孕烷X受体(Pregnane X receptor,PXR)是核受体超家族(NRs)中NR1I的重要成员之一,在保护机体免于内源性和外源性物质损伤方面具有重要作用。利用CRISPR/Cas9基因编辑技术建立PXR基因敲除的斑马鱼模型,为研究环境污染物的毒性机理及代谢...孕烷X受体(Pregnane X receptor,PXR)是核受体超家族(NRs)中NR1I的重要成员之一,在保护机体免于内源性和外源性物质损伤方面具有重要作用。利用CRISPR/Cas9基因编辑技术建立PXR基因敲除的斑马鱼模型,为研究环境污染物的毒性机理及代谢过程提供基础模型。根据PXR基因序列,设计gRNA靶位点,体外转录合成gRNA。同时,将设计合成的gRNA与Cas9 mRNA通过显微注射转入斑马鱼受精卵,经孵化、筛选出有效的突变体,并逐代培养杂交筛选出PXR基因敲除突变体。结果表明利用CRISPR/Cas9基因编辑技术成功敲除PXR基因,经测序分析获得稳定的PXR(+4/+4)基因纯合体。展开更多
Exposed to space plasma and solar radiation, electrostatic potential may build up in the lunar regolith, leading to a wealth of dust phenomena, including levitation, oscillation, and transport over the surface. Based ...Exposed to space plasma and solar radiation, electrostatic potential may build up in the lunar regolith, leading to a wealth of dust phenomena, including levitation, oscillation, and transport over the surface. Based on plasma sheath theory,the global near-surface plasma environment is modeled, and the dynamics of charged dust are investigated. Results show that sub-micron sized dust particles can be levitated by the electric field over the surface, forming a dust belt that changes in position and thickness depending on the solar zenith angle. On the dayside of the Moon, stably levitated particles are about ten times smaller, and collect in a thinner belt closer to the surface than do those on the nightside. Although the size and charge of stably levitated dust particles are dependent on ambient plasma conditions, initial charge and velocity, which are closely related to the dynamics of dust particles including charging, oscillation, and damping, will determine whether, or not, a particle can attain stable levitation. Horizontal electrostatic dust transport near to the terminator region may lead to net deposition of dust from the dark into the sunlit hemisphere. Finally, because of different charging processes that result due to rotation of the Moon, before precipitation,dust particles in the dusk terminator region may be transported much longer distances and oscillate to much higher altitude than these in the dawn terminator.展开更多
Earth's bow shock is the result of interaction between the supersonic solar wind and Earth's magnetopause. However, data limitations mean the model of the shape and position of the bow shock are based largely ...Earth's bow shock is the result of interaction between the supersonic solar wind and Earth's magnetopause. However, data limitations mean the model of the shape and position of the bow shock are based largely on near-Earth satellite data. The model of the bow shock in the distant magnetotail and other factors that affect the bow shock, such as the interplanetary magnetic field(IMF) B_y, remain unclear. Here, based on the bow shock crossings of ARTEMIS from January 2011 to January 2015, new coefficients of the tail-flaring angle a of the Chao model(one of the most accurate models currently available) were obtained by fitting data from the middle-distance magnetotail(near-lunar orbit, geocentric distance -20R_E>X>-50R_E). In addition, the effects of the IMF B_y on the flaring angle a were analyzed. Our results showed that:(1) the new fitting coefficients of the Chao model in the middle-distance magnetotail are more consistent with the observed results;(2) the tail-flaring angle a of the bow shock increases as the absolute value of the IMF B_y increases. Moreover, positive IMF B_y has a greater effect than negative IMF B_y on flaring angle. These results provide a reference for bow shock modeling that includes the IMF B_y.展开更多
Based on the magnetospheric kinetic theory, a model is developed to specify the flux of energetic electrons in the inner and middle magnetosphere. Under the assumption of adiabatic motion and isotropic particle distri...Based on the magnetospheric kinetic theory, a model is developed to specify the flux of energetic electrons in the inner and middle magnetosphere. Under the assumption of adiabatic motion and isotropic particle distribution maintained by pitch-angle scattering, the model calculates the electron flux by following bounce-averaged electric field, gradient, and curvature drift in the time dependent electric and magnetic field, meanwhile it counts the electron loss caused by pitch angle scattering. Using the model, the clectron flux distribution during a magnetic storm was calculated and compared with the observation data from the geosynchronous orbit. It is shown that the model can successfully reproduce most of the major electron flux enhancements observed at the geosynchronous orbit and generally tracks the satellite data well. The rms errors of the modeled logarithm of flux are between 0.5-1.0.展开更多
In this paper,we report on our study of the trajectories of solar wind electrons reflected by lunar electric and magnetic fields through analysis of reflectivity and distribution under different conditions.Our calcula...In this paper,we report on our study of the trajectories of solar wind electrons reflected by lunar electric and magnetic fields through analysis of reflectivity and distribution under different conditions.Our calculations and simulations showed that the variations of both the magnetic field and surface potential play important roles in changing the directions of the traces of electrons.Furthermore,we were able to distinguish the changes resulting from these two variations through further analysis of the results.Thus,both the magnitude of the crustal field and the surface potential can be acquired from the data of satellites such as the Lunar Prospector.These findings could also contribute to the design and development of new devices in future lunar programs.展开更多
文摘孕烷X受体(Pregnane X receptor,PXR)是核受体超家族(NRs)中NR1I的重要成员之一,在保护机体免于内源性和外源性物质损伤方面具有重要作用。利用CRISPR/Cas9基因编辑技术建立PXR基因敲除的斑马鱼模型,为研究环境污染物的毒性机理及代谢过程提供基础模型。根据PXR基因序列,设计gRNA靶位点,体外转录合成gRNA。同时,将设计合成的gRNA与Cas9 mRNA通过显微注射转入斑马鱼受精卵,经孵化、筛选出有效的突变体,并逐代培养杂交筛选出PXR基因敲除突变体。结果表明利用CRISPR/Cas9基因编辑技术成功敲除PXR基因,经测序分析获得稳定的PXR(+4/+4)基因纯合体。
基金supported by the National Natural Science Foundation of China(Grant No.41174115)
文摘Exposed to space plasma and solar radiation, electrostatic potential may build up in the lunar regolith, leading to a wealth of dust phenomena, including levitation, oscillation, and transport over the surface. Based on plasma sheath theory,the global near-surface plasma environment is modeled, and the dynamics of charged dust are investigated. Results show that sub-micron sized dust particles can be levitated by the electric field over the surface, forming a dust belt that changes in position and thickness depending on the solar zenith angle. On the dayside of the Moon, stably levitated particles are about ten times smaller, and collect in a thinner belt closer to the surface than do those on the nightside. Although the size and charge of stably levitated dust particles are dependent on ambient plasma conditions, initial charge and velocity, which are closely related to the dynamics of dust particles including charging, oscillation, and damping, will determine whether, or not, a particle can attain stable levitation. Horizontal electrostatic dust transport near to the terminator region may lead to net deposition of dust from the dark into the sunlit hemisphere. Finally, because of different charging processes that result due to rotation of the Moon, before precipitation,dust particles in the dusk terminator region may be transported much longer distances and oscillate to much higher altitude than these in the dawn terminator.
基金supported by the National Natural Science Foundation of China(Grant Nos.41322031,41404131,41574157,41031065&41304129)the Specialized Research Fund for State Key Laboratoriesthe Shandong Natural Science Foundation(Grant Nos.2013BSE27132,BS2013HZ001)
文摘Earth's bow shock is the result of interaction between the supersonic solar wind and Earth's magnetopause. However, data limitations mean the model of the shape and position of the bow shock are based largely on near-Earth satellite data. The model of the bow shock in the distant magnetotail and other factors that affect the bow shock, such as the interplanetary magnetic field(IMF) B_y, remain unclear. Here, based on the bow shock crossings of ARTEMIS from January 2011 to January 2015, new coefficients of the tail-flaring angle a of the Chao model(one of the most accurate models currently available) were obtained by fitting data from the middle-distance magnetotail(near-lunar orbit, geocentric distance -20R_E>X>-50R_E). In addition, the effects of the IMF B_y on the flaring angle a were analyzed. Our results showed that:(1) the new fitting coefficients of the Chao model in the middle-distance magnetotail are more consistent with the observed results;(2) the tail-flaring angle a of the bow shock increases as the absolute value of the IMF B_y increases. Moreover, positive IMF B_y has a greater effect than negative IMF B_y on flaring angle. These results provide a reference for bow shock modeling that includes the IMF B_y.
基金supported by the National Natural Science Foundation of China(Grant No.40704032)
文摘Based on the magnetospheric kinetic theory, a model is developed to specify the flux of energetic electrons in the inner and middle magnetosphere. Under the assumption of adiabatic motion and isotropic particle distribution maintained by pitch-angle scattering, the model calculates the electron flux by following bounce-averaged electric field, gradient, and curvature drift in the time dependent electric and magnetic field, meanwhile it counts the electron loss caused by pitch angle scattering. Using the model, the clectron flux distribution during a magnetic storm was calculated and compared with the observation data from the geosynchronous orbit. It is shown that the model can successfully reproduce most of the major electron flux enhancements observed at the geosynchronous orbit and generally tracks the satellite data well. The rms errors of the modeled logarithm of flux are between 0.5-1.0.
基金supported by the knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX2-yw-T13)the National Natural Science Foundation of China (Grant No. 40974108)
文摘In this paper,we report on our study of the trajectories of solar wind electrons reflected by lunar electric and magnetic fields through analysis of reflectivity and distribution under different conditions.Our calculations and simulations showed that the variations of both the magnetic field and surface potential play important roles in changing the directions of the traces of electrons.Furthermore,we were able to distinguish the changes resulting from these two variations through further analysis of the results.Thus,both the magnitude of the crustal field and the surface potential can be acquired from the data of satellites such as the Lunar Prospector.These findings could also contribute to the design and development of new devices in future lunar programs.
