Crystals of LiKGdF 5∶Er 3+, Tb 3+ grown by the hydrothermal synthesis technique with concentrations of 2% and 0.4% were analysed. By using site selective excitation measured at low temperature, luminescence and ex...Crystals of LiKGdF 5∶Er 3+, Tb 3+ grown by the hydrothermal synthesis technique with concentrations of 2% and 0.4% were analysed. By using site selective excitation measured at low temperature, luminescence and excitation spectra from Er 3+ and Tb 3+ ions embedded in LiKGdF 5 were clearly separated. The lifetimes of the emitting levels 4S 3/2 of Er 3+ and 5D 4 of Tb 3+ were also determined. Following the site selective spectroscopy study, the dominant energy transfer process from Tb 3+ to Er 3+ in the crystal was then investigated via transient experiments.展开更多
We present modeling work on three young stellar objects that are promis-ing targets for future high-resolution observations to investigate circumstellar disk evolution. The currently available data comprise the spectr...We present modeling work on three young stellar objects that are promis-ing targets for future high-resolution observations to investigate circumstellar disk evolution. The currently available data comprise the spectral energy distribution from optical to millimeter wavelengths which allow constraining the structure of the cir-cumstellar disk using self-consistent radiative transfer models. The results suggest that the assumption of well-mixed dust and gas leads to overestimation of flux in the far-infrared. Observational and theoretical arguments suggest that an overall decrease in far-infrared excess can be explained by dust settling towards the midplane. A new disk model is hence employed to take the effect of dust sedimentation into account. The extended model satisfactorily reproduces all existing observations. The three tar-gets studied here therefore deserve follow-up observations to reveal the evolutionary state of their protoplanetary disks.展开更多
[Objective] The paper aims to explore the influences of source sink change of wheat at different densities on wheat yield.[Method] 225 （D1） and 320 plant/m2（D2） were adopted,then cutting flag leaf （L1）,the secon...[Objective] The paper aims to explore the influences of source sink change of wheat at different densities on wheat yield.[Method] 225 （D1） and 320 plant/m2（D2） were adopted,then cutting flag leaf （L1）,the second last leaf （L2）,removing upper part of spike （L3） and controlling （CK） were used to conduct field experiment.[Result] The results showed that both of the two densities of wheat＇s 1 000-grain weight and grain filling rate after anthesis in a decreasing order of L3〉CK〉L2〉L1,and the grain weight per spike and dry matter amount translated after anthesis turned to be CK〉L2〉L1 〉L3.[Conclusion].Both of leaf-cutting and spikelet removing decreased the grain weight per spike and dry matter amount translated after anthesis.Removing upper part of spike increased wheat＇s 1 000-grain weight.But the decreasing of the sink and dry matter amount translated contributed to the decreasing of the yield of wheat.展开更多
文摘Crystals of LiKGdF 5∶Er 3+, Tb 3+ grown by the hydrothermal synthesis technique with concentrations of 2% and 0.4% were analysed. By using site selective excitation measured at low temperature, luminescence and excitation spectra from Er 3+ and Tb 3+ ions embedded in LiKGdF 5 were clearly separated. The lifetimes of the emitting levels 4S 3/2 of Er 3+ and 5D 4 of Tb 3+ were also determined. Following the site selective spectroscopy study, the dominant energy transfer process from Tb 3+ to Er 3+ in the crystal was then investigated via transient experiments.
基金Supported by the National Natural Science Foundation of China(Grant Nos.10733030,10921063 and 11173060)
文摘We present modeling work on three young stellar objects that are promis-ing targets for future high-resolution observations to investigate circumstellar disk evolution. The currently available data comprise the spectral energy distribution from optical to millimeter wavelengths which allow constraining the structure of the cir-cumstellar disk using self-consistent radiative transfer models. The results suggest that the assumption of well-mixed dust and gas leads to overestimation of flux in the far-infrared. Observational and theoretical arguments suggest that an overall decrease in far-infrared excess can be explained by dust settling towards the midplane. A new disk model is hence employed to take the effect of dust sedimentation into account. The extended model satisfactorily reproduces all existing observations. The three tar-gets studied here therefore deserve follow-up observations to reveal the evolutionary state of their protoplanetary disks.
基金Supported by Jiangsu High School Natural Science Fund(09KJB210004)Undergraduate Practice Innovation Project of Nanjing University of Information Science & Technology (09CX0025 )Educational Reform Project of Nanjing University of Information Science &Technology (09JY0036)~~
文摘[Objective] The paper aims to explore the influences of source sink change of wheat at different densities on wheat yield.[Method] 225 （D1） and 320 plant/m2（D2） were adopted,then cutting flag leaf （L1）,the second last leaf （L2）,removing upper part of spike （L3） and controlling （CK） were used to conduct field experiment.[Result] The results showed that both of the two densities of wheat＇s 1 000-grain weight and grain filling rate after anthesis in a decreasing order of L3〉CK〉L2〉L1,and the grain weight per spike and dry matter amount translated after anthesis turned to be CK〉L2〉L1 〉L3.[Conclusion].Both of leaf-cutting and spikelet removing decreased the grain weight per spike and dry matter amount translated after anthesis.Removing upper part of spike increased wheat＇s 1 000-grain weight.But the decreasing of the sink and dry matter amount translated contributed to the decreasing of the yield of wheat.
