Hexavalent chromium(Cr(Ⅵ))is a toxic element that has negative impacts on crop growth and yield.Using plant extracts to convert toxic Cr(Ⅵ)into less toxic Cr(Ⅲ)may be a more favorable option compared to chemical re...Hexavalent chromium(Cr(Ⅵ))is a toxic element that has negative impacts on crop growth and yield.Using plant extracts to convert toxic Cr(Ⅵ)into less toxic Cr(Ⅲ)may be a more favorable option compared to chemical reducing agents.In this study,the potential effects and mechanisms of using an aqueous extract of Psidium guajava L.leaves(AEP)in reducing Cr(Ⅵ)toxicity in rice were comprehensively studied.Firstly,the reducing power of AEP for Cr(Ⅵ)was confirmed by the cyclic voltammetry combined with X-ray photoelectron spectroscopy(XPS)assays.The highest Cr(Ⅵ)reduction efficiency reached approximately 78%under 1.5mg gallic acid equivalent(GAE)/mL of AEP and 10 mg/L Cr(Ⅵ)condition.Additionally,Cr(Ⅵ)stress had a significant inhibitory effect on rice growth.However,the exogenous application of AEP alleviated the growth inhibition and oxidative damage of rice under Cr(Ⅵ)stress by increasing the activity and level of enzymatic and non-enzymatic antioxidants.Furthermore,the addition of AEP restored the ultrastructure of root cells,promoted Cr adsorption onto root cell walls,and limited the translocation Cr to shoots.In shoots,AEP application also triggered the expression of specific genes involved in Cr defense and detoxification response,including photosynthesis pathways,antioxidant systems,flavonoids biosynthesis,and plant hormone signal transduction.These results suggest that AEP is an efficient reduction agent for Cr(Ⅵ),and exogenous application of AEP may be a promising strategy to mitigate the harm of Cr(Ⅵ)on rice,ultimately contributing to improved crop yield in Crcontaminated environments.展开更多
In the present scenario,modular multilevel converters(MMCs)are considered to be one of the most promising and effective topologies in the family of high-power converters because of their modular design and good scalab...In the present scenario,modular multilevel converters(MMCs)are considered to be one of the most promising and effective topologies in the family of high-power converters because of their modular design and good scalability;MMCs are extensively used in high-voltage and high-power applications.Based on their unique advantages,MMCs have attracted increasing attention from academic circles over the past years.Several studies have focused on different aspects of MMCs,including submodule topologies,modeling schemes,modulation strategies,control schemes for voltage balancing and circulating currents,fault diagnoses,and fault-tolerant control strategies.To summarize the current research status of MMCs,all the aforementioned research issues with representative research approaches,results and characteristics are systematically overviewed.In the final section,the current research status of MMCs and their future trends are emphasized.展开更多
基金supported by the Natural Science Foundation of Hunan Province of China(No.2019JJ40361)。
文摘Hexavalent chromium(Cr(Ⅵ))is a toxic element that has negative impacts on crop growth and yield.Using plant extracts to convert toxic Cr(Ⅵ)into less toxic Cr(Ⅲ)may be a more favorable option compared to chemical reducing agents.In this study,the potential effects and mechanisms of using an aqueous extract of Psidium guajava L.leaves(AEP)in reducing Cr(Ⅵ)toxicity in rice were comprehensively studied.Firstly,the reducing power of AEP for Cr(Ⅵ)was confirmed by the cyclic voltammetry combined with X-ray photoelectron spectroscopy(XPS)assays.The highest Cr(Ⅵ)reduction efficiency reached approximately 78%under 1.5mg gallic acid equivalent(GAE)/mL of AEP and 10 mg/L Cr(Ⅵ)condition.Additionally,Cr(Ⅵ)stress had a significant inhibitory effect on rice growth.However,the exogenous application of AEP alleviated the growth inhibition and oxidative damage of rice under Cr(Ⅵ)stress by increasing the activity and level of enzymatic and non-enzymatic antioxidants.Furthermore,the addition of AEP restored the ultrastructure of root cells,promoted Cr adsorption onto root cell walls,and limited the translocation Cr to shoots.In shoots,AEP application also triggered the expression of specific genes involved in Cr defense and detoxification response,including photosynthesis pathways,antioxidant systems,flavonoids biosynthesis,and plant hormone signal transduction.These results suggest that AEP is an efficient reduction agent for Cr(Ⅵ),and exogenous application of AEP may be a promising strategy to mitigate the harm of Cr(Ⅵ)on rice,ultimately contributing to improved crop yield in Crcontaminated environments.
基金Supported by the Science and Technology Program of State Grid Corporation of China(5100-201999330A-0-0-00)。
文摘In the present scenario,modular multilevel converters(MMCs)are considered to be one of the most promising and effective topologies in the family of high-power converters because of their modular design and good scalability;MMCs are extensively used in high-voltage and high-power applications.Based on their unique advantages,MMCs have attracted increasing attention from academic circles over the past years.Several studies have focused on different aspects of MMCs,including submodule topologies,modeling schemes,modulation strategies,control schemes for voltage balancing and circulating currents,fault diagnoses,and fault-tolerant control strategies.To summarize the current research status of MMCs,all the aforementioned research issues with representative research approaches,results and characteristics are systematically overviewed.In the final section,the current research status of MMCs and their future trends are emphasized.
