Yellowing of broccoli is a crucial limiting factor for its commercial value and consumer acceptance during postharvest.In this study,the impacts of exogenous melatonin(MEL)on chlorophyll content and fluorescence,as we...Yellowing of broccoli is a crucial limiting factor for its commercial value and consumer acceptance during postharvest.In this study,the impacts of exogenous melatonin(MEL)on chlorophyll content and fluorescence,as well as ultrastructure and membrane lipid metabolism of chloroplasts in broccoli were investigated during postharvest.The results showed that MEL treatment(200 μmol L^(-1))maintained the chlorophyll content,chloroplast autofluorescence and integral structure,and reduced the level ofserotonin in the chloroplasts in broccoli.Also,MEL treatment inhibited the membrane lipid peroxidation of chloroplasts,as indicated by low levels of superoxide anion(O_(2)^(-)),hydrogen peroxide(H_(2)O_(2))and malondialdehyde(MDA),and high levels of endogenous MEL.In addition,the stability and fluidity of chloroplast membranes were also better maintained in the treated broccoli via increasing the contents of phosphatidylglyceroland(PG),monogalactosyldiglyceride(MGDG),digalactosyldiglyceride(DGDG)and unsaturated fatty acids as well as decreasing saturated fatty acid content and the activities of lipoxygenase(LOX)and lipase(LPS).Thus,the application of MEL facilitated the maintenance of chloroplast integrity,thus contributing to yellowing postponement and the extension of the storage life of broccoli.展开更多
Mesoporous silica materials with high pore volume were successfully prepared by the chemical precipitation method, with water glass and a biodegradable nonionic surfactant polyethylene glycol （PEG）. The obtained mat...Mesoporous silica materials with high pore volume were successfully prepared by the chemical precipitation method, with water glass and a biodegradable nonionic surfactant polyethylene glycol （PEG）. The obtained materials were characterized by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, thermo gravimetric analyzer and differential scanning calorimetry （TG-DSC）, nitrogen adsorption-desorption measurements, and X-ray diffraction （XRD）. The results showed that the changes of the pore parameters depended on both the surfactant content and heat treatment temperature. When the content of PEG was 10wt% and the obtained PEG/SiO2 composite was heated at 600℃, the mesoporous silica with a pore volume of 2.2 cma/g, a BET specific surface area of 361.55 m^2/g, and a diameter of 2-4 μm could be obtained. The obtained mesoporous silica materials have potential applications in the fields of paint and plastic, as thickening, reinforcing, and flatting agents.展开更多
Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of double monomers. The composite particles formation mechanism was investigated. The effects of composite ...Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of double monomers. The composite particles formation mechanism was investigated. The effects of composite particles on the mechanical properties of nano-CaCO3-ABS （acrylonitrile-butadiene-styrene copolymer） composite material were studied. It was validated that the composite particles are made up of the nano-calcium carbonate cores and the shells of alternating copolymers of butyl acrylate （BA） and styrene （St）. The shells are chemically grafted and physically wrapped on the surface of nano-calcium carbonate particles. When the composite particles were filled in ABS matrix, the CaCO3 particles are homogeneously dispersed in the composite material as nanoscales. The impact strength of the composite material is obviously enhanced after filling appropriate amounts of composite particles. It can be concluded that the soapless emulsion polymerization of double monomers is an effective method for nano-CaCO3 surface treatment. 2008 University of Science and Technology Beijing. All rights reserved.展开更多
The study of rumor propagation dynamics is of great significance to reduce.false news and ensure the authenticity of news information.In this paper,a SI reaction-diffusion rumor propagation model with nonlinear satura...The study of rumor propagation dynamics is of great significance to reduce.false news and ensure the authenticity of news information.In this paper,a SI reaction-diffusion rumor propagation model with nonlinear saturation incidence is studied.First,through stability analysis,we obtain the conditions for the existence and local stability of the positive equilibrium point.By selecting suitable variable as the control parameter,the critical value of Turing bifurcation and the existence theorem of Turing bifurcation are obtained.Then,using the above theorem and multi-scale standard analysis,the expression of amplitude equation around Turing bifurcation point is obtained.By analyzing the amplitude equation,different types of Turing pattern are divided such as uniform steady-state mode,hexagonal mode,stripe mode and mixed structure mode.Further,in the numerical simulation part,by observing different patterns corresponding to different values of control variable,the correctness of the theory is verified.Finally,the effects of different network structures on patterns are investigated.The results show that there are significant differences in the distribution of users on different network structures.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.32372408)the National Natural Science Foundation of China for Youth(Grant No.32102041).
文摘Yellowing of broccoli is a crucial limiting factor for its commercial value and consumer acceptance during postharvest.In this study,the impacts of exogenous melatonin(MEL)on chlorophyll content and fluorescence,as well as ultrastructure and membrane lipid metabolism of chloroplasts in broccoli were investigated during postharvest.The results showed that MEL treatment(200 μmol L^(-1))maintained the chlorophyll content,chloroplast autofluorescence and integral structure,and reduced the level ofserotonin in the chloroplasts in broccoli.Also,MEL treatment inhibited the membrane lipid peroxidation of chloroplasts,as indicated by low levels of superoxide anion(O_(2)^(-)),hydrogen peroxide(H_(2)O_(2))and malondialdehyde(MDA),and high levels of endogenous MEL.In addition,the stability and fluidity of chloroplast membranes were also better maintained in the treated broccoli via increasing the contents of phosphatidylglyceroland(PG),monogalactosyldiglyceride(MGDG),digalactosyldiglyceride(DGDG)and unsaturated fatty acids as well as decreasing saturated fatty acid content and the activities of lipoxygenase(LOX)and lipase(LPS).Thus,the application of MEL facilitated the maintenance of chloroplast integrity,thus contributing to yellowing postponement and the extension of the storage life of broccoli.
基金the National Natural Science Foundation of China (No.20671010, 20236020, 20325621, 50642042).
文摘Mesoporous silica materials with high pore volume were successfully prepared by the chemical precipitation method, with water glass and a biodegradable nonionic surfactant polyethylene glycol （PEG）. The obtained materials were characterized by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, thermo gravimetric analyzer and differential scanning calorimetry （TG-DSC）, nitrogen adsorption-desorption measurements, and X-ray diffraction （XRD）. The results showed that the changes of the pore parameters depended on both the surfactant content and heat treatment temperature. When the content of PEG was 10wt% and the obtained PEG/SiO2 composite was heated at 600℃, the mesoporous silica with a pore volume of 2.2 cma/g, a BET specific surface area of 361.55 m^2/g, and a diameter of 2-4 μm could be obtained. The obtained mesoporous silica materials have potential applications in the fields of paint and plastic, as thickening, reinforcing, and flatting agents.
基金the National Natural Science Foundation of China(No.20236020,20325621)the National R & D Program of China(No.2001BA310A01).
文摘Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of double monomers. The composite particles formation mechanism was investigated. The effects of composite particles on the mechanical properties of nano-CaCO3-ABS （acrylonitrile-butadiene-styrene copolymer） composite material were studied. It was validated that the composite particles are made up of the nano-calcium carbonate cores and the shells of alternating copolymers of butyl acrylate （BA） and styrene （St）. The shells are chemically grafted and physically wrapped on the surface of nano-calcium carbonate particles. When the composite particles were filled in ABS matrix, the CaCO3 particles are homogeneously dispersed in the composite material as nanoscales. The impact strength of the composite material is obviously enhanced after filling appropriate amounts of composite particles. It can be concluded that the soapless emulsion polymerization of double monomers is an effective method for nano-CaCO3 surface treatment. 2008 University of Science and Technology Beijing. All rights reserved.
基金supported by the National Natural Science Foundation of China(Grant No.12002135)Young Science and Technology Talents Lifting Project of Jiangsu Association for Science and Technology.
文摘The study of rumor propagation dynamics is of great significance to reduce.false news and ensure the authenticity of news information.In this paper,a SI reaction-diffusion rumor propagation model with nonlinear saturation incidence is studied.First,through stability analysis,we obtain the conditions for the existence and local stability of the positive equilibrium point.By selecting suitable variable as the control parameter,the critical value of Turing bifurcation and the existence theorem of Turing bifurcation are obtained.Then,using the above theorem and multi-scale standard analysis,the expression of amplitude equation around Turing bifurcation point is obtained.By analyzing the amplitude equation,different types of Turing pattern are divided such as uniform steady-state mode,hexagonal mode,stripe mode and mixed structure mode.Further,in the numerical simulation part,by observing different patterns corresponding to different values of control variable,the correctness of the theory is verified.Finally,the effects of different network structures on patterns are investigated.The results show that there are significant differences in the distribution of users on different network structures.
