The data of uranium isotope abundance ratios measured by thermal ionization mass spectrometer MAT-261 were analyzed in the three aspects including distribution function, correlation and uncertainty. The measurement da...The data of uranium isotope abundance ratios measured by thermal ionization mass spectrometer MAT-261 were analyzed in the three aspects including distribution function, correlation and uncertainty. The measurement data were confirmed to be normal distribution. Uncertainty and correlation of the isotope abundance ratios measured by MAT-261 in the certified uranium sample were investigated. The conclusion obtained indicated that, the correlation only between abundance ratios R5/8 and R4/8 is strong, but the others is weak for the enriched uranium sample; For the natural uranium sample, the correlation among all abundance ratios is weak. On this base, the uncertainty of all abundance ratios measured by MAT-261 had been evaluated.展开更多
Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon ...Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon energy are measured and presented. By selecting suitable photon energy, exclusively molecular ion m/z=126 is obtained. At photon energy of 12.0 eV, the major ionic fragments at m/z=98, 97, 84, 83, 70, and 55 are obtained, which are assigned to C4H6N2O＋, C4H5N2O＋, C3H4N2O＋ （or C4H6NO＋）, C4H5NO＋, C2NO2＋, and C3H5N＋, respectively. With help of theoretical calculations, the detailed dissociation pathways of thymine at low energy are well established.展开更多
Based on the hexagonal crystallite model of graphite,the electrochemical characteristics of carbon atoms on the edge and basal plane were proposed by analyzing graphite crystal structure and bonds of carbon atoms in d...Based on the hexagonal crystallite model of graphite,the electrochemical characteristics of carbon atoms on the edge and basal plane were proposed by analyzing graphite crystal structure and bonds of carbon atoms in different sites.A spherical close-packed model for graphite particle was developed.The fractions of surface carbon atoms（SCA） and edge carbon atoms（ECA） were derived in the expression of crystallographic parameters and particle size,and the effects of ECA on the initial irreversible capacity and the mechanisms of action were analyzed and verified.The results show that the atoms on the edge are more active for electrochemical reactions,such as electrolyte decomposition and tendency to form stable bond with other atoms and groups.For the practical graphite particle,corresponding modifying factors were introduced to revise the difference in calculating results.The revised expression is suitable for the calculation of the fractions of SCA and ECA for carbon materials such as graphite,disordered carbon and modified graphite.展开更多
The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at...The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at B3LYP/6-311＋＋G（d,p） level, and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level. The ionization energies of toluene and the ap- pearance energies for major fragment ions, C7H7＋, C6H5＋, C5H6＋, C5H5＋, are determined to be 8.90, 11.15 or 11.03, 12.72, 13.69, 16.28 eV, respectively, which are all in good agree- ment with published experimental data. With the help of available published experimental data and theoretical results, four dissociative photoionization channels have been proposed： CTHT＋＋H, C6Hs＋＋CH3, C5H6＋WC2H2, CsHs＋＋C2H2＋H. Transition structures and intermediates for those isomerization processes are determined in this work. Especially, the structures of C5H6＋ and C5H5＋ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.展开更多
1 AMS ACTIVITIES IN JAPAN ANDAROUND THE WORLD. Following the first success of accelerator mass spectrometry (AMS) in detecting ^14C by Muller in 1977, its technique was rapidly embraced by the low energy nuclear physi...1 AMS ACTIVITIES IN JAPAN ANDAROUND THE WORLD. Following the first success of accelerator mass spectrometry (AMS) in detecting ^14C by Muller in 1977, its technique was rapidly embraced by the low energy nuclear physicists with encouragement from several archaeologists, biologists and environmental scientists.Subsequently, several smaller and not so smallel ectrostatic tandem accelerators have been resurrected as AMS machines, and many nuclear physics laboratories have commenced their AMS research program. In parallel, a number of new facilities which are dedicated to the AMS studies have been constructed. Up to now, more than 40 AMS laboratories are active around the world (Fig. 1). 4 AMS laboratories are actively operating in China. 8 AMS laboratories which are working in Japan are listed in Table 1. In this talk, I will look briefly at the development of the field, will survey its current status, especially the effort of the Japanese group, and will mention about the future.展开更多
The fabrication and characterization of a laser ionization source for ion mobility spectrometer （IMS） is described with the calculated parameter of the drift tube. Ions are created in air at ambient pressure using l...The fabrication and characterization of a laser ionization source for ion mobility spectrometer （IMS） is described with the calculated parameter of the drift tube. Ions are created in air at ambient pressure using laser ionization （ A = 248 nm） with air as the drift gas. Mobility spectra for positive ions at different electric fields are obtained with the length of drift tube of 25 and 50 mm, respectively. The distribution of the electric field in the drift tube （50 mm） has also been investigated by SIMION simulation with the ion shutter closed and open respectively.展开更多
The multiphoton ionization of acetone-water clusters were detected at 355 nm laser wavelength by using the time of flight mass spectrometer（TOF-MS）. The experiments show that all products are proto- nated. Three mai...The multiphoton ionization of acetone-water clusters were detected at 355 nm laser wavelength by using the time of flight mass spectrometer（TOF-MS）. The experiments show that all products are proto- nated. Three main products such as （CH3COCH3）,-（H2O）n_2 H^＋ , （CH3COCH3）,-（H2O）n-1 H^＋ and （CH3COCH3）,-（H2O）,H^＋ are concluded from the results. In order to study the equilibrium structures of the （CH3 COCH3 ）,-（H2O）n-2 H^＋ , the ab-initio calculation is used on them. The experiment is even done when the volume rate of acetone to water is 1：2.展开更多
Principally the basis of ISE is selecting of a support solid matrix and a nonsoluble compound or complexes of insighted cation, mixed with this solid. For preparing the ISE membranes there are some materials such PVC,...Principally the basis of ISE is selecting of a support solid matrix and a nonsoluble compound or complexes of insighted cation, mixed with this solid. For preparing the ISE membranes there are some materials such PVC, PE, organic polyelectrolytes, conducting polymers and inorganic compounds. The black white microscope photos are included, too. Detailed schemes and pictures of the electrodes and correlations were shown in the following article. Results are seen compatible for construction of the versatile ISE electrodes.展开更多
Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells a...Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon （MG-Si） was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics （CFD） were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.展开更多
A novel method for estimating the space range of battery-powered vertical take-off and landing(VTOL) aircraft is presented. The method is based on flight parameter optimization and numerical iteration. Subsystem model...A novel method for estimating the space range of battery-powered vertical take-off and landing(VTOL) aircraft is presented. The method is based on flight parameter optimization and numerical iteration. Subsystem models including required thrust, required power and battery discharge models are presented. The problem to be optimized is formulated, and then case study simulation is conducted using the established method for quantitative analysis. Simulation results show that the space range of battery-powered VTOL aircraft in a vertical plane is an oblate curve, which appears horizontally long but vertically short, and the peak point is not located on the vertical climb path. The method and results are confirmed by parameter analysis and validations.展开更多
The safety most important factor profile is one of the the plasma discharge. For limiter configuration, people usually use the following cylindrical approximation formula to calculate it q（r）=5r^2BT/RIp where r is t...The safety most important factor profile is one of the the plasma discharge. For limiter configuration, people usually use the following cylindrical approximation formula to calculate it q（r）=5r^2BT/RIp where r is the minor radius of the plasma toms, R is the major radius （in m） , BT is the toroidal magnetic field （in T）, Ip is the total toroidal current（in MA）.展开更多
The mechanism of addition of separate atoms to a growing center is considered with application of model of a pair interpenetration of atoms. Features of geometrical model are related with the electronic structure of a...The mechanism of addition of separate atoms to a growing center is considered with application of model of a pair interpenetration of atoms. Features of geometrical model are related with the electronic structure of atoms and the Pauli＇s exclusion principle. The forces providing self-organization of atoms in the bulk of a condensed substance are shown. The calculated interatomic distances in graphite and alloys of gold with silver coincide with those known from experiments with accuracy of 0.1%.展开更多
Recently, the anti-glycation and anticancer properties of curcumin longa and okra seed extract were studied alone and also in combination with the well-established drug metformin. The combined effect of curcumin with ...Recently, the anti-glycation and anticancer properties of curcumin longa and okra seed extract were studied alone and also in combination with the well-established drug metformin. The combined effect of curcumin with metformin and metformin with okra seed extract was found to be highly efficacious in inhibiting Advanced Glycation End-products （AGEs）. In order to understand the mechanistic implications of curcumin combined with metformin and its enhanced anti-glycation activity, a Curcumin-Metformin Adduct was chemically synthesized. This adduct was fully characterized by thin-layer chromatography, Nano Drop spectrophotometry and electrospray-ionization mass spectrometry. The adduct may be helpful not only in elucidating the mechanism of anti-glycation and anti-cancer activities but also in studying the role of curcumin in binding of AI3-oligomers and disaggregating fibrillar formation in Alzheimer＇s disease.展开更多
Symmetric covalent organic framework(COF)photocatalysts generally suffer from inefficient charge separation and short-lived photoexcited states.By performing density functional theory(DFT)and time-dependent density fu...Symmetric covalent organic framework(COF)photocatalysts generally suffer from inefficient charge separation and short-lived photoexcited states.By performing density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations,we find that partial substitution with one or two substituents(N or NH_(2))in the linkage of the representative symmetric COF(N_(0)-COF)gives rise to the separation of charge carriers in the resulting COFs(i.e.,N_(1)-COF,N_(2)-COF,(NH_(2))1-N_(0)-COF,and(NH_(2))2-N_(0)-COF).Moreover,we also find that the energy levels of the highest occupied crystal orbital(HOCO)and the lowest unoccupied crystal orbital(LUCO)of the N_(0)-COF can shift away from or toward the vacuum level,depending on the electron-withdrawing or electron-donating characters of the substituent.Therefore,we propose that partial substitution with carefully chosen electron-withdrawing or electron-donating substituents in the linkages of symmetric COFs can lead to efficient charge separation as well as appropriate HOCO and LUCO positions of the generated COFs for specific photocatalytic reactions.The proposed rule can be utilized to further boost the photocatalytic performance of many symmetric COFs.展开更多
We measured the photoelectron spectra of Al_(n)C_(4)^(−)(n=2−4)clusters by using size-selected anion photoelectron spectroscopy.The structures of Al_(n)C_(4)^(−/0)(n=2−4)clusters were explored with quantum chemistry c...We measured the photoelectron spectra of Al_(n)C_(4)^(−)(n=2−4)clusters by using size-selected anion photoelectron spectroscopy.The structures of Al_(n)C_(4)^(−/0)(n=2−4)clusters were explored with quantum chemistry calculations and were determined by comparing the theoretical results with the experimental spectra.It is found that the most stable structure of Al_(2)C_(4)^(−) anion is a C_(2v)symmetry planar structure with two Al atoms interacting with two C_(2)units.In addition,Al_(2)C_(4)^(−) anion also has a D∞h symmetry linear structure with two Al atoms located at the two ends of a C_(4)chain,which is slightly higher in energy than the planar structure.The most stable structure of neutral Al_(2)C_(4)has a D∞h symmetry linear structure.The most stable structure of Al_(3)C_(4)^(−) anion is a planar structure with three Al atoms interacting with two C_(2)units.Whereas neutral Al_(3)C_(4)cluster has a C_(2v)symmetric V-shaped bent structure.The global minima structures of both Al_(4)C_(4)^(−) and neutral Al_(4)C_(4)are C_(2)h symmetry planar structures with four Al atoms interacting with the ends of two C_(2)units.Adaptive natural density partitioning analyses of Al_(n)C_(4)^(−)(n=2−4)clusters show that the interactions between the Al atoms and C_(2)units have bothσandπcharacters.展开更多
文摘The data of uranium isotope abundance ratios measured by thermal ionization mass spectrometer MAT-261 were analyzed in the three aspects including distribution function, correlation and uncertainty. The measurement data were confirmed to be normal distribution. Uncertainty and correlation of the isotope abundance ratios measured by MAT-261 in the certified uranium sample were investigated. The conclusion obtained indicated that, the correlation only between abundance ratios R5/8 and R4/8 is strong, but the others is weak for the enriched uranium sample; For the natural uranium sample, the correlation among all abundance ratios is weak. On this base, the uncertainty of all abundance ratios measured by MAT-261 had been evaluated.
基金This work was supported by the Chinese Academy of Sciences and the National Natural Science Foundation of China （No.10805047）. Authors appreciate the kind help from Dr. Yang Pan in experiments.
文摘Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon energy are measured and presented. By selecting suitable photon energy, exclusively molecular ion m/z=126 is obtained. At photon energy of 12.0 eV, the major ionic fragments at m/z=98, 97, 84, 83, 70, and 55 are obtained, which are assigned to C4H6N2O＋, C4H5N2O＋, C3H4N2O＋ （or C4H6NO＋）, C4H5NO＋, C2NO2＋, and C3H5N＋, respectively. With help of theoretical calculations, the detailed dissociation pathways of thymine at low energy are well established.
基金Project (09001232) supported by the Doctoral Foundation of Henan University of Science and Technology,China
文摘Based on the hexagonal crystallite model of graphite,the electrochemical characteristics of carbon atoms on the edge and basal plane were proposed by analyzing graphite crystal structure and bonds of carbon atoms in different sites.A spherical close-packed model for graphite particle was developed.The fractions of surface carbon atoms（SCA） and edge carbon atoms（ECA） were derived in the expression of crystallographic parameters and particle size,and the effects of ECA on the initial irreversible capacity and the mechanisms of action were analyzed and verified.The results show that the atoms on the edge are more active for electrochemical reactions,such as electrolyte decomposition and tendency to form stable bond with other atoms and groups.For the practical graphite particle,corresponding modifying factors were introduced to revise the difference in calculating results.The revised expression is suitable for the calculation of the fractions of SCA and ECA for carbon materials such as graphite,disordered carbon and modified graphite.
文摘The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at B3LYP/6-311＋＋G（d,p） level, and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level. The ionization energies of toluene and the ap- pearance energies for major fragment ions, C7H7＋, C6H5＋, C5H6＋, C5H5＋, are determined to be 8.90, 11.15 or 11.03, 12.72, 13.69, 16.28 eV, respectively, which are all in good agree- ment with published experimental data. With the help of available published experimental data and theoretical results, four dissociative photoionization channels have been proposed： CTHT＋＋H, C6Hs＋＋CH3, C5H6＋WC2H2, CsHs＋＋C2H2＋H. Transition structures and intermediates for those isomerization processes are determined in this work. Especially, the structures of C5H6＋ and C5H5＋ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.
文摘1 AMS ACTIVITIES IN JAPAN ANDAROUND THE WORLD. Following the first success of accelerator mass spectrometry (AMS) in detecting ^14C by Muller in 1977, its technique was rapidly embraced by the low energy nuclear physicists with encouragement from several archaeologists, biologists and environmental scientists.Subsequently, several smaller and not so smallel ectrostatic tandem accelerators have been resurrected as AMS machines, and many nuclear physics laboratories have commenced their AMS research program. In parallel, a number of new facilities which are dedicated to the AMS studies have been constructed. Up to now, more than 40 AMS laboratories are active around the world (Fig. 1). 4 AMS laboratories are actively operating in China. 8 AMS laboratories which are working in Japan are listed in Table 1. In this talk, I will look briefly at the development of the field, will survey its current status, especially the effort of the Japanese group, and will mention about the future.
文摘The fabrication and characterization of a laser ionization source for ion mobility spectrometer （IMS） is described with the calculated parameter of the drift tube. Ions are created in air at ambient pressure using laser ionization （ A = 248 nm） with air as the drift gas. Mobility spectra for positive ions at different electric fields are obtained with the length of drift tube of 25 and 50 mm, respectively. The distribution of the electric field in the drift tube （50 mm） has also been investigated by SIMION simulation with the ion shutter closed and open respectively.
文摘The multiphoton ionization of acetone-water clusters were detected at 355 nm laser wavelength by using the time of flight mass spectrometer（TOF-MS）. The experiments show that all products are proto- nated. Three main products such as （CH3COCH3）,-（H2O）n_2 H^＋ , （CH3COCH3）,-（H2O）n-1 H^＋ and （CH3COCH3）,-（H2O）,H^＋ are concluded from the results. In order to study the equilibrium structures of the （CH3 COCH3 ）,-（H2O）n-2 H^＋ , the ab-initio calculation is used on them. The experiment is even done when the volume rate of acetone to water is 1：2.
文摘Principally the basis of ISE is selecting of a support solid matrix and a nonsoluble compound or complexes of insighted cation, mixed with this solid. For preparing the ISE membranes there are some materials such PVC, PE, organic polyelectrolytes, conducting polymers and inorganic compounds. The black white microscope photos are included, too. Detailed schemes and pictures of the electrodes and correlations were shown in the following article. Results are seen compatible for construction of the versatile ISE electrodes.
文摘Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon （MG-Si） was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics （CFD） were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.
文摘A novel method for estimating the space range of battery-powered vertical take-off and landing(VTOL) aircraft is presented. The method is based on flight parameter optimization and numerical iteration. Subsystem models including required thrust, required power and battery discharge models are presented. The problem to be optimized is formulated, and then case study simulation is conducted using the established method for quantitative analysis. Simulation results show that the space range of battery-powered VTOL aircraft in a vertical plane is an oblate curve, which appears horizontally long but vertically short, and the peak point is not located on the vertical climb path. The method and results are confirmed by parameter analysis and validations.
文摘The safety most important factor profile is one of the the plasma discharge. For limiter configuration, people usually use the following cylindrical approximation formula to calculate it q（r）=5r^2BT/RIp where r is the minor radius of the plasma toms, R is the major radius （in m） , BT is the toroidal magnetic field （in T）, Ip is the total toroidal current（in MA）.
文摘The mechanism of addition of separate atoms to a growing center is considered with application of model of a pair interpenetration of atoms. Features of geometrical model are related with the electronic structure of atoms and the Pauli＇s exclusion principle. The forces providing self-organization of atoms in the bulk of a condensed substance are shown. The calculated interatomic distances in graphite and alloys of gold with silver coincide with those known from experiments with accuracy of 0.1%.
文摘Recently, the anti-glycation and anticancer properties of curcumin longa and okra seed extract were studied alone and also in combination with the well-established drug metformin. The combined effect of curcumin with metformin and metformin with okra seed extract was found to be highly efficacious in inhibiting Advanced Glycation End-products （AGEs）. In order to understand the mechanistic implications of curcumin combined with metformin and its enhanced anti-glycation activity, a Curcumin-Metformin Adduct was chemically synthesized. This adduct was fully characterized by thin-layer chromatography, Nano Drop spectrophotometry and electrospray-ionization mass spectrometry. The adduct may be helpful not only in elucidating the mechanism of anti-glycation and anti-cancer activities but also in studying the role of curcumin in binding of AI3-oligomers and disaggregating fibrillar formation in Alzheimer＇s disease.
基金This work was supported by the National Key R&D Program of China(No.2018YFA0208602)the National Natural Science Foundation of China(No.21825301 and No.22003016)+2 种基金Shanghai Sailing Program(No.20YF1410000)Shanghai Municipal Science and Technology Major Project(No.2018SHZDZX03)Shanghai Science and Technology Committee(No.17520750100).
文摘Symmetric covalent organic framework(COF)photocatalysts generally suffer from inefficient charge separation and short-lived photoexcited states.By performing density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations,we find that partial substitution with one or two substituents(N or NH_(2))in the linkage of the representative symmetric COF(N_(0)-COF)gives rise to the separation of charge carriers in the resulting COFs(i.e.,N_(1)-COF,N_(2)-COF,(NH_(2))1-N_(0)-COF,and(NH_(2))2-N_(0)-COF).Moreover,we also find that the energy levels of the highest occupied crystal orbital(HOCO)and the lowest unoccupied crystal orbital(LUCO)of the N_(0)-COF can shift away from or toward the vacuum level,depending on the electron-withdrawing or electron-donating characters of the substituent.Therefore,we propose that partial substitution with carefully chosen electron-withdrawing or electron-donating substituents in the linkages of symmetric COFs can lead to efficient charge separation as well as appropriate HOCO and LUCO positions of the generated COFs for specific photocatalytic reactions.The proposed rule can be utilized to further boost the photocatalytic performance of many symmetric COFs.
基金supported by the Beijing Municipal Science&Technology Commission(No.Z191100007219009)the National Natural Science Foundation of China(No.21773255)。
文摘We measured the photoelectron spectra of Al_(n)C_(4)^(−)(n=2−4)clusters by using size-selected anion photoelectron spectroscopy.The structures of Al_(n)C_(4)^(−/0)(n=2−4)clusters were explored with quantum chemistry calculations and were determined by comparing the theoretical results with the experimental spectra.It is found that the most stable structure of Al_(2)C_(4)^(−) anion is a C_(2v)symmetry planar structure with two Al atoms interacting with two C_(2)units.In addition,Al_(2)C_(4)^(−) anion also has a D∞h symmetry linear structure with two Al atoms located at the two ends of a C_(4)chain,which is slightly higher in energy than the planar structure.The most stable structure of neutral Al_(2)C_(4)has a D∞h symmetry linear structure.The most stable structure of Al_(3)C_(4)^(−) anion is a planar structure with three Al atoms interacting with two C_(2)units.Whereas neutral Al_(3)C_(4)cluster has a C_(2v)symmetric V-shaped bent structure.The global minima structures of both Al_(4)C_(4)^(−) and neutral Al_(4)C_(4)are C_(2)h symmetry planar structures with four Al atoms interacting with the ends of two C_(2)units.Adaptive natural density partitioning analyses of Al_(n)C_(4)^(−)(n=2−4)clusters show that the interactions between the Al atoms and C_(2)units have bothσandπcharacters.
