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In recent years, extreme environmental cues such as abiotic stresses, including frequent droughts with irregular precipitation, salinity, metal contamination, and temperature fluctuations, have been escalating the damage to plants’ optimal productivity worldwide. Therefore, yield maintenance under extreme events needs improvement in multiple mechanisms that can minimize the influence of abiotic stresses. Polyamines (PAs) are pivotally necessary for a defensive purpose under adverse abiotic conditions, but their molecular interplay in this remains speculative. The PAs’ accretion is one of the most notable metabolic responses of plants under stress challenges. Recent studies reported the beneficial roles of PAs in plant development, including metabolic and physiological processes, unveiling their potential for inducing tolerance against adverse conditions. This review presents an overview of research about the most illustrious and remarkable achievements in strengthening plant tolerance to drought, salt, and temperature stresses by the exogenous application of PAs. The knowledge of underlying processes associated with stress tolerance and PA signaling pathways was also summarized, focusing on up-to-date evidence regarding the metabolic and physiological role of PAs with exogenous applications that protect plants under unfavorable climatic conditions. Conclusively, the literature proposes that PAs impart an imperative role in abiotic stress tolerance in plants. This implies potentially important feedback on PAs and plants’ stress tolerance under unfavorable cues.

Soil acidity is a serious problem in agricultural lands as it directly affects the soil, crop production, and human health. Soil acidification in agricultural lands occurs due to the release of protons (H + ) from the transforming reactions of various carbon, nitrogen, and sulfur-containing compounds. The use of biochar (BC) has emerged as an excellent tool to manage soil acidity owing to its alkaline nature and its appreciable ability to improve the soil’s physical, chemical, and biological properties. The application of BC to acidic soils improves soil pH, soil organic matter (SOM), cation exchange capacity (CEC), nutrient uptake, microbial activity and diversity, and enzyme activities which mitigate the adverse impacts of acidity on plants. Further, BC application also reduce the concentration of H + and Al 3+ ions and other toxic metals which mitigate the soil acidity and supports plant growth. Similarly, soil salinity (SS) is also a serious concern across the globe and it has a direct impact on global production and food security. Due to its appreciable liming potential BC is also an important amendment to mitigate the adverse impacts of SS. The addition of BC to saline soils improves nutrient homeostasis, nutrient uptake, SOM, CEC, soil microbial activity, enzymatic activity, and water uptake and reduces the accumulation of toxic ions sodium (Na + and chloride (Cl - ). All these BC-mediated changes support plant growth by improving antioxidant activity, photosynthesis efficiency, stomata working, and decrease oxidative damage in plants. Thus, in the present review, we discussed the various mechanisms through which BC improves the soil properties and microbial and enzymatic activities to counter acidity and salinity problems. The present review will increase the existing knowledge about the role of BC to mitigate soil acidity and salinity problems. This will also provide new suggestions to readers on how this knowledge can be used to ameliorate acidic and saline soils.

Drought stress affects plant growth and development by altering physiological and biochemical processes resulting in reduced crop productivity. Zinc (Zn) is an essential micronutrient that plays fundamental roles in crop resistance against the drought stress by regulating various physiological and molecular mechanisms. Under drought stress, Zn application improves seed germination, plant water relations, cell membrane stability, osmolyte accumulation, stomatal regulation, water use efficiency and photosynthesis, thus resulting in significantly better plant performance. Moreover, Zn interacts with plant hormones, increases the expression of stress proteins and stimulates the antioxidant enzymes for counteracting drought effects. To better appraise the potential benefits arising from optimum Zn nutrition, in the present review we discuss the role of Zn in plants under drought stress. Our aim is to provide a complete, updated picture in order to orientate future research directions on this topic.

Direct-drive electro-hydraulic servo valves play a key role in aerospace control systems, and their operational stability and safety reliability are crucial to the safety, stability, and efficiency of the entire control system. Based on the prediction of the performance change of the servo valve and the resulting judgement and prediction of its life, this can effectively avoid serious accidents and economic losses caused by failure due to performance degradation in the work. On the basis of existing research, factors such as opening, oil contamination, and pressure difference are used as prerequisites for the operation of direct-drive electro-hydraulic servo valves. In addition to the current research on pressure gain and leakage, the performance parameters of servo valves, such as overlap, threshold, and symmetry, are also expanded and selected as research objects, combined with pressure design servo valve performance degradation experiments for testing instruments such as flow and position sensors, and data are obtained on changes in various performance parameters. The experimental data are analyzed and a prediction model is built to predict the performance parameters of the servo valve by combining the existing popular neural networks, and the prediction error is calculated to verify the accuracy and validity of the model. The experimental results indicate that as the working time progresses, the degree of erosion and wear on the valve core and valve sleeve of the servo valve increases. Overall, it has been observed that the performance parameters of the servo valve show a slow trend of change under different working conditions, and the rate of change is generally higher under high pollution (level 9) conditions than under other conditions. The prediction results indicate that the predicted values of various performance parameters of the servo valve by the prediction model are lower than 0.2% compared to the experimental test set data. By comparing the two dimensions of the accuracy and prediction trend, this model meets industrial needs and outperforms deep learning algorithm models such as the exponential smoothing algorithm and ARIMA model. The experiments and results of this study provide theoretical support for the life prediction model of servo valves based on neural networks and machine learning in artificial intelligence, and provide a reference for the development of direct-drive electro-hydraulic servo valves in aerospace and other industrial fields for use and failure standards.

Direct-drive electro-hydraulic servo valves are widely used in the aerospace industry, in the military, and in remote sensing control, but there is little research and discussion on their performance degradation and service life prediction. Based on previous research, erosion wear is the primary physical failure form of direct-drive electro-hydraulic servo valves, and parameters such as opening, oil contamination, and pressure difference are used as influencing factors of direct-drive electro-hydraulic servo valves. Pressure gain and leakage are used as performance degradation indicators of servo valves, and multiple types of sensors are used for data monitoring. Experimental benches are arranged and verified through experiments. Based on the data and laws obtained from the experiments, the exponential smoothing algorithm and the ARIMA model algorithm were used to establish a prediction model for the servo valve, and the dynamic prediction of the performance indexes was carried out. The error calculation and analysis of the prediction results and the experimental results were then carried out using the Copula function and other mathematical knowledge to verify the accuracy and applicability of this prediction model. This study provides theoretical support and practical guidance for applying and designing direct-drive electro-hydraulic servo valves in industrial applications such as aerospace, sensor experiments, and remote sensing control.

The concentration of greenhouse gases (GHGs) in the atmosphere has been increasing since the beginning of the industrial revolution. Nitrous oxide (N2O) is one of the mightiest GHGs, and agriculture is one of the main sources of N2O emissions. In this paper, we reviewed the mechanisms triggering N2O emissions and the role of agricultural practices in their mitigation. The amount of N2O produced from the soil through the combined processes of nitrification and denitrification is profoundly influenced by temperature, moisture, carbon, nitrogen and oxygen contents. These factors can be manipulated to a significant extent through field management practices, influencing N2O emission. The relationships between N2O occurrence and factors regulating it are an important premise for devising mitigation strategies. Here, we evaluated various options in the literature and found that N2O emissions can be effectively reduced by intervening on time and through the method of N supply (30–40%, with peaks up to 80%), tillage and irrigation practices (both in non-univocal way), use of amendments, such as biochar and lime (up to 80%), use of slow-release fertilizers and/or nitrification inhibitors (up to 50%), plant treatment with arbuscular mycorrhizal fungi (up to 75%), appropriate crop rotations and schemes (up to 50%), and integrated nutrient management (in a non-univocal way). In conclusion, acting on N supply (fertilizer type, dose, time, method, etc.) is the most straightforward way to achieve significant N2O reductions without compromising crop yields. However, tuning the rest of crop management (tillage, irrigation, rotation, etc.) to principles of good agricultural practices is also advisable, as it can fetch significant N2O abatement vs. the risk of unexpected rise, which can be incurred by unwary management.

Herein, MnMgFe-layered double hydroxides/biochar (MnMgFe-LDHs/BC) composite was fabricated by immobilizing MnMgFe-LDHs on BC via the coprecipitation method, which was employed as an effective material for the detection and removal of Cd2+ from aqueous media. A lamellar structure of MnMgFe-LDHs with abundant surface-hydroxyl groups and various interlayer anions inside present a greater chance of trapping Cd2+. Meanwhile, the conductive BC with a porous structure provides numerous channels for the adsorption of Cd2+. Using the MnMgFe-LDHs/BC-based sensor, Cd2+ can be detected with a low limit of detection down to 0.03 ng/L. The feasibility of detecting Cd2+ in paddy water was also carried out, with satisfactory recoveries ranging from 97.3 to 102.3%. In addition, the MnMgFe-LDHs/BC material as an adsorbent was applied to remove Cd2+ from water with adsorption capacity of 118 mg/g, and the removal efficiency can reach 91%. These results suggest that the as-prepared MnMgFe-LDHs/BC can serve as a favorable platform for efficient determination and removal of Cd2+ in water.

Direct-drive electro-hydraulic servo valves are used extensively in aerospace, military and control applications, but little research has been conducted on their service life and physical failure wear. Based on computational fluid dynamics, the main failure forms of direct-drive electro-hydraulic servo valves are explored using their continuous phase flow and discrete phase motion characteristics, and then combined with the theory of erosion for calculation. A mathematical model of the direct-drive electro-hydraulic servo valve is established by using Solidworks software, and then imported into Fluent simulation software to establish its physical failure model and carry out simulation. Finally, the physical failure form of the direct drive electro-hydraulic servo valve is verified by the simulation results, and the performance degradation law is summarized. The results show that temperature, differential pressure, solid particle diameter and concentration, and opening degree all have an impact on the erosion and wear of direct-drive electro-hydraulic servo valves, in which differential pressure and solid particle diameter have a relatively large impact, and the servo valve must avoid working in the range of high differential pressure and solid particle diameter of 20–40 um as far as possible. This also provides further theoretical support and experimental guidance for the industrial application and life prediction of electro-hydraulic servo valves.

Rocks extracted from deep mining operations often undergo various complex temperature and dynamic load disturbances. In order to investigate the influence of temperature on the mechanical characteristics and fracture mechanisms of sandstone under different loading conditions, thermal treatments were conducted on sandstone samples at temperatures of 25 °C, 200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C. Subsequently, the quasi-static and dynamic mechanical properties of the treated samples were tested and recorded using an electronic universal testing machine and a Split Hopkinson Pressure Bar (SHPB). Simultaneously, detailed analyses and discussions of thermal damage and failure mechanisms of the specimens were carried out using Energy-Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman spectroscopy. The results indicate that with increasing temperature, the mass, density, and peak stress of the sandstone specimens decrease, while the porosity and peak strain increase. Transgranular (TG) fracture was identified as the primary failure mode during loading, accompanied by a small amount of intergranular (IG) fracture. Furthermore, high temperatures cause changes in the chemical properties of the sandstone, resulting in thermal decomposition of crystal grains and evaporation of mineral components, which are key factors that weaken the mechanical properties of sandstone. The significance of this study is to provide theoretical and technical support for site selection and safety assessment of underground engineering projects.

The conversion of farmland to forest in China has been recognized for its positive impact on above-ground vegetation and carbon sequestration. However, the impact on soil quality during land conversion, particularly in vulnerable karst areas, has received less attention. In this study conducted in a karst area of southwest China, eight different farmland conversion strategies were investigated to assess improvements in surface soil carbon, nitrogen, and ecosystem multi-functionality (EMF). Our results showed that farmland converted to afforestation areas or farmland that was abandoned contained higher amounts of carbon (total, organic, active) and ammonium nitrogen (NH 4 + -N) in the soil compared to farmland converted to grassland or maize crop. Soluble organic carbon levels were higher in afforestation and grassland areas compared to maize crop controls. By contrast, soil from grassland and abandoned land exhibited higher levels of nitrate nitrogen (NO 3 - -N) compared to afforestation land or maize crop controls. There were no differences in NH 4 + -N content between any condition, except for afforestation land that specifically contained the Zenia insignis plant species. Afforestation land consistently exhibited higher EMF values than grassland. Pearson correlation analysis revealed positive relationships between soil indices and EMF scores, except for NO 3 - -N.Random forest analysis explained 95% of the variation in soil EMF and identified specific soil factors: total carbon, organic carbon, active labile organic carbon, total nitrogen, and ammonium nitrogen, as the main drivers of soil multi-functionality. Our studies show how various reforestation strategies can enhance soil nutrient sequestration and improve soil multi-functionality of farmland in the karst areas.These findings provide insight into sustainable soil management practices for converting farmland into natural areas.