Accurate measurement of flash X-ray energy spectra plays an important role in highenergy flash radiography. In this paper, by virtue of Geant4 toolkit, we simulated the generation and transport of X-ray photons result...Accurate measurement of flash X-ray energy spectra plays an important role in highenergy flash radiography. In this paper, by virtue of Geant4 toolkit, we simulated the generation and transport of X-ray photons resulting from the interaction of a high-energy electron beam with a solid thin target. We obtained the flash X-ray energy spectral distribution in the plane perpendicular to the electron beam incident direction. Our results indicate that the flash X- ray spectrum is almost uniform in the azimuthal direction but is quite different in the radius direction. Specifically, as the radius increases, the incident X-ray dose decreases significantly. Our work paves a theoretical basis for selecting appropriate structures and layout of the spectrometer and facilitates the measurements of flash X-ray energy spectra.展开更多
AzoR is a homodimeric,flavin mononucleotide（FMN）-containing,NADH-dependent azoreductase from Escherichia coli.In this paper,we investigated the effect of the concentration of both AzoR and R59 G on the spectral beha...AzoR is a homodimeric,flavin mononucleotide（FMN）-containing,NADH-dependent azoreductase from Escherichia coli.In this paper,we investigated the effect of the concentration of both AzoR and R59 G on the spectral behavior of the bound FMN using two-dimensional fluorescence correlation spectra.Two cross peaks（530,490） and（580,530） were observed from the dilution-induced 2D asynchronous correlation map of wt AzoR,while only one cross peak appeared at（600,530） for R59 C mutant.This result indicated that the mutation at site 59 influenced the formation of dilution-induced intermediates.The specific activity of both AzoR and R59 G mutant was unaffected by dilution when the enzyme concentration is below 1 μmol/L,which suggested that no significant dissociation of FMN occurred at low concentrations.Additionally,in order to explore the origin of these intermediates,we carried out a2 D correlation analysis using excitation wavelength-dependent fluorescence emission spectroscopy.The results showed that there coexisted two types of FMN that emitted fluorescence at 530 nm and 500 nm,respectively.Taken together,these results suggested that the 2D method is a very powerful method to identify the heterogeneous distribution of the bound FMN in solution.展开更多
基金supported by State Key Laboratory of Particle Detection & ElectronicsNational Natural Science Foundation of China(No.10976028)
文摘Accurate measurement of flash X-ray energy spectra plays an important role in highenergy flash radiography. In this paper, by virtue of Geant4 toolkit, we simulated the generation and transport of X-ray photons resulting from the interaction of a high-energy electron beam with a solid thin target. We obtained the flash X-ray energy spectral distribution in the plane perpendicular to the electron beam incident direction. Our results indicate that the flash X- ray spectrum is almost uniform in the azimuthal direction but is quite different in the radius direction. Specifically, as the radius increases, the incident X-ray dose decreases significantly. Our work paves a theoretical basis for selecting appropriate structures and layout of the spectrometer and facilitates the measurements of flash X-ray energy spectra.
基金fund by sub-project of National Science and Technology Major Project on Water Pollution Prevention and Control(No.2012ZX07203-003-Z04)supported by the Fundamental Research Funds for the Central Universities(No. ZYGX2012J112)
文摘AzoR is a homodimeric,flavin mononucleotide（FMN）-containing,NADH-dependent azoreductase from Escherichia coli.In this paper,we investigated the effect of the concentration of both AzoR and R59 G on the spectral behavior of the bound FMN using two-dimensional fluorescence correlation spectra.Two cross peaks（530,490） and（580,530） were observed from the dilution-induced 2D asynchronous correlation map of wt AzoR,while only one cross peak appeared at（600,530） for R59 C mutant.This result indicated that the mutation at site 59 influenced the formation of dilution-induced intermediates.The specific activity of both AzoR and R59 G mutant was unaffected by dilution when the enzyme concentration is below 1 μmol/L,which suggested that no significant dissociation of FMN occurred at low concentrations.Additionally,in order to explore the origin of these intermediates,we carried out a2 D correlation analysis using excitation wavelength-dependent fluorescence emission spectroscopy.The results showed that there coexisted two types of FMN that emitted fluorescence at 530 nm and 500 nm,respectively.Taken together,these results suggested that the 2D method is a very powerful method to identify the heterogeneous distribution of the bound FMN in solution.
