This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix wi...This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix with nano-sized VCr precipitates.VCr is chemical-disordered and TiNi has a B2-ordered structure.The alloy was subjected to 400 keV He ion irradiation with a fluence of 1×10^(17)ions cm^(−2)at 450℃.The results show He bubbles within the chemical-disordered VCr matrix exhibit a near-spherical shape with a smaller size and higher density compared to that in chemical-ordered TiNi phase with a larger size,lower density,and faceted shape.This indicates the chemical-disordered VCr phase effectively suppresses He accumulation compared to the B2-ordered TiNi phase,emphasizing the dominance of chemical struc-tures in He bubble formation.The calculation of density functional theory(DFT)shows that Ti and Ni have lower vacancy formation energy than that of V and Cr,respectively,which results in the increased vacancy production in TiNi.Consequently,He bubbles in TiNi have a larger bubble size consistent with experimental observations of radiation-induced Ni segregation.These findings elucidate the roles of or-dered and disordered chemical structures in He bubble evolution,offering insights for the development of gas ion irradiation-resistant materials.展开更多
A laser phase determination method and a transfer function that includes a proportional term of a measured photoelectron energy spectrum are presented to directly measure the detailed temporal structure of a narrow ba...A laser phase determination method and a transfer function that includes a proportional term of a measured photoelectron energy spectrum are presented to directly measure the detailed temporal structure of a narrow bandwidth attosecond extreme-ultraviolet （EUV） pulse. The method is based on the spectrum measurement of an electron generated by EUV photo-ionization interacting with a femtosecond laser field. The results of the study suggest that measurements should be taken at 0° or 180° with respect to the linear laser polarization. The method has a temporal measurement range of about half a laser oscillation period. The temporal resolution also depends on the jitter and control precision of the laser and EUV pulses.展开更多
Laser phase relations of high-order harmonic generation （HHG） are calculated with the saddle point theory. The results show a two-peak structure including a symmetric and an asymmetric temporal distributions of the ...Laser phase relations of high-order harmonic generation （HHG） are calculated with the saddle point theory. The results show a two-peak structure including a symmetric and an asymmetric temporal distributions of the instantaneous frequency of HHG radiation. These distributions are fitted with Gaussian and polynomial functions, respectively. Two calculation formulae are presented to analyse attosecond x-rays with specified time duration and energy bandwidth in experiments.展开更多
Osteoarthritis(OA)is a debilitating degenerative disease affecting multiple joint tissues,including cartilage,bone,synovium,and adipose tissues.OA presents diverse clinical phenotypes and distinct molecular endotypes,...Osteoarthritis(OA)is a debilitating degenerative disease affecting multiple joint tissues,including cartilage,bone,synovium,and adipose tissues.OA presents diverse clinical phenotypes and distinct molecular endotypes,including inflammatory,metabolic,mechanical,genetic,and synovial variants.Consequently,innovative technologies are needed to support the development of effective diagnostic and precision therapeutic approaches.Traditional analysis of bulk OA tissue extracts has limitations due to technical constraints,causing challenges in the differentiation between various physiological and pathological phenotypes in joint tissues.This issue has led to standardization difficulties and hindered the success of clinical trials.Gaining insights into the spatial variations of the cellular and molecular structures in OA tissues,encompassing DNA,RNA,metabolites,and proteins,as well as their chemical properties,elemental composition,and mechanical attributes,can contribute to a more comprehensive understanding of the disease subtypes.Spatially resolved biology enables biologists to investigate cells within the context of their tissue microenvironment,providing a more holistic view of cellular function.Recent advances in innovative spatial biology techniques now allow intact tissue sections to be examined using various-omics lenses,such as genomics,transcriptomics,proteomics,and metabolomics,with spatial data.This fusion of approaches provides researchers with critical insights into the molecular composition and functions of the cells and tissues at precise spatial coordinates.Furthermore,advanced imaging techniques,including high-resolution microscopy,hyperspectral imaging,and mass spectrometry imaging,enable the visualization and analysis of the spatial distribution of biomolecules,cells,and tissues.Linking these molecular imaging outputs to conventional tissue histology can facilitate a more comprehensive characterization of disease phenotypes.This review summarizes the recent advancements in the molecular imaging modalities and methodologies for in-depth spatial analysis.It explores their applications,challenges,and potential opportunities in the field of OA.Additionally,this review provides a perspective on the potential research directions for these contemporary approaches that can meet the requirements of clinical diagnoses and the establishment of therapeutic targets for OA.展开更多
The equations ofstate of the neutron star matter are calculated in the relativistic mean-field approximation witl different hyperon coupling constants. The properties of neutron stars are studied by solving the Oppenh...The equations ofstate of the neutron star matter are calculated in the relativistic mean-field approximation witl different hyperon coupling constants. The properties of neutron stars are studied by solving the OppenheimerVolkoff equation. It manifests the properties of neutron stars - change explicitly as different hyperon coupling constants are concerned.展开更多
Quantitative investigations are made for the laser-duration dependence of the emission properties of high-order harmonic generation （HHG）. HHG emission properties produced by few-cycle lasers show some useful charac...Quantitative investigations are made for the laser-duration dependence of the emission properties of high-order harmonic generation （HHG）. HHG emission properties produced by few-cycle lasers show some useful characteristics. The cutoff energy is less than that by laser for infinite duration. The single energy distribution pulse decreases much faster than its duration as the laser duration grows. A two-cycle laser with carrier-envelope phase of 0° can produce a single distribution pulse peaked at the laser carrier phase 1.22 rad and spanned 1.18 rad with the cutoff energy 2.9Up ＋ Ip and a bandwidth 0.63Up, where Up is the ponderomotive potential of the laser field and Ip is the atomic ionization potential.展开更多
We calculate nonperturbatively the irfluence of a strong circularly polarized laser beam on the hydrogen atom energy levels by making use of the time-independent formalism proposed by one of us. The photoionization cr...We calculate nonperturbatively the irfluence of a strong circularly polarized laser beam on the hydrogen atom energy levels by making use of the time-independent formalism proposed by one of us. The photoionization cross section of the hydrogen atom irradiated by this laser beam and the angular distribution of photoelectrons are also calculated. From the numerical results we clearly see the intensity dependence of the whole photoionization process,including the intensity dependence of the photoelectron energies.展开更多
New IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule, kappa-carrageenan (KC) were prepared by gamma irradiation and their properties were studied, The results show that bot...New IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule, kappa-carrageenan (KC) were prepared by gamma irradiation and their properties were studied, The results show that both the gel strength and the swelling capacity of the IPN hydrogels were enhanced significantly as compared with those of the pure hydrogels of PDADMAC.展开更多
The in vitro interaction of nicotine and hemoglobin (Hb) in a metabolizing System was studied by spectroscopy assays. Visible spectra showed two isobestics, and fluorescence spectra showed static quenching with increa...The in vitro interaction of nicotine and hemoglobin (Hb) in a metabolizing System was studied by spectroscopy assays. Visible spectra showed two isobestics, and fluorescence spectra showed static quenching with increasing of nicotine dose. Meanwhile, the CD spectra intensity reduced, showing the conformation of Hb varied markedly through the interaction. All these results suggested that the interaction of nicotine or its metabolites and Hb might do harm to physicological function of Hb.展开更多
The diluted magnetic semiconductor Ga1-xMnxN was achieved by low-pressure metal organic vapour-phase epitaxy （LP-MOVPE）. Proton-induced x-ray emission was employed non-destructively, quickly and accurately to determ...The diluted magnetic semiconductor Ga1-xMnxN was achieved by low-pressure metal organic vapour-phase epitaxy （LP-MOVPE）. Proton-induced x-ray emission was employed non-destructively, quickly and accurately to determine the Mn-doped content. The magnetic property was measured by a superconducting-quantuminterference-device （SQID） magnetometer. Apparent ferromagnetic hysteresis loops measured at or above room temperature are presented. No ferromagnetic secondary phases were detected by high-resolution x-ray diffraction. The experimental results show that the ferromagnetic signal firstly decreases and then increases with the increasing Mn-doped content from 0.23% to 4.69% and it is the weakest when Mn content is 0.51%. The annealing treatment could make the ferromagnetic property stronger.展开更多
In this paper the laser-phase determination methods and transfer equations are presented to directly reconstruct the detailed temporal structures of ultra-short extreme ultraviolet （xuv） pulses from the measured pho...In this paper the laser-phase determination methods and transfer equations are presented to directly reconstruct the detailed temporal structures of ultra-short extreme ultraviolet （xuv） pulses from the measured photoelectron energy spectra （PES）. Each transfer equation includes one of PID （proportional-integral-differential） terms of PES. The intensity and instantaneous frequency of attosecond xuv can be retrieved from the integral term of PES. The intensity profiles of narrow bandwidth atto- and femtosecond xuvs can be rebuilt from the proportional and differential terms of PES respectively. The methods and equations may be used to improve time resolutions in measuring ultrashort pulses.展开更多
Composition in amorphous Si1-xCx：H heteroepitaxial thin films on Si （100） by plasma enhanced chemical vapour deposition （PECVD） is analysed. The unknown x （0.45-3.57） and the depth profile of hydrogen in the th...Composition in amorphous Si1-xCx：H heteroepitaxial thin films on Si （100） by plasma enhanced chemical vapour deposition （PECVD） is analysed. The unknown x （0.45-3.57） and the depth profile of hydrogen in the thin films are characterized by Rutherford backscattering spectrum （RBS）, resonance-nuclear reaction analysis （R-NRA） and elastic recoil detection （ERD）, respectively. In addition, the depth profile of hydrogen in the unannealed thin films is compared to that of the annealed thin films with rapid thermal annealing （RTA） or laser spike annealing （LSA） in nitrogen atmosphere. The results indicate that the stoichiometric amorphous SiC can be produced by PECVD when the ratio of CH4/SiH4 is approximately equal to 25. The content of hydrogen decreases suddenly from 35% to 1% after 1150℃ annealing. RTA can reduce hydrogen in SiC films effectively than LSA.展开更多
An effective Hamiltonian including current-current coupling from the global color symmetry model is -R2 2derived.Retardation effects are introduced by the factor ( R/ ) e ,instead of δ (r) in the correlation kernel,f...An effective Hamiltonian including current-current coupling from the global color symmetry model is -R2 2derived.Retardation effects are introduced by the factor ( R/ ) e ,instead of δ (r) in the correlation kernel,from which the retardation gap equation with α-α coupling in the 3po vacuum is obtained,qq condensations of different retardation parameters R with or without the α-α term are calculated.The results show the effects of retardation,and indicate that the typical value of R is about 2 fm-1 at reasonable value of qq condensation.And while taking typical value 1 fm-1 of R,the condensation <qq>1/3 is about 13% larger than that with no retardation effect.With the α-αterms,the condensation (qq) 1/3 is about 17%o larger than that without it for all values of the parameter R.This shows that the retardation effects and the α-α terms are important for further studying in the Iow-energy region.展开更多
The γ induced polymerization of styrene in the presence of polar additives such as tributylphosphate, triethyl amine and ethanol was studied at dose rate of 5.0×10^(17) eV/ml. min. The re-sult shows that radiati...The γ induced polymerization of styrene in the presence of polar additives such as tributylphosphate, triethyl amine and ethanol was studied at dose rate of 5.0×10^(17) eV/ml. min. The re-sult shows that radiation induced polymerization of styrene was sensitized by the three kinds ofadditives at the approximate same rate and the experimental results were in agreement with thetheoretical calculation of WAS equation. The cause of sensitization is due to the proton transfer.展开更多
This paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measu...This paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measurements of the pulse natural properties of x-ray intensity and the instantaneous frequency profiles. As a direct procedure without any previous pulse profile assumptions and time-resolved measurements as well as data fitting analysis, this method can be used to improve the time resolutions of attosecond timing and measurements with metrological precision. The measurement range is half of a laser optical cycle.展开更多
Superconducting materials with high critical temperature have the potential to revolutionize many fields,including military,electronic communications,and power energy.Therefore,scientists around the world have been ti...Superconducting materials with high critical temperature have the potential to revolutionize many fields,including military,electronic communications,and power energy.Therefore,scientists around the world have been tirelessly working with the ultimate goal of achieving high-temperature superconductivity.In 2023,a preprint by Lee et al.in South Korea claimed the discovery of ultra-high-temperature superconductivity with a critical temperature of up to 423 K in Cu-doped lead-apatite(LK-99)(arXiv:2307.12008,arXiv:2307.12037),which caused a worldwide sensation and attention.Herein,the electronic structures,phonon dynamics,and electrical conductivities of LK-99 and its parent compound lead-apatite have been calculated using first-principles methods.The results show that the lead-apatite compound and the LK-99 compound are insulator and half-metal respectively.The flat band characteristic is consistent with previous calculations.The electrical conductivity of the LK-99 compound shows two extreme points,and the electrical conductivity along the C-axis increases significantly after 400 K.The phonon dispersion spectra of the compounds were investigated,demonstrating their dynamic instability.展开更多
We show that the collapse of the entangled quantum state makes the entropy increase in an isolated system. The second law of thermodynamics is thus proven in its most genera/form.
Two hexagonal GaN epilayers （samples A and B） with multiple buffer layers and single buffer layer are grown on Si （111） by metal-organic vapour phase epitaxy （MOVPE）. From the results of Rutherford backscatteri...Two hexagonal GaN epilayers （samples A and B） with multiple buffer layers and single buffer layer are grown on Si （111） by metal-organic vapour phase epitaxy （MOVPE）. From the results of Rutherford backscattering （RBS）/channeling and high resolution x-ray diffraction （HRXRD）, we obtain the lattice constant （a and c） of two GaN epilayers （aA = 0.3190 nm, cA = 0.5184 nm and aB = 0.3192 nm, CB = 0.5179 nm）, the crystal quality of two GaN epilayers （ ХminA=4.87%, ХminB =7.35% along 〈1-↑213〉 axis） and the tetragonal distortion eT of the two samples along depth （sample A is nearly fully relaxed, sample B is not relaxed enough）. Comparing the results with the two samples, it is indicated that sample A with multiple buffer layers have better crystal quality than sample B with a single buffer layer, and it is a good way to grow GaN epilayer on Si （111） substrates using multiple buffer layers to improve crystal quality and to reduce lattice mismatch.展开更多
Titration calorimetry has been used to study the thermodynamics of reaction in toluene solution of 2-thenoyltriflueroacetone(TTA)complexes of rare earths(RE=Y,Nd,Eu,Yb)with N,N dimethylheptyl-acetamide(N503)at 298.15 ...Titration calorimetry has been used to study the thermodynamics of reaction in toluene solution of 2-thenoyltriflueroacetone(TTA)complexes of rare earths(RE=Y,Nd,Eu,Yb)with N,N dimethylheptyl-acetamide(N503)at 298.15 K.The heat of the reaction was determined with a TRONAC Model 1250 automatic isoperibol calorimeter.The data and figures of titration curve were recorded by the com- puter automatically.An iterative technique of least-square analysis was used to calculate the equilibrium con- stants and the thermodynamic functions including the entropy and free energy changes,minimizing the error square sum by a computer program.展开更多
The stopping powers of Br and C in Ag Elm have been measured with the method of elastic recoil detection in energy range 0.28-0.42MeV/amu.The results have been compared with the theoretical calculations of TRIM-90.
基金supported by the National Magnetic Con-finement Fusion Energy Research Project from the Ministry of Science and Technology of China(No.2022YFE03030004 and 2019YFE03120003)the National Natural Science Foundation of China(No.12275010,12275176,12275001,12335017,11921006,U21B2082,U22B2064 and U20B2025)+3 种基金the Beijing Municipal Natural Science Foundation(No.1222023)the Shenzhen Science and Technology Program(No.RCYX20210609103904028)Engang Fu acknowledges the support from the Science Fund or Creative Research Groups of NSFC,the Ion Beam Materials Laboratory(IBML)and Electron Microscopy Laboratory(EML)the High-performance Computing Platform(HPC)at Peking University.Xing Liu acknowledges the discussion with Prof.Ning Gao and Dr.Yifan Zhang.
文摘This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix with nano-sized VCr precipitates.VCr is chemical-disordered and TiNi has a B2-ordered structure.The alloy was subjected to 400 keV He ion irradiation with a fluence of 1×10^(17)ions cm^(−2)at 450℃.The results show He bubbles within the chemical-disordered VCr matrix exhibit a near-spherical shape with a smaller size and higher density compared to that in chemical-ordered TiNi phase with a larger size,lower density,and faceted shape.This indicates the chemical-disordered VCr phase effectively suppresses He accumulation compared to the B2-ordered TiNi phase,emphasizing the dominance of chemical struc-tures in He bubble formation.The calculation of density functional theory(DFT)shows that Ti and Ni have lower vacancy formation energy than that of V and Cr,respectively,which results in the increased vacancy production in TiNi.Consequently,He bubbles in TiNi have a larger bubble size consistent with experimental observations of radiation-induced Ni segregation.These findings elucidate the roles of or-dered and disordered chemical structures in He bubble evolution,offering insights for the development of gas ion irradiation-resistant materials.
文摘A laser phase determination method and a transfer function that includes a proportional term of a measured photoelectron energy spectrum are presented to directly measure the detailed temporal structure of a narrow bandwidth attosecond extreme-ultraviolet （EUV） pulse. The method is based on the spectrum measurement of an electron generated by EUV photo-ionization interacting with a femtosecond laser field. The results of the study suggest that measurements should be taken at 0° or 180° with respect to the linear laser polarization. The method has a temporal measurement range of about half a laser oscillation period. The temporal resolution also depends on the jitter and control precision of the laser and EUV pulses.
文摘Laser phase relations of high-order harmonic generation （HHG） are calculated with the saddle point theory. The results show a two-peak structure including a symmetric and an asymmetric temporal distributions of the instantaneous frequency of HHG radiation. These distributions are fitted with Gaussian and polynomial functions, respectively. Two calculation formulae are presented to analyse attosecond x-rays with specified time duration and energy bandwidth in experiments.
基金the NHMRC Investigator grant fellowship (APP1176298)the EMCR grant from the Centre for Biomedical Technologies (QUT)+4 种基金the QUT Postgraduate Research Award (QUTPRA)QUT HDR TOP-UP scholarshipQUT HDR Tuition Fee Sponsorshipfunding support from the Academy of Finland (315820)the Jane and Aatos Erkko Foundation (190001).
文摘Osteoarthritis(OA)is a debilitating degenerative disease affecting multiple joint tissues,including cartilage,bone,synovium,and adipose tissues.OA presents diverse clinical phenotypes and distinct molecular endotypes,including inflammatory,metabolic,mechanical,genetic,and synovial variants.Consequently,innovative technologies are needed to support the development of effective diagnostic and precision therapeutic approaches.Traditional analysis of bulk OA tissue extracts has limitations due to technical constraints,causing challenges in the differentiation between various physiological and pathological phenotypes in joint tissues.This issue has led to standardization difficulties and hindered the success of clinical trials.Gaining insights into the spatial variations of the cellular and molecular structures in OA tissues,encompassing DNA,RNA,metabolites,and proteins,as well as their chemical properties,elemental composition,and mechanical attributes,can contribute to a more comprehensive understanding of the disease subtypes.Spatially resolved biology enables biologists to investigate cells within the context of their tissue microenvironment,providing a more holistic view of cellular function.Recent advances in innovative spatial biology techniques now allow intact tissue sections to be examined using various-omics lenses,such as genomics,transcriptomics,proteomics,and metabolomics,with spatial data.This fusion of approaches provides researchers with critical insights into the molecular composition and functions of the cells and tissues at precise spatial coordinates.Furthermore,advanced imaging techniques,including high-resolution microscopy,hyperspectral imaging,and mass spectrometry imaging,enable the visualization and analysis of the spatial distribution of biomolecules,cells,and tissues.Linking these molecular imaging outputs to conventional tissue histology can facilitate a more comprehensive characterization of disease phenotypes.This review summarizes the recent advancements in the molecular imaging modalities and methodologies for in-depth spatial analysis.It explores their applications,challenges,and potential opportunities in the field of OA.Additionally,this review provides a perspective on the potential research directions for these contemporary approaches that can meet the requirements of clinical diagnoses and the establishment of therapeutic targets for OA.
文摘The equations ofstate of the neutron star matter are calculated in the relativistic mean-field approximation witl different hyperon coupling constants. The properties of neutron stars are studied by solving the OppenheimerVolkoff equation. It manifests the properties of neutron stars - change explicitly as different hyperon coupling constants are concerned.
基金Supported by the National Natural Science Foundation of China under Grant No 10675014. I am grateful to Protessor K. Burnett at Oxford University and Professor M. Lewenstein at the Institut de Ciencies Fotoniques for useful discussions. Acknowledgments are also made to B. S. Zhao at Xi＇an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, D. X. Jiang, Y. L. Ye and J. X. Chen at Peking University for discussions, and Haip- ing He for her assistance.
文摘Quantitative investigations are made for the laser-duration dependence of the emission properties of high-order harmonic generation （HHG）. HHG emission properties produced by few-cycle lasers show some useful characteristics. The cutoff energy is less than that by laser for infinite duration. The single energy distribution pulse decreases much faster than its duration as the laser duration grows. A two-cycle laser with carrier-envelope phase of 0° can produce a single distribution pulse peaked at the laser carrier phase 1.22 rad and spanned 1.18 rad with the cutoff energy 2.9Up ＋ Ip and a bandwidth 0.63Up, where Up is the ponderomotive potential of the laser field and Ip is the atomic ionization potential.
文摘We calculate nonperturbatively the irfluence of a strong circularly polarized laser beam on the hydrogen atom energy levels by making use of the time-independent formalism proposed by one of us. The photoionization cross section of the hydrogen atom irradiated by this laser beam and the angular distribution of photoelectrons are also calculated. From the numerical results we clearly see the intensity dependence of the whole photoionization process,including the intensity dependence of the photoelectron energies.
文摘New IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule, kappa-carrageenan (KC) were prepared by gamma irradiation and their properties were studied, The results show that both the gel strength and the swelling capacity of the IPN hydrogels were enhanced significantly as compared with those of the pure hydrogels of PDADMAC.
基金We thank the financial support of the National Natural Science Foundation of China(Grant.No.19935020)Research Fund for Doctoral Program of Higher Education.
文摘The in vitro interaction of nicotine and hemoglobin (Hb) in a metabolizing System was studied by spectroscopy assays. Visible spectra showed two isobestics, and fluorescence spectra showed static quenching with increasing of nicotine dose. Meanwhile, the CD spectra intensity reduced, showing the conformation of Hb varied markedly through the interaction. All these results suggested that the interaction of nicotine or its metabolites and Hb might do harm to physicological function of Hb.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10375004 and 10575007, and the Key Laboratory of Heavy Ion Physics （Peking University）, Ministry of Education of China.
文摘The diluted magnetic semiconductor Ga1-xMnxN was achieved by low-pressure metal organic vapour-phase epitaxy （LP-MOVPE）. Proton-induced x-ray emission was employed non-destructively, quickly and accurately to determine the Mn-doped content. The magnetic property was measured by a superconducting-quantuminterference-device （SQID） magnetometer. Apparent ferromagnetic hysteresis loops measured at or above room temperature are presented. No ferromagnetic secondary phases were detected by high-resolution x-ray diffraction. The experimental results show that the ferromagnetic signal firstly decreases and then increases with the increasing Mn-doped content from 0.23% to 4.69% and it is the weakest when Mn content is 0.51%. The annealing treatment could make the ferromagnetic property stronger.
文摘In this paper the laser-phase determination methods and transfer equations are presented to directly reconstruct the detailed temporal structures of ultra-short extreme ultraviolet （xuv） pulses from the measured photoelectron energy spectra （PES）. Each transfer equation includes one of PID （proportional-integral-differential） terms of PES. The intensity and instantaneous frequency of attosecond xuv can be retrieved from the integral term of PES. The intensity profiles of narrow bandwidth atto- and femtosecond xuvs can be rebuilt from the proportional and differential terms of PES respectively. The methods and equations may be used to improve time resolutions in measuring ultrashort pulses.
基金Supported by the National Natural Science Foundation of China under Grant No 10575007 The authors thank Professor G. B. Zhang. for providing the samples.
文摘Composition in amorphous Si1-xCx：H heteroepitaxial thin films on Si （100） by plasma enhanced chemical vapour deposition （PECVD） is analysed. The unknown x （0.45-3.57） and the depth profile of hydrogen in the thin films are characterized by Rutherford backscattering spectrum （RBS）, resonance-nuclear reaction analysis （R-NRA） and elastic recoil detection （ERD）, respectively. In addition, the depth profile of hydrogen in the unannealed thin films is compared to that of the annealed thin films with rapid thermal annealing （RTA） or laser spike annealing （LSA） in nitrogen atmosphere. The results indicate that the stoichiometric amorphous SiC can be produced by PECVD when the ratio of CH4/SiH4 is approximately equal to 25. The content of hydrogen decreases suddenly from 35% to 1% after 1150℃ annealing. RTA can reduce hydrogen in SiC films effectively than LSA.
文摘An effective Hamiltonian including current-current coupling from the global color symmetry model is -R2 2derived.Retardation effects are introduced by the factor ( R/ ) e ,instead of δ (r) in the correlation kernel,from which the retardation gap equation with α-α coupling in the 3po vacuum is obtained,qq condensations of different retardation parameters R with or without the α-α term are calculated.The results show the effects of retardation,and indicate that the typical value of R is about 2 fm-1 at reasonable value of qq condensation.And while taking typical value 1 fm-1 of R,the condensation <qq>1/3 is about 13% larger than that with no retardation effect.With the α-αterms,the condensation (qq) 1/3 is about 17%o larger than that without it for all values of the parameter R.This shows that the retardation effects and the α-α terms are important for further studying in the Iow-energy region.
文摘The γ induced polymerization of styrene in the presence of polar additives such as tributylphosphate, triethyl amine and ethanol was studied at dose rate of 5.0×10^(17) eV/ml. min. The re-sult shows that radiation induced polymerization of styrene was sensitized by the three kinds ofadditives at the approximate same rate and the experimental results were in agreement with thetheoretical calculation of WAS equation. The cause of sensitization is due to the proton transfer.
文摘This paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measurements of the pulse natural properties of x-ray intensity and the instantaneous frequency profiles. As a direct procedure without any previous pulse profile assumptions and time-resolved measurements as well as data fitting analysis, this method can be used to improve the time resolutions of attosecond timing and measurements with metrological precision. The measurement range is half of a laser optical cycle.
基金supported by the National Natural Science Foun-dation of China(Nos.11921006,11975034,11375018,12005048,12335017,U20B2025,and U21B2082)the Beijing Municipal Natural Science Foundation(1222023)the Shenzhen Science and Technology Program(RCYK20210609103904028).
文摘Superconducting materials with high critical temperature have the potential to revolutionize many fields,including military,electronic communications,and power energy.Therefore,scientists around the world have been tirelessly working with the ultimate goal of achieving high-temperature superconductivity.In 2023,a preprint by Lee et al.in South Korea claimed the discovery of ultra-high-temperature superconductivity with a critical temperature of up to 423 K in Cu-doped lead-apatite(LK-99)(arXiv:2307.12008,arXiv:2307.12037),which caused a worldwide sensation and attention.Herein,the electronic structures,phonon dynamics,and electrical conductivities of LK-99 and its parent compound lead-apatite have been calculated using first-principles methods.The results show that the lead-apatite compound and the LK-99 compound are insulator and half-metal respectively.The flat band characteristic is consistent with previous calculations.The electrical conductivity of the LK-99 compound shows two extreme points,and the electrical conductivity along the C-axis increases significantly after 400 K.The phonon dispersion spectra of the compounds were investigated,demonstrating their dynamic instability.
基金The project supported by National Natural Science Foundation of China under Grant No.10305001
文摘We show that the collapse of the entangled quantum state makes the entropy increase in an isolated system. The second law of thermodynamics is thus proven in its most genera/form.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10375004 and 10575007, and the Bilateral China-Belgium Cooperation under Grant No BIL04/05. The authors thank Dr K. Cheng for providing the GaN samples.
文摘Two hexagonal GaN epilayers （samples A and B） with multiple buffer layers and single buffer layer are grown on Si （111） by metal-organic vapour phase epitaxy （MOVPE）. From the results of Rutherford backscattering （RBS）/channeling and high resolution x-ray diffraction （HRXRD）, we obtain the lattice constant （a and c） of two GaN epilayers （aA = 0.3190 nm, cA = 0.5184 nm and aB = 0.3192 nm, CB = 0.5179 nm）, the crystal quality of two GaN epilayers （ ХminA=4.87%, ХminB =7.35% along 〈1-↑213〉 axis） and the tetragonal distortion eT of the two samples along depth （sample A is nearly fully relaxed, sample B is not relaxed enough）. Comparing the results with the two samples, it is indicated that sample A with multiple buffer layers have better crystal quality than sample B with a single buffer layer, and it is a good way to grow GaN epilayer on Si （111） substrates using multiple buffer layers to improve crystal quality and to reduce lattice mismatch.
基金This project was supported by the National Natural Science Foundation of China
文摘Titration calorimetry has been used to study the thermodynamics of reaction in toluene solution of 2-thenoyltriflueroacetone(TTA)complexes of rare earths(RE=Y,Nd,Eu,Yb)with N,N dimethylheptyl-acetamide(N503)at 298.15 K.The heat of the reaction was determined with a TRONAC Model 1250 automatic isoperibol calorimeter.The data and figures of titration curve were recorded by the com- puter automatically.An iterative technique of least-square analysis was used to calculate the equilibrium con- stants and the thermodynamic functions including the entropy and free energy changes,minimizing the error square sum by a computer program.
基金Supported by Doctoral Programme Foundation of Institution of Higher Education。
文摘The stopping powers of Br and C in Ag Elm have been measured with the method of elastic recoil detection in energy range 0.28-0.42MeV/amu.The results have been compared with the theoretical calculations of TRIM-90.
