion, lower peri-ilium muscle forces, particularly in the abductors, and a sharper initial peak and flatter second peak of hip joint reaction force (HRF). Finite element analysis (FEA) showed a trend of increasing stress during the second–fourth phases of the gait cycle, with lower stress levels in other phases. At high-stress gait phases, the mean stress of maximum p¯100 differed significantly between IS and TS (p Conclusion: PAO early postoperative gait shows a normalized trend, but abnormalities persist. IS and TS are both capable of resisting mechanical strain failure, with no significant mechanical advantage found for transverse screw fixation during PAO early postoperative gait. Additionally, it is important to note that the TS may have a higher risk of cyclic fatigue failure due to the localized greater stress concentration. Furthermore, the most medial screw is crucial for pelvic stability.</p

A New Type of Electron Relay Station in Proteins: Three-Piece S:Π∴S↔S∴Π:S Resonance Structure

A type of relay station for electron transfer in proteins, three-piece five-electron bonding, is introduced in this paper, which is also first proposed here. The ab initio calculations predict the formation of S:Π∴S↔S∴Π:S resonance binding with an aromatic ring located in the middle of two sulfur-containing groups, which may participate in electron-hole transport in proteins. These special structures can lower the local ionization energies to capture electron holes efficiently and may be easily formed and broken because of their proper binding energies. In addition, the UV–vis spectra provide evidence of the formations of the three-piece five-electron binding. The cooperation of three adjacent pieces may be advantage to promote electron transfer a longer distance

Two Aromatic Rings Coupled a Sulfur-Containing Group to Favor Protein Electron Transfer by Instantaneous Formations of π∴S:π↔π:S∴π or π∴π:S↔π:π∴S Five-Electron Bindings

The cooperative interactions among two aromatic rings with a S-containing group are described, which may participate in electron hole transport in proteins. Ab initio calculations reveal the possibility for the formations of the π∴S:π↔π:S∴π and π∴π:S↔π:π∴S five-electron bindings in the corresponding microsurrounding structures in proteins, both facilitating electron hole transport as efficient relay stations. The relay functionality of these two special structures comes from their low local ionization energies and proper binding energies, which varies with the different aromatic amino acids, S-containing residues, and the arrangements of the same aromatic rings according to the local microsurroundings in proteins

Water Promoting Electron Hole Transport between Tyrosine and Cysteine in Proteins via a Special Mechanism: Double Proton Coupled Electron Transfer

The proton/electron transfer reactions between cysteine residue (Cys) and tyrosinyl radical (Tyr^•) are an important step for many enzyme-catalyzed processes. On the basis of the statistical analysis of protein data bank, we designed three representative models to explore the possible proton/electron transfer mechanisms from Cys to Tyr^• in proteins. Our ab initio calculations on simplified models and quantum mechanical/molecular mechanical (QM/MM) calculations on real protein environment reveal that the direct electron transfer between Cys and Tyr^• is difficult to occur, but an inserted water molecule can greatly promote the proton/electron transfer reactions by a double-proton-coupled electron transfer (dPCET) mechanism. The inserted H₂O plays two assistant roles in these reactions. The first one is to bridge the side chains of Tyr^• and Cys via two hydrogen bonds, which act as the proton pathway, and the other one is to enhance the electron overlap between the lone-pair orbital of sulfur atom and the π-orbital of phenol moiety and to function as electron transfer pathway. This water-mediated dPCET mechanism may offer great help to understand the detailed electron transfer processes between Tyr and Cys residues in proteins, such as the electron transfer from Cys₄₃₉ to Tyr₇₃₀^• in the class I ribonucleotide reductase

Superior Selective CO₂ Adsorption and Separation over N₂ and CH₄ of Porous Carbon Nitride Nanosheets: Insights from GCMC and DFT Simulations

Development of high-performance materials for the capture and separation of CO2 from the gas mixture is significant to alleviate carbon emission and mitigate the greenhouse effect. In this work, a novel structure of C9N7 slit was developed to explore its CO2 adsorption capacity and selectivity using Grand Canonical Monte Carlo (GCMC) and Density Functional Theory (DFT) calculations. Among varying slit widths, C9N7 with the slit width of 0.7 nm exhibited remarkable CO2 uptake with superior CO2/N2 and CO2/CH4 selectivity. At 1 bar and 298 K, a maximum CO2 adsorption capacity can be obtained as high as 7.06 mmol/g, and the selectivity of CO2/N2 and CO2/CH4 was 41.43 and 18.67, respectively. In the presence of H2O, the CO2 uptake of C9N7 slit decreased slightly as the water content increased, showing better water tolerance. Furthermore, the underlying mechanism of highly selective CO2 adsorption and separation on the C9N7 surface was revealed. The closer the adsorption distance, the stronger the interaction energy between the gas molecule and the C9N7 surface. The strong interaction between the C9N7 nanosheet and the CO2 molecule contributes to its impressive CO2 uptake and selectivity performance, suggesting that the C9N7 slit could be a promising candidate for CO2 capture and separation