Boric acid is a weak acid and has been used as a lubrication additive because of its special structure. In this study, we report that boric acid could achieve a robust superlubricity (μ < 0.01) as an ...additive in polyethylene glycol (PEG) aqueous solution at the Si3N4/SiO2 interfaces. The superlow and steady friction coefficient of approximately 0.004–0.006 could be achieved with boric acid under neutral conditions (pH of approximately 6.4), which is different from the acidic conditions leading to superlubricity. The influence of various factors, including boric acid concentration, sliding speed, applied load, PEG molecular weight, and the volume of lubricant on the superlubricity, were investigated. The results reveal that the PEG aqueous solution with the boric acid additive could achieve superlubricity under a wide range of conditions. The surface composition analysis shows that the synergy effect between boric acid and PEG provides sufficient H+ ions to realize the running-in process. Moreover, a composite tribochemical film composed of silica and ammonia-containing compounds were formed on the ball surface, contributing to the superlubricity. The film thickness calculation shows that superlubricity was achieved in a mixed lubrication region, and therefore, the superlubricity state was dominated by both the composite tribochemical film formed via the tribochemical reaction on the contact surfaces and the hydrodynamic lubricating film between the contact surfaces. Such a liquid superlubricity achieved under neutral conditions is of importance for both scientific understanding and engineering applications.
The liquid-superlubricity state has rarely been studied under an average contact pressure exceeding 300 MPa at the macroscale. In this work, a robust macroscale liquid-superlubricity state ...(μ ≈ 0.005) under an extreme pressure of 600 MPa was reported, which was enabled by the combination of graphene-oxide (GO) nanosheets with an ionic liquid (IL) between the frictional pairs of Si3N4/sapphire. The analysis indicated that a composite boundary layer (formed by IL) at the interface contributed to the excellent antiwear performance, thereby providing a lubricating condition under extreme pressure. Notably, GO nanosheets were directly observed to adsorb on worn surfaces, thereby proving the transformation of the shear interface from Si3N4/sapphire into GO/GO nanosheets. The extreme pressure property and extremely low shear stress between the interlayers of GO nanosheets contributed to the achievement of superlubricity. Therefore, the synergistic effect between GO nanosheets and IL played a dominant role in achieving liquid-superlubricity under extreme pressure at the macroscale. This study provided a novel method to achieve liquid-superlubricity under extreme conditions—by the synergistic effect of 2D materials and liquid molecules—accelerating the achievement of liquid-superlubricity in industrial applications.
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With the rapid development of the computer and sensor field, inertial sensor data have been widely used in human activity recognition. At present, most relevant studies divide human activities into ...basic actions and transitional actions, in which basic actions are classified by unified features, while transitional actions usually use context information to determine the category. For the existing single method that cannot well realize human activity recognition, this paper proposes a human activity classification and recognition model based on smartphone inertial sensor data. The model fully considers the feature differences of different properties of actions, uses a fixed sliding window to segment the human activity data of inertial sensors with different attributes and, finally, extracts the features and recognizes them on different classifiers. The experimental results show that dynamic and transitional actions could obtain the best recognition performance on support vector machines, while static actions could obtain better classification effects on ensemble classifiers; as for feature selection, the frequency-domain feature used in dynamic action had a high recognition rate, up to 99.35%. When time-domain features were used for static and transitional actions, higher recognition rates were obtained, 98.40% and 91.98%, respectively.
The de Gennes extrapolation length is a direction dependent measure of the spatial evolution of the pairing gap near the boundary of a superconductor and thus provides a viable means to probe its ...symmetry. It is expected to be infinite and isotropic for plain s-wave pairing, and finite and anisotropic for d-wave. Here, we synthesize single-layer FeSe films on SrTiO3(001) (STO) substrates by molecular beam epitaxy and measure the de Gennes extrapolation length by scanning tunneling microscopy/spectroscopy. We find a 40% reduction of the superconducting gap near specular 110Fe edges, yielding an extrapolation length of 8.0 nm. However, near specular 010Fe edges, the extrapolation length is nearly infinite. These findings are consistent with a phase changing pairing with 2-fold symmetry, indicating d-wave superconductivity. This is further supported by the presence of in-gap states near the specular 110Fe edges, but not the 010Fe edges. This work provides direct experimental evidence for d-wave superconductivity in single-layer FeSe/STO and demonstrates quasiparticle scattering at boundaries to be a viable phase sensitive probe of pairing symmetry in Fe-based superconductors.
Non-methane hydrocarbon compounds (NMHCs) paly the leading role in the formation of ozone (O3) and secondary organic aerosols (SOA), which can affect severely global climate change, air quality, and ...human health. NMHCs pollution became a meaningful and crucial research topic in Beijing. From the Eleventh Five-Year Plan to the present, volatile organic compounds (VOCs) have received widespread and great attention in environmental governance, especially the NMHCs. Due to successive stages to control air pollution, the concentration of NMHCs has dropped gradually nearly three years in Beijing. In this study, 54 NMHCs was measured from March 1 to March 30 in 2021. The mean concentration of NMHCs was 33.54 ± 16.69 ppbv during the whole observation period. The mean concentration of NMHCs was 40.69 ± 17.09 ppbv during the haze days, which was greater than non-haze days (26.68 ± 12.75 ppbv). Alkenes, alkanes, aromatics, and acetylene accounted for 34.22%, 33.02%, 32.60%, and 016% in total ozone formation potential (OFP), respectively. Aromatics accounted for 96.61% in total secondary organic aerosol potential (SOAP). All the sources of NMHCs (except for fuel evaporation) made non-negligible contribution to O3 formation. Solvent usage and gasoline exhaust contributed 52.19%, which were the largest contributor to SOAP. Therefore, Beijing should focus on the NMHCs pollution caused by the local emission (especially solvent usage and gasoline exhaust) to control and solve secondary pollution further in this study.
•Characteristics and sources of NMHCs are studied in typical secondary transformation.•NMHCs sources are identified by positive matrix factorization (PMF) model.•The mixed source of solvent usage and gasoline exhaust is the greatest contributors to OFP and SOAP.•Beijing should focus on the NMHCs pollution caused by the local emission.
Sputum HMGB1 levels were significantly higher in patients with severe asthma than in those with mild-to-moderate asthma, and HMGB1 levels increased with the degree of airflow limitation. ...HMGB1 ...could be an independent risk factor affecting the predicted value of FEV1%. Additionally, HMGB1 overexpression was more pronounced in patients with moderate-to-severe and severe asthma than in healthy subjects, suggesting that high HMGB1 levels correlated positively with disease severity. ...elevated HMGB1 levels may be a potential biomarker of asthma severity. ...our results suggest that HMGB1 could be a potential biomarker of asthma severity. Funding This work was supported by grants from the National Key Research and Development Program of China (Nos. 2022YFF0710800 and 2018YFC1313600), Major International (Regional) Joint Research Project of China (No. 81820108001), National Natural Science Foundation of China (Nos. 81670029 and 82000038), Jiangsu Key Principal Investigator of Medicine (No. 3.Manti, SLeonardi, SParisi, GFDe Vivo, DSalpietro, ASpinuzza, A. High mobility group box 1: biomarker of inhaled corticosteroid treatment response in children with moderate-severe asthma.
Abstract
m
5
C is one of the longest-known RNA modifications, however, its developmental dynamics, functions, and evolution in mRNAs remain largely unknown. Here, we generate quantitative mRNA m
5
C ...maps at different stages of development in 6 vertebrate and invertebrate species and find convergent and unexpected massive methylation of maternal mRNAs mediated by NSUN2 and NSUN6. Using
Drosophila
as a model, we reveal that embryos lacking maternal mRNA m
5
C undergo cell cycle delays and fail to timely initiate maternal-to-zygotic transition, implying the functional importance of maternal mRNA m
5
C. From invertebrates to the lineage leading to humans, two waves of m
5
C regulatory innovations are observed: higher animals gain cis-directed NSUN2-mediated m
5
C sites at the 5' end of the mRNAs, accompanied by the emergence of more structured 5'UTR regions; humans gain thousands of trans-directed NSUN6-mediated m
5
C sites enriched in genes regulating the mitotic cell cycle. Collectively, our studies highlight the existence and regulatory innovations of a mechanism of early embryonic development and provide key resources for elucidating the role of mRNA m
5
C in biology and disease.
Recently, persulfate-based advanced oxidation processes (persulfate-AOPs) are booming rapidly due to their promising potential in treating refractory contaminants. As a type of popular ...two-dimensional material, layered double hydroxides (LDHs) are widely used in energy conversion, medicine, environment remediation and other fields for the advantages of high specific surface area (SSA), good tunability, biocompatibility and facile fabrication. These excellent physicochemical characteristics may enable LDH-based materials to be promising catalysts in persulfate-AOPs. In this work, we make a summary of LDHs and their composites in persulfate-AOPs from different aspects. Firstly, we introduce different structure and important properties of LDH-based materials briefly. Secondly, various LDH-based materials are classified according to the type of foreign materials (metal or carbonaceous materials, mainly). Latterly, we discuss the mechanisms of persulfate activation (including radical pathway and nonradical pathway) by these catalysts in detail, which involve (i) bimetallic synergism for radical generation, (ii) the role of carbonaceous materials in radical generation, (iii) singlet oxygen (1O2) production and several special nonradical mechanisms. In addition, the catalytic performance of LDH-based catalysts for contaminants are also summarized. Finally, challenges and future prospects of LDH-based composites in environmental remediation are proposed. We expect this review could bring new insights for the development of LDH-based catalyst and exploration of reaction mechanism.
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•Systematic introduction of different persulfate activation mechanisms by LDH-based catalysts.•Unique “intercalation effect” of LDH-based catalysts have been discussed.•Discussion on the effect of tailoring the morphology of LDHs for improving catalytic performance.
When a metal makes contact with a band insulator, charge transfer occurs across the interface leading to band bending and a Schottky barrier with rectifying behavior. The nature of metal–Mott ...insulator junctions, however, is still debated due to challenges in experimental probes of such vertical heterojunctions with buried interfaces. Here, we grow lateral polymorphic heterostructures of single-layer metallic 1H and Mott insulating 1T NbSe2 by molecular beam epitaxy. We find a one-dimensional metallic channel along the interface due to the appearance of quasiparticle states with an intensity decay following 1/x 2, indicating an impenetrable barrier. Near the interface, the Mott gap exhibits a strong spatial dependence arising from the difference in lattice constants between the two phases, consistent with our density functional theory calculations. These results provide clear experimental evidence for an impenetrable barrier at the metal–Mott insulator junction and the high tunability of a Mott insulator by strain.
To provide high-precision timing services of the BeiDou Navigation Satellite System (BDS), this work performs a detailed investigation of integrated BDS-3 and BDS-2 real-time precise point ...positioning (PPP) time transfer with the ultrarapid products. Compared with the final precise clock products, the average standard deviation (STD) of estimated BDS-3 MEO/IGSO satellites is 0.1 ns, while the corresponding value of BDS-2 is 0.2 ns. The precision of real-time BDS-3/2 PPP time transfer can achieve better than 0.5 ns. The phenomenon of reconvergence and abnormal jumps in receiver clock series can be effectively reduced because of the evenly distributed MEO satellites.
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