The quality of straw affects N release after straw retention. As straw with high C： N ratio could result in N immobilization, additional N is needed to compensate N demand of crops. However, more and more N fertilize...The quality of straw affects N release after straw retention. As straw with high C： N ratio could result in N immobilization, additional N is needed to compensate N demand of crops. However, more and more N fertilizers have been applied to the soil to improve crop yields in China, which not only increases production cost but also reduces soil quality. Therefore, reasonable application of N fertilizer becomes a key problem after straw retention. This study aimed to assess the effects of applying maize straw with high quality alfalfa straw on mineral N content, microbial biomass and enzyme activity under controlled conditions. The effect of applying maize straw with alfalfa straw was compared with that of maize straw in combination with N fertilizer under the same C： N ratio （25：1）. The laboratory incubation experiment consisted of four treatments： （1） soil with no addition （CK）; （2） soil amended with maize straw （M）; （3） soil amended with alfalfa straw and maize straw with an adjusted C： N ratio of 25：1 （MM）; （4） soil amended with inorganic nitrogen fertilizer and maize straw with an adjusted C：N ratio of 25：1 （MF）. The results showed that application of maize straw leaded to an N immobilization during the 270 d of incubation. Combined application of alfalfa and maize straw and or mineral N fertilizer alleviates the N immobilization and increase soil mineral N content. Compared to MF treatment, MM treatment prolonged N availability during the incubation. MM and MF treatments increased the soil microbial biomass carbon and nitrogen contents, and soil invertase and β-glycosidase activities. There was no difference between MM and M treatment in soil urease activity. MF treatment had significantly negative influence on soil urease activity compared with M treatment. The amount of added N significantly affected mineral N content, soil microbial biomass and enzyme activity. The mixture of alfalfa straw and maize straw sustains higher level of mineral N content, microbial biomass and enzyme activity as it had high N input compared to maize straw in combination with N fertilizer. It is concluded that alfalfa straw may be a better N source than N fertilizer in alleviating N immobilization caused by maize straw retention.展开更多
A three-dimensional quantitative structure-activity relationship （3D-QSAR） study of a series of 7,8-dialkyl-l,3-diaminopyrrolo-[3,2-f] quinazolines with anticancer activity as dihydrofo- late reductase （DHFR） inhi...A three-dimensional quantitative structure-activity relationship （3D-QSAR） study of a series of 7,8-dialkyl-l,3-diaminopyrrolo-[3,2-f] quinazolines with anticancer activity as dihydrofo- late reductase （DHFR） inhibitors was carried out by using the comparative molecular field analysis （CoMFA）, on the basis of our reported 2D-QSAR of these compounds. The es- tablished 3D-QSAR model has good quality of statistics and good prediction ability; the non cross-validation correlation coefficient and the cross-validation value of this model are 0.993 and 0.619, respectively, the F value is 193.4, and the standard deviation SD is 0.208. This model indicates that the steric field factor plays a much more important role than the electrostatic one, in satisfying agreement with the published 2D-QSAR model. However, the 3D-QSAR model offers visual images of the steric field and the electrostatic field. The 3D-QSAR study further suggests the following： to improve the activity, the substituent R^1 should be selected to be a group with an adaptive bulk like Et or i-Pr, and the substituent R should be selected to be a larger alkyl. In particular, based on our present 3D-QSAR as well as the published 2D-QSAR, the experimentMly-proposed hydrophobic binding mechanism on the receptor-binding site of the DHFR can be further explained in theory. Therefore, the QSAR studies help to further understand the ＂hydrophobic binding＂ action mechanism of this kind of compounds, and to direct the molecular design of new drugs with higher activity.展开更多
The promotional effects of Zr on the structure, reduction, carburization and catalytic behavior of precipitated iron-based Fischer-Tropsch synthesis （FTS） catalysts were investigated. The catalysts were characterize...The promotional effects of Zr on the structure, reduction, carburization and catalytic behavior of precipitated iron-based Fischer-Tropsch synthesis （FTS） catalysts were investigated. The catalysts were characterized by N2 physisorption, temperature-programmed reduction （TPR）, and M6ssbauer effect spectroscopy （MES） techniques. As revealed by N2 physisorption, Zr decreased the BET surface area and pore volume of the catalyst. The results of TPR and MES show that Zr suppresses the reduction and carburization of Fe catalysts because of the interaction between Fe and Zr. The FTS reaction results indicate that Zr decreases the FTS activity of Fe catalysts but improves the catalysts＇ stability. In addition, Zr promoter restraines the formation of light hydrocarbons （methane and C2-C4） and shifts the production distribution to the heavy hydrocarbons.展开更多
In this paper, trellis shaping is applied to reducing the Peak-to-Average Power Ratio(PAPR) of NC-OFDM signals due to the fact that the total number of active subcarriers and their locations might change continuously ...In this paper, trellis shaping is applied to reducing the Peak-to-Average Power Ratio(PAPR) of NC-OFDM signals due to the fact that the total number of active subcarriers and their locations might change continuously in a dynamic spectrum access network.A new branch metric of trellis shaping is proposed which reduces the PAPR of OFDM signals through minimizing the variance of the power by VA decoder.The overall performance considerably depends on the type of signal mapping, and therefore a new type of 64QAM mapping method is designed.Simulation results show that this scheme significantly reduces the PAPR.Finally, a significant phenomenon is demonstrated that the PAPR of NC-OFDM signals in which the deactivated carriers is distributed in the Bernoulli distribution has better performance than that of OFDM signals.展开更多
For energy storage system,it is still a huge challenge to achieve high energy density and high power density simultaneously.One potential solution is to fabricate electrochemical capacitors(ECs),which store electric e...For energy storage system,it is still a huge challenge to achieve high energy density and high power density simultaneously.One potential solution is to fabricate electrochemical capacitors(ECs),which store electric energy through surface ion adsorption or redox reactions.Here we report a new electrode material,heavy nitrogen-doped(9.29 at.%)black titania(TiO2-x:N).This unique hybrid material,consisting of conductive amorphous shells supported on nanocrystalline cores,has rapid N-mediated redox reaction(TiO2-xNy+zH++ze■-TiO2-xNyHz),especially in acidic solutions,providing a specific capacitance of 750 Fg-1at 2 m V s-1(707 Fg-1at 1 A g-1),great rate capability(503 F g-1at 20 Ag-1),and maintain stable after initial fading.Being a new developed supercapacitor material,nitrogen-doped black titania may revive the oxide-based supercapacitors.展开更多
Vesicular pH modulates the function of many organelles and plays a pivotal role in cell metabolism processes such as proliferation and apoptosis. Here, we introduce a simple colorimetric redox-polyaniline nanoindicato...Vesicular pH modulates the function of many organelles and plays a pivotal role in cell metabolism processes such as proliferation and apoptosis. Here, we introduce a simple colorimetric redox-polyaniline nanoindicator, which can detect and quantify a broader biogenic pH range with superior sensitivity compared to pre-established trafficking agents employing one-dimensional turn-on of the fluorescence resonance-energy-transfer （FRET） signal. We fabricated polyaniline- based nanoprobes, which exhibited convertible transition states according to the proton levels, as an in situ indicator of vesicular transport pH. Silica-coated Fe304-MnO heterometal nanoparticles were synthesised and utilised as a metal oxidant to polymerise the aniline monomer. Finally, silica-coated polyaniline nanoparticles with adsorbed cyanine dye fluorophores Cy3 and Cy7 （FPSNIcyB and FPSNIcy7） were fabricated as proton-sensitive nanoindicators. Owing to the selective quenching induced by the local pH variations of vesicular transport, FPSNIcy3 and FPSNIcy7 demonstrated excellent intracellular trafficking and provided sensitive optical indication of minute proton levels.展开更多
文摘The quality of straw affects N release after straw retention. As straw with high C： N ratio could result in N immobilization, additional N is needed to compensate N demand of crops. However, more and more N fertilizers have been applied to the soil to improve crop yields in China, which not only increases production cost but also reduces soil quality. Therefore, reasonable application of N fertilizer becomes a key problem after straw retention. This study aimed to assess the effects of applying maize straw with high quality alfalfa straw on mineral N content, microbial biomass and enzyme activity under controlled conditions. The effect of applying maize straw with alfalfa straw was compared with that of maize straw in combination with N fertilizer under the same C： N ratio （25：1）. The laboratory incubation experiment consisted of four treatments： （1） soil with no addition （CK）; （2） soil amended with maize straw （M）; （3） soil amended with alfalfa straw and maize straw with an adjusted C： N ratio of 25：1 （MM）; （4） soil amended with inorganic nitrogen fertilizer and maize straw with an adjusted C：N ratio of 25：1 （MF）. The results showed that application of maize straw leaded to an N immobilization during the 270 d of incubation. Combined application of alfalfa and maize straw and or mineral N fertilizer alleviates the N immobilization and increase soil mineral N content. Compared to MF treatment, MM treatment prolonged N availability during the incubation. MM and MF treatments increased the soil microbial biomass carbon and nitrogen contents, and soil invertase and β-glycosidase activities. There was no difference between MM and M treatment in soil urease activity. MF treatment had significantly negative influence on soil urease activity compared with M treatment. The amount of added N significantly affected mineral N content, soil microbial biomass and enzyme activity. The mixture of alfalfa straw and maize straw sustains higher level of mineral N content, microbial biomass and enzyme activity as it had high N input compared to maize straw in combination with N fertilizer. It is concluded that alfalfa straw may be a better N source than N fertilizer in alleviating N immobilization caused by maize straw retention.
基金This work was supported by the National Natural Science Foundation of China （No.20673148）. We also heartily thank the College of Life Sciences, Sun Yat-Sen University for the SYBYL 6.9 computation environment support.
文摘A three-dimensional quantitative structure-activity relationship （3D-QSAR） study of a series of 7,8-dialkyl-l,3-diaminopyrrolo-[3,2-f] quinazolines with anticancer activity as dihydrofo- late reductase （DHFR） inhibitors was carried out by using the comparative molecular field analysis （CoMFA）, on the basis of our reported 2D-QSAR of these compounds. The es- tablished 3D-QSAR model has good quality of statistics and good prediction ability; the non cross-validation correlation coefficient and the cross-validation value of this model are 0.993 and 0.619, respectively, the F value is 193.4, and the standard deviation SD is 0.208. This model indicates that the steric field factor plays a much more important role than the electrostatic one, in satisfying agreement with the published 2D-QSAR model. However, the 3D-QSAR model offers visual images of the steric field and the electrostatic field. The 3D-QSAR study further suggests the following： to improve the activity, the substituent R^1 should be selected to be a group with an adaptive bulk like Et or i-Pr, and the substituent R should be selected to be a larger alkyl. In particular, based on our present 3D-QSAR as well as the published 2D-QSAR, the experimentMly-proposed hydrophobic binding mechanism on the receptor-binding site of the DHFR can be further explained in theory. Therefore, the QSAR studies help to further understand the ＂hydrophobic binding＂ action mechanism of this kind of compounds, and to direct the molecular design of new drugs with higher activity.
文摘The promotional effects of Zr on the structure, reduction, carburization and catalytic behavior of precipitated iron-based Fischer-Tropsch synthesis （FTS） catalysts were investigated. The catalysts were characterized by N2 physisorption, temperature-programmed reduction （TPR）, and M6ssbauer effect spectroscopy （MES） techniques. As revealed by N2 physisorption, Zr decreased the BET surface area and pore volume of the catalyst. The results of TPR and MES show that Zr suppresses the reduction and carburization of Fe catalysts because of the interaction between Fe and Zr. The FTS reaction results indicate that Zr decreases the FTS activity of Fe catalysts but improves the catalysts＇ stability. In addition, Zr promoter restraines the formation of light hydrocarbons （methane and C2-C4） and shifts the production distribution to the heavy hydrocarbons.
基金Supported by the National Natural Science Foundation of China (No.60832008)National Basic Research Program of China (973 Program, No.2009CB320403)
文摘In this paper, trellis shaping is applied to reducing the Peak-to-Average Power Ratio(PAPR) of NC-OFDM signals due to the fact that the total number of active subcarriers and their locations might change continuously in a dynamic spectrum access network.A new branch metric of trellis shaping is proposed which reduces the PAPR of OFDM signals through minimizing the variance of the power by VA decoder.The overall performance considerably depends on the type of signal mapping, and therefore a new type of 64QAM mapping method is designed.Simulation results show that this scheme significantly reduces the PAPR.Finally, a significant phenomenon is demonstrated that the PAPR of NC-OFDM signals in which the deactivated carriers is distributed in the Bernoulli distribution has better performance than that of OFDM signals.
基金financially supported by the National key R&D Program of China(2016YFB0901600)the Key Research Program of Chinese Academy of Sciences(QYZDJ-SSWJSC013)Chen IW was supported by U.S.Department of Energy BES grant DE-FG02-11ER46814used the facilities(Laboratory for Research on the Structure of Matter)supported by NSF grant DMR-1120901。
文摘For energy storage system,it is still a huge challenge to achieve high energy density and high power density simultaneously.One potential solution is to fabricate electrochemical capacitors(ECs),which store electric energy through surface ion adsorption or redox reactions.Here we report a new electrode material,heavy nitrogen-doped(9.29 at.%)black titania(TiO2-x:N).This unique hybrid material,consisting of conductive amorphous shells supported on nanocrystalline cores,has rapid N-mediated redox reaction(TiO2-xNy+zH++ze■-TiO2-xNyHz),especially in acidic solutions,providing a specific capacitance of 750 Fg-1at 2 m V s-1(707 Fg-1at 1 A g-1),great rate capability(503 F g-1at 20 Ag-1),and maintain stable after initial fading.Being a new developed supercapacitor material,nitrogen-doped black titania may revive the oxide-based supercapacitors.
文摘Vesicular pH modulates the function of many organelles and plays a pivotal role in cell metabolism processes such as proliferation and apoptosis. Here, we introduce a simple colorimetric redox-polyaniline nanoindicator, which can detect and quantify a broader biogenic pH range with superior sensitivity compared to pre-established trafficking agents employing one-dimensional turn-on of the fluorescence resonance-energy-transfer （FRET） signal. We fabricated polyaniline- based nanoprobes, which exhibited convertible transition states according to the proton levels, as an in situ indicator of vesicular transport pH. Silica-coated Fe304-MnO heterometal nanoparticles were synthesised and utilised as a metal oxidant to polymerise the aniline monomer. Finally, silica-coated polyaniline nanoparticles with adsorbed cyanine dye fluorophores Cy3 and Cy7 （FPSNIcyB and FPSNIcy7） were fabricated as proton-sensitive nanoindicators. Owing to the selective quenching induced by the local pH variations of vesicular transport, FPSNIcy3 and FPSNIcy7 demonstrated excellent intracellular trafficking and provided sensitive optical indication of minute proton levels.
