A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scat...A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field.Combined with transmission electron microscopy,Vickers micro-hardness tests and electron backscattered diffraction measurements,all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix,which suggested excellent thermal stability of the 9 Cr-ODS steel.展开更多
The construction of a new beamline,BL10U1,was completed at the Shanghai synchrotron radiation facility in 2020.This multipurpose beamline was designed to provide X-ray scattering techniques such as ultra-small-angle X...The construction of a new beamline,BL10U1,was completed at the Shanghai synchrotron radiation facility in 2020.This multipurpose beamline was designed to provide X-ray scattering techniques such as ultra-small-angle X-ray scattering(USAXS),small-angle X-ray scattering(SAXS),wide-angle X-ray scattering,and microfocus SAXS(μSAXS)for a broad user community.To realize fast time-resolved USAXS experiments,the beamline adopted an in-vacuum undulator with a total length of 1.6 m as the photon source.An in-house cryogenic-cooled double multilayer monochromator was installed to deliver a photon flux of approximately 10^(13) photons/s at a photon energy of 10 keV.The three-year successful operation of this beamline demonstrated that the monochromator operated smoothly,as expected.BL10U1 has three end stations in succession:USAXS end station,μSAXS end station,and end station for industrial applications.The minimum scattering vector q~0.0042 nm^(-1) at 10 keV can be achieved at the USAXS end station equipped with a 28 m-long and 1.8 m-diameter vacuum flight tube.At theμSAXS end station,a beam spot of less than 10×8μm was achieved for micro-SAXS experiments.In contrast,in situ experimental instruments up to 5 m high and 8 m wide can be mounted at the industrial application end station,which offers industrial scientists the opportunity to use their large industrial equipment.BL10U1 opens up a new capability to investigate phenomena such as non-equilibrium and dynamic processes of materials with a wide length scale from angstroms to micrometers with millisecond time resolution.In this paper,we also report beamline design considerations and commissioning results.展开更多
Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can ...Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can be obtained by such measurements, focusing in particular on studies of the vortex lattice structure and form factor in LuNi2B2C, TmNi2B2C, CeCoIn5 and Ba（Fe0.93Co0.07）2As2.展开更多
Dimer impurity in the solution of a generation five(G5) polyamidoamine(PAMAM) dendrimer has been investigated by small-angle neutron scattering(SANS). The existence of dimer impurity in dendrimer solution was evidence...Dimer impurity in the solution of a generation five(G5) polyamidoamine(PAMAM) dendrimer has been investigated by small-angle neutron scattering(SANS). The existence of dimer impurity in dendrimer solution was evidenced by indirect Fourier transform(IFT) analysis of the SANS data, in which the maximum dimension of particles in solution was found to be about twice the diameter of G5 dendrimer. We then developed an analytical model which accounts for the scattering contribution from both dendrimer monomer and dimer. The experimental data were well fitted by using the established model. The results showed that the amount of dimer impurities is significant for the measured three batches of G5 PAMAM dendrimers.展开更多
The BL19U2 at the Shanghai Synchrotron Radiation Facility is a small-angle X-ray scattering beamline dedicated to structural studies pertaining to biological macromolecules in solution.The beamline has been officially...The BL19U2 at the Shanghai Synchrotron Radiation Facility is a small-angle X-ray scattering beamline dedicated to structural studies pertaining to biological macromolecules in solution.The beamline has been officially opened to users in March 2015,and since then,a series of technological innovations has been developed to optimize beamline performance,thereby significantly improving the data collection efficiency and broadening the application scope of biological small-angle X-ray scattering.BL19U2 is ideal for the high-throughput screening of weakly scattered proteins,protein assemblies,nucleic acids,inorganic nanomaterials,and organic drug molecules.This paper describes the design and overview of the BL19U2 beamline.Versatile sample environments at the experimental station and some recent scientific highlights are presented.展开更多
Fluorine-free electrolytes have attracted great attention because of its low-cost and environmental friendliness. However, so far, little is known about the solution structures of these electrolytes. Here,we compare t...Fluorine-free electrolytes have attracted great attention because of its low-cost and environmental friendliness. However, so far, little is known about the solution structures of these electrolytes. Here,we compare the solvation phenomenon of sodium tetraphenylborate(NaBPh_(4)) salt dissolved in organic solvents of propylene carbonate(PC), 1,2-dimethoxyethane(DME), acetonitrile(ACN) and tetrahydrofuran(THF). Small-angle X-ray scattering(SAXS) reveals a unique two-peak structural feature in this saltconcentrated PC electrolyte, while solutions using other solvents only have one scattering peak.Molecular dynamics(MD) simulations further reveal that there are anion-based clusters in addition to the short-range charge ordering in the concentrated NaBPh4/PC electrolyte. Raman spectroscopy confirms the existence of considerable contact ion pairs(CIPs). This work emphasizes the importance of global and local structural analysis, which will provide valuable clues for understanding the structureperformance relationship of electrolytes.展开更多
Elucidating the structure of large biomolecules such as multi-domain proteins or protein complexes is challenging due to their high flexibility in solution. Recently, an ＂integrative structural biology＂ approach has...Elucidating the structure of large biomolecules such as multi-domain proteins or protein complexes is challenging due to their high flexibility in solution. Recently, an ＂integrative structural biology＂ approach has been proposed, which aims to determine the protein structure and characterize protein flexibility by combining complementary high- and lowresolution experimental data using computer simulations. Small-angle x-ray scattering（SAXS） is an efficient technique that can yield low-resolution structural information, including protein size and shape. Here, we review computational methods that integrate SAXS with other experimental datasets for structural modeling. Finally, we provide a case study of determination of the structure of a protein complex formed between the tandem SH3 domains in c-Cb1-associated protein and the proline-rich loop in human vinculin.展开更多
In the present work,the precipitate compositions and precipitate amounts of these elements（including the size distribution,volume fraction,and inter-precipitate distance） on the Cu-containing 7000 series aluminum al...In the present work,the precipitate compositions and precipitate amounts of these elements（including the size distribution,volume fraction,and inter-precipitate distance） on the Cu-containing 7000 series aluminum alloys（7150 and 7085 Al alloys）,are investigated by anomalous small-angle x-ray scattering（ASAXS） at various energies.The scattering intensity of 7150 alloy with T6 aging treatment decreases as the incident x-ray energy approaches the Zn absorption edge from the lower energy side,while scattering intensity does not show a noticeable energy dependence near the Cu absorption edge.Similar results are observed in the 7085 alloy in an aging process（120℃） by employing in-situ ASAXS measurements,indicating that the precipitate compositions should include Zn element and should not be strongly related to Cu element at the early stage after 10 min.In the aging process,the precipitate particles with an initial average size of ~ 8 ？A increase with aging time at an energy of 9.60 ke V,while the increase with a slower rate is observed at an energy of 9.65 ke V as near the Zn absorption edge.展开更多
This paper reports that at a newly constructed small-angle x-ray scattering station of Beijing Synchrotron Radia- tion Facility, the topological shape of ligand-free bovine serum albumin in solution has been investiga...This paper reports that at a newly constructed small-angle x-ray scattering station of Beijing Synchrotron Radia- tion Facility, the topological shape of ligand-free bovine serum albumin in solution has been investigated. An appropriate scattering curve is obtained and the calculated value of the gyration radius is 31.2~=t=0.25 ~_ （11=0.1 nm） which is co- incident with other ones＇ results. It finds that the low-resolution structure models obtained by making use of ab initio reconstruction methods are fitting the crystal structure of human serum albumin very well. All of these results perform the potential of the beamline to apply to structural biology studies. The characteristics, the defects, and the improving measures of the station in future are also discussed.展开更多
The present work deals with a detailed analysis of the small-angle X-ray scattering of nanoporous atomistic models for amorphous germanium. Structures with spherical nanovoids, others with arbitrarily oriented ellipso...The present work deals with a detailed analysis of the small-angle X-ray scattering of nanoporous atomistic models for amorphous germanium. Structures with spherical nanovoids, others with arbitrarily oriented ellipsoidal ones, with monodisperse and polydisperse size distributions, were first generated. After relaxing the as-generated structure, we compute its radial distribution function, and then we deduce by the Fourier transform technique its X-ray scattering pattern. Using a smoothing procedure, the computed small-angle X-ray scattering patterns are corrected for the termination errors due to the finite size of the model, allowing so, for the first time at our best knowledge, a rigorous quantitative analysis of this scattering. The Guinier’s law is found to be valid irrespective of size and shape of the nanovoids over a scattering vector-range extending beyond the expected limit. A weighted combination of the Guinier’s forms accounts for well the nanovoid size distribution in the amorphous structure. The invariance of the Q-factor and its relationship to the void volume fraction are also confirmed. Our findings support then the quantitative analyses of available small-angle X-ray scattering data for amorphous germanium.展开更多
Synchrotron radiation based experimental techniques known as Anomalous Small-Angle X-ray Scattering (ASAXS) provide deep insight into the nanostructure of uncountable material systems in condensed matter research i.e....Synchrotron radiation based experimental techniques known as Anomalous Small-Angle X-ray Scattering (ASAXS) provide deep insight into the nanostructure of uncountable material systems in condensed matter research i.e. solid state physics, chemistry, engineering and life sciences thereby rendering the origin of the macroscopic functionalization of the various materials via correlation to its structural architecture on a nanometer length scale. The techniques constitute a system of linear equations, which can be treated by matrix theory. The study aims to analyze the significance of the solutions of the stated matrix equations by use of the so-called condition numbers first introduced by A. Turing, J. von Neumann and H. Goldstine. Special attention was given for the comparison with direct methods i.e. the Gaussian elimination method. The mathematical roots of ill-posed ASAXS equations preventing matrix inversion have been identified. In the framework of the theory of von Neumann and Goldstine the inversion of certain matrices constituted by ASAXS gradually becomes impossible caused by non-definiteness. In Turing’s theory which starts from more general prerequisites, the principal minors of the same matrices approach singularity thereby imposing large errors on inversion. In conclusion both theories recommend for extremely ill-posed ASAXS problems avoiding inversion and the use of direct methods for instance Gaussian elimination.展开更多
The objective of this study is to design an elastic neutron scattering system<span><span style="font-family:;" "=""> according to the angle with a sample using thermal neutron beam...The objective of this study is to design an elastic neutron scattering system<span><span style="font-family:;" "=""> according to the angle with a sample using thermal neutron beam at the Dalat <span>Nuclear Reactor (DNR). The system is used for research and training in the</span> field <span>of material structure analysis by neutron scattering and diffraction tech</span>nique</span></span><span><span style="font-family:;" "="">s</span></span><span><span style="font-family:;" "="">. It is designed on the basis of inheriting the neutron measurement spectrometer systems at the DNR and the scattered neutron measurement systems in the world. The measuring system, which was installed at the hori<span>zontal channel</span></span></span><span><span style="font-family:;" "=""> </span></span><span><span style="font-family:;" "="">4 of the DNR, consists of </span></span><span><span style="font-family:;" "="">5-helium-3 detectors and a fully</span></span><span><span style="font-family:;" "=""> electronic system to record the scatter counts <span>and a mechanical system with the possibility of rotating at 15</span></span></span><span><span style="font-family:;" "=""><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span><span><span style="font-family:;" "="">-</span></span><span><span style="font-family:;" "="">75</span></span><span><span style="font-family:;" "=""><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span><span><span style="font-family:;" "=""> </span></span><span><span style="font-family:;" "="">angles. The constructed system is tested for <span>evaluation of the accuracy, stability and reliability of the mechanical and</span> electronic systems of moving detector</span></span><span><span style="font-family:;" "="">s</span></span><span><span style="font-family:;" "=""> by angles.</span></span>展开更多
The dynamic behaviors of water contained in calcium-silicate-hydrate（C-S-H） gel with different water content values from 10%to 30%（by weight）,are studied by using an empirical diffusion model（EDM） to analyze the...The dynamic behaviors of water contained in calcium-silicate-hydrate（C-S-H） gel with different water content values from 10%to 30%（by weight）,are studied by using an empirical diffusion model（EDM） to analyze the experimental data of quasi-elastic neutron scattering（QENS） spectra at measured temperatures ranging from 230 K to 280 K.In the study,the experimental QENS spectra with the whole Q-range are considered.Several important parameters including the bound/immobile water elastic coefficient A,the bound water index BWI,the Lorentzian with a half-width at half-maximum（HWHM） Γ;（Q） and Γ;（Q）,the self-diffusion coefficients D;and D;of water molecules,the average residence times τ;and τ;,and the proton mean squared displacement（MSD）(u;) are obtained.The results show that the QENS spectra can be fitted very well not only for small Q（≤1 A;） but also for large Q.The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI.The distinction between bound/immobile and mobile water,which includes confined water and ultra-confined water,can be seen by the fitted MSD.All the MSD tend to be the smallest value below 0.25 A;（the MSD of bound/immobile water） as the Q increases to 1.9 A;no matter what the temperature and water content are.Furthermore,by the abrupt changes of the fitted values of D;,τ;,and Γ;（Q）,a crossover temperature at 250 K,namely the liquid-to-crystal-like transition temperature,can be identified for confined water in large gel pores（LGPs） and/or small gel pores（SGPs） contained in the C-S-H gel sample with 30% water content.展开更多
Resonant cyclotron scattering （RCS） in pulsar magnetospheres is considered. The photon diffusion equation （Kompaneets equation） for RCS is derived. The photon system is modeled three dimensionally. Numerical calcu...Resonant cyclotron scattering （RCS） in pulsar magnetospheres is considered. The photon diffusion equation （Kompaneets equation） for RCS is derived. The photon system is modeled three dimensionally. Numerical calculations show that there exist not only up scattering but also down scattering of RCS, depending on the parameter space. RCS＇s possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars （INSs） are pointed out. The optical/UV excess of INSs may be caused by the down scattering of RCS. The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data. In our model, the INSs are proposed to be normal neutron stars, although the quark star hypothesis is still possible. The low pulsation amplitude of INSs is a natural consequence in the RCS model.展开更多
The influence of pseudogap on the inelastic neutron scattering spectra of the underdoped lanthanum cuprate is studied on the basis of the model which incorporates both the superconducting state and pseudogap state. It...The influence of pseudogap on the inelastic neutron scattering spectra of the underdoped lanthanum cuprate is studied on the basis of the model which incorporates both the superconducting state and pseudogap state. It is found that the striking effects of the influence of the pseudogap on the incommensurability of the spin excitation spectrum are that in the superconducting state the pseudogap makes the intensity of the incommensurate peak increase, in the normal state the pseudogap not only makes the intensity of the incommensurate peak increase, but also sharpens the incommensurate peak and increases incommensurability.展开更多
An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulatio...An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulations and careful mechanical designs,a shielding configuration has been successfully developed to satisfy safety requirements of below 3μSv/h dose rate at its exterior,meanwhile fulfilling space,floor load and nonmagnetic requirements.Composite materials are utilized to form the sandwich-type shielding walls:the inner layer of boron carbide rubber,the middle layer of steel-encased lead and the outer layer of borated polyethylene.Special-shaped liftable shielding blocks are incorporated to facilitate a continuous adjustment of the neutron energy while preventing radiation leakage.Our work has demonstrated that by utilizing composite shielding materials,along with the sandwich structure and liftable shielding blocks,a compact and lightweight shielding solution can be achieved.This enables the realization of advanced neutron scattering instruments that provide expanded space of measurement,larger energy and momentum coverage,and higher flux on the sample.This shielding represents the first of its kind in neutron scattering instruments in China.Following its successful operation,it has been subsequently employed by other neutron instruments across the country.展开更多
Coal seam CO_(2) sequestration is an important option to address global warming.A better knowledge on coal pore structure evolution during gas adsorption can provide guidance for coal seams CO_(2) seques-tration.Howev...Coal seam CO_(2) sequestration is an important option to address global warming.A better knowledge on coal pore structure evolution during gas adsorption can provide guidance for coal seams CO_(2) seques-tration.However,few investigations on the pore structure evolution differences between the deep and shallow coal were conducted during gas adsorption.In this study,based on the real-time synchrotron radiation small-angle X-ray scattering(SAXS)observation,the average pore diameter and pore surface fractal dimension evolution differences between deep and shallow coal were investigated from the as-pects of coal compositions and stress history.Two types of coal deformation(inner-swelling and outer-swelling)coexist during gas adsorption.Coal compositions have significant impact on the dominance of deformation type.The dominance of inner-swelling in deep coal is induced by the higher ash contents,and there is the decrease of average pore diameter during gas adsorption.The impact of stress-history(burial depth)on adsorption-induced deformation is more prominent than that of gas adsorption ca-pacity.In deep coal,the surface fractal dimension evolution presents a negative correlation with the evolution of pore diameters.In shallow coal,the surface fractal dimension evolution presents a Langmuir-type correlation with the adsorption time.展开更多
Small angle neutron scattering(SANS) technique has been used to investigate the Ni_(50)Mo_(50) system prepared by mechanical alloying(MA). Significant changes of the scattering intensity have been observed among the s...Small angle neutron scattering(SANS) technique has been used to investigate the Ni_(50)Mo_(50) system prepared by mechanical alloying(MA). Significant changes of the scattering intensity have been observed among the samples with different milling time.Interesting fractal-like behavior of the sample system have been found and attempts have been made to determine the fractal dimensions. It is expected that the fractal dimension can be related to the different stages of MA to some extent.展开更多
In this article we describe a range of simulations (lattice dynamics and molecular dynamics) of the inelastic incoherent neutron scattering spectra of ices (normal ice, ice Ⅱ and ice Ⅷ). These simulations use a vari...In this article we describe a range of simulations (lattice dynamics and molecular dynamics) of the inelastic incoherent neutron scattering spectra of ices (normal ice, ice Ⅱ and ice Ⅷ). These simulations use a variety of different intermolecular potentials from simple classic pair-wise (rigid and non-rigid molecule) potentials to sophisticated polarisable potentials. It was found that MCY makes stretching and bending interactions too weak while others do them well. We demonstrate that in order to reproduce the measured neutron spectrum, greater anisotropy (or orientational variation) is required than these potentials presently provide.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0702400)。
文摘A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field.Combined with transmission electron microscopy,Vickers micro-hardness tests and electron backscattered diffraction measurements,all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix,which suggested excellent thermal stability of the 9 Cr-ODS steel.
基金This work was supported by the National Key R&D Program of China(No.2020YFA0405802)the Shanghai Large Scientific Facilities Center.
文摘The construction of a new beamline,BL10U1,was completed at the Shanghai synchrotron radiation facility in 2020.This multipurpose beamline was designed to provide X-ray scattering techniques such as ultra-small-angle X-ray scattering(USAXS),small-angle X-ray scattering(SAXS),wide-angle X-ray scattering,and microfocus SAXS(μSAXS)for a broad user community.To realize fast time-resolved USAXS experiments,the beamline adopted an in-vacuum undulator with a total length of 1.6 m as the photon source.An in-house cryogenic-cooled double multilayer monochromator was installed to deliver a photon flux of approximately 10^(13) photons/s at a photon energy of 10 keV.The three-year successful operation of this beamline demonstrated that the monochromator operated smoothly,as expected.BL10U1 has three end stations in succession:USAXS end station,μSAXS end station,and end station for industrial applications.The minimum scattering vector q~0.0042 nm^(-1) at 10 keV can be achieved at the USAXS end station equipped with a 28 m-long and 1.8 m-diameter vacuum flight tube.At theμSAXS end station,a beam spot of less than 10×8μm was achieved for micro-SAXS experiments.In contrast,in situ experimental instruments up to 5 m high and 8 m wide can be mounted at the industrial application end station,which offers industrial scientists the opportunity to use their large industrial equipment.BL10U1 opens up a new capability to investigate phenomena such as non-equilibrium and dynamic processes of materials with a wide length scale from angstroms to micrometers with millisecond time resolution.In this paper,we also report beamline design considerations and commissioning results.
基金Acknowledgements M.R. Eskildsen was supported by the U. S. National Science Foundation through grant DMR-0804887. Collaboration and stimulating discussions are acknowledged with： A. B. Abrahamsen, T. M. Artemova, E. D. Bauer, A. D. Bianchi, T. D. Blasius, S. L. Bud＇ko, P. C. Canfield, P. Das, L. DeBeer-Schmitt, J. M. Densmore, C. D. Dewhurst, Z. Fisk, E. M. Forgan, J. L. Gavilano, S. Gerber, A. I. Coldman, M. Ichioka, R. Ikeda, N. Jenkins, M. Kenzelmann, V. G. Kogan, J. Kohlbrecher, A. Kreyssig, M. Laver, K. Machida, J. Mesot, R. Movshovich, N. Ni, T. O＇Brien, C. Petrovic, R. Prozorov, K. Rovira, J. L. Sarrao, I. S. Veshchunov, L. Ya. Vinnikov. J. S. White and M. Zolliker.
文摘Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can be obtained by such measurements, focusing in particular on studies of the vortex lattice structure and form factor in LuNi2B2C, TmNi2B2C, CeCoIn5 and Ba（Fe0.93Co0.07）2As2.
基金financially supported by the National Natural Science Foundation of China (Nos. 11475267, 11005159, and 21725402)
文摘Dimer impurity in the solution of a generation five(G5) polyamidoamine(PAMAM) dendrimer has been investigated by small-angle neutron scattering(SANS). The existence of dimer impurity in dendrimer solution was evidenced by indirect Fourier transform(IFT) analysis of the SANS data, in which the maximum dimension of particles in solution was found to be about twice the diameter of G5 dendrimer. We then developed an analytical model which accounts for the scattering contribution from both dendrimer monomer and dimer. The experimental data were well fitted by using the established model. The results showed that the amount of dimer impurities is significant for the measured three batches of G5 PAMAM dendrimers.
基金the National Natural Science Foundation of China(Nos.U1832215 and U1832144)the Youth Innovation Promotion Association of Chinese Academy Science(No.2017319).
文摘The BL19U2 at the Shanghai Synchrotron Radiation Facility is a small-angle X-ray scattering beamline dedicated to structural studies pertaining to biological macromolecules in solution.The beamline has been officially opened to users in March 2015,and since then,a series of technological innovations has been developed to optimize beamline performance,thereby significantly improving the data collection efficiency and broadening the application scope of biological small-angle X-ray scattering.BL19U2 is ideal for the high-throughput screening of weakly scattered proteins,protein assemblies,nucleic acids,inorganic nanomaterials,and organic drug molecules.This paper describes the design and overview of the BL19U2 beamline.Versatile sample environments at the experimental station and some recent scientific highlights are presented.
基金supported as part of the Joint Center for Energy Storage Research,an Energy Innovation Hub funded by the U.S.Department of Energy,Office of Science,Basic Energy Sciencesthe supported by U.S.National Science Foundation(Grant No.2120559)。
文摘Fluorine-free electrolytes have attracted great attention because of its low-cost and environmental friendliness. However, so far, little is known about the solution structures of these electrolytes. Here,we compare the solvation phenomenon of sodium tetraphenylborate(NaBPh_(4)) salt dissolved in organic solvents of propylene carbonate(PC), 1,2-dimethoxyethane(DME), acetonitrile(ACN) and tetrahydrofuran(THF). Small-angle X-ray scattering(SAXS) reveals a unique two-peak structural feature in this saltconcentrated PC electrolyte, while solutions using other solvents only have one scattering peak.Molecular dynamics(MD) simulations further reveal that there are anion-based clusters in addition to the short-range charge ordering in the concentrated NaBPh4/PC electrolyte. Raman spectroscopy confirms the existence of considerable contact ion pairs(CIPs). This work emphasizes the importance of global and local structural analysis, which will provide valuable clues for understanding the structureperformance relationship of electrolytes.
基金Project supported by the National Key Basic Research Program of China(Grant Nos.2013CB910203 and 2011CB911104)the National Natural Science Foundation of China(Grant No.31270760)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB08030102)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20113402120013)
文摘Elucidating the structure of large biomolecules such as multi-domain proteins or protein complexes is challenging due to their high flexibility in solution. Recently, an ＂integrative structural biology＂ approach has been proposed, which aims to determine the protein structure and characterize protein flexibility by combining complementary high- and lowresolution experimental data using computer simulations. Small-angle x-ray scattering（SAXS） is an efficient technique that can yield low-resolution structural information, including protein size and shape. Here, we review computational methods that integrate SAXS with other experimental datasets for structural modeling. Finally, we provide a case study of determination of the structure of a protein complex formed between the tandem SH3 domains in c-Cb1-associated protein and the proline-rich loop in human vinculin.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11005143,11405259,and 51274046)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China(Grant No.[2014]1685)
文摘In the present work,the precipitate compositions and precipitate amounts of these elements（including the size distribution,volume fraction,and inter-precipitate distance） on the Cu-containing 7000 series aluminum alloys（7150 and 7085 Al alloys）,are investigated by anomalous small-angle x-ray scattering（ASAXS） at various energies.The scattering intensity of 7150 alloy with T6 aging treatment decreases as the incident x-ray energy approaches the Zn absorption edge from the lower energy side,while scattering intensity does not show a noticeable energy dependence near the Cu absorption edge.Similar results are observed in the 7085 alloy in an aging process（120℃） by employing in-situ ASAXS measurements,indicating that the precipitate compositions should include Zn element and should not be strongly related to Cu element at the early stage after 10 min.In the aging process,the precipitate particles with an initial average size of ~ 8 ？A increase with aging time at an energy of 9.60 ke V,while the increase with a slower rate is observed at an energy of 9.65 ke V as near the Zn absorption edge.
基金Project supported by the Chinese Academy of Science Innovation Key Project (Grant No KJCX2-SW-N06)
文摘This paper reports that at a newly constructed small-angle x-ray scattering station of Beijing Synchrotron Radia- tion Facility, the topological shape of ligand-free bovine serum albumin in solution has been investigated. An appropriate scattering curve is obtained and the calculated value of the gyration radius is 31.2~=t=0.25 ~_ （11=0.1 nm） which is co- incident with other ones＇ results. It finds that the low-resolution structure models obtained by making use of ab initio reconstruction methods are fitting the crystal structure of human serum albumin very well. All of these results perform the potential of the beamline to apply to structural biology studies. The characteristics, the defects, and the improving measures of the station in future are also discussed.
文摘The present work deals with a detailed analysis of the small-angle X-ray scattering of nanoporous atomistic models for amorphous germanium. Structures with spherical nanovoids, others with arbitrarily oriented ellipsoidal ones, with monodisperse and polydisperse size distributions, were first generated. After relaxing the as-generated structure, we compute its radial distribution function, and then we deduce by the Fourier transform technique its X-ray scattering pattern. Using a smoothing procedure, the computed small-angle X-ray scattering patterns are corrected for the termination errors due to the finite size of the model, allowing so, for the first time at our best knowledge, a rigorous quantitative analysis of this scattering. The Guinier’s law is found to be valid irrespective of size and shape of the nanovoids over a scattering vector-range extending beyond the expected limit. A weighted combination of the Guinier’s forms accounts for well the nanovoid size distribution in the amorphous structure. The invariance of the Q-factor and its relationship to the void volume fraction are also confirmed. Our findings support then the quantitative analyses of available small-angle X-ray scattering data for amorphous germanium.
文摘Synchrotron radiation based experimental techniques known as Anomalous Small-Angle X-ray Scattering (ASAXS) provide deep insight into the nanostructure of uncountable material systems in condensed matter research i.e. solid state physics, chemistry, engineering and life sciences thereby rendering the origin of the macroscopic functionalization of the various materials via correlation to its structural architecture on a nanometer length scale. The techniques constitute a system of linear equations, which can be treated by matrix theory. The study aims to analyze the significance of the solutions of the stated matrix equations by use of the so-called condition numbers first introduced by A. Turing, J. von Neumann and H. Goldstine. Special attention was given for the comparison with direct methods i.e. the Gaussian elimination method. The mathematical roots of ill-posed ASAXS equations preventing matrix inversion have been identified. In the framework of the theory of von Neumann and Goldstine the inversion of certain matrices constituted by ASAXS gradually becomes impossible caused by non-definiteness. In Turing’s theory which starts from more general prerequisites, the principal minors of the same matrices approach singularity thereby imposing large errors on inversion. In conclusion both theories recommend for extremely ill-posed ASAXS problems avoiding inversion and the use of direct methods for instance Gaussian elimination.
文摘The objective of this study is to design an elastic neutron scattering system<span><span style="font-family:;" "=""> according to the angle with a sample using thermal neutron beam at the Dalat <span>Nuclear Reactor (DNR). The system is used for research and training in the</span> field <span>of material structure analysis by neutron scattering and diffraction tech</span>nique</span></span><span><span style="font-family:;" "="">s</span></span><span><span style="font-family:;" "="">. It is designed on the basis of inheriting the neutron measurement spectrometer systems at the DNR and the scattered neutron measurement systems in the world. The measuring system, which was installed at the hori<span>zontal channel</span></span></span><span><span style="font-family:;" "=""> </span></span><span><span style="font-family:;" "="">4 of the DNR, consists of </span></span><span><span style="font-family:;" "="">5-helium-3 detectors and a fully</span></span><span><span style="font-family:;" "=""> electronic system to record the scatter counts <span>and a mechanical system with the possibility of rotating at 15</span></span></span><span><span style="font-family:;" "=""><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span><span><span style="font-family:;" "="">-</span></span><span><span style="font-family:;" "="">75</span></span><span><span style="font-family:;" "=""><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span><span><span style="font-family:;" "=""> </span></span><span><span style="font-family:;" "="">angles. The constructed system is tested for <span>evaluation of the accuracy, stability and reliability of the mechanical and</span> electronic systems of moving detector</span></span><span><span style="font-family:;" "="">s</span></span><span><span style="font-family:;" "=""> by angles.</span></span>
文摘The dynamic behaviors of water contained in calcium-silicate-hydrate（C-S-H） gel with different water content values from 10%to 30%（by weight）,are studied by using an empirical diffusion model（EDM） to analyze the experimental data of quasi-elastic neutron scattering（QENS） spectra at measured temperatures ranging from 230 K to 280 K.In the study,the experimental QENS spectra with the whole Q-range are considered.Several important parameters including the bound/immobile water elastic coefficient A,the bound water index BWI,the Lorentzian with a half-width at half-maximum（HWHM） Γ;（Q） and Γ;（Q）,the self-diffusion coefficients D;and D;of water molecules,the average residence times τ;and τ;,and the proton mean squared displacement（MSD）(u;) are obtained.The results show that the QENS spectra can be fitted very well not only for small Q（≤1 A;） but also for large Q.The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI.The distinction between bound/immobile and mobile water,which includes confined water and ultra-confined water,can be seen by the fitted MSD.All the MSD tend to be the smallest value below 0.25 A;（the MSD of bound/immobile water） as the Q increases to 1.9 A;no matter what the temperature and water content are.Furthermore,by the abrupt changes of the fitted values of D;,τ;,and Γ;（Q）,a crossover temperature at 250 K,namely the liquid-to-crystal-like transition temperature,can be identified for confined water in large gel pores（LGPs） and/or small gel pores（SGPs） contained in the C-S-H gel sample with 30% water content.
基金Supported by the National Natural Science Foundation of China
文摘Resonant cyclotron scattering （RCS） in pulsar magnetospheres is considered. The photon diffusion equation （Kompaneets equation） for RCS is derived. The photon system is modeled three dimensionally. Numerical calculations show that there exist not only up scattering but also down scattering of RCS, depending on the parameter space. RCS＇s possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars （INSs） are pointed out. The optical/UV excess of INSs may be caused by the down scattering of RCS. The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data. In our model, the INSs are proposed to be normal neutron stars, although the quark star hypothesis is still possible. The low pulsation amplitude of INSs is a natural consequence in the RCS model.
文摘The influence of pseudogap on the inelastic neutron scattering spectra of the underdoped lanthanum cuprate is studied on the basis of the model which incorporates both the superconducting state and pseudogap state. It is found that the striking effects of the influence of the pseudogap on the incommensurability of the spin excitation spectrum are that in the superconducting state the pseudogap makes the intensity of the incommensurate peak increase, in the normal state the pseudogap not only makes the intensity of the incommensurate peak increase, but also sharpens the incommensurate peak and increases incommensurability.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12004426,U2030106,and 12304185)the National Key Scientific Instrument and Equipment Development Project of NSFC(Grant No.11227906)the National Key R&D Program of China(Grant No.2023YFA1406500)。
文摘An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulations and careful mechanical designs,a shielding configuration has been successfully developed to satisfy safety requirements of below 3μSv/h dose rate at its exterior,meanwhile fulfilling space,floor load and nonmagnetic requirements.Composite materials are utilized to form the sandwich-type shielding walls:the inner layer of boron carbide rubber,the middle layer of steel-encased lead and the outer layer of borated polyethylene.Special-shaped liftable shielding blocks are incorporated to facilitate a continuous adjustment of the neutron energy while preventing radiation leakage.Our work has demonstrated that by utilizing composite shielding materials,along with the sandwich structure and liftable shielding blocks,a compact and lightweight shielding solution can be achieved.This enables the realization of advanced neutron scattering instruments that provide expanded space of measurement,larger energy and momentum coverage,and higher flux on the sample.This shielding represents the first of its kind in neutron scattering instruments in China.Following its successful operation,it has been subsequently employed by other neutron instruments across the country.
基金supported by the National Natural Science Foundation of China (grant Nos.U1910206,52004293,52225402)Beijing Natural Science Foundation (grant No.8232057)+4 种基金the Open Project Program of State Key Laboratory of Coal and CBM Co-mining (grant No.2022KF21)Fundamental Research Funds for the Central Universities (grant No.FRF-TP-20-034A1)the Open Project Program of Key Laboratory of Deep Earth Science and Engineering (Sichuan University)Ministry of Education (grant No.DESE 202004)China Postdoctoral Science Foundation (grant No.2018M641526).
文摘Coal seam CO_(2) sequestration is an important option to address global warming.A better knowledge on coal pore structure evolution during gas adsorption can provide guidance for coal seams CO_(2) seques-tration.However,few investigations on the pore structure evolution differences between the deep and shallow coal were conducted during gas adsorption.In this study,based on the real-time synchrotron radiation small-angle X-ray scattering(SAXS)observation,the average pore diameter and pore surface fractal dimension evolution differences between deep and shallow coal were investigated from the as-pects of coal compositions and stress history.Two types of coal deformation(inner-swelling and outer-swelling)coexist during gas adsorption.Coal compositions have significant impact on the dominance of deformation type.The dominance of inner-swelling in deep coal is induced by the higher ash contents,and there is the decrease of average pore diameter during gas adsorption.The impact of stress-history(burial depth)on adsorption-induced deformation is more prominent than that of gas adsorption ca-pacity.In deep coal,the surface fractal dimension evolution presents a negative correlation with the evolution of pore diameters.In shallow coal,the surface fractal dimension evolution presents a Langmuir-type correlation with the adsorption time.
文摘Small angle neutron scattering(SANS) technique has been used to investigate the Ni_(50)Mo_(50) system prepared by mechanical alloying(MA). Significant changes of the scattering intensity have been observed among the samples with different milling time.Interesting fractal-like behavior of the sample system have been found and attempts have been made to determine the fractal dimensions. It is expected that the fractal dimension can be related to the different stages of MA to some extent.
基金We would like to thank National Natural Science Foundation of China(Grand No.10144001)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,for their financial supports.
文摘In this article we describe a range of simulations (lattice dynamics and molecular dynamics) of the inelastic incoherent neutron scattering spectra of ices (normal ice, ice Ⅱ and ice Ⅷ). These simulations use a variety of different intermolecular potentials from simple classic pair-wise (rigid and non-rigid molecule) potentials to sophisticated polarisable potentials. It was found that MCY makes stretching and bending interactions too weak while others do them well. We demonstrate that in order to reproduce the measured neutron spectrum, greater anisotropy (or orientational variation) is required than these potentials presently provide.
