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Introduction: The progression of placental diseases such as preeclampsia is closely related to trophoblast dysfunction. Recent studies indicated the dysregulation of N6-methyladenosine (m6A) RNA modification in trophoblast disorders, while the function of METTL3, a methyltransferase of m6A, in trophoblasts remains to be studied.Methods: The expression of METTL3 was determined by real-time PCR and immunoblotting. METTL3 expression in trophoblast cell lines HTR-8/SVneo and JEG-3 was knocked down using shRNA. The invasion of trophoblast cells in Matrigel was determined using xCELLigence. The m6A-containing transcripts was determined by m6A-sequencing in HTR-8/SVneo cells. The myosin light chain kinase (MYLK) gene was transfected into HTR-8/SVneo cells.Results: The expression of METTL3 was downregulated in preeclamptic placentae compared to normal placentae. Knockdown of METTL3 repressed the invasion of extravillous trophoblast cells. Mechanistically, METTL3 promoted the stability of MYLK mRNA through m6A modification. Overexpression of MYLK rescued retarded cell invasion by METTL3 depletion.Discussion: Collectively, our results highlight an essential role of METTL3-MYLK axis in trophoblast invasion. [ABSTRACT FROM AUTHOR]

The superior tribological properties of bearings with low friction appear to be actualized by not a single lubrication, but the adaptive multi-mode co-lubrication in which the interface can adjust according to the friction conditions. This study attempts to reveal the friction adaptive mechanism of textures under grease lubrication. The single-stage linear groove surfaces (SLGSs) and the multi-stage bionic texture surfaces (MBTSs) were respectively designed, and MXenes lithium composite grease (MLCG) with MXenes as an additive was prepared. Compared with the non-textured surface, the friction coefficient of MBTS-1.5 is reduced by 67.6%, and the wear rate is reduced by 45.4%. The friction contact area presents an adaptive multi-mode lubrication trend from oil to grease-solid synergistic lubrication. [Display omitted] • MBTSs can help to improve the flow characteristics of grease. • MXenes and thickener could achieve the synergistic self-repairing effect. • MXenes can form a beneficial friction layer at the friction interface. • Multi-mode lubrication system has excellent adaptability and reliability. [ABSTRACT FROM AUTHOR]

[Display omitted] • A drought risk assessment framework was constructed using the random forest algorithm. • The drought vulnerability dimension was enriched by considering the impact of ecosystem resilience. • The spatial distribution pattern of drought risk under the influence of ecosystem resilience was assessed. Drought caused by global warming has a profound impact on the stability of terrestrial ecosystems and agricultural production. As one of the key indicators to measure the response of ecosystems to climate change, the spatial difference of ecosystem resilience will also affect the accuracy of regional drought risk assessment. In this study, the 12-month standardized precipitation evapotranspiration index (SPEI-12) was used to identify drought characteristics and combined with meteorological elements to characterize drought hazard. Drought vulnerability was characterized using crop and environmental sensitivity, disaster prevention, and mitigation capacity. Specifically, ecosystem resilience was also considered in assessing vulnerability. And drought exposure was investigated by considering crop sown area and population density. Based on this, a drought risk assessment framework was constructed using the random forest algorithm and applied to the Huang-Huai-Hai (HHH) Plain, China. The results showed that: (1) approximately 66.34 % of the HHH Plain had a drought hazard level above moderate; among them, southern Hebei, northern Anhui, northern Henan, and scattered small areas in Shandong were extreme high hazard areas. (2) The northeast Anhui, central and southern Shandong, and northeast Jiangsu were extreme high drought vulnerability areas, accounting for 10.34% of the total area. (3) The drought risk in the HHH Plain was low in the south and north, and high in the center. Among these, the drought risk in the border regions of Shandong and Anhui, the northeast part of Jiangsu, as well as central Henan were extreme high, accounting for 11.23%. (4) The drought risk assessment framework constructed by considering ecosystem resilience was more suitable for HHH Plain. This study result could provide scientific reference for managing water resources and preventing drought. [ABSTRACT FROM AUTHOR]

The effects of functionally gradient structure of graphene nanoplatelets (GNPs) reinforced Ni 3 Al metal matrix composites (GNMMCs) prepared by laser melting deposition on the tribological performance, as well as friction-induced vibration and noise are investigated. Results show that GNMMCs with GNPs gradient structure can improve the tribological performance and weaken the intensity of high frequency vibration and noise under the variable loadings, which are affected by the synergy effects of lubricant and gradient structure. High level of GNPs content in contact interface layer allows an easier GNPs deposition and promote the formation of smooth surface. GNMMCs with gradient hardness change has the abilities of absorbing heavy loads and resisting the deformation of contact interface. Hence, friction-induced vibration and noise is reduced. Image 1 • The gradient Ni 3 Al self-lubricating composites (GNMMCs) is prepared. • Friction and wear behavior is tested under two kinds of loading conditions. • The sources of friction-induced vibration and noise are investigated. • The inherent correlation between noise signals and worn states is discussed. [ABSTRACT FROM AUTHOR]

M50 steel is the main material used in aircraft bearings, and its friction performance will directly affect the reliability and service life of the whole bearing. Hence, this paper focuses on the tribological behavior and self-healing function of as-prepared M50 steel-based self-lubricating material covered with surface micropores filled with Sn-Ag-Cu (MMSAC). Friction results show that MMSAC exhibits the distinguished tribological behavior. Analysis indicates that this is mainly due to the lubricating film formed on the worn surface and the self-healing behavior on the worn surface of MMSAC. Sn-Ag-Cu in micropores can precipitate onto the friction surface to form the lubricating film, while the volume expansion caused by the oxidation of Sn and Cu plays an important role in filling cracks. [ABSTRACT FROM AUTHOR]

A dislocation-density-based model is selected to investigate the mechanisms of the improvement in the mechanical and tribological performance of the tribo-layer during sliding friction. Ni 3 Al matrix composites are used for validating the analysis model. The experimental results show that the existing model can be successfully applied to predict the friction and mechanical performance of the tribo-layer which is formed during the sliding contact. The thermal effect caused by the frictional heat and crack propagation have been incorporated into the model. The grain growth and the thermal effect play an important role in the improvement of the wear resistance and decrease of friction. [ABSTRACT FROM AUTHOR]

• A new drought index, i.e., the water storage deficit index was defined. • There is a large variation in the propagation time of drought in different regions. • The sensitivity of vegetation to drought is influenced by the type of vegetation. • There is a significant time lag effect of drought on vegetation. Due to climate change and human activities, drought has become one of the most complex natural disasters in the Huang-Huai-Hai River basin, China. The purpose of the current research is to analyze the response of vegetation to drought in the Huang-Huai-Hai River basin by calculating the lag time correlation coefficient between the enhanced vegetation index (EVI) and drought indices. First, the water storage deficit index (WSDI) calculated from the total water storage anomalies (TWSA) was used as the hydrological drought index. The meteorological drought index we used was the self-calibrating Palmer drought severity index (scPDSI) provided by the Climate Research Unit (CRU). Then, the relationship between hydrological and meteorological drought was obtained based on the wavelet coherent change. Finally, the response of different vegetation types to drought was analyzed based on the lag time correlation coefficient. The results showed that: the average time of hydrological drought lagged meteorological drought in the three first-level basins of the Huang-Huai-Hai River basin, respectively, was 50 days (Yellow River basin), 43 days (Huaihe River basin), and 35 days (Haihe River basin); the lag time correlation coefficient of the different time scales (1–12 months) can reflect the sensitivity of vegetation to drought in different vegetation types and regions. The forest was the least sensitive to drought in the Huang-Huai-Hai River basin, followed by cropland, while grassland was the most sensitive to drought. It was discovered that hydrological drought had a huge influence on vegetation rather than meteorological drought by comparing the maximum lag time correlation coefficients of EVI with drought indices (scPDSI and SPEI). This study stresses the importance of taking into account the effects of various types of drought on the vegetation in the Huang-Huai-Hai River basin. This will help us better understand how drought affects vegetation. [ABSTRACT FROM AUTHOR]

The wear fatigue of slewing bearings at the contact areas of raceways (AISI 4140 steel (AS)) and rollers (AISI 52100 steel) seriously reduces the service life of equipment. AS-SnAgCu-TiC composites (AS-SACT) were prepared by filling multi-solid lubricants into surface biomimetic textures of AS to improve the wear resistance. Tribological properties were tested using a block-on-ring tribometer. The materials of block and ring were AS and AISI 52100 steel, respectively. Compared with that of AS, coefficient of friction of AS-SACT was decreased by 67.93%, and wear height was reduced by 42.19%. Wear triggered the diffusion of SnAgCu from the bionic textures to worn surface. The hard phase of nano-TiC was wrapped by a cluster of multi-layer lubricants to form spherical particles, which not only converted sliding to rolling contact, but also repaired pits and furrows on worn surface. Hence, AS-SACT with self-repairing behavior had excellent properties of antifriction and wear resistance. [Display omitted] •Tribological properties of AISI 4140 steel were improved by texture and SnAgCu–TiC. •Average COF of AS-SnAgCu-TiC was 67.93% lower than that of AS (AISI 4140 steel). •Wear defects were filled with solid lubricants to produce self-repairing behavior. •Spherical particles transformed the frictional mode from sliding to rolling. •Nano-TiC particles wrapped by SnAgCu can promote wear defects to be filled. [ABSTRACT FROM AUTHOR]

The textured surface is one of the hotspots in the field of tribology research on reducing friction and wear. By calculating and optimizing the micro-texture structure, researchers designed and prepared textures with excellent tribological properties on the mechanical part surfaces. In this work, the tribological performance of 42CrMo matrix composite textured surfaces (CTSs) with different textured densities under grease lubrication was studied. The CTS was composed of 42CrMo alloys and SnAgCu-MXenes-Ti 3 C 2 (SACM). The results showed that when the textured density ρ of CTS was 36%, the friction coefficient (0.090) and wear rate (5.4 × 10−9 mm3N−1m−1) of counterpart ball could be respectively reduced by 75.7% and 38.6% compared with those of counterpart ball against the untextured sample. CTS could enhance the stability of friction system. Mxenes-Ti 3 C 2 wrapped by SnAgCu could form the lubricating layer containing sub-micron rollers on the worn surface, effectively reducing the friction and wear of samples under grease conditions. [Display omitted] • The composite textured surfaces (CTSs) were designed and prepared. • MXenes wrapped by SnAgCu could form sub-micrometer rollers in wear scar. • CTS exerted tribological enhancement function under starvation. • CTS could produce excellent synergistic effect with grease. [ABSTRACT FROM AUTHOR]

Inspired by shell surface structure, the surface textures were extracted by curve fitting method and the corresponding bionic wavy textures filled with SnAgCu-WS 2 composite solid lubricants were prepared on the surface of TC4. The coupling effect of bionic wavy textures and SnAgCu-WS 2 and the effect of variable reciprocating friction frequency on the tribological properties of TC4 were explored. The results show that bionic textures improve the precipitation efficiency of SnAgCu-WS 2 , and the sliding effect of WS 2 promotes the spreading and repairing of composite solid lubricants in the wear track, thus improving the formation quality of the lubricating film and its adaptability to the change of reciprocating frequency. [Display omitted] • Bionic textures with lubricants were used to improve tribological performance of TC4. • Bionic wavy textures improve the precipitation efficiency of SnAgCu-WS 2. • Sliding effect of WS 2 promotes spreading and repairing of lubricants in wear track. • Coupling effects improve adaptability to the change of reciprocating frequency. • The average friction coefficient of TWs-SACW02 is reduced to 0.219 at 20 N and 1 Hz. [ABSTRACT FROM AUTHOR]

Multilayer graphene (MLG) shows an attractive prospect for the demanding engineering applications. This paper reports the mechanical and tribological properties of MLG reinforced Ni 3 Al matrix composites (NMCs) under dry sliding at varying sliding speed. The hardness and elastic modulus of the NMCs are significantly influenced with MLG content. It is found that the hardness and elastic modulus of the NMCs are found to be increased by increasing MLG content up to 1.0 wt.%, while decreased when MLG content is above 1.0 wt.%. Tribological experiments suggest that MLG can dramatically improve the wear resistance and decrease the friction coefficient of the NMCs. Such marked improvement of wear resistance is attributed to the reinforcing mechanisms of MLG, such as crack deflection and pull-out, and reduction of friction coefficient is related to the formation of a tribofilm on the sliding contact surface. [ABSTRACT FROM AUTHOR]

Highlights: [•] Tribological properties of NATMs from RT to 800°C were tested. [•] Ti3SiC2–MoS2 brought about an improvement in tribological behavior of NATMs. [•] Synergetic effect of Ti3SiC2–MoS2 was key to tribological performance of NATMs. [•] NATM5 showed the best self-lubricating performance and tribological properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] Tribological properties of NMSC from RT to 800°C were tested. [•] Tribological properties of NMSC strongly depended on the addition content of WAh. [•] WAh and TiC brought about an improvement in tribological properties of NMSC. [•] NE showed the excellent tribological properties from RT to 800°C. [ABSTRACT FROM AUTHOR]

Abstract: Investigations in graphene of controlling friction and wear of Ni3Al matrix self-lubricating composites (NMSC) are needed for moving mechanical assemblies. The friction and wear behaviors of NMSC with graphene nanoplatelets (GNPs) against Si3N4 ball are tested using a constant load of 10N and a constant speed of 0.2m/s from room temperature (RT) to 600°C. Tribological test results have revealed that small amounts of GNPs in the NMSC are able to drastically reduce the friction coefficients and wear rates over the effective operating range (RT-400°C). A possible explanation for these results is that the refinement of grains accompanying the slippage of laminated sheets between GNPs could provide a source of the stress dissipation and form the GNP protective layer during sliding process, leading to the reduction of wear rates as well as the friction coefficients. It is concluded that GNPs hold great potential applications as an effective solid lubricant for moderate loads and stress, and can be easily used for the preparation of the self-lubricating composites in the future. [Copyright &y& Elsevier]

Abstract: This paper reports on preparation technique and tribological properties of multilayer graphene (MLG) reinforced TiAl matrix composites (GTMC). GTMC are successfully prepared by spark plasma sintering (SPS). Structural characterization of starting MLG and the sintered GTMC are performed using Raman spectroscopy and field emission scanning electron microscopy, which indicates that MLG homogeneously distributes in GTMC. Tribological studies suggest that MLG plays an important role in decreasing friction coefficients by a factor of 4 and wear by almost 4–9 times of magnitude. Such marked reductions are attributed to the fact that MLG easily shears and forms a conformal anti-wear protective layer on the sliding contact interfaces, thus drastically reduces the friction coefficients and wear rates of GTMC. MLG can actually act as an effective reinforcement and lubricant phase in GTMC. [Copyright &y& Elsevier]

Highlights: [•] Tribological properties of TMSC from RT to 600°C are tested. [•] ATBC brings about an improvement in tribological behavior of TMSC. [•] Synergetic effect of ATBC is key to tribological performance of TMSC. [•] TB shows the best self-lubricating performance and tribological properties. [ABSTRACT FROM AUTHOR]

Abstract: The SiCf/W–20Cu composites are prepared by spark plasma sintering (SPS) process at 1200°C for 10min under a pressure of 30MPa, using titanium nitride (TiN) coated SiC fibers (SiCf) and W–20Cu composite powders. Effects of amounts of the TiN coated SiCf on the phases, microstructure and properties of the composites are investigated. The results show that the transverse rupture strength of the 0.8wt.% TiN coated SiCf/W–20Cu composites is enhanced 50%, while an increase of 31% in the thermal conductivity is observed, if compared to the base W–20Cu alloy. When the amount of the TiN coated SiCf is less than 1.0wt.%, the SiCf/W–20Cu composites without silicon, ditungsten carbide and tungsten carbide, as well as graphite phases are obtained. The TiN coating can be effective to control the detrimental interfacial reaction between the SiCf and W–20Cu alloy based matrix. [Copyright &y& Elsevier]

Inspired by the ability of tree frog toes to regulate body fluids, this control mechanism is applied to the tooth surface of slewing bearing (AISI 4140 steel (AS)) by adopting the regular hexagonal microtexture. SnAgCu-TiC (SACT) lubricants are filled in the microtextures. Results of two-factor analysis of variance show that there is a significant interaction between the microtexture and lubricants. When the microtextures with 1000 µm side are filled with SnAgCu-4 wt% nano-TiC (AS-SACT410), coefficient of friction (COF) of sample is the lowest. Compared with AS (0.437), COF of AS-SACT410 is reduced to 0.085, decreased by 80.55%. Macroscopic anti-friction originates because SnAgCu wraps around nano-TiC to form tribofilms containing submicron rollers, achieving substantially reduced COF. [Display omitted] • Bionic texture with lubricants was used to improve the friction performance of AS. • The synergistic effect is confirmed by two-factor analysis of variance. • SnAgCu wraps nano-TiC particles to form tribofilms containing submicron rollers. • The sliding friction is converted to rolling friction by the submicron rollers. • Compared with AS (0.437), COF of AS-SACT410 is reduced to 0.085 under dry friction. [ABSTRACT FROM AUTHOR]

Dry sliding tribological tests of Ni3Al matrix self-lubricating composites (NMSC) with addition of 15wt% Ti3SiC2 are undertaken against Si3N4, Al2O3, WC-6Co at 25–800°C. The results show that the tribological properties are strongly dependent on the counterface materials. NMSC against Si3N4 shows the lower friction coefficients (0.31–0.48) and wear rates (0.34–2.1×10−5 mm3 N−1 m−1) from 25 to 800°C, while there is no clear difference in tribological performance of NMSC against Al2O3 or WC-6Co. NMSC against Si3N4 may be the optimal design for the excellently tribological performance. [ABSTRACT FROM AUTHOR]

Abstract: The effect of sliding speed and load on the friction and wear behavior of NiAl–10wt%Ti3SiC2 composites (NAT) at room temperature was investigated through determination of friction coefficients and wear rates in different conditions and analysis of morphologies and compositions of wear debris and worn surfaces of both NAT and Si3N4 ball. The results showed that the friction coefficients decreased and wear rates increased with increase in load, whereas they both decreased with increase in sliding speed. The transition in the wear mode from mild to severe wear was strongly influenced by the sliding speed and load. [Copyright &y& Elsevier]

Abstract: The dry sliding friction and wear behavior of Ti3SiC2/(WC–10Co) composites (TWCs) against GCr15 steel pair at room temperature was investigated through the determination of friction coefficient and wear rate under different conditions and the analysis of the morphologies and compositions of wear debris, worn surfaces of TWC and GCr15 steel. The friction coefficients of TWC with 3wt.% WC–10Co were in the range of 0.40–0.48, and the wear rate varied from 0.6×10−4 mm3 (Nm)−1 to 1×10−4 mm3 (Nm)−1. At the load of 10N and sliding speed of 0.353m/s, the glazes were formed on the worn surfaces of TWC. The wear mechanisms were complicated, including micro-cutting and abrasive wear of TWC, oxidation wear of GCr15 steel, as well as adhesive wear caused by the glaze flaking. [Copyright &y& Elsevier]