Fruit cracking is an important problem in horticultural crop production.Polygalacturonase(SlPG)and expansin(SlEXP1)proteins cooperatively disassemble the polysaccharide network of tomato fruit cell walls during ripeni...Fruit cracking is an important problem in horticultural crop production.Polygalacturonase(SlPG)and expansin(SlEXP1)proteins cooperatively disassemble the polysaccharide network of tomato fruit cell walls during ripening and thereby,enable softening.A Golden 2-like(GLK2)transcription factor,SlGLK2 regulates unripe fruit chloroplast development and results in elevated soluble solids and carotenoids in ripe fruit.To determine whether SlPG,SlEXP1,or SlGLK2 influence the rate of tomato fruit cracking,the incidence of fruit epidermal cracking was compared between wild-type,Ailsa Craig(WT)and fruit with suppressed SlPG and SlEXP1 expression(pg/exp)or expressing a truncated nonfunctional Slglk2(glk2).Treating plants with exogenous ABA increases xylemic flow into fruit.Our results showed that ABA treatment of tomato plants greatly increased cracking of fruit from WT and glk2 mutant,but not from pg/exp genotypes.The pg/exp fruit were firmer,had higher total soluble solids,denser cell walls and thicker cuticles than fruit of the other genotypes.Fruit from the ABA treated pg/exp fruit had cell walls with less water-soluble and more ionically and covalently-bound pectins than fruit from the other lines,demonstrating that ripening-related disassembly of the fruit cell wall,but not elimination of SlGLK2,influences cracking.Cracking incidence was significantly correlated with cell wall and wax thickness,and the content of cell wall protopectin and cellulose,but not with Ca^(2+)content.展开更多
The temperature-dependent structural changes in 1-butyl-3-methylimidazolium tetrafluoride([Bmim]FeCl4)magnetic ionic liquid(MIL)were investigated by using in-situ X-ray absorption fine structure(XAFS)combined with Ram...The temperature-dependent structural changes in 1-butyl-3-methylimidazolium tetrafluoride([Bmim]FeCl4)magnetic ionic liquid(MIL)were investigated by using in-situ X-ray absorption fine structure(XAFS)combined with Raman spectroscopy and DFT calculations.XAFS re sults revealed that the coordination number and bond length of Fe-Cl in the anion of[Bmim]FeCl4 MIL decreased with increments in temperature.These results directly reflected the dissociation of tetrahedral structure[FeCl4]^-,and the formation of bridge-chain[Fe2 Cl5]^+,and[FeCl2]^+species in the anion of[Bmim]FeCl4 MIL.These behaviors indicated that[FeCl4]^-dissociation was endothermic,and was promoted by increased temperature.The results obtained through XAFS were in agreement with those obtained through Raman spectroscopy and DFT calculations.展开更多
Li-O_(2) batteries gain widespread attention as a can didate for next-generati on energy storage devices due to their extraordinary theoretic specific energy.The semi-open structure of Li-O_(2) batteries causes many p...Li-O_(2) batteries gain widespread attention as a can didate for next-generati on energy storage devices due to their extraordinary theoretic specific energy.The semi-open structure of Li-O_(2) batteries causes many parasitic reactions,especially related to water.Water is a double-edged sword,which destroys Li anode and simultaneously triggers a solution-based pathway of the discharge product.In this work,hexamethyldisilazane(HMDS)is introduced into the electrolyte of an aprotic Li-O_(2) battery.HMDS has a strong ability to combine with a trace of water to gen erate a hydrophobic hexamethyldisiloxa ne(MM),which eliminates water from the electrolyte decomposition and then prevents the Li anode from producing the insulating LiOH with water.In this case,the hydrophobic MM disperses in the ether-based electrolyte,forming a dispersion hydrophobic electrolyte.This electrolyte can anchor water from the environment on the cathode side,which triggers a solution-based pathway and regulates the growth morphology of the discharge product and consequently increases the discharge capacity.Compared with the Li-O_(2) battery without the HMDS,the HMDS-containing Li-O_(2) battery contributes an about 13-fold increase of cyclability(400 cycles,1800 h)in the extreme environment of saturated water vapor.This work opens a new approach for directly operating aprotic Li-O_(2) batteries in ambient air.展开更多
With global warming,heat stress is becoming a more frequent event and a major limiting factor for crop production.The evaluation of thermo-tolerance is essential for the cultivators to obtain the heat resistant genoty...With global warming,heat stress is becoming a more frequent event and a major limiting factor for crop production.The evaluation of thermo-tolerance is essential for the cultivators to obtain the heat resistant genotypes and breeders to improve the thermo-tolerance of plants.Therefore,it is very important to perfect the existing evaluation system for thermo-tolerance.In this study,30 tomato genotypes were treated with heat stress at germination,seedling and flowering stages.Each index was different and diverse in different tomato genotypes by doing variability analysis,difference analysis and Student's t test.Before principal component analysis(PCA),a positive treatment for the negative and moderation indexes was performed.After correlation analysis,the authors performed PCA(including dimensionality reduction(DR),no dimensionality reduction(NDR)and optimal index(OI)),combining with subordinate function(SF),weight and cluster analysis.No matter at germination or seedling stage,the members of the groups were basically identical for DR,NDR and OI.Then 10 tomato genotypes were chosen from 30 randomly for verification.Compared all the evaluation systems,OI was the simplest and also could get as credible results as other methods.Therefore,in this study,OI could be adopted and improve the efficiency during the evaluation.At germination stage,germination power(GP)can accurately evaluate the thermo-tolerance,and at seedling stage,it was fresh weight(FW),internode length(IL)and dry matter percentage of seedling(DMP).Finally,all the indexes in the three stages were applied correlation analysis.Seedling stage showed significant positive correlation with flowering stage.In conclusion,this work improves the current system and set up a new comprehensive evaluation method named OI,which also improves the efficiency,guarantees reliability in screening thermo-tolerance of tomato for cultivators and expedites the process of breeding for resistance.展开更多
L-band Er doped fiber(EDF)laser sources are in great demand for extending communication bandwidth.However,the gain performance is limited by the low emission cross section(σe)of Er^(3+)at wavelengths longer than 1590...L-band Er doped fiber(EDF)laser sources are in great demand for extending communication bandwidth.However,the gain performance is limited by the low emission cross section(σe)of Er^(3+)at wavelengths longer than 1590 nm.In our study,we revealed the mechanism of regulating Er emission behavior in silicate glass,and provided a linear model to predict the se of Er-doped silicate glass with R^(2)=92.3%.Theσe1600 was increased to 23.5×10^(-22)cm^(2)through erbium coordination engineering.Results were elucidated using X-ray absorption fine structure(XAFS)spectra,molecular dynamics(MD)simulations and fluorescence.Furthermore,this work validates this model in Er doped silicate fibers and obtained>20 dB amplification in the range of 1585e1625 nm.This coordination engineering shows significant potential in applications of Er-doped silicate glasses and fibers.It provides an attractive prospect for expanding communication bandwidth by efficiently manipulating the emission of erbium to cover long wavelength.展开更多
Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically...Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically active surface area(ECSA)for the oxygen reduction reaction(ORR)in hydrogen-based proton-exchange membrane fuel cells.Accordingly,a facile,low-cost,and hydrogen-assisted two-step method is developed in this work,to massively prepare carbon-supported uniform,small-sized,and surfactant-free Pd nanoparticles(NPs)with ultrathin~3-atomic-layer Pt shells(Pd@Pt_(3L) NPs/C).Comprehensive physicochemical characterizations,electrochemical analyses,fuel cell tests,and density functional theory calculations reveal that,benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects,Pd@Pt_(3L) NPs/C exhibits not only significantly enhanced ECSA,electrocatalytic activity,and noble-metal(NM)utilization compared to commercial Pt/C,showing 81.24 m^(2)/gPt,0.710 mA/cm^(2),and 352/577 mA/mgNM/Pt in ECSA,area-,and NM-/Pt-mass-specific activity,respectively;but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test.More importantly,the corresponding 25-cm^(2) H2-air/O_(2) fuel cell with the low cathodic Pt loading of~0.152 mgPt/cm^(2)geo achieves the high power density of 0.962/1.261 W/cm^(2)geo at the current density of only 1,600 mA/cm^(2)geo,which is much higher than that for the commercial Pt/C.This work not only develops a high-performance and practical Pt-based ORR electrocatalyst,but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure,which can be further expanded to other metal shells for other energy-conversion applications.展开更多
The interaction between isolated transition-metal atoms and neighboring dopants in single-atom catalysts(SACs)plays a key role in adsorption strength tuning and catalytic performance engineering.Clarifying the local c...The interaction between isolated transition-metal atoms and neighboring dopants in single-atom catalysts(SACs)plays a key role in adsorption strength tuning and catalytic performance engineering.Clarifying the local coordination structures of SACs is therefore of great importance and yet very challenging at the atomic level.展开更多
The development of highly active nitrogendoped carbon-based transition metal(M-N-C)compounds for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs)greatly helps reduce fuel cell cost,thus...The development of highly active nitrogendoped carbon-based transition metal(M-N-C)compounds for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs)greatly helps reduce fuel cell cost,thus rapidly promoting their commercial applications.Among different M-N-C electrocatalysts,the series of Fe-N-C materials are highly favored because of their high ORR activity.However,there remains a debate on the effect of Fe,and rare investigations focus on the influence of Fe addition in the second heat treatment usually performed after acid leaching in the catalyst synthesis.It is thus very critical to explore the influences of Fe on the ORR electrocatalytic activity,which will,in turn,guide the design of Fe-N-C materials with enhanced performance.Herein,a series of Fe-N-C electrocatalysts are synthesize and the influence of Fe on the ORR activity are speculated both experimentally and theoretically.It is deduced that the active site lies in the structure of Fe-N4,accompanied with the addition of appropriate Fe,and the number of active sites increases without the occurrence of agglomeration particles.Moreover,it is speculated that Fe plays an important role in stabilizing N as well as constituting active sites in the second pyrolyzing process.展开更多
The structure of [Bmim]2CuCl4 ionic liquids （Bmim： 1-butyl-3-methylimidazolium） with different ratios of H2O and C2H5OH was investigated using X-ray absorption fine structure （XAFS） technique. In this study, XAFS...The structure of [Bmim]2CuCl4 ionic liquids （Bmim： 1-butyl-3-methylimidazolium） with different ratios of H2O and C2H5OH was investigated using X-ray absorption fine structure （XAFS） technique. In this study, XAFS was employed to directly probe the conformational variations of copper ions in [Bmim]2CuCl4 with the addition of either water or ethanol. XAFS analysis confirmed that the structure of ionic liquids gradually transformed from tetrahedral to octahedral configuration with the increase in ratio of H2O. Our results also showed that water molecules coordinated with the copper ions of [Bmim]2CuCl4, leading to the conformational change in ionic liquids. However, the XAFS spectra of [Bmim]zCuCIa/C2H5OH indicated no coordination of anhydrous ethanol with the copper ions of [Bmim]2CuC14. The structure of [Bmim]2CuCl4 ionic liquids is maintained as the tetrahedral configuration in presence of ethanol. Therefore, anhydrous ethanol causes little variation in the structure of ionic liquids and it is a good solvent for the dilution of ionic liquids.展开更多
基金supported by National Natural Science Foundation of China(31701924)the National Science Foundation(US IOS 0957264)+1 种基金Fundamental Research Funds for the Central Universities,China(KYZ201609)the US NSF support to ALTP(IOS 0544504 and 0957264).
文摘Fruit cracking is an important problem in horticultural crop production.Polygalacturonase(SlPG)and expansin(SlEXP1)proteins cooperatively disassemble the polysaccharide network of tomato fruit cell walls during ripening and thereby,enable softening.A Golden 2-like(GLK2)transcription factor,SlGLK2 regulates unripe fruit chloroplast development and results in elevated soluble solids and carotenoids in ripe fruit.To determine whether SlPG,SlEXP1,or SlGLK2 influence the rate of tomato fruit cracking,the incidence of fruit epidermal cracking was compared between wild-type,Ailsa Craig(WT)and fruit with suppressed SlPG and SlEXP1 expression(pg/exp)or expressing a truncated nonfunctional Slglk2(glk2).Treating plants with exogenous ABA increases xylemic flow into fruit.Our results showed that ABA treatment of tomato plants greatly increased cracking of fruit from WT and glk2 mutant,but not from pg/exp genotypes.The pg/exp fruit were firmer,had higher total soluble solids,denser cell walls and thicker cuticles than fruit of the other genotypes.Fruit from the ABA treated pg/exp fruit had cell walls with less water-soluble and more ionically and covalently-bound pectins than fruit from the other lines,demonstrating that ripening-related disassembly of the fruit cell wall,but not elimination of SlGLK2,influences cracking.Cracking incidence was significantly correlated with cell wall and wax thickness,and the content of cell wall protopectin and cellulose,but not with Ca^(2+)content.
基金sponsored by the National Natural Science Foundation of China(Nos.21802095,11805261)Shanghai Sailing Program(No.19YF1458200)+1 种基金the China Postdoctoral Science Foundation(No.2017M621468)the Joint Funds of the National Natural Science Foundation of China(No.U1832152)。
文摘The temperature-dependent structural changes in 1-butyl-3-methylimidazolium tetrafluoride([Bmim]FeCl4)magnetic ionic liquid(MIL)were investigated by using in-situ X-ray absorption fine structure(XAFS)combined with Raman spectroscopy and DFT calculations.XAFS re sults revealed that the coordination number and bond length of Fe-Cl in the anion of[Bmim]FeCl4 MIL decreased with increments in temperature.These results directly reflected the dissociation of tetrahedral structure[FeCl4]^-,and the formation of bridge-chain[Fe2 Cl5]^+,and[FeCl2]^+species in the anion of[Bmim]FeCl4 MIL.These behaviors indicated that[FeCl4]^-dissociation was endothermic,and was promoted by increased temperature.The results obtained through XAFS were in agreement with those obtained through Raman spectroscopy and DFT calculations.
基金supported by the National Natural Science Foundation of China(21875278)Science and Technology Commission of Shanghai Municipality(20511107800).
文摘Li-O_(2) batteries gain widespread attention as a can didate for next-generati on energy storage devices due to their extraordinary theoretic specific energy.The semi-open structure of Li-O_(2) batteries causes many parasitic reactions,especially related to water.Water is a double-edged sword,which destroys Li anode and simultaneously triggers a solution-based pathway of the discharge product.In this work,hexamethyldisilazane(HMDS)is introduced into the electrolyte of an aprotic Li-O_(2) battery.HMDS has a strong ability to combine with a trace of water to gen erate a hydrophobic hexamethyldisiloxa ne(MM),which eliminates water from the electrolyte decomposition and then prevents the Li anode from producing the insulating LiOH with water.In this case,the hydrophobic MM disperses in the ether-based electrolyte,forming a dispersion hydrophobic electrolyte.This electrolyte can anchor water from the environment on the cathode side,which triggers a solution-based pathway and regulates the growth morphology of the discharge product and consequently increases the discharge capacity.Compared with the Li-O_(2) battery without the HMDS,the HMDS-containing Li-O_(2) battery contributes an about 13-fold increase of cyclability(400 cycles,1800 h)in the extreme environment of saturated water vapor.This work opens a new approach for directly operating aprotic Li-O_(2) batteries in ambient air.
基金This work was supported by grants from the Natural Science Foundation of Youth Jiangsu Province(BIC20160579).
文摘With global warming,heat stress is becoming a more frequent event and a major limiting factor for crop production.The evaluation of thermo-tolerance is essential for the cultivators to obtain the heat resistant genotypes and breeders to improve the thermo-tolerance of plants.Therefore,it is very important to perfect the existing evaluation system for thermo-tolerance.In this study,30 tomato genotypes were treated with heat stress at germination,seedling and flowering stages.Each index was different and diverse in different tomato genotypes by doing variability analysis,difference analysis and Student's t test.Before principal component analysis(PCA),a positive treatment for the negative and moderation indexes was performed.After correlation analysis,the authors performed PCA(including dimensionality reduction(DR),no dimensionality reduction(NDR)and optimal index(OI)),combining with subordinate function(SF),weight and cluster analysis.No matter at germination or seedling stage,the members of the groups were basically identical for DR,NDR and OI.Then 10 tomato genotypes were chosen from 30 randomly for verification.Compared all the evaluation systems,OI was the simplest and also could get as credible results as other methods.Therefore,in this study,OI could be adopted and improve the efficiency during the evaluation.At germination stage,germination power(GP)can accurately evaluate the thermo-tolerance,and at seedling stage,it was fresh weight(FW),internode length(IL)and dry matter percentage of seedling(DMP).Finally,all the indexes in the three stages were applied correlation analysis.Seedling stage showed significant positive correlation with flowering stage.In conclusion,this work improves the current system and set up a new comprehensive evaluation method named OI,which also improves the efficiency,guarantees reliability in screening thermo-tolerance of tomato for cultivators and expedites the process of breeding for resistance.
基金supported by the research project of National Key R&D Program of China(2022YFE0204800)National Natural Science Foundation of China(Grant Number 62205355)+5 种基金Shanghai Sailing Program(Grant Number 22YF1454900,23YF1413400)Natural Science Foundation of Shanghai(Grant No.24ZR1474600)International Partnership Program of the Chinese Academy of Sciences(grant number:181231KYSB20200040)Chinese Academy of Sciences President's International Fellowship Initiative(grant number:2023VMB0008)Youth Innovation Promotion Association CASsupported by the Advanced R&D Platform for Glass(APG).
文摘L-band Er doped fiber(EDF)laser sources are in great demand for extending communication bandwidth.However,the gain performance is limited by the low emission cross section(σe)of Er^(3+)at wavelengths longer than 1590 nm.In our study,we revealed the mechanism of regulating Er emission behavior in silicate glass,and provided a linear model to predict the se of Er-doped silicate glass with R^(2)=92.3%.Theσe1600 was increased to 23.5×10^(-22)cm^(2)through erbium coordination engineering.Results were elucidated using X-ray absorption fine structure(XAFS)spectra,molecular dynamics(MD)simulations and fluorescence.Furthermore,this work validates this model in Er doped silicate fibers and obtained>20 dB amplification in the range of 1585e1625 nm.This coordination engineering shows significant potential in applications of Er-doped silicate glasses and fibers.It provides an attractive prospect for expanding communication bandwidth by efficiently manipulating the emission of erbium to cover long wavelength.
基金the National Natural Science Foundation of China(No.21975157)the China Postdoctoral Science Foundation(No.2021M692062)the Science and Technology Commission of Shanghai Municipality(No.20511104004).
文摘Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically active surface area(ECSA)for the oxygen reduction reaction(ORR)in hydrogen-based proton-exchange membrane fuel cells.Accordingly,a facile,low-cost,and hydrogen-assisted two-step method is developed in this work,to massively prepare carbon-supported uniform,small-sized,and surfactant-free Pd nanoparticles(NPs)with ultrathin~3-atomic-layer Pt shells(Pd@Pt_(3L) NPs/C).Comprehensive physicochemical characterizations,electrochemical analyses,fuel cell tests,and density functional theory calculations reveal that,benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects,Pd@Pt_(3L) NPs/C exhibits not only significantly enhanced ECSA,electrocatalytic activity,and noble-metal(NM)utilization compared to commercial Pt/C,showing 81.24 m^(2)/gPt,0.710 mA/cm^(2),and 352/577 mA/mgNM/Pt in ECSA,area-,and NM-/Pt-mass-specific activity,respectively;but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test.More importantly,the corresponding 25-cm^(2) H2-air/O_(2) fuel cell with the low cathodic Pt loading of~0.152 mgPt/cm^(2)geo achieves the high power density of 0.962/1.261 W/cm^(2)geo at the current density of only 1,600 mA/cm^(2)geo,which is much higher than that for the commercial Pt/C.This work not only develops a high-performance and practical Pt-based ORR electrocatalyst,but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure,which can be further expanded to other metal shells for other energy-conversion applications.
基金supported by the National Natural Science Foundation of China(NSFCnos.22002088 and 21733004)+5 种基金the International Cooperation Program of Shanghai Science and Technology Committee(STCSMno.17520711200)the Shanghai Sailing Program(no.20YF1420500)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(no.SL2020 MS007)S.B.acknowledges the support from the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(no.2015M3D3 A1A01064929)F.J.acknowledges the support from NSFC under the grant no.21802095.
文摘The interaction between isolated transition-metal atoms and neighboring dopants in single-atom catalysts(SACs)plays a key role in adsorption strength tuning and catalytic performance engineering.Clarifying the local coordination structures of SACs is therefore of great importance and yet very challenging at the atomic level.
基金funded by the National Natural Science Foundation of China(Grant Nos.21533005 and 21802095)the National Key R&D Program of China(2016YFB0101201).
文摘The development of highly active nitrogendoped carbon-based transition metal(M-N-C)compounds for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs)greatly helps reduce fuel cell cost,thus rapidly promoting their commercial applications.Among different M-N-C electrocatalysts,the series of Fe-N-C materials are highly favored because of their high ORR activity.However,there remains a debate on the effect of Fe,and rare investigations focus on the influence of Fe addition in the second heat treatment usually performed after acid leaching in the catalyst synthesis.It is thus very critical to explore the influences of Fe on the ORR electrocatalytic activity,which will,in turn,guide the design of Fe-N-C materials with enhanced performance.Herein,a series of Fe-N-C electrocatalysts are synthesize and the influence of Fe on the ORR activity are speculated both experimentally and theoretically.It is deduced that the active site lies in the structure of Fe-N4,accompanied with the addition of appropriate Fe,and the number of active sites increases without the occurrence of agglomeration particles.Moreover,it is speculated that Fe plays an important role in stabilizing N as well as constituting active sites in the second pyrolyzing process.
基金supported by the National Natural Science Foundation of China(11079007,21306220)
文摘The structure of [Bmim]2CuCl4 ionic liquids （Bmim： 1-butyl-3-methylimidazolium） with different ratios of H2O and C2H5OH was investigated using X-ray absorption fine structure （XAFS） technique. In this study, XAFS was employed to directly probe the conformational variations of copper ions in [Bmim]2CuCl4 with the addition of either water or ethanol. XAFS analysis confirmed that the structure of ionic liquids gradually transformed from tetrahedral to octahedral configuration with the increase in ratio of H2O. Our results also showed that water molecules coordinated with the copper ions of [Bmim]2CuCl4, leading to the conformational change in ionic liquids. However, the XAFS spectra of [Bmim]zCuCIa/C2H5OH indicated no coordination of anhydrous ethanol with the copper ions of [Bmim]2CuC14. The structure of [Bmim]2CuCl4 ionic liquids is maintained as the tetrahedral configuration in presence of ethanol. Therefore, anhydrous ethanol causes little variation in the structure of ionic liquids and it is a good solvent for the dilution of ionic liquids.
