Using the hybrid finite difference method,we solve the Fokker-Planck equation to study the effect of seed electron injection on acceleration of radiation belt electrons driven by chorus waves.Numerical results show th...Using the hybrid finite difference method,we solve the Fokker-Planck equation to study the effect of seed electron injection on acceleration of radiation belt electrons driven by chorus waves.Numerical results show that in the absence of injection chorus waves can accelerate electrons at large pitch angles(e >60°),producing enhancements in the phase space density(PSD) of(1-2 MeV) electrons by a factor of 100-1000 within 1-2 days.In the presence of injection,chorus waves yield increase in PSD of electrons by accelerating the injected seed electrons.Meanwhile,the PSD evolution increases as the pitch angle increases but decreases as electron energy increases.Moreover,the PSD evolution can extend to higher energies with a time scale of 1-2 days for 1-2 MeV energies.When the injection increases by a factor of 10 higher than the initial value and remains for about two days,maximum values of PSD for 1 or 2 MeV increase to 6 or 3 times respectively higher than those without injection in two days.The current results suggest that the injected seed electrons play an important role in the evolution of the radiation belt electrons.展开更多
Generation of intense, fully coherent radiation with wide spectral coverage has been a long-standing challenge for laser technologies. Several techniques have been developed in recent years to extend the spectral cove...Generation of intense, fully coherent radiation with wide spectral coverage has been a long-standing challenge for laser technologies. Several techniques have been developed in recent years to extend the spectral coverage in optical physics, but none of them hold the potential to produce X-ray laser pulses with very high-peak power. Urgent demands for intense X-ray light sources have prompted the development of free-electron lasers(FELs), which have been proved to be very useful tools in many scientific areas. In this paper, we give an overview of the basic principle of FELs, techniques for realizing fully coherent FELs, and the development of fully coherent FEL facilities in China.展开更多
Fruit, seed morphology and seed coat sculpturing were recorded for 10 species belongs to 9 genera and five tribes of Brassicaceae in eastern region of Saudi Arabia by using light microscope (LM) and scanning electron ...Fruit, seed morphology and seed coat sculpturing were recorded for 10 species belongs to 9 genera and five tribes of Brassicaceae in eastern region of Saudi Arabia by using light microscope (LM) and scanning electron microscope (SEM). Four seed patterns were recognized based on surface sculpturing pattern;Reticulate, with four subtypes, undulate, verrucate and ocellate. The results of numerical analysis showed that species were grouped into two major clusters and each cluster divided into two groups. The cluster analysis indicates that the characters of fruit and seed are very important characters for identification and taxonomical classification of the tribes. The results indicate that the most tribes of Brassicaceae are polyphyletic, and some are related to each other’s as Lepidieae, Alyssieae and Sisymbrieae.展开更多
Eremanthus erythropappus(DC.)MacLeish is an important forest species native to the Brazilian savanna biome,an environment with well-defined rainy and dry seasons.Its seeds are desiccation tolerant,non-dormant and disp...Eremanthus erythropappus(DC.)MacLeish is an important forest species native to the Brazilian savanna biome,an environment with well-defined rainy and dry seasons.Its seeds are desiccation tolerant,non-dormant and dispersed at the end of dry season.This exposes them to the first sporadic rains that can trigger germination but the subsequent dry days can compromise survival of the newly germinated seed.This study evaluates if the damages caused by drying of germinating E.erythropappus seeds,at the stage when they have lost desiccation tolerance,are lethal.The percentage of normal seedlings was evaluated when seeds with different imbibition times were dried to their initial water content and then pre-humidified and rehydrated.Desiccation tolerance was fully lost after 0.5 mm of hypocotyl-radicle protrusion(approximately 72 h)when the radicle had root hairs,a possible indicator of sensitivity to desiccation.Disintegration of cell contents and ultrastructural damage to the seeds subjected to drying were observed by electron scanning microscope.Root hairs disappeared after drying,reappearing after pre-humidification,possibly an attempt to increase the surface area of the radicle for water uptake.However,the hypocotylradicle axis became darkened,probably by antioxidant system failure,causing seed death.展开更多
基金supported by the Initiative Project of Chinese Academy of Sciences (Grant No. YYYJ-1110)
文摘Using the hybrid finite difference method,we solve the Fokker-Planck equation to study the effect of seed electron injection on acceleration of radiation belt electrons driven by chorus waves.Numerical results show that in the absence of injection chorus waves can accelerate electrons at large pitch angles(e >60°),producing enhancements in the phase space density(PSD) of(1-2 MeV) electrons by a factor of 100-1000 within 1-2 days.In the presence of injection,chorus waves yield increase in PSD of electrons by accelerating the injected seed electrons.Meanwhile,the PSD evolution increases as the pitch angle increases but decreases as electron energy increases.Moreover,the PSD evolution can extend to higher energies with a time scale of 1-2 days for 1-2 MeV energies.When the injection increases by a factor of 10 higher than the initial value and remains for about two days,maximum values of PSD for 1 or 2 MeV increase to 6 or 3 times respectively higher than those without injection in two days.The current results suggest that the injected seed electrons play an important role in the evolution of the radiation belt electrons.
文摘目的利用电子舌和气相色谱-质谱(gas chromatography-mass spectrometry,GC-MS)技术检测纯白莲蓉、纯红莲蓉、大师手工纯白莲蓉、低糖纯白莲蓉和绿色食品级纯白莲蓉馅料5种不同品种的莲蓉馅料的风味差异。方法采用电子舌对莲蓉馅料的甜味等主要风味指标进行评价,结合GC-MS技术分析脂肪酸成分,并通过偏最小二乘法回归分析(partial least squares regression,PLSR)建立电子舌和游离脂肪酸的评价模型,预测莲蓉馅料的风味。结果5种莲蓉馅料在甜味和咸味上存在显著差异(P<0.05),其中,绿色食品级纯白莲蓉馅料的甜味强度最高,手工纯白莲蓉馅料的咸味强度最高。利用GC-MS技术共检测出油酸和亚油酸等9种游离脂肪酸,在电子舌和脂肪酸联合评价的PLSR回归模型中,甜味、鲜味、丰富性和油脂味模型的决定系数R2在校正集上分别为:0.94、0.94、0.95、0.91,在交叉验证集上分别为:0.90、0.88、0.91、0.83,其均方根误差(root mean squared error,RMSE)在校正集上分别为:0.21、0.14、0.14、0.18,在交叉验证集上分别为0.28、0.21、0.20、0.25。与莲蓉馅料单独电子舌或游离脂肪酸风味评价相比,联合评价表现出更好的预测能力,特别在油脂味评价上,交叉验证集的决定系数大幅度提升,从电子舌评价的0.15、游离脂肪酸评价的0.67增加到0.83,决定系数更接近于1,均方根误差较小,显示出更高的拟合度。结论电子舌和脂肪酸联合评价为莲蓉馅料风味的仪器评价研究提供参考数据。
基金supported by the National Key Research and Development Program of China(No.2016YFA0401900)the National Natural Science Foundation of China(Nos.11475250 and11775293)+1 种基金the Young Elite Scientist Sponsorship Program of CAST(2015QNRC001)the Ten Thousand Talent Program
文摘Generation of intense, fully coherent radiation with wide spectral coverage has been a long-standing challenge for laser technologies. Several techniques have been developed in recent years to extend the spectral coverage in optical physics, but none of them hold the potential to produce X-ray laser pulses with very high-peak power. Urgent demands for intense X-ray light sources have prompted the development of free-electron lasers(FELs), which have been proved to be very useful tools in many scientific areas. In this paper, we give an overview of the basic principle of FELs, techniques for realizing fully coherent FELs, and the development of fully coherent FEL facilities in China.
文摘Fruit, seed morphology and seed coat sculpturing were recorded for 10 species belongs to 9 genera and five tribes of Brassicaceae in eastern region of Saudi Arabia by using light microscope (LM) and scanning electron microscope (SEM). Four seed patterns were recognized based on surface sculpturing pattern;Reticulate, with four subtypes, undulate, verrucate and ocellate. The results of numerical analysis showed that species were grouped into two major clusters and each cluster divided into two groups. The cluster analysis indicates that the characters of fruit and seed are very important characters for identification and taxonomical classification of the tribes. The results indicate that the most tribes of Brassicaceae are polyphyletic, and some are related to each other’s as Lepidieae, Alyssieae and Sisymbrieae.
基金CNPq(National Council for Scientific and Technological Development).Project number 310225/2015-9
文摘Eremanthus erythropappus(DC.)MacLeish is an important forest species native to the Brazilian savanna biome,an environment with well-defined rainy and dry seasons.Its seeds are desiccation tolerant,non-dormant and dispersed at the end of dry season.This exposes them to the first sporadic rains that can trigger germination but the subsequent dry days can compromise survival of the newly germinated seed.This study evaluates if the damages caused by drying of germinating E.erythropappus seeds,at the stage when they have lost desiccation tolerance,are lethal.The percentage of normal seedlings was evaluated when seeds with different imbibition times were dried to their initial water content and then pre-humidified and rehydrated.Desiccation tolerance was fully lost after 0.5 mm of hypocotyl-radicle protrusion(approximately 72 h)when the radicle had root hairs,a possible indicator of sensitivity to desiccation.Disintegration of cell contents and ultrastructural damage to the seeds subjected to drying were observed by electron scanning microscope.Root hairs disappeared after drying,reappearing after pre-humidification,possibly an attempt to increase the surface area of the radicle for water uptake.However,the hypocotylradicle axis became darkened,probably by antioxidant system failure,causing seed death.
