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Due to global warming, high temperature stress severely impacts maize growth and development, especially during the early filling stage. Supplemental irrigation is an effective measure to mitigate high temperature stress in maize. However, the underlying mechanism for alleviating transient high temperature stress during the early grain-filling stage is still unclear. A two-year field experiment involving high temperature during the early filling stage (HT), supplemental irrigation under high temperature stress (HTW), supplemental irrigation under control condition (W), and control treatment (CK) by using heat-tolerant variety ZD958 and heat-sensitive variety XY335 was conducted. Compared with the CK treatment, the HT treatment significantly decreased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). HT also significantly reduced the Pn, soluble sugar content in stem, and dry matter accumulation, thus reducing kernel number per ear and yield by 11.2–17.6% and 23.4–23.7% in the both variety, respectively. However, compared with HT, the HTW treatment reduced the daily mean canopy temperature of ZD958 and XY335 by 2.6 °C and 2.8 °C, respectively. Accordingly, HTW increased SPAD value, photosynthetic performance, starch and soluble sugars content in stems and leaves, and antioxidant enzymes activities, but reduced the malondialdehyde (MDA). Moreover, HTW increased the grain sink capacity, prolonged the effective filling days by 1.4–6.5 d, and increased the average filling rate by 14.8–41.0% compared with HT. Finally, grain yield of HTW was increased by 15.8–22.3% compared with HT. Therefore, supplemental irrigation could effectively enhanced maize heat resistance by reduce canopy temperature. This study provides important insights into enhancing maize resistance and yield stability under a warming climate.

Abstract Modular multilevel converters (MMC) are widely used in power systems. However, relevant studies and reports show that MMC connected with the grid may cause oscillation problems. When the bridge arm resistance is large enough, the operating conditions will be stable because of overdamping in the system. According to this idea, a virtual damping strategy is proposed, which is equivalent to increasing the resistance of the bridge arm without any actual power loss. Meanwhile, from the perspective of the impedance‐based analysis method, it is explained that this virtual damping control strategy can improve the stability margin of the system to realize the suppression of oscillation. In order to verify the effectiveness of the control method, the MMC simulation model is established under Matlab/Simulink. The simulation results show that the proposed virtual damping control can effectively suppress the MMC oscillation problem.

Abstract The increase in wind power penetration leads to the risk of energy supply interruption in integrated electricity‐heat energy systems (IHES). This paper presents an analytical‐based approach for the efficient operational reliability evaluation of the IHES. The wind power distribution characteristic model considering correlation is constructed based on Hidden Markov Model (HMM). To reduce computational complexity, a critical system state identification (CSSI) method is proposed that characterises both random device failures and wind power uncertainty. Under each critical system state, the analytical function relationship between the reliability index and the uncertainty factors is established based on the virtual stochastic response surface (VSRS) method. The analytical function can directly calculate the reliability index when the wind power output varies, avoiding a large number of repeated calculations of the optimal load‐shedding model of the system and reducing the time required for reliability assessment. This allows the operator to evaluate the operational reliability of the integrated energy system in real‐time. The numerical simulation of the test system combining the IEEE 33‐node distribution system and the existing 28‐node heating system proves the effectiveness of the proposed method.

The canopy of perennial evergreen fruit trees in southern China has a unique Bidirectional Reflectance Factor (BRF) due to its complex multi-branch structure and density changes. This study aimed to address the lack of clarity regarding the changes in BRF of evergreen fruit trees in southern China. Litchi, a typical fruit tree in this region, was chosen as the subject for establishing a three-dimensional (3D) real structure model. The canopy BRF of litchi was simulated under different leaf components, illumination geometry, observed geometry, and leaf area index (LAI) using a 3D radiation transfer model. The corresponding changes in characteristics were subsequently analyzed. The findings indicate that the chlorophyll content and equivalent water thickness of leaves exert significant influences on canopy BRF, whereas the protein content exhibit relatively weak effects. Variation in illumination and observation geometry results in the displacement of hotspots, with the solar zenith angle and view zenith angle exerting significant influence on the BRF. As the LAI of the litchi orchard increases, the distribution of hotspots becomes more concentrated, and the differences in angle information are relatively smaller when observed from multiple angles. With the increase in LAI in litchi orchards, the BRF on the principal plane would be saturated, but observation at hotspots could alleviate this phenomenon. The above analysis provides a reference for quantitative inversion of vegetation parameters using remote sensing monitoring information of typical perennial evergreen fruit trees.

Abstract Objective Gastric cancer (GC) is a malignant tumor rooting in the gastric mucosal epithelium, ranking the first among various malignant tumors. Therefore, the influence of microRNA-128-3p (miR-128-3p) by regulation of Tuftelin1 (TUFT1) on GC cells was investigated. Methods The expression levels of miR-128-3p and TUFT1 in GC tissues and cells were detected. The correlation between miR-128-3p expression and overall survival of GC patients was analyzed. Human GC cells MGC803 were transfected with miR-128-3p or TUFT1-related oligonucleotides to figure their roles in viability, apoptosis, invasion, as well as epithelial-mesenchymal transition (EMT). The relationship between miR-128-3p and TUFT1 was validated. Results miR-128-3p expression was low and TUFT1 expression was high in GC tissues. miR-128-3p expression was positively correlated with the overall survival of patients with GC. miR-128-3p targeted TUFT1. Up-regulated miR-128-3p or suppressed TUFT1 repressed viability, invasion, and EMT, and accelerated apoptosis of GC cells. Overexpressed TUFT1 reduced miR-128-3p-mediated growth inhibition of GC cells. Conclusion The study stresses that miR-128-3p can inhibit TUFT1 expression, thereby repressing GC cell activities.

Drought stress, a major abiotic stress, significantly affects wheat (Triticum aestivum L.) production globally. To identify genes and metabolic pathways crucial for responding to short-term drought stress, we conducted transcriptomic and metabolomic analyses of winter wheat cultivar Jimai 418 at four developmental stages: jointing (GS31), booting (GS45), anthesis (GS65), and 8 days after anthesis (DAA8). Transcriptomic analysis identified 14,232 differentially expressed genes (DEGs) under drought stress compared to the control. Specifically, 1387, 4573, 7380, and 892 DEGs were identified at the four developmental stages, respectively. Enriched pathways associated with these DEGs included plant hormone signal transduction, mitogen-activated protein kinase (MAPK) signaling, galactose metabolism, and starch and sucrose metabolism. Totals of 222, 633, 358, and 38 differentially accumulated metabolites (DAMs) were identified at the four stages, respectively. Correlation analysis of both datasets revealed DEGs and DAMs associated with plant hormone signal transduction, arginine and proline metabolism, ABC transporters, and amino acid biosynthesis. These findings offer significant insights into Jimai 418’s molecular response to short-term drought stress. The identified DEGs, DAMs, and enriched pathways contribute to our understanding of wheat drought tolerance. This research will facilitate further investigations into drought tolerance mechanisms and guide the breeding of wheat varieties with enhanced drought resistance.

The ports of a three-phase voltage source converter have multiple frequency electrical parameters, which makes HVDC systems with these converters present multiple input multiple output (MIMO) characteristics. The generalized Nyquist criterion of the MIMO model is often used to analyze the system stability. However, this model is more difficult to obtain than the single-input single-output (SISO) model, and the stability margin and the oscillation frequency band are difficult to capture. To solve these problems, this paper took the two-terminal HVDC transmission system as the research object to derive a SISO model that can be measured by a port. Moreover, this study also proposed a method for analyzing the system stability through envelope SISO open-loop gains. Finally, the key port and parameters affecting the system stability were analyzed according to the stability margin, which provided theoretical support for the design of the system parameters. The established model and the proposed analysis method were verified in a MATLAB/Simulink simulation model.

Abstract This paper presents an in‐depth analysis for the two‐variable impedance model of a grid‐connected system. The two‐variable model describes the impedance using the frequency as well as the operating point variable. The impedance‐based stability analysis method cannot be directly applied because the conventional models are derived for a specific steady‐state operating point and the operating point varies during operation. Thus, this paper develops a new analysis method to shed light on the role the two‐variable model plays instability analysis. The proposed method not only analyzes the system stability at different operating points, but also enables the controller design to ensure system stability. Experimental results are presented to demonstrate the effectiveness of the proposed method.

Smoking is an independent risk factor for the cardiovascular diseases. Nicotine, a major component of tobacco, is responsible for the impaired endothelial-dependent vasorelaxation in smokers. Procyanidin B2 (PCB2), a natural flavonoid, has been reported to possess several potential beneficial effects on the cardiovascular system. However, whether PCB2 prevents nicotine-induced endothelial dysfunction remains unknown. In this study, we demonstrated that PCB2 improved nicotine-impaired endothelium-dependent vasorelaxation in mouse thoracic aortas. Mechanistically, PCB2 increased the expression levels of dihydrofolate reductase (DHFR) and GTP cyclohydrolase 1 (GCH1), two important enzymes in the synthesis of tetrahydrobiopterin (BH4), in mouse aortas and cultured ECs. GSK0660, a selective antagonist of peroxisome proliferator-activated receptor δ (PPARδ), abolished the PCB2-induced effects on BH4 synthesis, nitric oxide (NO) production and vasodilation. Collectively, we demonstrated that PCB2 mitigates nicotine-induced endothelial dysfunction through a PPARδ-BH4 dependent manner, thereby suggesting a novel role of PCB2 in preventing vascular dysfunction caused by nicotine exposure.

Enhancing maize lodging resistance with plant growth retardants (PGRs) is common in maize production. However, the underlying mechanisms of yield formation as affected by PGRs are still poorly understood. A field experiment contained PGR application (a mixture of ethephon and cycocel, EC) with normal (T1) and double (T2) doses and water control (CK) was conducted at four maize plant densities (4.5, 6.0, 7.5, and 9.0 plants m−2) in 2020 and 2021. In this two-year study, the grain yield and kernel number per ear (KNE) of EC treatments were reduced by 4.8–9.0% and 3.3–12.2%, respectively, compared with CK under densities of 4.5, 6.0, and 7.5 plants m−2 without lodging. However, under the density of 9.0 plants m−2, EC treatments had no pronounced effects on grain yield and yield components. Across all densities, EC significantly decreased the leaf area index (LAI), and the lowest LAI was recorded in T2. The concentrations of nonstructural carbohydrates (NSCs; starch and soluble sugar) in the stem were significantly decreased by 9.9–10.2% in T2 averaged all densities. The sucrose and starch concentrations in grains also declined in the EC treatments. The key enzymes (cell wall acid invertase, sucrose synthase, and adenosine diphosphate pyrophosphorylase) and grain polyamine concentrations showed a slight downward trend under EC treatments compared to CK. NSCs in stems and grains, kernel enzyme activities, and polyamines in grains presented significant positive correlations with KNE. Additionally, structural carbohydrate (SC; including cellulose, hemicellulose, and lignin) concentrations in stems were improved with enhanced lodging resistance by spraying EC. Significant negative relationships were observed between SC with kernel number m-2 (KNM) and yield, suggesting that improved SC in stems might affect the availability of NSCs for kernel set. Although the lowest kernel weight and KNE were obtained at 9.0 plant m−2, relatively high LAI still ensured high KNM and high yield. Collectively, EC treatment increased SC in stems, enhanced lodging resistance of maize and reduced NSC availability for kernels, ultimately presenting adverse effects on maize kernel number and yield under relative low density.

Sulfur fertilizers play an important role in increasing the yield and improving the dough quality of bread wheat, but their regulatory mechanism remains unclear. In this study, 0 kg·ha−1 (S0) and 60 kg·ha−1 (S60) of sulfur were applied on the anthesis date; subsequently, immature wheat grains at 8, 13, and 18 days post-anthesis (DPA) were subjected to integrated transcriptomic and metabolomic analyses to investigate the changes in the gene/metabolite activity in a typical strong-gluten wheat, Gaoyou2018 (GY2018). Our data show that the S60 treatment could significantly increase the grain yield and grain protein content by 13.2 and 3.6%, respectively. The transcriptomic analysis revealed that 10,694 differentially expressed genes (DEGs) were induced by S60 from 8 to 18 DPA when compared with their corresponding no-sulfur controls, and most DEGs were mainly involved in lipid metabolism and amino acid metabolism pathways. Ninety-seven MYB transcription factors (TFs) were identified as responsive to the S60 treatment; of these, 66 showed significantly differential expression at 13 DPA, and MYB118 might participate in the process of sulfur metabolism by regulating glucosinolate synthesis. In total, 542 significantly enriched differentially expressed (DE) metabolites (DEMs) were identified following the S60 treatment, which mainly included secondary metabolites, carbohydrates, and amino acids. Several metabolites (e.g., glutathione, sucrose, GDP-alpha-D-glucose, and amino acids) exhibited altered abundances following the S60 treatment. The combination of transcriptomic and metabolomic analyses highlighted the important role of amino acid metabolism (especially cysteine, methionine, and glutathione metabolism) and starch and sucrose metabolism pathways after S60 application. Our results provide valuable information enhancing our understanding of the molecular mechanism of the response to sulfur and provide useful clues for grain protein quality formation and yield improvement in bread wheat.

Phased warming in late winter and early spring can increase winter wheat grain yield. However, the effects of different durations of warming during this period on winter wheat grain yield and quality are not yet clear. Therefore, this study conducted field warming experiments in a movable polyethylene greenhouse during the late winter and early spring stages of the three wheat growing seasons from 2019 to 2022. The results showed that the accumulated growing degree days (GDD) of the warming treatment during the warming period were increased by 87.3–215.7 °C d compared to the control (CK). The warming treatment advanced and prolonged the duration of vegetative growth and spike differentiation after regreening, promoted spike and flower development, and increased grain length, grain width, and grain area. During the three growing seasons, the longer the warming duration (WD) of the warming treatment, the more obvious were the observed promoting effects on the kernel number per spike and 1000-kernel weight. From 2019 to 2021, compared to the CK, the spike number per unit area and grain yield of the warming treatments increased with the prolongation of WD. However, in the 2022 growing season the spike number per unit area and grain yield of the warming treatment were increased with longer WD, reaching the maximum at WD of 56 days and then gradually decreasing with longer WD. Compared to CK, the grain protein content, wet gluten content, and sedimentation value of the warming treatment decreased with the prolongation of WD. The promotion effect of longer WD on grain starch content and protein yield was more significant. In summary, the accumulated GDD during the warming period compared to CK was 155.8–181.2 °C d, and at WD of 50–56 days a relatively higher grain yield and protein yield could be obtained.

Increased complexity of microbial networks can contribute to increased biodiversity and multifunctionality and thus crop productivity. However, it is not clear which combination ratio of regular and controlled-release urea will increase the soil microbial community complexity and improve maize yield in the North China Plain. To address this knowledge gap, a 2-year field experiment was conducted to explore the effects of the combination of regular (U) and controlled release (S) urea ratios [no fertilizer control (CT), regular urea alone (U), controlled-release urea alone (S), controlled-release urea mixed with regular urea 3:7 (SU3), controlled-release urea mixed with regular urea 5:5 (SU5), and controlled-release urea mixed with regular urea 7:3 (SU7)] on XianYu 688 yield and its rhizosphere and bulk soil microbial community composition and network complexity at different fertility stages. The combination of controlled-release and regular urea increased the N agronomic efficiency, N partial factors productivity, maize yield, and grain number per spike, with the maximum maize yield (9,186 kg ha–1) being achieved when the ratio of controlled-release urea to regular urea was 3:7 (SU3, p < 0.05). Maize yield increased by 13% in the SU3 treatment compared to the CT treatment. Rhizosphere soil microbial diversity remained stable at the silking stage of maize while increased at the physiological maturity stage of maize, with the increasing controlled-release to regular N fertilizer ratios (from 3:7 to 7:3, p < 0.05). This result suggests that a combination of regular and controlled-release N fertilizer can still substantially increase soil microbial diversity in the later stages of maize growth. The combination of controlled-release and regular urea is more effective in improving microbial network total links and average degree, and N agronomic efficiency (R2 = 0.79, p < 0.01), N partial factor productivity (R2 = 0.79, p < 0.01), spikes per unit area (R2 = 0.54, p < 0.05), and maize yield (R2 = 0.42, p < 0.05) increased with the microbial network complexity. This result indicates that the higher microbial network complexity is strongly associated with the higher N agronomic efficiency and N partial factors productivity and maize yield. In conclusion, the ratio of controlled-release to regular urea at SU3 not only increases the yield of maize and N agronomic efficiency but also enhances microbial diversity and network complexity in the North China Plain.

Abstract Grid‐connected inverter have been extensively used in the renewable energy grid‐connect systems, such as solar and wind. Interaction between the grid and the inverter may generate harmonic resonances that lead to reduced power quality and even instability. To analyse the stability of the inverter‐grid system using impedance‐based stability criterion, inverter impedance has to be known. Impedance measurement in the dq‐domain requires the precise synchronous phase angle to obtain accurate measurement. For impedance measurement in the stationary frame, inaccuracy usually results from not considering the effects of grid impedance and the frequency coupling. A new impedance measurement method in the stationary frame is proposed to obtain accurate measurement. The proposed method takes into account the grid impedance and its interaction with the inverter. Thus, it overcomes the limitations of current impedance measurement methods. More important, the proposed method enables accurate stability analysis results, whereas current methods may fail. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed measurement method.

Against the background of long-term climate change, quantifying the response of maize growth and development to climate change during critical growth stages will contribute to future decision-making in maize production. However, there have been few reports on the impact of climate change on maize dry matter accumulation and yield formation using long-term field trial data. In this study, field trial data from 13 agricultural meteorological stations in the Beijing–Tianjin–Hebei region from 1981 to 2017 were analyzed using partial correlation analysis and multiple regression models to investigate the effects of climate change on maize growth and yield. The results showed that the average temperature (Tavg) and accumulated effective precipitation (EP) during the maize growing season increased while the accumulated solar radiation (SRD) decreased from 1981 to 2017. During the seedling stage (GS1, VE-V8) and ear development stage (GS2, V8-R1), Tavg increased by 0.34 °C and 0.36 °C/decade, respectively, and EP increased by 1.83 mm and 3.35 mm/decade, respectively. The significant increase in Tavg during GS1 was the main reason for the inhibitory effect of climate change on maize growth, development, and biomass accumulation. However, the increase in SRD during the grain formation stage (GS3, R1–R3) and grain filling stage (GS4, R3–R6) was favorable for yield formation, increasing the grain number per ear (GN) and grain weight (GW) by 5.00% and 2.84%, respectively. SRD significantly increased after the silk stage, partially offsetting the adverse effects of temperature on maize yield formation, but the final result was a 0.18% and 0.94% reduction in maize plant dry weight (TDW) and grain yield (GY), respectively, due to the combined effects of the three climate factors. Spatially, climate change mainly had a negative impact on maize in the eastern and western parts of the central region of Beijing–Tianjin–Hebei, with a maximum GY reduction of up to 34.06%. The results of this study can provide a scientific basis for future decision-making in maize production against the background of climate change.

Global warming has increased the occurrence of high temperature stress in plants, including maize, resulting in decreased the grain number and yield. Previous studies indicate that heat stress mainly damages the pollen grains and thus lowered maize grain number. Other field studies have shown that heat stress after pollination results in kernel abortion. However, the mechanism by which high temperature affect grain abortion following pollination remains unclear. Hence, this study investigated the field grown heat-resistant maize variety “Zhengdan 958” (ZD958) and heat-sensitive variety “Xianyu 335” (XY335) under a seven-day heat stress treatment (HT) after pollination. Under HT, the grain numbers of XY335 and ZD958 were reduced by 10.9% (p = 0.006) and 5.3% (p = 0.129), respectively. The RNA sequencing analysis showed a higher number of differentially expressed genes (DEGs) between HT and the control in XY335 compared to ZD958. Ribulose diphosphate carboxylase (RuBPCase) genes were downregulated by heat stress, and RuBPCase activity was significantly lowered by 14.1% (p = 0.020) in XY335 and 5.3% (p = 0.436) in ZD958 in comparison to CK. The soluble sugar and starch contents in the grains of XY335 were obviously reduced by 26.1 and 58.5%, respectively, with no distinct change observed in ZD958. Heat stress also inhibited the synthesis of grain starch, as shown by the low activities of metabolism-related enzymes. Under HT, the expression of trehalose metabolism genes in XY335 were upregulated, and these genes may be involved in kernel abortion at high temperature. In conclusion, this study revealed that post-pollination heat stress in maize mainly resulted in reduced carbohydrate availability for grain development, though the heat-resistant ZD958 was nevertheless able to maintain growth.

The cooling system, including the thermal grease, heatsinks, plays an important role in the power converters for its reliable operation. While in the long-term operation situation, the cooling system will degrade with different kinds of failure mechanism of the components and finally result in the damage to the power converters. In this paper, the method was proposed to monitor the thermal network parameters of the cooling system using the cooling curves of junction temperature. By establishing the relationship between the RC parameters of Cauer network and time constants of cooling curves, the thermal parameters about cooling system can be obtained. Experimental tests are performed to verify the accuracy of proposed method. Results indicate the degradation state of the cooling system can be evaluated by monitoring the variation of thermal network parameters of the cooling system.

Summary. The use of chemical fungicides is costly and potentially harmful to the environment. The trend towards the environmentally-friendly pesticides has led to the search for new antifungal agents from various sources, including Chinese medicinal herbs. This study aimed to confirm the antifungal potential of selected Chinese medicinal herbs, under in vitro and greenhouse conditions, against Verticillium dahliae, the causal agent of Verticillium wilt of cotton. Preliminary screening of 26 medicinal herbs for antifungal potential showed varied responses, reducing the radial colony growth of V. dahliae, and fungicidal potential. The strongest efficacy was observed for extracts from Prunus mume and Rhus chinensis, followed by Coptis chinensis, Cortex phellodendri chinensis (dried bark of Phellodendron chinense) and Curcuma longa. The efficacy of the four most effective herbs (R. chinensis, P. mume, C. chinensis and C. phellodendri chinensis) under greenhouse conditions correlated with in vitro tests. However, Prunus mume and Rhus chinensis gave the greatest reduction in severity of Verticillium wilt. The greatest improvements in plant height, fresh weight and number of leaves were obtained with P. mume and R. chinensis, followed by C. chinensis and C. phellodendri chinensis. Greatest improvements in plant growth resulted from P. mume and R. chi-nensis. Alternative control with Chinese medicinal herbs showing the greatest antifungal potential could provide economical, safe and non-hazardous tools for management of Verticillium wilt and increased cotton quality from sustainable production.