We present measurements of the 2p-3d transition opacity of a hot molybdenum-scandium sample with nearly half-vacant molybdenum M-shell configurations.A plastic-tamped molybdenum-scandium foil sample is radiatively hea...We present measurements of the 2p-3d transition opacity of a hot molybdenum-scandium sample with nearly half-vacant molybdenum M-shell configurations.A plastic-tamped molybdenum-scandium foil sample is radiatively heated to high temperature in a compact D-shaped gold Hohlraum driven by∼30 kJ laser energy at the SG-100 kJ laser facility.X rays transmitted through the molybdenum and scandium plasmas are diffracted by crystals and finally recorded by image plates.The electron temperatures in the sample in particular spatial and temporal zones are determined by the K-shell absorption of the scandium plasma.A combination of the IRAD3D view factor code and the MULTI hydrodynamic code is used to simulate the spatial distribution and temporal behavior of the sample temperature and density.The inferred temperature in the molybdenum plasma reaches a average of 138±11 eV.A detailed configuration-accounting calculation of the n=2–3 transition absorption of the molybdenum plasma is compared with experimental measurements and quite good agreement is found.The present measurements provide an opportunity to test opacity models for complicated M-shell configurations.展开更多
A self-consistent and precise method to determine the time-dependent radiative albedo,i.e.,the ratio of the reemission flux to the incident flux,for an indirect-drive inertial confinement fusion Hohlraum wall material...A self-consistent and precise method to determine the time-dependent radiative albedo,i.e.,the ratio of the reemission flux to the incident flux,for an indirect-drive inertial confinement fusion Hohlraum wall material is proposed.A specially designed symmetrical triple-cavity gold Hohlraum is used to create approximately constant and near-equilibrium uniform radiation with a peak temperature of 160 eV.The incident flux at the secondary cavity waist is obtained from flux balance analysis and from the shock velocity of a standard sample.The results agree well owing to the symmetrical radiation in the secondary cavity.A self-consistent and precise time-dependent radiative albedo is deduced from the reliable reemission flux and the incident flux,and the result from the shock velocity is found to have a smaller uncertainty than that from the multi-angle flux balance analysis,and also to agree well with the result of a simulation using the HYADES opacity.展开更多
Research on anion exchange membrane fuel cells(AEMFCs)mainly focuses on the membrane module,and improving its performance has always been the focus of researchers.To create high-performance anion exchange membranes(AE...Research on anion exchange membrane fuel cells(AEMFCs)mainly focuses on the membrane module,and improving its performance has always been the focus of researchers.To create high-performance anion exchange membranes(AEMs),a series of side chain type AEMs were prepared by introducing different proportions of side chains containing anisotropic poly cations with relatively stable piperidinium ring cations and side quaternary ammonium cations as cation groups,using poly(p-terphenyl isatin)(PTI),a main chain polymer without aryl ether bonds.The dense surface of the PTI-N-n series membranes is shown by SEM images;TEM images show that the ion domains are clearly distributed in the membrane,so a continuous ion transport channel is constructed.PTI-N-100 has the highest hydroxide conductivity at 80℃,reaching 96.83 mS cm^(-1) due to multiple transport sites.The PTI-N-100 membrane has a peak power density of 180 mW cm^(2) based on the highest ionic conductivity.Therefore,we believe that the introduction of multi-cations contributes to the performance of anion exchange membranes.展开更多
A radiative shock(RS)is one in which the density and temperature structures are affected by radiation from the shock-heated matter.RS plays a special role in astrophysics as it nontrivially combines both hydrodynamics...A radiative shock(RS)is one in which the density and temperature structures are affected by radiation from the shock-heated matter.RS plays a special role in astrophysics as it nontrivially combines both hydrodynamics and radiation physics.In most astrophysical shocks,the temperature and density conditions lead to strong emission,with radiation thus playing a major role therein.展开更多
In indirect-driven laser fusion experiments,the movement of the laser absorption layer will distort the radiation uniformity on the capsule.The gold foam has advantages in symmetry control and lowering wall plasma blo...In indirect-driven laser fusion experiments,the movement of the laser absorption layer will distort the radiation uniformity on the capsule.The gold foam has advantages in symmetry control and lowering wall plasma blowoff when used in an inertial confinement fusion(ICF)hohlraum.This work investigates the motion of the laser absorption cutoff position using lowdensity foam gold walls.It is found that the motion of the laser absorption cutoff position can be significantly mitigated through optimal initial low density,tailored to a specific laser shape.For a short square laser pulse,the laser absorption cutoff position remains almost stationary at an initial density of approximately 0.6 g cm^(-3).For a long-shaped laser pulse,the minimal motion of the laser absorption cutoff position is observed at an initial density of about 0.1 g cm^(-3).This approach allows for the adjustment of the symmetry of the hohlraum radiation source.The insights gained from this study serve as a crucial reference for optimizing the hohlraum wall density.展开更多
Experiments exploring the propagation of heat waves within cylindrical CH foams were performed on the Shenguang-Ⅲ prototype laser facility in 2012.In this paper,the radiation fluxes out of CH foam cylinders at differ...Experiments exploring the propagation of heat waves within cylindrical CH foams were performed on the Shenguang-Ⅲ prototype laser facility in 2012.In this paper,the radiation fluxes out of CH foam cylinders at different angles are analyzed theoretically using the two-dimensional radiation hydrodynamics code LARED-R.Owing to the difficulty in validating opacity and equation of state(EOS)data for high-Z plasmas,and to uncertainties in the measured radiation temperature Tr and the original foam densityρ0,multipliers are introduced to adjust the Au material parameters,Tr,andρ0 in our simulations to better explain the measurements.The dependences of the peak radiation flux Fmax and the breakout time of the heat wave thalf(defined as the time corresponding to the radiation flux at half-maximum)on the radiation source,opacity,EOS,andρ0 scaling factors(η_(src),η_(op),η_(eos),and η_(ρ))are investigated via numerical simulations combined with fitting.Then,with the uncertainties in the measured Tr andρ0 fixed at 3.6%and 3.1%,respectively,experimental data are exploited as fiducial values to determine the ranges ofη_(op) andηeos.It is found that the ranges ofη_(op) andηeos fixed by this experiment overlap partially with those found in our previous work[Meng et al.,Phys.Plasmas 20,092704(2013)].Based on the scaled opacity and EOS parameters,the values of F_(max) and t_(half) obtained via simulations are in good agreement with the measurements,with maximum errors∼9.5%and within 100 ps,respectively.展开更多
高光谱图像变化检测可提供地球表面的时间维变化信息,对城乡规划和管理至关重要。因具有较高的光谱分辨率,高光谱图像常被用于检测更精细的变化。针对高光谱变化检测的问题,提出一种基于协同稀疏与非局部低秩张量的高光谱图像变化检测...高光谱图像变化检测可提供地球表面的时间维变化信息,对城乡规划和管理至关重要。因具有较高的光谱分辨率,高光谱图像常被用于检测更精细的变化。针对高光谱变化检测的问题,提出一种基于协同稀疏与非局部低秩张量的高光谱图像变化检测方法。该方法首先求得前后时间点的高光谱差分图像,再根据差分图像中图像块的非局部分布特点,提取不同的非局部张量簇。然后基于协同稀疏正则化和低秩正则化建立协同稀疏与非局部低秩张量变化检测模型,并采用交替方向乘子法对模型求解得到表示系数。最后根据表示系数求得张量在不同类别中的投影残差,进而根据投影残差最小准则判断该张量块是否发生变化。在Farmland数据集和Urban area in San Francisco City数据集上进行实验,实验结果表明该方法取得较好的高光谱变化检测精度。展开更多
Powdered activated coke(PAC)is a good adsorbent of SO_(2),but its adsorption capacity is affected by many factors in the preparation process.To prepare the PAC with a high SO_(2)adsorption capacity using JJ-coal under...Powdered activated coke(PAC)is a good adsorbent of SO_(2),but its adsorption capacity is affected by many factors in the preparation process.To prepare the PAC with a high SO_(2)adsorption capacity using JJ-coal under flue gas atmosphere,six parameters(oxygen-coal equivalent ratio,reaction temperature,reaction time,O_(2)concentration,CO_(2)concentration,and H_(2)O concentration)were screened and optimized using the response surface methodology(RSM).The results of factor screening experiment show that reaction temperature,O_(2)concentration,and H_(2)O(g)concentration are the significant factors.Then,a quadratic polynomial regression model between the significant factors and SO_(2)adsorption capacity was established using the central composite design(CCD).The model optimization results indicate that when reaction temperature is 904.74℃,O_(2)concentration is 4.67%,H_(2)O concentration is 27.98%,the PAC(PAC-OP)prepared had a higher SO_(2)adsorption capacity of 68.15 mg/g while its SO_(2)adsorption capacity from a validation experiment is 68.82 mg/g,and the error with the optimal value is 0.98%.Compared to two typical commercial activated cokes(ACs),PAC-OP has relatively more developed pore structures,and its SBET and Vtot are 349 m^(2)/g and 0.1475 cm3/g,significantly higher than the 186 m^(2)/g and 0.1041 cm3/g of AC1,and the 132 m^(2)/g and 0.0768 cm3/g of AC2.Besides,it also has abundant oxygen-containing functional groups,its surface O content being 12.09%,higher than the 10.42%of AC1 and 10.49%of AC2.Inevitably,the SO_(2)adsorption capacity of PAC-OP is also significantly higher than that of both AC1 and AC2,which is 68.82 mg/g versus 32.53 mg/g and 24.79 mg/g,respectively.展开更多
The as-cast microstructures of high carbon high speed steels （HC-HSS） made by sand casting, centrifugal casting and electromagnetic centrifugal casting, respectively, were studied by using of optical microscopy （OM...The as-cast microstructures of high carbon high speed steels （HC-HSS） made by sand casting, centrifugal casting and electromagnetic centrifugal casting, respectively, were studied by using of optical microscopy （OM） and D/max2200pc X-ray diffraction. The results show that the microstructure of as-cast HC- HSS is dominated by alloy carbides （W2C, VC, Cr7C3）, martensite and austenite. The centrifugal casting and electromagnetic centrifugal casting apparently improve the solidification structure of HCoHSS. With the increase of magnetic intensity （B）, the volume fraction of austenite in the HC-HSS solidification structure increases significantly while the eutectic ledeburite decreases. Moreover, the secondary carbides precipitated from the austenite are finer with more homogeneous distribution in the electromagnetic centrifugal castings. It has also been found that the lath of eutectic carbide in ledeburite becomes finer and carbide phase spacing in eutectic ledeburite increases along with the higher magnetic field strength.展开更多
(±)-Crataegusnorin A(la/1b) and B(2a/2b),two pairs of rare 8,9’-epoxy-type norlignan enantiomers featuring a y-butyrolactone ring,were isolated from the fruit of Crataegus pinnatifida.Their structures were deter...(±)-Crataegusnorin A(la/1b) and B(2a/2b),two pairs of rare 8,9’-epoxy-type norlignan enantiomers featuring a y-butyrolactone ring,were isolated from the fruit of Crataegus pinnatifida.Their structures were determined via extensive spectroscopic analyses.Gauge-independent atomic orbital(GIAO) NMR chemical shift calculations,combined with the advanced statistical method DP4+were employed to establish the relative configurations of four compounds.Next,chiral separation was accomplished by chiral chromatographic column and the absolute configurations of the four compounds were unambiguously assigned by comparison between their experimental electronic circular dichroism curves with the quantum-mechanically calculated curves based on time-dependent density functional theory(TDDFT).All the isolates were evaluated fo r their neuroprotective activities against H2O2-induced cell injury in human neuroblastoma SH-SY5Y cells.The results showed that two pairs of enantiomers 1a/1b and 2a/2b displayed diff;erent effect on neuroprotective activity.Among them,compound 2a displayed the most potent neuroprotective effect Further flow cytometry analysis indicated that 2a could protect SH-SY5Y cells from oxidative damage through inhibiting cell apoptosis.展开更多
Purpose The Filed of View(FOV)of eXTP/LAD is limited by lead-glass capillary plate collimators placed in front of the Silicon Drift Detectors(SDDs)for reducing the background contamination caused by the photons of Cos...Purpose The Filed of View(FOV)of eXTP/LAD is limited by lead-glass capillary plate collimators placed in front of the Silicon Drift Detectors(SDDs)for reducing the background contamination caused by the photons of Cosmic X-ray Background(CXB)leaking from outside the FOV.The core quality parameters of lead-glass capillary plate collimators are Open Area Ratio(OAR)and FOV.The performance of lead-glass capillary plate collimators is determined by its design specification such as pore-to-pore misalignment,pore perpendicularity with collimator surface and pore diameter.Since the design specification is the result of a large number of micropores,we use the full width at half maximum(FWHM)and peak value of point spread function(PSF)to characterize the capillary plate collimator performance.In order to quickly evaluate the performances of collimators,we developed a direct PSF measurement method using divergent beams.Methods In this paper,the simulation package of the divergent beamsmeasurement setup is developed based on Geant4.The simulation parameters of scintillator absorption length are corrected by experimental data.We simulate the PSF of collimators with different distribution of pore diameter and misalignment by parallel beams and divergent beams.By comparing the peak value and FWHM of collimators PSF,the feasibility in replacing parallel beams measurement with divergent beams measurement is studied.Results It is verified that the influence of the geometric size of 33μm radius of the micro-focus of X-ray tube can be ignored.The results show that the FWHM of collimators is increased with error root mean square error(RMS)of the distribution of collimators pore diameter and pore inclination angle.The peak value of PSF is mainly influenced by pore non-parallelism of the pores,and it decreases with an increase in pore inclination angle.Comparison of parallel beams PSF and divergent beams PSF shows well consistency of peak value and FWHM of collimator.But,the peak value of the divergent beams PSF is mainly affected by 展开更多
基金supported by the National Nature Science Foundation of China(Grant Nos.12335015,12375238,12374261,11734013,and 11704350)the Presidential Foundation of the China Academy of Engineering Physics(Grant No.YZJJLX2017010)+2 种基金the CAEP Foundation(Grant No.CX2019023)the Science Challenge Project(Grant Nos.TZ2018001 and TZ2018005)the National Key R&D Program of China(Grant No.2017YFA0403200).
文摘We present measurements of the 2p-3d transition opacity of a hot molybdenum-scandium sample with nearly half-vacant molybdenum M-shell configurations.A plastic-tamped molybdenum-scandium foil sample is radiatively heated to high temperature in a compact D-shaped gold Hohlraum driven by∼30 kJ laser energy at the SG-100 kJ laser facility.X rays transmitted through the molybdenum and scandium plasmas are diffracted by crystals and finally recorded by image plates.The electron temperatures in the sample in particular spatial and temporal zones are determined by the K-shell absorption of the scandium plasma.A combination of the IRAD3D view factor code and the MULTI hydrodynamic code is used to simulate the spatial distribution and temporal behavior of the sample temperature and density.The inferred temperature in the molybdenum plasma reaches a average of 138±11 eV.A detailed configuration-accounting calculation of the n=2–3 transition absorption of the molybdenum plasma is compared with experimental measurements and quite good agreement is found.The present measurements provide an opportunity to test opacity models for complicated M-shell configurations.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12004351).
文摘A self-consistent and precise method to determine the time-dependent radiative albedo,i.e.,the ratio of the reemission flux to the incident flux,for an indirect-drive inertial confinement fusion Hohlraum wall material is proposed.A specially designed symmetrical triple-cavity gold Hohlraum is used to create approximately constant and near-equilibrium uniform radiation with a peak temperature of 160 eV.The incident flux at the secondary cavity waist is obtained from flux balance analysis and from the shock velocity of a standard sample.The results agree well owing to the symmetrical radiation in the secondary cavity.A self-consistent and precise time-dependent radiative albedo is deduced from the reliable reemission flux and the incident flux,and the result from the shock velocity is found to have a smaller uncertainty than that from the multi-angle flux balance analysis,and also to agree well with the result of a simulation using the HYADES opacity.
基金The authors gratefully acknowledge the financial support of this work by Natural Science Foundation of China(grant no 22075031)Jilin Provincial Science&Technology Department(grant no 20220201105GX)。
文摘Research on anion exchange membrane fuel cells(AEMFCs)mainly focuses on the membrane module,and improving its performance has always been the focus of researchers.To create high-performance anion exchange membranes(AEMs),a series of side chain type AEMs were prepared by introducing different proportions of side chains containing anisotropic poly cations with relatively stable piperidinium ring cations and side quaternary ammonium cations as cation groups,using poly(p-terphenyl isatin)(PTI),a main chain polymer without aryl ether bonds.The dense surface of the PTI-N-n series membranes is shown by SEM images;TEM images show that the ion domains are clearly distributed in the membrane,so a continuous ion transport channel is constructed.PTI-N-100 has the highest hydroxide conductivity at 80℃,reaching 96.83 mS cm^(-1) due to multiple transport sites.The PTI-N-100 membrane has a peak power density of 180 mW cm^(2) based on the highest ionic conductivity.Therefore,we believe that the introduction of multi-cations contributes to the performance of anion exchange membranes.
基金supported by the National Natural Science Foundation of China(12335015,12375238,12173031,12303049,and 12105269)。
文摘A radiative shock(RS)is one in which the density and temperature structures are affected by radiation from the shock-heated matter.RS plays a special role in astrophysics as it nontrivially combines both hydrodynamics and radiation physics.In most astrophysical shocks,the temperature and density conditions lead to strong emission,with radiation thus playing a major role therein.
基金supported by the Presidential Foundation of China Academy of Engineering Physics (No. YZJJLX 2018011)National Natural Science Foundation of China (Nos. 11775204, 11734013, 12105269 and 12004351)
文摘In indirect-driven laser fusion experiments,the movement of the laser absorption layer will distort the radiation uniformity on the capsule.The gold foam has advantages in symmetry control and lowering wall plasma blowoff when used in an inertial confinement fusion(ICF)hohlraum.This work investigates the motion of the laser absorption cutoff position using lowdensity foam gold walls.It is found that the motion of the laser absorption cutoff position can be significantly mitigated through optimal initial low density,tailored to a specific laser shape.For a short square laser pulse,the laser absorption cutoff position remains almost stationary at an initial density of approximately 0.6 g cm^(-3).For a long-shaped laser pulse,the minimal motion of the laser absorption cutoff position is observed at an initial density of about 0.1 g cm^(-3).This approach allows for the adjustment of the symmetry of the hohlraum radiation source.The insights gained from this study serve as a crucial reference for optimizing the hohlraum wall density.
基金This work was supported by the National Key R&D Program of China under Grant No.2017YFA0403200.
文摘Experiments exploring the propagation of heat waves within cylindrical CH foams were performed on the Shenguang-Ⅲ prototype laser facility in 2012.In this paper,the radiation fluxes out of CH foam cylinders at different angles are analyzed theoretically using the two-dimensional radiation hydrodynamics code LARED-R.Owing to the difficulty in validating opacity and equation of state(EOS)data for high-Z plasmas,and to uncertainties in the measured radiation temperature Tr and the original foam densityρ0,multipliers are introduced to adjust the Au material parameters,Tr,andρ0 in our simulations to better explain the measurements.The dependences of the peak radiation flux Fmax and the breakout time of the heat wave thalf(defined as the time corresponding to the radiation flux at half-maximum)on the radiation source,opacity,EOS,andρ0 scaling factors(η_(src),η_(op),η_(eos),and η_(ρ))are investigated via numerical simulations combined with fitting.Then,with the uncertainties in the measured Tr andρ0 fixed at 3.6%and 3.1%,respectively,experimental data are exploited as fiducial values to determine the ranges ofη_(op) andηeos.It is found that the ranges ofη_(op) andηeos fixed by this experiment overlap partially with those found in our previous work[Meng et al.,Phys.Plasmas 20,092704(2013)].Based on the scaled opacity and EOS parameters,the values of F_(max) and t_(half) obtained via simulations are in good agreement with the measurements,with maximum errors∼9.5%and within 100 ps,respectively.
文摘高光谱图像变化检测可提供地球表面的时间维变化信息,对城乡规划和管理至关重要。因具有较高的光谱分辨率,高光谱图像常被用于检测更精细的变化。针对高光谱变化检测的问题,提出一种基于协同稀疏与非局部低秩张量的高光谱图像变化检测方法。该方法首先求得前后时间点的高光谱差分图像,再根据差分图像中图像块的非局部分布特点,提取不同的非局部张量簇。然后基于协同稀疏正则化和低秩正则化建立协同稀疏与非局部低秩张量变化检测模型,并采用交替方向乘子法对模型求解得到表示系数。最后根据表示系数求得张量在不同类别中的投影残差,进而根据投影残差最小准则判断该张量块是否发生变化。在Farmland数据集和Urban area in San Francisco City数据集上进行实验,实验结果表明该方法取得较好的高光谱变化检测精度。
基金This work was financial supported by the National Key R&D Program of China(Grant No.2017YFB0602902).
文摘Powdered activated coke(PAC)is a good adsorbent of SO_(2),but its adsorption capacity is affected by many factors in the preparation process.To prepare the PAC with a high SO_(2)adsorption capacity using JJ-coal under flue gas atmosphere,six parameters(oxygen-coal equivalent ratio,reaction temperature,reaction time,O_(2)concentration,CO_(2)concentration,and H_(2)O concentration)were screened and optimized using the response surface methodology(RSM).The results of factor screening experiment show that reaction temperature,O_(2)concentration,and H_(2)O(g)concentration are the significant factors.Then,a quadratic polynomial regression model between the significant factors and SO_(2)adsorption capacity was established using the central composite design(CCD).The model optimization results indicate that when reaction temperature is 904.74℃,O_(2)concentration is 4.67%,H_(2)O concentration is 27.98%,the PAC(PAC-OP)prepared had a higher SO_(2)adsorption capacity of 68.15 mg/g while its SO_(2)adsorption capacity from a validation experiment is 68.82 mg/g,and the error with the optimal value is 0.98%.Compared to two typical commercial activated cokes(ACs),PAC-OP has relatively more developed pore structures,and its SBET and Vtot are 349 m^(2)/g and 0.1475 cm3/g,significantly higher than the 186 m^(2)/g and 0.1041 cm3/g of AC1,and the 132 m^(2)/g and 0.0768 cm3/g of AC2.Besides,it also has abundant oxygen-containing functional groups,its surface O content being 12.09%,higher than the 10.42%of AC1 and 10.49%of AC2.Inevitably,the SO_(2)adsorption capacity of PAC-OP is also significantly higher than that of both AC1 and AC2,which is 68.82 mg/g versus 32.53 mg/g and 24.79 mg/g,respectively.
基金supported by the special fund for basic scientifi c research of central colleges,Chang’an University (CHD2010JC015)the innovation fund of small and medium-sized enterprise of Science & Technology Ministry of China under grant no. 10C26213201139Beijing Education Committee patent outcome conversion item
文摘The as-cast microstructures of high carbon high speed steels （HC-HSS） made by sand casting, centrifugal casting and electromagnetic centrifugal casting, respectively, were studied by using of optical microscopy （OM） and D/max2200pc X-ray diffraction. The results show that the microstructure of as-cast HC- HSS is dominated by alloy carbides （W2C, VC, Cr7C3）, martensite and austenite. The centrifugal casting and electromagnetic centrifugal casting apparently improve the solidification structure of HCoHSS. With the increase of magnetic intensity （B）, the volume fraction of austenite in the HC-HSS solidification structure increases significantly while the eutectic ledeburite decreases. Moreover, the secondary carbides precipitated from the austenite are finer with more homogeneous distribution in the electromagnetic centrifugal castings. It has also been found that the lath of eutectic carbide in ledeburite becomes finer and carbide phase spacing in eutectic ledeburite increases along with the higher magnetic field strength.
基金supported by Career Development Support Plan for Young and Middle-aged Teachers in Shenyang Pharmaceutical University(No.ZQN2018006)the Project of Innovation Team Foundation(No.LT2015027)。
文摘(±)-Crataegusnorin A(la/1b) and B(2a/2b),two pairs of rare 8,9’-epoxy-type norlignan enantiomers featuring a y-butyrolactone ring,were isolated from the fruit of Crataegus pinnatifida.Their structures were determined via extensive spectroscopic analyses.Gauge-independent atomic orbital(GIAO) NMR chemical shift calculations,combined with the advanced statistical method DP4+were employed to establish the relative configurations of four compounds.Next,chiral separation was accomplished by chiral chromatographic column and the absolute configurations of the four compounds were unambiguously assigned by comparison between their experimental electronic circular dichroism curves with the quantum-mechanically calculated curves based on time-dependent density functional theory(TDDFT).All the isolates were evaluated fo r their neuroprotective activities against H2O2-induced cell injury in human neuroblastoma SH-SY5Y cells.The results showed that two pairs of enantiomers 1a/1b and 2a/2b displayed diff;erent effect on neuroprotective activity.Among them,compound 2a displayed the most potent neuroprotective effect Further flow cytometry analysis indicated that 2a could protect SH-SY5Y cells from oxidative damage through inhibiting cell apoptosis.
基金We would like to acknowledge support from the Strategic Priority Program on Space Science,China,the Chinese Academy of Sciences,Grant No.XDA15020500.
文摘Purpose The Filed of View(FOV)of eXTP/LAD is limited by lead-glass capillary plate collimators placed in front of the Silicon Drift Detectors(SDDs)for reducing the background contamination caused by the photons of Cosmic X-ray Background(CXB)leaking from outside the FOV.The core quality parameters of lead-glass capillary plate collimators are Open Area Ratio(OAR)and FOV.The performance of lead-glass capillary plate collimators is determined by its design specification such as pore-to-pore misalignment,pore perpendicularity with collimator surface and pore diameter.Since the design specification is the result of a large number of micropores,we use the full width at half maximum(FWHM)and peak value of point spread function(PSF)to characterize the capillary plate collimator performance.In order to quickly evaluate the performances of collimators,we developed a direct PSF measurement method using divergent beams.Methods In this paper,the simulation package of the divergent beamsmeasurement setup is developed based on Geant4.The simulation parameters of scintillator absorption length are corrected by experimental data.We simulate the PSF of collimators with different distribution of pore diameter and misalignment by parallel beams and divergent beams.By comparing the peak value and FWHM of collimators PSF,the feasibility in replacing parallel beams measurement with divergent beams measurement is studied.Results It is verified that the influence of the geometric size of 33μm radius of the micro-focus of X-ray tube can be ignored.The results show that the FWHM of collimators is increased with error root mean square error(RMS)of the distribution of collimators pore diameter and pore inclination angle.The peak value of PSF is mainly influenced by pore non-parallelism of the pores,and it decreases with an increase in pore inclination angle.Comparison of parallel beams PSF and divergent beams PSF shows well consistency of peak value and FWHM of collimator.But,the peak value of the divergent beams PSF is mainly affected by
