[Objectives]This study was conducted to provide a new way for the rapid reproduction of Symplocos paniculata.[Methods]With mature embryos of S.paniculata as explants,through the study of somatic embryogenesis,the effe...[Objectives]This study was conducted to provide a new way for the rapid reproduction of Symplocos paniculata.[Methods]With mature embryos of S.paniculata as explants,through the study of somatic embryogenesis,the effects of different media on the induction and differentiation of S.paniculata somatic embryos were discussed,and the somatic embryogenesis system for S.paniculata was preliminarily established.[Results]Calli suitable for somatic embryogenesis could be induced using modified MS(referred to as GMS)as the basic medium with the addition of 0.2 mg/L 6-BA and 0.1 mg/L NAA;the best medium combination for somatic embryo differentiation was GMS+0.25 mg/L 6-BA+0.15 mg/L NAA,and the differentiation rate could reach 71.99%;and plant regeneration needed to be carried out at low sugar concentrations.[Conclusions]This study provides a technical basis for resources protection,genetic transformation,artificial seed production,and large-scale development and utilization of S.paniculata.展开更多
Shallow lakes,one of the most widespread water bodies in the world,are easily shifted to a new trophic state due to external interferences.Shifting hydrologic conditions and climate change can cause cyanobacterial har...Shallow lakes,one of the most widespread water bodies in the world,are easily shifted to a new trophic state due to external interferences.Shifting hydrologic conditions and climate change can cause cyanobacterial harmful algal blooms(CyanoHABs)in shallow lakes,which pose serious threats to ecological integrity and human health.This study analyzed the effects of hydrologic and meteorological variables on cyanobacterial blooms in Yangtze-connected lakes(Lake Dongting and Poyang)and isolated lakes(Lake Chao and Tai).The results show that(i)chlorophyll-a(Chl-a)concentration tends to decrease exponentially with increasing relative lake level fluctuations(RLLF)and precipitation,but to increase linearly with increasing wind speed and air temperature;(ii)Chl-a concentrations in lakes were significantly higher when RLLF<100,precipitation<2.6 mm,wind speed>2.6 ms^(-1),or air temperature>17.8℃;(iii)the Chl-a concentration of Yangtze-isolated lakes was more significantly affected by water level amplitude,precipitation,wind speed and air temperature than the Yangtze-connected lakes;(iv)the RLLF and the ratio of wind speed to mean water depth could be innovative coupling factors to examine variation characteristics of Chl-a in shallow lakes with greater correlation than single factors.展开更多
The development of skeletal muscle is a crucial factor in determining the meat yield and economic benefits of broiler production.Recent research has shown that mulberry leaves and their extracts can be used to signifi...The development of skeletal muscle is a crucial factor in determining the meat yield and economic benefits of broiler production.Recent research has shown that mulberry leaves and their extracts can be used to significantly improve the growth performance of livestock and poultry.The present study aims to elucidate the mechanisms involved in the regulation of skeletal muscle development in broiler offspring by dietary mulberry-leaf flavonoids(MLF)supplementation from the perspective of maternal effect theory.A total of 270 Qiling broiler breeder hens were randomly assigned to 3 treatments with different doses of MLF(0,30,60 mg/kg)for 8 weeks before collecting their fertilized eggs.The chicken offspring at 13 and 19 d of embryonic stage,and from 1 to 28 d old after hatching were included in this study.The results showed that maternal supplementation increased the breast muscle weight and body weight of the offspring at the embryo and chick stages(P<0.05).This was followed by increased cross-sectional area of pectoral muscle fibres at 14 d(P<0.05).Further determination revealed a tendency towards increased serum levels of insulin-like growth factor 1(IGF-1)(P=0.092)and muscle fibre count(P=0.167)at 1 d post-hatching following maternal MLF treatment,while serum uric acid(UA)was decreased at 14 d after hatching(P<0.05).Moreover,maternal MLF supplementation significantly up-regulated the mRNA expression of the myogenic regulatory factor Myf5 in skeletal muscle at the both embryonic and growth stages(P<0.05).The relative abundance of the downstream protein of BMPR2,Smad1 and p-Smad1/5/9 in the TGFβsignalling pathway was significantly increased by maternal MLF treatment.Meanwhile,the increased expression of the target protein p-mTOR in the breast muscle of the offspring chicks is in accordance with the improved growth rate of the breast and the body.In conclusion,maternal MLF supplementation can promote muscle protein metabolism and muscle fibre development of chick embryos through upregulation of Myf5 expression and BMP/p-Smad1/5/9 axis,thereby improving growth performance of slow growing broiler.展开更多
In the past three years,a number of oil-immersed ultra-high-voltage shunt reactors have experienced discharge defects when being put into operation,resulting in an overload of acetylene.However,detecting and identifyi...In the past three years,a number of oil-immersed ultra-high-voltage shunt reactors have experienced discharge defects when being put into operation,resulting in an overload of acetylene.However,detecting and identifying these discharge defects caused by switching impulse voltage is challenging under steady-state conditions.This poses unpredictable and difficult-to-assess safety risks for the longterm operation of the equipment and subsequent transient processes.Hence,comprehending the discharge behavior of oilpressboard(PB)insulation under switching impulse voltage and devising a method to identify defects becomes crucial.This study focuses on investigating the frequent arc reignition(FAR)pattern exhibited by typical defects under both standard and oscillation switching impulse voltages.The objective is to uncover the mechanism behind FAR and propose a defect recognition strategy suitable for transient processes.The study reveals the FAR process will occur at least once during the breakdown process;the FAR phenomenon is the weakest in the surface defect with a weak vertical electric field.The average recovery voltage percentage and the average discharge interval of the FAR process decrease with increasing impulse amplitude or oscillation frequency.Additionally,the average number of discharges decreases with higher oscillation frequency,while it initially increases and then decreases with increaseing amplitude.Based on the analysis of the number of FAR processes and their variation in terms of amplitude or discharge interval,a method for recognizing oil-PB defects during switching transient processes is developed and successfully applied to a case study involving acetylene overload in a 1000 kV shunt reactor.展开更多
Converter transformers are the core device in ultrahigh voltage direct current(UHVDC)transmission systems,and the oil-paper insulation at its rectifying valve side deals with the composite AC-DC voltage.A detailed inv...Converter transformers are the core device in ultrahigh voltage direct current(UHVDC)transmission systems,and the oil-paper insulation at its rectifying valve side deals with the composite AC-DC voltage.A detailed investigation of the partial discharge(PD)mechanism in the oil-paper insulation under the composite AC-DC voltage is,therefore,very important.The oilpaper insulated needle plate electrode simulation model for the electric field and charge distribution can be established using hydrodynamic drift-diffusion theory and bipolar charge carrier theory,and the simulation results can reflect the morphological changes of PD.The development characteristics of PD under composite AC-DC voltage are researched.In addition,the effects of simulation time,the AC-DC component proportion,and model parameters on PD are also explored.Results indicate that differences in applied voltage,interface charge,and geometry structure can cause changes in the electric field strength,which consequently influences the PD process in the simulation model.Oil-immersed paperboard is a type of liquid-immersed dielectric(LID).When the LID is arranged in perpendicular,only the positive streamers have narrow channels oriented toward the LID.When the LID is arranged in parallel,the PDs are in the form of creeping discharges and the negative streamers are more dispersed.The development characteristics of PD and its influencing factors reported here may provide theoretical and simulation support to explain the physical mechanism of PD at the rectifying valve side of the converter transformer.展开更多
Overuse of nitrogen(N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water.Biochar, a sustainable soil amendment agent, has been widely studied ...Overuse of nitrogen(N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water.Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite(NO2-) or nitrate(NO3-). Although positively charged ammonium(NH4+) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO2- and/or NO3-.In practice, dicyandiamide(DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH4+. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg-1 d-1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg-1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH4+ in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH4+and DCD could possibly enhance the effectiveness of DCD.展开更多
基金Supported by Changsha Science and Technology Plan Key Project(kq1801080)State Key Laboratory of Woody Oil Resource Utilization Project(2019XK2002)。
文摘[Objectives]This study was conducted to provide a new way for the rapid reproduction of Symplocos paniculata.[Methods]With mature embryos of S.paniculata as explants,through the study of somatic embryogenesis,the effects of different media on the induction and differentiation of S.paniculata somatic embryos were discussed,and the somatic embryogenesis system for S.paniculata was preliminarily established.[Results]Calli suitable for somatic embryogenesis could be induced using modified MS(referred to as GMS)as the basic medium with the addition of 0.2 mg/L 6-BA and 0.1 mg/L NAA;the best medium combination for somatic embryo differentiation was GMS+0.25 mg/L 6-BA+0.15 mg/L NAA,and the differentiation rate could reach 71.99%;and plant regeneration needed to be carried out at low sugar concentrations.[Conclusions]This study provides a technical basis for resources protection,genetic transformation,artificial seed production,and large-scale development and utilization of S.paniculata.
基金The Natural Key Scientific and Technological Project for Water Pollution Control and Management(2017ZX07401-004).
文摘Shallow lakes,one of the most widespread water bodies in the world,are easily shifted to a new trophic state due to external interferences.Shifting hydrologic conditions and climate change can cause cyanobacterial harmful algal blooms(CyanoHABs)in shallow lakes,which pose serious threats to ecological integrity and human health.This study analyzed the effects of hydrologic and meteorological variables on cyanobacterial blooms in Yangtze-connected lakes(Lake Dongting and Poyang)and isolated lakes(Lake Chao and Tai).The results show that(i)chlorophyll-a(Chl-a)concentration tends to decrease exponentially with increasing relative lake level fluctuations(RLLF)and precipitation,but to increase linearly with increasing wind speed and air temperature;(ii)Chl-a concentrations in lakes were significantly higher when RLLF<100,precipitation<2.6 mm,wind speed>2.6 ms^(-1),or air temperature>17.8℃;(iii)the Chl-a concentration of Yangtze-isolated lakes was more significantly affected by water level amplitude,precipitation,wind speed and air temperature than the Yangtze-connected lakes;(iv)the RLLF and the ratio of wind speed to mean water depth could be innovative coupling factors to examine variation characteristics of Chl-a in shallow lakes with greater correlation than single factors.
基金supported by National Natural Science Founda-tion of China (No.32202724)Beijing Natural Science Foundation (No.6222036)China Agriculture Research System program (CARS-40 and CARS 41-G11).
文摘The development of skeletal muscle is a crucial factor in determining the meat yield and economic benefits of broiler production.Recent research has shown that mulberry leaves and their extracts can be used to significantly improve the growth performance of livestock and poultry.The present study aims to elucidate the mechanisms involved in the regulation of skeletal muscle development in broiler offspring by dietary mulberry-leaf flavonoids(MLF)supplementation from the perspective of maternal effect theory.A total of 270 Qiling broiler breeder hens were randomly assigned to 3 treatments with different doses of MLF(0,30,60 mg/kg)for 8 weeks before collecting their fertilized eggs.The chicken offspring at 13 and 19 d of embryonic stage,and from 1 to 28 d old after hatching were included in this study.The results showed that maternal supplementation increased the breast muscle weight and body weight of the offspring at the embryo and chick stages(P<0.05).This was followed by increased cross-sectional area of pectoral muscle fibres at 14 d(P<0.05).Further determination revealed a tendency towards increased serum levels of insulin-like growth factor 1(IGF-1)(P=0.092)and muscle fibre count(P=0.167)at 1 d post-hatching following maternal MLF treatment,while serum uric acid(UA)was decreased at 14 d after hatching(P<0.05).Moreover,maternal MLF supplementation significantly up-regulated the mRNA expression of the myogenic regulatory factor Myf5 in skeletal muscle at the both embryonic and growth stages(P<0.05).The relative abundance of the downstream protein of BMPR2,Smad1 and p-Smad1/5/9 in the TGFβsignalling pathway was significantly increased by maternal MLF treatment.Meanwhile,the increased expression of the target protein p-mTOR in the breast muscle of the offspring chicks is in accordance with the improved growth rate of the breast and the body.In conclusion,maternal MLF supplementation can promote muscle protein metabolism and muscle fibre development of chick embryos through upregulation of Myf5 expression and BMP/p-Smad1/5/9 axis,thereby improving growth performance of slow growing broiler.
基金National Natural Science Foundation of China(Young Scientistic Program),Grant/Award Number:52007148State Key Laboratory of Intense Pulsed Radiation Simulation and Effect through Open Foundation,Grant/Award Number:SKLIPR2114。
文摘In the past three years,a number of oil-immersed ultra-high-voltage shunt reactors have experienced discharge defects when being put into operation,resulting in an overload of acetylene.However,detecting and identifying these discharge defects caused by switching impulse voltage is challenging under steady-state conditions.This poses unpredictable and difficult-to-assess safety risks for the longterm operation of the equipment and subsequent transient processes.Hence,comprehending the discharge behavior of oilpressboard(PB)insulation under switching impulse voltage and devising a method to identify defects becomes crucial.This study focuses on investigating the frequent arc reignition(FAR)pattern exhibited by typical defects under both standard and oscillation switching impulse voltages.The objective is to uncover the mechanism behind FAR and propose a defect recognition strategy suitable for transient processes.The study reveals the FAR process will occur at least once during the breakdown process;the FAR phenomenon is the weakest in the surface defect with a weak vertical electric field.The average recovery voltage percentage and the average discharge interval of the FAR process decrease with increasing impulse amplitude or oscillation frequency.Additionally,the average number of discharges decreases with higher oscillation frequency,while it initially increases and then decreases with increaseing amplitude.Based on the analysis of the number of FAR processes and their variation in terms of amplitude or discharge interval,a method for recognizing oil-PB defects during switching transient processes is developed and successfully applied to a case study involving acetylene overload in a 1000 kV shunt reactor.
基金This work was supported in part by the Science and Technology Project of State Grid Corporation of China(No.52060020002P).
文摘Converter transformers are the core device in ultrahigh voltage direct current(UHVDC)transmission systems,and the oil-paper insulation at its rectifying valve side deals with the composite AC-DC voltage.A detailed investigation of the partial discharge(PD)mechanism in the oil-paper insulation under the composite AC-DC voltage is,therefore,very important.The oilpaper insulated needle plate electrode simulation model for the electric field and charge distribution can be established using hydrodynamic drift-diffusion theory and bipolar charge carrier theory,and the simulation results can reflect the morphological changes of PD.The development characteristics of PD under composite AC-DC voltage are researched.In addition,the effects of simulation time,the AC-DC component proportion,and model parameters on PD are also explored.Results indicate that differences in applied voltage,interface charge,and geometry structure can cause changes in the electric field strength,which consequently influences the PD process in the simulation model.Oil-immersed paperboard is a type of liquid-immersed dielectric(LID).When the LID is arranged in perpendicular,only the positive streamers have narrow channels oriented toward the LID.When the LID is arranged in parallel,the PDs are in the form of creeping discharges and the negative streamers are more dispersed.The development characteristics of PD and its influencing factors reported here may provide theoretical and simulation support to explain the physical mechanism of PD at the rectifying valve side of the converter transformer.
基金This research was supported by the National Institute of Food and Agriculture(NIFA)of the United States Department of Agriculture(USDA)through Grant No.2016-67020-25275 to the Florida Agricultural and Mechanical University.
文摘Overuse of nitrogen(N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water.Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite(NO2-) or nitrate(NO3-). Although positively charged ammonium(NH4+) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO2- and/or NO3-.In practice, dicyandiamide(DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH4+. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg-1 d-1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg-1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH4+ in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH4+and DCD could possibly enhance the effectiveness of DCD.
