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As ionic liquids (ILs) continue to be prepared, there is a growing need to develop theoretical methods for predicting the properties of ILs, such as gas solubility. In this work, different strategies were employed to obtain the solubility of CO2 and N2, where a conductor-like screening model for real solvents (COSMO-RS) was used as the basis. First, experimental data on the solubility of CO2 and N2 in ILs were collected. Then, the solubility of CO2 and N2 in ILs was predicted using COSMO-RS based on the structures of cations, anions, and gases. To further improve the performance of COSMO-RS, two options were used, i.e., the polynomial expression to correct the COSMO-RS results and the combination of COSMO-RS and machine learning algorithms (eXtreme Gradient Boosting, XGBoost) to develop a hybrid model. The results show that the COSMO-RS with correction can significantly improve the prediction of CO2 solubility, and the corresponding average absolute relative deviation (AARD) is decreased from 43.4% to 11.9%. In contrast, such an option cannot improve that of the N2 dataset. Instead, the results obtained from coupling machine learning algorithms with the COSMO-RS model agree well with the experimental results, with an AARD of 0.94% for the solubility of CO2 and an average absolute deviation (AAD) of 0.15% for the solubility of N2. [ABSTRACT FROM AUTHOR]

In this study, a porous structure for a porous liquid storage medium is generated, and the homogenization theory based on displacement boundary conditions is used to predict the effective mechanical properties. The relationship between the porous material's macroscopic mechanical properties and microstructure is next analyzed. In order to establish the relationship between the microstructure of porous materials and their macroscopic mechanical properties, assuming that the pores grow along the z direction, a method is proposed to generate 3D open-cell porous materials based on six design parameters (i.e., the number of pores, porosity, irregularity of pore distribution, the randomness of pore growth in the x and y directions, and randomness of pore size). Since the porosity of oil-bearing materials ranges from 20 to 30%, the porosity of the RVE (Representative Volume Element) was kept under control at about 25%, and the effect of the six design factors on the mechanical properties of the RVE was investigated. Utilizing SLA 3D printing technology, specimens were produced, and compression tests were used to show how useful the results of the numerical analysis were. The results demonstrated that after the number of RVE pores reaches 9, the numerical results have good repeatability. The irregularity of the initial pore distribution has little effect on the effective mechanical properties of the RVE. At the same time, the increase in the randomness of pore growth and the randomness of pore size increases the degree of weakening of the mechanical properties in the z-direction, while reducing the degree of weakening in the x and y directions, but the latter has a smaller impact. Furthermore, there is a superimposition effect of design parameters on the RVE. [ABSTRACT FROM AUTHOR]

In this study, a porous structure for a porous liquid storage medium is generated, and the homogenization theory based on displacement boundary conditions is used to predict the effective mechanical properties. The relationship between the porous material's macroscopic mechanical properties and microstructure is next analyzed. In order to establish the relationship between the microstructure of porous materials and their macroscopic mechanical properties, assuming that the pores grow along the z direction, a method is proposed to generate 3D open-cell porous materials based on six design parameters (i.e., the number of pores, porosity, irregularity of pore distribution, the randomness of pore growth in the x and y directions, and randomness of pore size). Since the porosity of oil-bearing materials ranges from 20 to 30%, the porosity of the RVE (Representative Volume Element) was kept under control at about 25%, and the effect of the six design factors on the mechanical properties of the RVE was investigated. Utilizing SLA 3D printing technology, specimens were produced, and compression tests were used to show how useful the results of the numerical analysis were. The results demonstrated that after the number of RVE pores reaches 9, the numerical results have good repeatability. The irregularity of the initial pore distribution has little effect on the effective mechanical properties of the RVE. At the same time, the increase in the randomness of pore growth and the randomness of pore size increases the degree of weakening of the mechanical properties in the z-direction, while reducing the degree of weakening in the x and y directions, but the latter has a smaller impact. Furthermore, there is a superimposition effect of design parameters on the RVE. [ABSTRACT FROM AUTHOR]

The carbon brush/collector ring device of the hydro--generator unit often encounter problems such as overheating and sparking due to the contact problem of the friction interface. Ionic liquids have excellent lubricating properties under current--carrying conditions without destroying the electrical continuity between the contact surfaces, it can improve the safety and reliability of the unit' s operation. To further explore the adaptability, reliability and related mechanism of ionic liquids as lubricants for carbon brush/collector ring assemblies, three types of ionic liquids, including imidazoles, quaternary phosphines, and functionalized ionic liquids, were selected in the experiment, and the tribological performance under current-carrying friction conditions were evaluated. The results show that functionalized ionic liquids have the best lubricating performance among the three types of ionic liquids, which can reduce the friction coefficient and contact resistance to the greatest extent, making the interface contact more stable. The length of the alkyl side chain of imidazole ionic liquids strongly affects the lubricity of the current--carrying interface, and imidazole ionic liquids with longer alkyl side chains have better tribological properties. The current-carrying and lubricating properties of ionic liquids under current-carrying friction conditions are related to the properties of the lubricant and the double-layer protective composite film formed on the wear surface, and the functionalized ionic liquids with special functionalities are more easily adsorbed on the surface of carbon brushes to form strong lubricating film. [ABSTRACT FROM AUTHOR]

Cu nanowires and a nanoporous Ag matrix were fabricated through directional solidification and selective dissolution of Ag–Cu eutectic alloys. Ag-39.9at.%Cu eutectic alloys were directionally solidified at growth rates of 14, 25, and 34 μm/s at a temperature gradient of 10 K/cm. The Cu phase in the Ag matrix gradually changed from lamellar to fibrous with an increase in the growth rate. The Ag matrix phase was selectively dissolved, and Cu nanowires of 300–600 nm in diameter and tens of microns in length were prepared in 0.1 M borate buffer with a pH of 9.18 at a constant potential of 0.7 V (vs. SCE). The nanoporous Ag matrix was fabricated through selective dissolution of Cu fiber phase in 0.1 M acetate buffer with a pH of 6.0 at a constant potential of 0.5 V (vs. SCE). The diameter of Ag pores decreased with increasing growth rate. The diameter and depth of Ag pores increased when corrosion time was extended. The depth of the pores was 30 μm after 12 h. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to propose a wheel/rail mixed lubrication model to study the water lubrication behavior of wheel/rail contact interface. Design/methodology/approach: The numerical simulation method is applied in this paper. A deterministic mixed lubrication model considering surface roughness and transient state is established. The quasi-system numerical and finite difference method are used for numerical solution. The model is verified by comparing with the experimental data in the literature under the same conditions. Findings: Under wet conditions, the change of train speed will change the lubrication state of the wheel/rail contact interface. With an increasing speed, the average film thickness and the film thickness ratio increase, while the adhesion coefficient, the contact load ratio and the contact area ratio decrease. When the creep ratio increases from 0% to 0.5%, the wheel/rail adhesion coefficient and subsurface stress increase sharply. With the increase of axle load, the average film thickness decreases and the adhesion coefficient increases. Practical implications: This paper aims to improve the mixed lubrication theory by analyzing the characteristics of wheel/rail friction and lubrication, so as to provide some guidance and theory for train driving behavior. Originality/value: Using the deterministic model, the lubrication state of the wheel/rail contact interface affected by various external factors and the adhesion behavior of wheel/rail progressive process from boundary lubrication to mixed lubrication are studied. [ABSTRACT FROM AUTHOR]

Due to the trade‐off between purity and flux, the development of high‐purity, high‐flux oil–water separation materials is still an arduous challenge. Herein, to achieve emulsion separation with high purity and high permeability, fluorinated graphene/poly(vinyl alcohol) aerogel (FGPA) with strong honeycomb was obtained via a facile freeze‐drying method, and the separation mechanism was investigated via computational fluid dynamics (CFDs) simulation. The as‐prepared FGPA exhibited superhydrophobicity‐superoleophobicity and cyclic compression stability. Under the complex pore and superhydrophobicity, FGPA could separate water‐in‐oil emulsions with droplet sizes several times smaller than their own aperture only under gravity with ultrahigh flux (3255 L m−2 h−1) and ultrahigh purity (99.9%). Also, the separation process as visualized using simulations revealed that the vortex accelerates the demulsification behavior and promotes the gathering of water droplets rebounding on the superhydrophobic surface, so that the water droplets are intercepted. Therefore, FGPA has broad practical application potential in high‐flux and high‐purity oil–water emulsion separation. [ABSTRACT FROM AUTHOR]

In this study, the wear failure behaviour of coated self-lubricating spherical plain bearings under different working conditions in the light-load and low-frequency range was studied using a swing wear life tester. The commercial GE17ES bearing was the main research object, and the wear state of the bearing was monitored in real time using torque and temperature rise signals. Furthermore, a scanning electron microscope and an energy dispersive X-ray spectroscope were adopted to analyse the wear failure mechanism of bearings. The results indicated that the friction torque and temperature rise signal changes were mainly divided into three stages, and the characteristics of similar changes could be maintained under different working conditions. Furthermore, at the end of the bearing life, the torque and temperature rise had abrupt changes almost at the same time, which indicated the occurrence of bearing failure. In general, the wear failure mechanisms of bearings included abrasive wear and adhesive wear. Moreover, fatigue wear and oxidation wear were under some conditions. The torque and temperature rise comprehensively reflected the service state of coated self-lubricating spherical plain bearings, which could be used as a physical criterion for determining bearing failure. These results had a strong prospect of engineering application, and were expected to provide a reference for determining the failure behaviour of multi-type coated self-lubricating spherical plain bearings in the future, and provided theoretical support for establishing relevant test standards. [ABSTRACT FROM AUTHOR]

Exploring a rapid, reliable, and practical means to detect blockages and leakages in liquid pipelines and accurately locate their positions is of great importance in practical engineering applications. Here, we report a bubble motion-based triboelectric sensor (BM-TES) for detecting and locating the blockages and leaks inside a plastic tube. This simple-designed, environment-friendly, non-damaging sensor is composed of several ring-shaped Cu electrodes distributed on a polytetrafluoroethylene tube. The self-powered movement of the bubble under the action of buoyancy makes the inner wall of the tube change from the original solid-liquid phase to the gas-solid-liquid phase, which results in a short-term contact and separation between the liquid and the wall. Based on the fractional triboelectric effect of the liquid-solid contact, an obvious real-time stable voltage peak will be generated where the detection bubble passes. The obvious peaks of the open-circuit voltage with respect to time correspond with the electrode distribution. Then, the peaks can be utilized as a robust and sensitive indicator for detecting blockage and leakage, as the number of obvious peaks of the open-circuit voltage is directly related to the blockage and leakage location. The blockage and leakage in a fluid tube were successfully detected using the BM-TES with an accuracy of 10 cm. In addition, the BE-TES was able to detect the water flow velocity in the pipe. The experimental results showed that BM-TES can provide a new strategy and method for liquid tube monitoring and has great potential application value in related fields. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) has affected numerous elderly individuals worldwide. Panax notoginseng has been shown to ameliorate AD symptoms, and notoginsenoside R2 is a key saponin identified in this plant. Purpose: In the current study, we aimed to explore whether notoginsenoside R2 could improve the prognosis of AD. Methods: Herein, primary rat cortical neurons were isolated and they were treated with amyloid beta-peptide (A β) 25–35 oligomers. Cellular apoptosis was examined via flow cytometry and Western blotting. miR-27a and SOX8 mRNA expression levels were quantified by quantitative reverse transcription-polymerase chain reaction. Furthermore, the interaction between miR-27a and SOX8 was investigated by utilizing a dual-luciferase reporter assay. Finally, an AD mouse model was established to validate the in vitro findings. Results: Notoginsenoside R2 alleviated A β 25-35-triggered neuronal apoptosis and inflammation. During this process, miR-27a expression was decreased by notoginsenoside R2, and miR-27a negatively modulated SOX8 expression. Furthermore, activation of SOX8 upregulated β -catenin expression, thus suppressing apoptosis and neuroinflammation. Conclusions: Our animal experiments revealed that notoginsenoside R2 enhanced the cognitive function of AD mice and inhibited neuronal apoptosis. Notoginsenoside R2 ameliorated AD symptoms by reducing neuronal apoptosis and inflammation, thus suggesting a novel direction for AD pharmacotherapy. [ABSTRACT FROM AUTHOR]

In this paper, the contact characteristics of the carbon brush/slip ring of the hydrogenerator under the eccentric vibration of the rotor are studied. The influence of spring parameters on the contact loss of the carbon brush/slip ring was studied by establishing the motion model of the carbon brush/slip ring for theoretical calculation and fitting the motion trajectory curve with MATLAB software. Studies have shown that the loss of contact is mainly related to the spring damping coefficient and the precompression. By optimizing these two parameters, the contact stability of the carbon brush on the ring surface of the slip ring can be improved. It provides a theoretical reference for the design and optimization of the parameters of the carbon brush/slip ring spring. [ABSTRACT FROM AUTHOR]

Three‐dimensional (3D) printing of all‐aromatic polyimides (PIs) is attracting extensive attention due to the advantages of excellent comprehensive performances and complex structures. It still remains challenges because of some drawbacks, such as poor solubility and infusibility, and the environmental unfriendly preparation. Here, polyamide acid salt (PAAS) hydrogels were prepared by the reaction of polyamide acid (PAA) with organic amines in water. PAAS hydrogels had remarkable rheological properties, which made it applied in direct ink writing 3D printing. The printed objects were finally converted into high‐performances PI objects with prominent mechanical properties and thermal stability. Not only so, the advantages also include simple preparation, less organic solvent, low thermal imidization temperature (250°C), controllable macrostructure and porous microstructure, and the present 3D printed PI by PAAS was expected to significantly promote the application potentials. In this study, thermal conductivity (100°C) of the PI objects after structure design and 3D printing was reduced from 0.102 W m−1 K−1 to 0.061 W m−1 K−1, and density was reduced from 0.4562 g cm−3 to 0.2731 g cm−3. [ABSTRACT FROM AUTHOR]

For liquid–porous material interactions (LPMI), three variational principles are developed in Biot's theory of porous materials in association with Darcy's Law. First one takes solid acceleration, and fluid velocity, acceleration, pressure with time derivative as five variables, while second and third, respectively, have three and two variables when Darcy's Law used as variational constraint reducing variables. These principles provide a means to derive approximate solutions and finite-element (FE) models for LPMI. Each LPMI element includes fluid and solid together with it being no longer necessary to distinguish fluid domain from solid. Examples illustrate applications to establish FE model for numerical solutions of LPMI. Solution of a one-dimensional problem reveals that LPMI behaves a coupled-frequency separation measured by a defined-coupling factor. Dynamic response explores coupled-dynamic absorber mechanism in LPMI system, from which it is found that the external force at fluid does not contribute to fluid response but fully absorbed by solid local resonance if the force frequency equals the solid natural frequency; while in the reverse case when the force frequency equals the fluid one, the force at solid does not produce the solid response but fully absorbed by fluid local resonance. New findings with defined LPMI coupling factor provide guidelines for designing LPMI system with expected dynamic behaviour meeting engineering requirements. [ABSTRACT FROM AUTHOR]

Based on the energy flow theory of nonlinear dynamical system, the stabilities, bifurcations, possible periodical/chaotic motions of nonlinear water-lubricated bearing-shaft coupled systems are investigated in this paper. It is revealed that the energy flow characteristics around the equlibrium point of system behaving in the three types with different friction-paramters. (a) Energy flow matrix has two negative and one positive energy flow factors, constructing an attractive local zero-energy flow surface, in which free vibrations by initial disturbances show damped modulated oscillations with the system tending its equlibrium state, while forced vibrations by external forces show stable oscillations. (b) Energy flow matrix has one negative and two positive energy flow factors, spaning a divergence local zero-energy flow surface, so that the both free and forced vibrations are divergence oscillations with the system being unstable. (c) Energy flow matrix has a zero-energy flow factor and two opposite factors, which constructes a local zero-energy flow surface dividing the local phase space into stable, unstable and central subspace, and the simulation shows friction self-induced unstable vibrations for both free and forced cases. For a set of friction parameters, the system behaves a periodical oscillation, where the bearing motion tends zero and the shaft motion reaches a stable limit circle in phase space with the instant energy flow tending a constant and the time averaged one tending zero. Numerical simulations have not found any possible chaotic motions of the system. It is discovered that the damping matrices of cases (a), (b) and (c) respectively have positive, negative and zero diagonal elements, resulting in the different dynamic behavour of system, which gives a giderline to design the water-lubricated bearing unit with expected performance by adjusting the friction parameters for applications. [ABSTRACT FROM AUTHOR]

For liquid–porous material interactions (LPMI), three variational principles are developed in Biot's theory of porous materials in association with Darcy's Law. First one takes solid acceleration, and fluid velocity, acceleration, pressure with time derivative as five variables, while second and third, respectively, have three and two variables when Darcy's Law used as variational constraint reducing variables. These principles provide a means to derive approximate solutions and finite-element (FE) models for LPMI. Each LPMI element includes fluid and solid together with it being no longer necessary to distinguish fluid domain from solid. Examples illustrate applications to establish FE model for numerical solutions of LPMI. Solution of a one-dimensional problem reveals that LPMI behaves a coupled-frequency separation measured by a defined-coupling factor. Dynamic response explores coupled-dynamic absorber mechanism in LPMI system, from which it is found that the external force at fluid does not contribute to fluid response but fully absorbed by solid local resonance if the force frequency equals the solid natural frequency; while in the reverse case when the force frequency equals the fluid one, the force at solid does not produce the solid response but fully absorbed by fluid local resonance. New findings with defined LPMI coupling factor provide guidelines for designing LPMI system with expected dynamic behaviour meeting engineering requirements. [ABSTRACT FROM AUTHOR]

Biological nitrogen (N2) fixation as a source of new N input into the soil by free-living diazotrophs is important for achieving sustainable rice agriculture. However, the dominant environmental drivers or factors influencing N2 fixation and the functional significance of the diazotroph community structure in paddy soil across a climatic gradient are not yet well understood. Thus, we characterized the diazotroph community and identified the ecological predictors of N2 fixation potential in four different climate zones (mid-temperate, warm-temperate, subtropical, and tropical paddy soils) in eastern China. Comprehensive nifH gene sequencing, functional activity detection, and correlation analysis with environmental factors were estimated. The potential nitrogenase activity (PNA) was highest in warm-temperate regions, where it was 6.2-, 2.9-, and 2.2-fold greater than in the tropical, subtropical, and mid-temperate regions, respectively; nifH gene abundance was significantly higher in warm-temperate and subtropical zones than in the tropical or mid-temperate zones. Diazotroph diversity was significantly higher in the tropical climate zone and significantly lower in the mid-temperate zone. Non-metric multidimensional scaling and canonical correlation analysis indicated that paddy soil diazotroph populations differed significantly among the four climate zones, mainly owing to differences in climate and soil pH. Structural equation models and automatic linear models revealed that climate and nutrients indirectly affected PNA by affecting soil pH and diazotroph community, respectively, while diazotroph community, C/P, and nifH gene abundance directly affected PNA. And C/P ratio, pH, and the diazotroph community structure were the main predictors of PNA in paddy soils. Collectively, the differences in diazotroph community structure have ecological significance, with important implications for the prediction of soil N2-fixing functions under climate change scenarios. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD), the most prevalent representation of dementia, is a neurodegenerative disease resulting from the degenerative disturbance of the central nervous system. Previous studies have indicated that miR-107 is reduced in the brain neocortex of patients with AD; however, its underlying mechanism is not clear. Therefore, the objective of this study was to explore the question of whether miR-107 participates in AD development. The study confirmed that the miR-107 expression levels were dramatically decreased in patients with AD and in beta-amyloid (Aβ) (Aβ)-treated SH-SY5Y cells compared with control groups. Upregulation of miR-107 reversed the inhibitory role of Aβ on cell proliferation and viability. In addition, miR-107 upregulation also ameliorated the Aβ-induced inflammation and apoptosis of SH-SY5Y cells. Furthermore, using bioinformatic prediction, dual-luciferase reporter assay (DLRA), quantitative polymerase chain reaction (qPCR), and Western blot (WB), miR-107 was confirmed to reduce the expression level of FGF7, and it subsequently deactivated the FGFR2/PI3K/Akt pathway. Moreover, FGF7 overexpression counteracted the role of miR-107 in the viability, proliferation, inflammation, and apoptosis of Aβ-induced SH-SY5Y cells. [ABSTRACT FROM AUTHOR]

Although cumulative N2O emissions are greater in the winter fallow season than in the rice-growing period, the mechanisms by which the emissions affect fallow paddy fields remain unclear. We aimed to identify N2O flux characteristics and illustrate how key nirS-, nirK- and nosZ-containing denitrifiers affect N2O emission levels in acidic fallow paddy soil. Five water-filled pore space (WFPS) levels were set at 25%, 50%, 75%, 100% and 125%, respectively. During the 48-h-long, high-flux incubation period, the N2O flux was the highest in soil samples with 75% WFPS, followed by those with 100% WFPS. The size of nirS-containing denitrifier community was more sensitive to the shifts in soil moisture and showed a stronger correlation with N2O flux than that of nirK-containing denitrifiers, whereas higher N2O concentrations induced an increase in the levels of nosZ-containing bacteria. After incubation for 48 h, nirK- and nosZ-denitrifying bacterial composition varied remarkably under 50%, 75%, and 100% WFPS treatments. However, the composition of nirS-containing denitrifying bacterial community gradually varied with an increase in soil moisture from 25% to 100% WFPS. Certain dominant OTUs of nirK- nirS- and nosZ-containing denitrifiers were highly abundant, especially under treatments of 50%, 75% and 100% WFPS, which were closely associated with the N2O flux. Thus, nirK, nirS and nosZ-containing denitrifiers respond to soil moisture differently, and enriched species might mainly be involved in controlling N2O flux in fallow paddy soils via denitrification, while the abundance of nirS-containing denitrifiers might affect N2O emission levels more significantly than that of nirK-containing denitrifiers. [ABSTRACT FROM AUTHOR]

The treatment of neural deficiency after cerebral infarction is challenging, with limited therapeutic options. The transplantation of mesenchymal stem cells (MSCs) to the ischemic penumbra is a potential therapeutic approach. In the present study, a cerebral infarction model was generated by performing middle cerebral artery occlusion (MCAO) in SD rats. The expression of CXCR4 increased, and the number of MSCs migrating to the peri‐infarct area was higher in rats transplanted with preconditioned MSCs than in rats transplanted with untreated MSCs. The rate of apoptosis, as evaluated by TUNEL staining and immunoblotting assays, was reduced in rats receiving preconditioned MSCs. A significant amelioration of neural regeneration and improved neurological function were observed in rats injected with preconditioned MSCs compared with those injected with untreated MSCs. However, the application of an siRNA targeting CXCL12 significantly inhibited the protective role of preconditioned MSCs against apoptosis and promoted the migration of MSCs to the ischemic area, leading to impaired neuronal regeneration and limited recovery of neuronal function. Hypoxic preconditioning of MSCs prior to transplantation suppressed apoptosis and increased their migration abilities, leading to the promotion of neuronal regeneration and improvement in neural function after transplantation. This preconditioning strategy may be considered as a potential approach for the modification of MSCs prior to cell transplantation therapy in patients with cerebral infarction. Significance of the Study: We found that hypoxic preconditioning of MSCs improved their ability to promote neuronal regeneration and the recovery of neuronal function. Moreover, we showed that CXCR4 inhibited apoptosis, improved cell homing, and promoted neuronal differentiation, without influencing angiogenesis. Our study provides a relatively safe preconditioning method for potential use for cell transplantation therapy in ischemic cerebral infarction. The results presented here will facilitate the development of novel strategies and techniques to improve the tolerance and migration ability of transplanted cells for the treatment of cerebral infarction sequelae. [ABSTRACT FROM AUTHOR]

In order to reduce the possibility of cotton fabrics causing fire and improve the waterproofness of the fabric, a superhydrophobic flame retardant (SFR) coating was fabricated on cotton fabric using a simple two-step process. Firstly, the fabric was pretreated with diammonium phosphate solution, and then H-ZrO2 (ZrO2 which is modified by hexadecyltrimethoxysilane) was adhered to the surface of the fabric using polydimethylsiloxane. The morphology, chemical composition and element distribution of the coating were detected and characterized using SEM, ATR-FTIR, XPS and EDS. In addition, the flame-retardant properties of the coated fabric samples were tested using thermal stability and vertical burning tests. Superhydrophobic fabric was tested and evaluated by subjecting the coated fabric to abrasion, washing, acid–base soaking and ultraviolet irradiation tests, and the contact angles of the sample before and after the test were investigated. The results showed that the coated fabric has a strong hydrophobic ability. When the H-ZrO2 content in the solution is 0.8 g, the coated fabric has a maximum contact angle of 154°. Moreover, the coating has good wear resistance, acid and alkali resistance and UV resistance. Importantly, the modified fabric shows excellent flame-retardant performance. [ABSTRACT FROM AUTHOR]

Fungal denitrifiers play important roles in soil nitrogen cycling, but we have very limited knowledge about their distribution and functions in ecosystems. In this study, three types of arable soils were collected across different climate zones in China, including quaternary red clay soils, alluvial soils, and black soils. The composition and abundance of fungal nirK -containing denitrifiers was determined by MiSeq high-throughput sequencing and qPCR, respectively. Furthermore, a substrate-induced inhibition approach was used to explore N2O emissions from fungal denitrification. The results showed that the arable soils contained a wide range of nirK -containing fungal denitrifiers, with four orders and eight genera. Additionally, approximately 57.30% of operational taxonomic unit (OTUs) belonged to unclassified nirK -containing fungi. Hypocreales was the most predominant order, with approximately 40.51% of the total number of OTUs, followed by Sordariales, Eurotiales, and Mucorales. It was further indicated that 53% of fungal nirK OTUs were shared by the three types of soils (common), and this group of fungi comprised about 98% of the total relative abundance of the nirK -containing population, indicating that the distribution of fungal nirK -containing denitrifiers was quite homogenous among the soil types. These common OTUs were determined by multiple soil characteristics, while the composition of unique OTUs was manipulated by the specific properties of each soil type. Furthermore, fungal N2O emissions were significantly and positively correlated with fungal nirK abundance in the soils, whereas it was not clearly related to fungal nirK compositions. In conclusion, although the arable soils hosted diverse nirK -containing fungal denitrifiers, fungal nirK compositions were highly homogenous among the soil types, which could be a consequence of enduring agricultural practices. The abundance of fungal nirK -containing denitrifiers, rather than their composition, may play more significant roles in relation to N2O emission from fungal denitrification. [ABSTRACT FROM AUTHOR]

Aims: Tree species and seasonal change influence N2O flux and microbial communities, but the mechanisms are unclear. We studied N2O flux in soils planted with slash pine and oil-seed camellia trees. We sampled on typical days of the four seasons. We tested whether N-cycling communities respond more to tree species or seasonal change. We assessed how tree species affect N2O flux.Methods: We used qPCR and RFLP to determine abundance and community composition of amoA-containing bacteria (AOB) and archaea (AOA), and denitrifiers that contain the narG, nirK, nirS, and nosZ genes.Results: N2O flux rate and soil characteristics varied significantly between forest soils and sampling seasons. Abundance of all detected genes, but not of the nirS gene, was significantly affected by tree species. Differences in gene abundance between days in different seasons were found only for narG, nirK, and nosZ. Functional microbial community composition in the soil varied between the tree species for most of the genes studied, but varied, not significantly, slightly among sampling days. Differences in the abundance and community composition of nitrifiers and denitrifiers between tree species depended on soil concentration of NH4+, NO3−, and dissolved organic carbon (DOC). N2O flux rate was affected by community composition, but not abundance of nitrifiers and denitrifiers. Temperature, NO3−, and DOC concentrations significantly affected N2O flux.Conclusions: Tree species influenced N2O flux more than seasonal change, by altering community composition and environmental factors rather than nitrifier/denitrifier abundance. [ABSTRACT FROM AUTHOR]

Agricultural management significantly affects methane (CH4) and nitrous oxide (N2O) emissions from paddy fields. However, little is known about the underlying microbiological mechanism. Field experiment was conducted to investigate the effect of the water regime and straw incorporation on CH4 and N2O emissions and soil properties. Quantitative PCR was applied to measure the abundance of soil methanogens, methane-oxidising bacteria, nitrifiers, and denitrifiers according to DNA and mRNA expression levels of microbial genes, including mcrA, pmoA, amoA, and nirK/nirS/nosZ. Field trials showed that the CH4 and N2O flux rates were negatively correlated with each other, and N2O emissions were far lower than CH4 emissions. Drainage and straw incorporation affected functional gene abundance through altered soil environment. The present (DNA-level) gene abundances of amoA, nosZ, and mcrA were higher with straw incorporation than those without straw incorporation, and they were positively correlated with high concentrations of soil exchangeable NH4+ and dissolved organic carbon. The active (mRNA-level) gene abundance of mcrA was lower in the drainage treatment than in continuous flooding, which was negatively correlated with soil redox potential (Eh). The CH4 flux rate was significantly and positively correlated with active mcrA abundance but negatively correlated with Eh. The N2O flux rate was significantly and positively correlated with present and active nirS abundance and positively correlated with soil Eh. Thus, we demonstrated that active gene abundance, such as of mcrA for CH4 and nirS for N2O, reflects the contradictory relationship between CH4 and N2O emissions regulated by soil Eh in acidic paddy soils. [ABSTRACT FROM AUTHOR]

Machining of deep hole keyway often suffers from low processing accuracy, low processing symmetry degree between keyway and the reference plane and is difficult to control. In order to enhance the processing quality, a mathematical model of space symmetry error was established based on space projection, orthogonal combination and linear fitting methods so as to study rotatable and shift-able space objects. The space symmetry error was separated into included angle error and displacement error between the fitting straight line and the benchmark line. Through included angle rotation and location measurement along with quantitative translation, the space symmetry error compensation was realized. On the basis of the proposed methods, a Double combined manual self-centering fixture (DCMSF) was designed to realize the radial self-centering and axial location for effective clamping of deep hole keyway, and the reference plane of built-in straight slot was derived out to make it detectable and controllable. Meanwhile, an Online multi-degree of freedom symmetry detection device (OMFSDD) and corresponding Numerical control (NC) programs were also designed for automatic detection and control of symmetry error. Subsequently, mass production of high symmetric deep hole keyway were realized by means of NC gear shaper servo control of rotating shaft angle compensation and bi-directional cutter back-off amount translation compensation, and combination of NC control of fixed angle processing. Deep hole keyway processing experiments indicate that the proposed method can steadily keep the symmetry within 0.03 mm. Thus, the rationality and accuracy of the proposed method was validated which provides a novel approach to high precision deep hole keyway processing. [ABSTRACT FROM AUTHOR]

Rice fields are an important source of nitrous oxide (NO), where rice plants could act as a key factor controlling NO fluxes during the flooding-drying process; however, the microbial driving mechanisms are unclear. In this study, specially designed equipment was used to grow rice plants and collect emitted NO from the root-growing zone (zone A), root-free zones (zones B, C, and D) independently, at tillering and booting stages under flooding and drying conditions. Soil samples from the four zones were also taken separately. Nitrifying and denitrifying community abundances were detected using quantitative polymerase chain reaction (qPCR). The NO emission increased significantly along with drying, but the NO emission capabilities varied among the four zones under drying, while zone B possessed the highest NO fluxes that were 2.7~4.5 times higher than those from zones C and D. However, zone A showed NO consumption potential. Notably, zone B also harbored the highest numbers of narG-containing denitrifiers and amoA-containing nitrifiers under drying at both tillering and booting stages. This study demonstrates that drying caused significant increase in NO emission from rhizosphere soil, in which the higher abundance of AOB would help to produce more nitrate and significantly higher narG-containing microbes would drive more NO production and emission. [ABSTRACT FROM AUTHOR]

Objective: Paddy soils contain relatively greater organic matter and water contents than other soils thereby limiting effective mRNA extraction. A modification of the conventional mRNA soil extraction method specific to paddy soils is described. Results: Two main modifications for co-extraction of DNA and RNA are: (1) addition of 20 % (w/v) sodium dodecyl sulphate to 10 % (w/v) hexadecyltrimethylammonium bromide extraction buffer, and (2) fresh soil, initially frozen at −80 °C, is immediately immersed in extraction buffer. The high-quality total RNA extracted can be directly used in downstream analyses without an additional step to remove humic acid. RNA purification was conducted to remove 5S rRNA, and the mRNA was enriched by selectively digesting rRNA. cDNA synthesised by reverse transcriptase was not contaminated by the reagents or genomic DNA. Conclusion: The modified method for mRNA extraction from paddy soil is suitable for analysing the expression of microbial genes from fresh paddy soil. [ABSTRACT FROM AUTHOR]

Purpose: Soils derived from different parent materials are known to support quite distinct indigenous community structures. Crop cultivation is also an important factor regulating bacterial community structure in soils. However, the extent to which the soil parent material imposes limits on the diversity of organisms present and the extent to which cropping practices are able to supplant the effects of soil parent materials are largely unknown. Materials and methods: Five ancient paddy soils developed on three different parent materials were collected from the major rice production regions in southern China. The 16S rRNA genes were amplified from each soil DNA sample and then analyzed using Tag-pyrosequencing and terminal restriction fragment length polymorphism (T-RFLP) to characterize bacterial communities and their relative abundance. Total bacterial abundance was determined by 16S rRNA gene quantitative PCR (qPCR). Canonical correspondence analysis (CCA) was used to investigate the relationship between the bacterial distribution and soil properties. Results and discussion: Cluster analysis of the T-RFLP and pyrosequencing data indicated that although the bacterial communities in the surface layers (0-20 cm) could be distinguished from those recovered from depths of 20-40 and 40-60 cm in all soils, the bacterial community structures in soils with similar parent materials clustered regardless of soil depth. Bacteria of the phylum Proteobacteria dominated in all soils with significantly higher proportions in the top soils. The relative abundances of Chloroflexi and Acidobacteria were closely associated with the soil parent material. This suggested that the changes in bacterial community compositions induced by rice cultivation did not mask those determined by soil parent material. CCA indicated that soil pH, available Mn, and total K and Fe contents explained most of the variance in bacterial distribution due to differences in parent materials. qPCR revealed that the bacterial abundance in top soils (0-20 cm) also varied with parent material. Conclusions: The nature of the parent material is an important factor in determining soil bacterial community structure, and although long-term rice cultivation resulted in shifts in this structure, the community retained characteristics of the original populations. [ABSTRACT FROM AUTHOR]

This study examines the effects of land use change on nitrate concentration and the abundances of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and narG-containing denitrifiers in shallow groundwater. The results reveal a general increase of nitrate in shallow groundwater following the change of land use from paddy fields to vegetable patches. Furthermore, a significant relationship between NO-N concentrations was observed both in groundwater and in soil at soil depths of 0-20, 20-40, 40-60, 60-80, and 80-100 cm. With regard to gene abundance in groundwater, the AOB amoA gene was most abundant and the AOA amoA gene copy numbers were lowest from the field with long-term paddy cultivation compared with the field under vegetable cultivation. The narG gene copy numbers were higher from the field under short-term vegetable cultivation compared with fields under long-term vegetable cultivation. The NO-N concentrations in groundwater correlated positively with AOA amoA gene copy numbers, negatively with the AOB amoA gene, but with no significant relationship with the narG gene. In conclusion, land use change from paddy fields to vegetable patches increases nitrate in groundwater, which is correlated significantly with nitrate in soil and the abundance of the amoA gene, but is not related to the narG gene in groundwater. This study also suggests that the removal of groundwater nitrate pollution is not feasible through biological denitrification without additional denitrifiers and that it might even become more aggravated because of the AOA. [ABSTRACT FROM AUTHOR]

Purpose: Soil microbial communities can be strongly influenced by agricultural practices, but little is known about bacterial community successions as land use changes. The objective of this study was to determine microbial community shifts following major land use changes in order to improve our understanding of land use impacts on microbial community composition and functions. Materials and methods: Four agricultural land use patterns were selected for the study, including old rice paddy fields (ORP), Magnolia nursery planting (MNP), short-term vegetable (STV), and long-term vegetable (LTV) cultivation. All four systems are located in the same region with same soil parent material (alluvium), and the MNP, STV, and LTV systems had been converted from ORP for 10, 3, and 30 years, respectively. Soil bacteria and ammonia oxidizer community compositions were analyzed by 454 pyrosequencing and terminal restriction fragment length polymorphism, respectively. Quantitative PCR was used to determine 16S rRNA and amoA gene copy numbers. Results and discussion: The results showed that when land use was changed from rice paddy to upland systems, the relative abundance of Chloroflexi increased whereas Acidobacteria decreased significantly. While LTV induced significant shifts of bacterial composition, MNP had the highest relative abundance of genera GP1, GP2, and GP3, which were mainly related to the development of soil acidity. The community composition of ammonia-oxidizing bacteria (AOB) but not ammonia-oxidizing archaea was strongly impacted by the agricultural land use patterns, with LTV inducing the growth of a single super predominant AOB group. The land use changes also induced significant shifts in the abundance of 16S rRNA and bacterial amoA genes, but no significant differences in the abundance of archaea amoA was detected among the four land use patterns. Soil total phosphorous, available phosphorous, NO, and soil organic carbon contents and pH were the main determinants in driving the composition of both bacteria and AOB communities. Conclusions: These results clearly show the significant impact of land use change on soil microbial community composition and abundance and this will have major implications on the microbial ecology and nutrient cycling in these systems, some of which is unknown. Further research should be directed to studying the impacts of these microbial community shifts on nutrient dynamics in these agroecosystems so that improved nutrient management systems can be developed. [ABSTRACT FROM AUTHOR]

As part of a long-term sloped land use experiment established in 1995 at Taoyuan Agro-ecosystem Research Station (111°26′ E, 28°55′ N) in China, soil samples were collected from three land use types, including cropland (CL), natural forest, and tea plantation. Quantitative polymerase chain reaction and terminal restriction fragment length polymorphism were used to determine the abundance and community composition of amoA-containing bacteria (AOB) and archaea (AOA). The results indicate that land use type induced significant changes in soil potential nitrification rate and community composition, diversity, and abundance of AOB and AOA. Both AOB and AOA community compositions were generally similar between upper and lower slope positions (UP and LP), except within CL. The LP soils had significantly ( p < 0.05) higher diversity and abundance of both AOB and AOA than in the UP. Potential nitrification rate was significantly correlated ( p < 0.05) with diversity and abundance of AOA, but not with AOB. Among land use types, the NO and amoA-containing AOA runoff loss was greatest in CL. Nitrate-N runoff loss was significantly correlated ( p < 0.05) with the loss of AOA amoA copies in the runoff water. Furthermore, relationships between NO-N runoff loss and abundance of AOA but not of AOB at both slope positions were significantly correlated ( p < 0.05). These findings suggest that AOA are more important than AOB in nitrification and NO-N runoff loss in acidic soils across sloped land use types. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO) assimilation by autotrophic bacteria is an important process in the soil carbon cycle with major environmental implications. The long-term impact of fertilizer on CO assimilation in the bacterial community of paddy soils remains poorly understood. To narrow this knowledge gap, the composition and abundance of CO-assimilating bacteria were investigated using terminal restriction fragment length polymorphism and quantitative PCR of the cbbL gene [that encodes ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO)] in paddy soils. Soils from three stations in subtropical China were used. Each station is part of a long-term fertilization experiment with three treatments: no fertilizer (CK), chemical fertilizers (NPK), and NPK combined with rice straw (NPKM). At all of the stations, the cbbL-containing bacterial communities were dominated by facultative autotrophic bacteria such as Rhodopseudomonas palustris, Bradyrhizobium japonicum, and Ralstonia eutropha. The community composition in the fertilized soil (NPK and NPKM) was distinct from that in unfertilized soil (CK). The bacterial cbbL abundance (3-8 × 10 copies g soil) and RubisCO activity (0.40-1.76 nmol CO g soil min) in paddy soils were significantly positively correlated, and both increased with the addition of fertilizer. Among the measured soil parameters, soil organic carbon and pH were the most significant factors influencing the community composition, abundance, and activity of the cbbL-containing bacteria. These results suggest that long-term fertilization has a strong impact on the activity and community of cbbL-containing bacterial populations in paddy soils, especially when straw is combined with chemical fertilizers. [ABSTRACT FROM AUTHOR]

Purpose: Free amino acids (FAAs) and peptides, and dissolved organic nitrogen (DON) comprise key pools in terrestrial soil carbon (C) and nitrogen (N) cycles. A comparative study of organic and conventional arable farming systems was conducted in Shanghai, China to determine the influence of management practices on characterization of AA and peptide dynamics. Materials and methods: Soils from an accredited organic farm (OS), transitional farm (TS), and neighboring conventionally managed farm (CS) were sampled from agricultural areas in Shanghai, China, and the AA and peptide behavior of top soils were evaluated by C labeled techniques. Results and discussion: Results showed that organic management resulted in significant increases ( P < 0.05) in AA and peptide rate acquisition, possibly due to higher soil organic C (SOC) and soil respiration in OS, compared to TS and CS. The half-life of valine (Val), valine-proline-proline (Val-Pro-Pro), glutamate (Glu), and glutamate-phenylalanine (Glu-Phe) averaged across the three soils (OS, TS, and CS) was 10.6 ± 2.3, 9.4 ± 2.2, 7.1 ± 1.9, and 6.7 ± 1.5 h, respectively. The relative AA and peptide C amounts partitioned into respiration (15-32% of total) versus biomass production (68-85% of total C) was also affected by management strategy and generally followed the order CS>TS>OS; OS was significantly different from TS and CS; however, a significant difference was not detected between TS and CS. We hypothesize that AA and peptide mineralization acts as a purely biological process, as CHCl fumigation and autoclaving resulted in no observable mineralization. Results showed that AA and peptide addition to soil resulted in rapid N mineralization and subsequent NO-N production, which followed a progression based on soil N mineralization rate of OS>TS>CS. AAs and peptides were only weakly sorbed onto the soil solid phase; however, our results suggested that this did not limit soil bioavailability. Conclusions: The results of our study indicated that soil management regimes have a substantial effect on AA and peptide behavior (mineralization, microbial uptake, and sorption, among other attributes) in horticultural production systems. Therefore, we propose that SOC and total microbial activity are likely key determinants governing AA and peptide behavior in horticultural soils. [ABSTRACT FROM AUTHOR]

Powder Bed Fusion (PBF) is an additive manufacturing technology used to produce metal-based materials. PBF materials have a unique microstructure as a result from repeated and sharp heating/cooling cycles. Many researches have been carried out on relations between processing parameters of the PBF technology, obtained microstructures and mechanical properties. However, there are few studies on the tribological properties of PBF materials at various contact conditions. This article describes previous and recent studies related to the friction performance. This is a critical aspect if PBF materials are applied to friction pair components. This paper discusses wear rates and wear mechanisms of PBF materials under dry friction, boundary lubrication and micro-motion conditions. PBF materials have higher hardness due to fine grains. PBF materials have a higher wear resistance than traditional materials due to their solid solution strengthening. In addition, hard particles on the surface of PBF components can effectively reduce wear. The reasonable combination of process parameters can effectively improve the density of parts and thus further improve the wear resistance. This review paper summarized the wear behavior of PBF materials, the wear mechanism of metal materials from dry friction to different lubrication conditions, and the wear behavior under fretting wear. This will help to control the processing parameters and material powder composition of parts, so as to achieve the required material properties of parts and further improve the wear performance. [ABSTRACT FROM AUTHOR]