This study investigates the effect of high current density electropulsing on the material in a rapid stress relaxation process.An AISI 1020 steel was shot-peened to induce surface compressive residual stresses in a co...This study investigates the effect of high current density electropulsing on the material in a rapid stress relaxation process.An AISI 1020 steel was shot-peened to induce surface compressive residual stresses in a controlled manner and subsequently electropulsed to investigate the changes in microstructure and defect configuration.AISI 1020 steel was chosen as it has a simple microstructure(plain ferritic)and composition with low alloying conditions.It is an appropriate material to study the effect of trans-mitting electric pulses on the microstructural defect evolution.A combination of electron-backscattered diffraction and transmission electron microscopy proved to be an effective tool in characterizing the post-electropulsing effects critically.By application of electropulsing,a reduction in the surface residual stress layer was noticed.Also,reductions in misorientation and dislocation density together with the disentan-glement of dislocations within the cold-worked layer were observed after electropulsing.Additionally,the annihilation of shot-peening-induced deformation bands beyond the residual layer depth was observed.These effects have been rationalised by taking into account the various possibilities of athermal effects of electropulsing.展开更多
Mechano luminescence(ML),which involves the emission of light under mechanical stimuli,shows great potential in various applications such as sensing,imaging,and energy harvesting.Current research suggests that the lum...Mechano luminescence(ML),which involves the emission of light under mechanical stimuli,shows great potential in various applications such as sensing,imaging,and energy harvesting.Current research suggests that the luminescence mechanism of ML is typically connected to specific defects present within the material.In this study,we focus on the investigation of ML defects in Pr^(3+)-doped NaNbO_(3)/LiNbO_(3)heterojunctions,employing a combination of experimental and theoretical approaches.Through experimental analysis,we confirmed the presence of the heterojunction and its influence on ML intensity,and the optimal doping ratio for the heterojunction in ML was established.Furthermore,we examined the influence of varying Pr^(3+)doping concentrations on ML behavior and a proof-of-concept was demonstrated using the X-rays charged heterostructural phosphor as a stress sensor for biological applications.The position and concentration of internal defects in the ML material were scrutinized through thermo luminescence tests employing the variable heating rate method and positron annihilation.Complementing the experimental findings,theoretical simulations were conducted to elucidate the underlying mechanisms responsible for the observed ML defects.Density functional theory calculations were employed to investigate the energy levels,charge transfer processes,and lattice distortions within the heterojunctions under mechanical stress.Theoretical predictions were compared and validated against the experimental results.The integration of experimental and theoretical approaches provides a comprehensive understanding of the ML behavior of Pr^(3+)-doped NaNbO_(3)/LiNbO_(3)heterojunctions.The insights gained from this research contribute to the development of novel ML materials and pave the way for their applications in next-generation sensing and energy conversion devices.展开更多
The stability of matrix graphite under neutron irradiation and in corrosive environments is crucial for the safe operation of molten salt reactors(MSRs).Raman spectroscopy and a slow positron beam were employed to inv...The stability of matrix graphite under neutron irradiation and in corrosive environments is crucial for the safe operation of molten salt reactors(MSRs).Raman spectroscopy and a slow positron beam were employed to investigate the effects of He ion irradiation fluences and subsequent annealing on the microstructure and defects of the matrix graphite.He ions with 500 keV energy and fluences ranging from 1.1×10^(15)ions∕cm^(2)to 3.5×10^(17)ions∕cm^(2)were used to simulate neutron irradiation at 300 K.The samples with an irradiation fluence of 3.5×10^(16)ions∕cm^(2)were subjected to isochronal annealing at different temperatures(573 K,873 K and 1173 K)for 3 h.The Raman results revealed that the D peak gradually increased,whereas the intrinsic G peak decreased with increasing irradiation fluence.At the same irradiation fluence,the D peak gradually decreased,whereas the intrinsic G peak increased with increasing annealing temperature.Slow positron beam analysis demonstrated that the density or size of irradiation defects(vacancy type)increased with higher irradiation fluence,but decreased rapidly with increasing annealing temperature.The Raman spectral analysis of sample cross sections subjected to high irradiation fluences revealed the emergence of amorphization precisely at the depth where ion damage was most pronounced,whereas the surface retained its crystalline structure.Raman and positron annihilation analyses indicated that the matrix graphite exhibited good irradiation resistance to He ions at 300 K.However,vacancy-type defects induced by He ion irradiation exhibit poor thermal stability and can be easily removed during annealing.展开更多
Zinc phthalocyanines(ZnPc)are widely recognized as efficient triplet photosensitizers in photodynamic therapy and photocatalysis,owing to their intense absorption in the visible range and long triplet-state lifetimes....Zinc phthalocyanines(ZnPc)are widely recognized as efficient triplet photosensitizers in photodynamic therapy and photocatalysis,owing to their intense absorption in the visible range and long triplet-state lifetimes.However,their application in triplet-triplet annihilation(TTA)upconversion is lacking to date.In this study,we synthesized a new ZnPc photosensitizer,4I-ZnPc,and composed a TTA upconversion system using rubrene as the energy acceptor.Upon photoexcitation at 663 nm,yellow fluorescence from rubrene was observed in deoxygenated dichloromethane,demonstrating TTA upconversion with an anti-Stokes shift of 0.331 eV and a quantum yield of 1.82%(out of the 50%maximum).Using nanosecond transient absorption spectroscopy,we determined the triplet lifetime of 4I-ZnPc,the triplet-triplet energy transfer efficiency,and the fluorescence quantum yield.These measurements provide critical insights into the photophysical processes governing the TTA upconversion system.Our results highlight the potential advantages and limitations of ZnPc as a triplet photosensitizer for TTA upconversion.展开更多
Correction:Nuclear Science and Techniques(2025)36:4 https://doi.org/10.1007/s41365-024-01548-5 In this article,the caption for Fig(s)1,3,and 4 was inadvert-ently truncated.The incorrect and the corrected captions are ...Correction:Nuclear Science and Techniques(2025)36:4 https://doi.org/10.1007/s41365-024-01548-5 In this article,the caption for Fig(s)1,3,and 4 was inadvert-ently truncated.The incorrect and the corrected captions are given below.展开更多
This paper presents the findings of a two-week monitoring project on Gender Based Violence(GBV)in Tanzanian and explores how the media outlets frame the marginalized voices,institutional narratives,and intersectional ...This paper presents the findings of a two-week monitoring project on Gender Based Violence(GBV)in Tanzanian and explores how the media outlets frame the marginalized voices,institutional narratives,and intersectional inclusivity.Drawing qualitative approach and analysis of media coverage of GBV during the 202416 Days of Activism campaign remarkably November 25 to December 10,2024,it reveals the extent that media platforms amplify or marginalize survivor voices.Through two weeks of media monitoring across print,broadcast,and social media including sources notably Mwananchi,TBC1,Cloud FM,and advocacy-driven digital platforms and campaigns through#EndGBVNow and#16DaysOfActivism the study explores recurring themes,language use,tone,and inclusivity.Guided by critical gender theories including Judith Butler’s gender performativity and Gave Tuchman’s symbolic annihilation,the analysis reveals media’s dual role in either perpetuating or challenging patriarchal narratives.Findings indicate that traditional media often foreground prevailing institutional voices while underrepresenting marginalized groups,especially rural women and women with disabilities,portraying harmful cultural practices like FGM and child marriage as community challenges rather than universal human rights violation.Conversely,social media emerged as a transformative space for survivor-led advocacy.Hence the study calls for inclusive,ethical,and survivor-centered media reporting as well as strategic integration of digital and mainstream media to promote justice and policy reform in GBV reporting.展开更多
By means of an improved mapping method and a variable separation method, a series of variable separation solutions including solitary wave solutions, periodic wave solutions and rational function solutions） to the （...By means of an improved mapping method and a variable separation method, a series of variable separation solutions including solitary wave solutions, periodic wave solutions and rational function solutions） to the （2＋1）-dimensional breaking soliton system is derived. Based on the derived solitary wave excitation, we obtain some special annihilation solitons and chaotic solitons in this short note.展开更多
Positron is an excellent probe of lattice defects in solids. A thermallized positron delocalized in lattice can be trapped at open volume defects, e.g. vacancies, dislocations, grain boundaries etc. Positron anni- hil...Positron is an excellent probe of lattice defects in solids. A thermallized positron delocalized in lattice can be trapped at open volume defects, e.g. vacancies, dislocations, grain boundaries etc. Positron anni- hilation spectroscopy is a non-destructive technique lattice defects in solids on the atomic scale. Positron which enables characterization of open volume lifetime and Doppler broadening of annihilation photo-peak are the most common observables related to positron annihilation process. Positron lifetime spectroscopy enables to identify defects in solids and to determine their concentrations while coinci- dence measurement of Doppler broadening provides information about local chemical environment of defects. This article provides a review of the state-of-art of defect characterization in bulk metallic mate- rials by positron annihilation spectroscopy. Advanced analysis of positron annihilation data and recent developments of positron annihilation methodology are described and discussed on examples of defect studies of metallic materials. Future develonment in the field in proposed as well.展开更多
Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-t...Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP(Compact Strip Production) technique was investigated. The value of each strengthening mechanism andits contribution percentage to yield strength were achieved. The results show that refinementstrengthening is the predominant strengthening mode; precipitation strengthening and dislocationstrengthening are second to it, their contributions to yield strength are almost equal.展开更多
Three kinds of specimens were produced from hot strips of similar composition and same thickness (nominal gauge 4.0mm) but produced using different technologies, and the dislocation density of these strips was quantit...Three kinds of specimens were produced from hot strips of similar composition and same thickness (nominal gauge 4.0mm) but produced using different technologies, and the dislocation density of these strips was quantitatively measured by positron annihilation technique test. The dislocation morphology and evolution in microstructure of each pass for producing the 1.9mm hot strip using CSP (compact strip production) technology were observed under an H-800 transmission electron microscope; its density was also quantitatively measured using the positron annihilation technique test, and the factors influencing the dislocation density during the production process were analyzed. The experimental results show that the dislocation density in the microstructure produced using CSP technology is higher than that in the microstructure produced using conventional technology. This result was discussed and confirmed on the basis of the finite element simulation and the theory relevant to dislocations.展开更多
Based on the littlest Higgs model, we investigate the spin correlation of the top quark pair production via the process e^＋e^- →tt at the high energy linear e^＋e^- collider （ILC） with a centre-of-mass energy √S ...Based on the littlest Higgs model, we investigate the spin correlation of the top quark pair production via the process e^＋e^- →tt at the high energy linear e^＋e^- collider （ILC） with a centre-of-mass energy √S = 800 GeV. Our numerical results show that the gauge boson ZH generates very small corrections to the spin correlation observable C in all the parameter space allowed by the electroweak data. However, with reasonable values of the free parameters, the value of the relative correction parameter RBH = （CBH-CSM）/CSM can reach 10%, which might be detected in future ILC experiments.展开更多
Grain growth and shrinkage are essential to the thermal and mechanical stability of nanocrystalline metals,which are assumed to be governed by the coordinated deformation between neighboring grain boundaries(GBs)in th...Grain growth and shrinkage are essential to the thermal and mechanical stability of nanocrystalline metals,which are assumed to be governed by the coordinated deformation between neighboring grain boundaries(GBs)in the nanosized grains.However,the dynamics of such coordination has rarely been reported,especially in experiments.In this work,we systematically investigate the atomistic mechanism of coordinated GB deformation during grain shrinkage in an Au nanocrystal film through combined stateof-the-art in situ shear testing and atomistic simulations.We demonstrate that an embedded nanograin experiences shrinkage and eventually annihilation during a typical shear loading cycle.The continuous grain shrinkage is accommodated by the coordinated evolution of the surrounding GB network via dislocation-mediated migration,while the final grain annihilation proceeds through the sequential dislocation-annihilation-induced grain rotation and merging of opposite GBs.Both experiments and simulations show that stress distribution and GB structure play important roles in the coordinated deformation of different GBs and control the grain shrinkage/annihilation under shear loading.Our findings establish a mechanistic relation between coordinated GB deformation and grain shrinkage,which reveals a general deformation phenomenon in nanocrystalline metals and enriches our understanding on the atomistic origin of structural stability in nanocrystalline metals under mechanical loading.展开更多
Let R be a ring. R is called right AP-injective if, for any a E R, there exists a left ideal of R such that lr（a） = Ra＋Xa. We extend this notion to modules. A right R-module M with S = End（MR） is called quasi AP-...Let R be a ring. R is called right AP-injective if, for any a E R, there exists a left ideal of R such that lr（a） = Ra＋Xa. We extend this notion to modules. A right R-module M with S = End（MR） is called quasi AP-injective if, for any s∈S, there exists a left ideal Xs of S such that ls（Ker（s）） = Ss＋Xs. In this paper, we give some characterizations and properties of quasi AP-injective modules which generalize results of Page and Zhou.展开更多
In this paper, a series of Sb-doped and Bi-doped Cu_(2)Sn_(1-x)M_(x)Se_(3) samples(M = Sb, Bi) are prepared by vacuum melting combined with the spark plasma sintering process. The effects of different atomic doping am...In this paper, a series of Sb-doped and Bi-doped Cu_(2)Sn_(1-x)M_(x)Se_(3) samples(M = Sb, Bi) are prepared by vacuum melting combined with the spark plasma sintering process. The effects of different atomic doping amounts on their properties are discussed. Structural studies indicate that all obtained samples comprise a single Cu_(2)SnSe_(3) phase. Sb and Bi atoms are experimentally demonstrated to be efficient cation dopants for increasing the transport performance. Compared with that doping on the cation site,Bi doping is much more efficient in increasing the electron concentration of the Cu_(2)SnSe_(3) system. Ultimately, a high figure of merit of 0.36 is achieved in the Cu_(2)Sn_(0.94)Sb_(0.06) Se_(3) sample at 773 K due to the enhanced power factor and lowered lattice thermal conductivity,which are 1.73 times higher than those of the pure sample.Our results provide an efficient approach to enhance thermoelectric performance via other doping atoms, which could also be applied to copper-based chalcogenide materials.展开更多
The annealing tests heated by pulsed current(PC)or furnace for AZ31B magnesium sheets were carried out,and the effects of PC on the microstructure and dislocation density of the alloy were analyzed.The results show th...The annealing tests heated by pulsed current(PC)or furnace for AZ31B magnesium sheets were carried out,and the effects of PC on the microstructure and dislocation density of the alloy were analyzed.The results show that PC strengthens the migration of boundaries,and then the twin grains,most of which distribute in the coarse grains,“spheroidize”to equiaxed grains,thus separating the coarse grains and refining the microstructure.This process homogenizes the initial microstructure and eliminate the typically lamellar twin grains.Moreover,PC also strengthens the dislocation annihilation.When the specimens were annealed by PC at 300℃for 4 min,the dislocation density was even lower than that annealed by furnaces at 400℃for 3 h before deformation.Furthermore,dislocation annihilation is enhanced with the increase of peak current density and the decrease of pulsed frequency.展开更多
Positron annihilation lifetime spectra measurements were performed on C_(60)-containing chitosan as a function of temperature ranging from 290 to 380K.Both the ortho-positronium annihilation lifetimeт_(3) and its int...Positron annihilation lifetime spectra measurements were performed on C_(60)-containing chitosan as a function of temperature ranging from 290 to 380K.Both the ortho-positronium annihilation lifetimeт_(3) and its intensity Is increase with increasing temperature,however,the values of I_(3) in C_(60)-containing chitosan are smaller than that in pure chitosan,and the slope ofт_(3) with temperature is also suppressed after C_(60) linked.The existing three models for positron annihilation in polymer have been compared to analyze the experiment result.It is realized that only the spur reaction model,combined with the free volume model,can explain it satisfactorily.The ortho-positronium lifetime and intensity were affected by the local physicochemical environment of material,i.e.,free-volume structure,electron scavenging and trapping sites,etc.The linked C_(60) that play a significant chemical inhibition and quenching role on positronium formation and annihilation isfirst observed.The microstructure change brought by C_(60) group has also been discussed.展开更多
In this paper, the damage to methyl silicone rubber induced by irradiation with protons of 150 keV energy wasstudied. The surface morphology, tensile strength, Shore hardness, cross-linking density and glass transitio...In this paper, the damage to methyl silicone rubber induced by irradiation with protons of 150 keV energy wasstudied. The surface morphology, tensile strength, Shore hardness, cross-linking density and glass transition temperaturewere examined. Positron annihilation lifetime spectrum analysis (PALS) was perfomed to reveal the damage mechanisms ofthe rubber. The results showed that tensile strength and Shore hardness of the rubber increased first and then decreased withincreasing irradiation fluence. The PALS characteristics τ_3 and I_3, as well as the free volume V_f, decreased with increasingirradiation fluence up to 10^(15) cm^(-2), and then increased slowly. It indicates that proton irradiation causes a decrease of freevolume in the methyl silicone rubber when the fluence is less than 10^(15)cm^(-2), while the free volume increases when thefluence is greater than 10^(15)cm^(-2). The results on cross-linking density indicate that the cross-linking induced by protonirradiation is dominant at smaller proton fluences, increasing the tensile strength and Shore hardness of the rubber, while thedegradation of rubber dominates at greater fluence, leading to a decrease of tensile strength and Shore hardness.展开更多
Taking two Laguerre-Gaussian beams with topological charge 1 = ±1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre-Gaussian beams with different phases, amplitu...Taking two Laguerre-Gaussian beams with topological charge 1 = ±1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre-Gaussian beams with different phases, amplitudes, waist widths, off-axis distances, and their propagation in free space. It is shown by detailed numerical illustrative examples that the number and location of composite vortices at the waist plane are variable by varying the relative phase β, amplitude ratio η, waist width ratio ξ, or off-axis distance ratio μ. The net topological charge lnet is not always equal to the sum lsum of charges of the two component beams. The motion, creation and annihilation of composite vortices take place in the free-space propagation, and the net charge during the propagation remains unchanged and equals to the net charge at the waist plane.展开更多
Thermally activated delayed fluorescence(TADF)organic molecules feature with long-lived delayed fluorescence,because they can undergo not only efficient intersystem crossing(ISC),but also efficient reverse intersystem...Thermally activated delayed fluorescence(TADF)organic molecules feature with long-lived delayed fluorescence,because they can undergo not only efficient intersystem crossing(ISC),but also efficient reverse intersystem crossing(RISC)at room temperature.As a new type of luminescent molecules,they have exhibited successful applications in organic light emitting diodes(OLEDs).Aside from OLEDs,they are also found to have potential applications in time-resolved luminescence imaging based on long-lived fluorescence property.Meanwhile,due to their excited triplet characteristic originated from efficient ISC,they were found to be applied in triplet-triplet annihilation upconversion(TTA-UC),photodynamic therapy(PDT)and organic photocatalytic synthesis.This review briefly summarizes the characteristics and excellent photophysical properties of TADF organic compounds,then covers their applications to date aside from OLEDs based on their highly efficient ISC ability and RISC ability at room temperature.展开更多
We apply perturbative QCD to the radiative decays of charmonia J/ψ and χcJ into light mesons. We perform a complete numerical calculation for the quark-gluon loop diagrams involved in these processes. The calculated...We apply perturbative QCD to the radiative decays of charmonia J/ψ and χcJ into light mesons. We perform a complete numerical calculation for the quark-gluon loop diagrams involved in these processes. The calculated J/ψ decay branching ratios into p-wave mesons f2（1270） and f1（1285） fit the data well, while that of fo（980） （if treated as an ss meson） is predicted to be 1.6×10^-4, which implies that f0（1710） can not be the ss or （uu＋dd）/√2 meson. Decays of p-wave charmonia χcJ→ρ（ω;φ）γ （J = 0, 1, 2） are also studied, and the branching ratio of χc1→ργ is predicted to be 1.4×10^-5, which may be tested by CLEO-c collaboration and BESlg collaboration with future experiments.展开更多
基金supported by the National Research Foundation of Singapore,Rolls-Royce Singapore Pte.Ltd.,and Nanyang Technological University through grants#002123-00009 and #002124-00009.
文摘This study investigates the effect of high current density electropulsing on the material in a rapid stress relaxation process.An AISI 1020 steel was shot-peened to induce surface compressive residual stresses in a controlled manner and subsequently electropulsed to investigate the changes in microstructure and defect configuration.AISI 1020 steel was chosen as it has a simple microstructure(plain ferritic)and composition with low alloying conditions.It is an appropriate material to study the effect of trans-mitting electric pulses on the microstructural defect evolution.A combination of electron-backscattered diffraction and transmission electron microscopy proved to be an effective tool in characterizing the post-electropulsing effects critically.By application of electropulsing,a reduction in the surface residual stress layer was noticed.Also,reductions in misorientation and dislocation density together with the disentan-glement of dislocations within the cold-worked layer were observed after electropulsing.Additionally,the annihilation of shot-peening-induced deformation bands beyond the residual layer depth was observed.These effects have been rationalised by taking into account the various possibilities of athermal effects of electropulsing.
基金supported by the National Natural Science Foundation of China(52201008,52372003)Natural Science Foundation of Heilongjiang Province of China(ZD2023E004)+1 种基金Fundamental Research Funds for the Central Universities(3072020CF2515,3072022CFJ2504)the State Key Laboratory of Particle Detection and Electronics(SKLPDE-KF-202311)。
文摘Mechano luminescence(ML),which involves the emission of light under mechanical stimuli,shows great potential in various applications such as sensing,imaging,and energy harvesting.Current research suggests that the luminescence mechanism of ML is typically connected to specific defects present within the material.In this study,we focus on the investigation of ML defects in Pr^(3+)-doped NaNbO_(3)/LiNbO_(3)heterojunctions,employing a combination of experimental and theoretical approaches.Through experimental analysis,we confirmed the presence of the heterojunction and its influence on ML intensity,and the optimal doping ratio for the heterojunction in ML was established.Furthermore,we examined the influence of varying Pr^(3+)doping concentrations on ML behavior and a proof-of-concept was demonstrated using the X-rays charged heterostructural phosphor as a stress sensor for biological applications.The position and concentration of internal defects in the ML material were scrutinized through thermo luminescence tests employing the variable heating rate method and positron annihilation.Complementing the experimental findings,theoretical simulations were conducted to elucidate the underlying mechanisms responsible for the observed ML defects.Density functional theory calculations were employed to investigate the energy levels,charge transfer processes,and lattice distortions within the heterojunctions under mechanical stress.Theoretical predictions were compared and validated against the experimental results.The integration of experimental and theoretical approaches provides a comprehensive understanding of the ML behavior of Pr^(3+)-doped NaNbO_(3)/LiNbO_(3)heterojunctions.The insights gained from this research contribute to the development of novel ML materials and pave the way for their applications in next-generation sensing and energy conversion devices.
基金supported by the National Natural Science Foundation of China(Nos.12005289,52072397)State Key Laboratory of Nuclear Detection and Electronics,University of Science and Technology of China(SKLPDE-KF-202316).
文摘The stability of matrix graphite under neutron irradiation and in corrosive environments is crucial for the safe operation of molten salt reactors(MSRs).Raman spectroscopy and a slow positron beam were employed to investigate the effects of He ion irradiation fluences and subsequent annealing on the microstructure and defects of the matrix graphite.He ions with 500 keV energy and fluences ranging from 1.1×10^(15)ions∕cm^(2)to 3.5×10^(17)ions∕cm^(2)were used to simulate neutron irradiation at 300 K.The samples with an irradiation fluence of 3.5×10^(16)ions∕cm^(2)were subjected to isochronal annealing at different temperatures(573 K,873 K and 1173 K)for 3 h.The Raman results revealed that the D peak gradually increased,whereas the intrinsic G peak decreased with increasing irradiation fluence.At the same irradiation fluence,the D peak gradually decreased,whereas the intrinsic G peak increased with increasing annealing temperature.Slow positron beam analysis demonstrated that the density or size of irradiation defects(vacancy type)increased with higher irradiation fluence,but decreased rapidly with increasing annealing temperature.The Raman spectral analysis of sample cross sections subjected to high irradiation fluences revealed the emergence of amorphization precisely at the depth where ion damage was most pronounced,whereas the surface retained its crystalline structure.Raman and positron annihilation analyses indicated that the matrix graphite exhibited good irradiation resistance to He ions at 300 K.However,vacancy-type defects induced by He ion irradiation exhibit poor thermal stability and can be easily removed during annealing.
基金supported by the National Natural Science Foundation of China(Nos.22473104 and 22403086)support of the China Postdoctoral Science Foundation(No.2023M733378).
文摘Zinc phthalocyanines(ZnPc)are widely recognized as efficient triplet photosensitizers in photodynamic therapy and photocatalysis,owing to their intense absorption in the visible range and long triplet-state lifetimes.However,their application in triplet-triplet annihilation(TTA)upconversion is lacking to date.In this study,we synthesized a new ZnPc photosensitizer,4I-ZnPc,and composed a TTA upconversion system using rubrene as the energy acceptor.Upon photoexcitation at 663 nm,yellow fluorescence from rubrene was observed in deoxygenated dichloromethane,demonstrating TTA upconversion with an anti-Stokes shift of 0.331 eV and a quantum yield of 1.82%(out of the 50%maximum).Using nanosecond transient absorption spectroscopy,we determined the triplet lifetime of 4I-ZnPc,the triplet-triplet energy transfer efficiency,and the fluorescence quantum yield.These measurements provide critical insights into the photophysical processes governing the TTA upconversion system.Our results highlight the potential advantages and limitations of ZnPc as a triplet photosensitizer for TTA upconversion.
文摘Correction:Nuclear Science and Techniques(2025)36:4 https://doi.org/10.1007/s41365-024-01548-5 In this article,the caption for Fig(s)1,3,and 4 was inadvert-ently truncated.The incorrect and the corrected captions are given below.
文摘This paper presents the findings of a two-week monitoring project on Gender Based Violence(GBV)in Tanzanian and explores how the media outlets frame the marginalized voices,institutional narratives,and intersectional inclusivity.Drawing qualitative approach and analysis of media coverage of GBV during the 202416 Days of Activism campaign remarkably November 25 to December 10,2024,it reveals the extent that media platforms amplify or marginalize survivor voices.Through two weeks of media monitoring across print,broadcast,and social media including sources notably Mwananchi,TBC1,Cloud FM,and advocacy-driven digital platforms and campaigns through#EndGBVNow and#16DaysOfActivism the study explores recurring themes,language use,tone,and inclusivity.Guided by critical gender theories including Judith Butler’s gender performativity and Gave Tuchman’s symbolic annihilation,the analysis reveals media’s dual role in either perpetuating or challenging patriarchal narratives.Findings indicate that traditional media often foreground prevailing institutional voices while underrepresenting marginalized groups,especially rural women and women with disabilities,portraying harmful cultural practices like FGM and child marriage as community challenges rather than universal human rights violation.Conversely,social media emerged as a transformative space for survivor-led advocacy.Hence the study calls for inclusive,ethical,and survivor-centered media reporting as well as strategic integration of digital and mainstream media to promote justice and policy reform in GBV reporting.
基金The project supported by the Natural Science Foundation of Zhejiang Province under Grant No. Y604106, the Foundation of New Century 151 Talent Engineering of Zhejiang Province, and the Natural Science Foundation of Zhejiang Lishui University under Grant No. KZ05010 Acknowledgments The authors would like to thank professor Chun-Long Zheng for his fruitful and helpful suggestions.
文摘By means of an improved mapping method and a variable separation method, a series of variable separation solutions including solitary wave solutions, periodic wave solutions and rational function solutions） to the （2＋1）-dimensional breaking soliton system is derived. Based on the derived solitary wave excitation, we obtain some special annihilation solitons and chaotic solitons in this short note.
基金Financial support by the Czech Science Agency(project 1612828S)
文摘Positron is an excellent probe of lattice defects in solids. A thermallized positron delocalized in lattice can be trapped at open volume defects, e.g. vacancies, dislocations, grain boundaries etc. Positron anni- hilation spectroscopy is a non-destructive technique lattice defects in solids on the atomic scale. Positron which enables characterization of open volume lifetime and Doppler broadening of annihilation photo-peak are the most common observables related to positron annihilation process. Positron lifetime spectroscopy enables to identify defects in solids and to determine their concentrations while coinci- dence measurement of Doppler broadening provides information about local chemical environment of defects. This article provides a review of the state-of-art of defect characterization in bulk metallic mate- rials by positron annihilation spectroscopy. Advanced analysis of positron annihilation data and recent developments of positron annihilation methodology are described and discussed on examples of defect studies of metallic materials. Future develonment in the field in proposed as well.
基金This work was financially supported by the state foundation for key projects: Fundamental Research on New Generation of Steels (No: G1998061500).
文摘Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP(Compact Strip Production) technique was investigated. The value of each strengthening mechanism andits contribution percentage to yield strength were achieved. The results show that refinementstrengthening is the predominant strengthening mode; precipitation strengthening and dislocationstrengthening are second to it, their contributions to yield strength are almost equal.
文摘Three kinds of specimens were produced from hot strips of similar composition and same thickness (nominal gauge 4.0mm) but produced using different technologies, and the dislocation density of these strips was quantitatively measured by positron annihilation technique test. The dislocation morphology and evolution in microstructure of each pass for producing the 1.9mm hot strip using CSP (compact strip production) technology were observed under an H-800 transmission electron microscope; its density was also quantitatively measured using the positron annihilation technique test, and the factors influencing the dislocation density during the production process were analyzed. The experimental results show that the dislocation density in the microstructure produced using CSP technology is higher than that in the microstructure produced using conventional technology. This result was discussed and confirmed on the basis of the finite element simulation and the theory relevant to dislocations.
基金Supported by the National Natural Science Foundation of China under Grant No 10475037, and the Programme for New Century Excellent Talents in University （NCET-04-0290）.
文摘Based on the littlest Higgs model, we investigate the spin correlation of the top quark pair production via the process e^＋e^- →tt at the high energy linear e^＋e^- collider （ILC） with a centre-of-mass energy √S = 800 GeV. Our numerical results show that the gauge boson ZH generates very small corrections to the spin correlation observable C in all the parameter space allowed by the electroweak data. However, with reasonable values of the free parameters, the value of the relative correction parameter RBH = （CBH-CSM）/CSM can reach 10%, which might be detected in future ILC experiments.
基金supports of the National Key Research and Development Program of China(No.2018YFB2000704)the National Natural Science Foundation of China(51771172 and 52071284)+2 种基金the Innovation Fund of the Zhejiang Kechuang New Materials Research Institute(ZKN-18-Z02)financial support from the National Natural Science Foundation of China(11902289)computational support from the Super Cloud Computing Center in Beijing。
文摘Grain growth and shrinkage are essential to the thermal and mechanical stability of nanocrystalline metals,which are assumed to be governed by the coordinated deformation between neighboring grain boundaries(GBs)in the nanosized grains.However,the dynamics of such coordination has rarely been reported,especially in experiments.In this work,we systematically investigate the atomistic mechanism of coordinated GB deformation during grain shrinkage in an Au nanocrystal film through combined stateof-the-art in situ shear testing and atomistic simulations.We demonstrate that an embedded nanograin experiences shrinkage and eventually annihilation during a typical shear loading cycle.The continuous grain shrinkage is accommodated by the coordinated evolution of the surrounding GB network via dislocation-mediated migration,while the final grain annihilation proceeds through the sequential dislocation-annihilation-induced grain rotation and merging of opposite GBs.Both experiments and simulations show that stress distribution and GB structure play important roles in the coordinated deformation of different GBs and control the grain shrinkage/annihilation under shear loading.Our findings establish a mechanistic relation between coordinated GB deformation and grain shrinkage,which reveals a general deformation phenomenon in nanocrystalline metals and enriches our understanding on the atomistic origin of structural stability in nanocrystalline metals under mechanical loading.
文摘Let R be a ring. R is called right AP-injective if, for any a E R, there exists a left ideal of R such that lr（a） = Ra＋Xa. We extend this notion to modules. A right R-module M with S = End（MR） is called quasi AP-injective if, for any s∈S, there exists a left ideal Xs of S such that ls（Ker（s）） = Ss＋Xs. In this paper, we give some characterizations and properties of quasi AP-injective modules which generalize results of Page and Zhou.
基金financially supported by the National Key Research and Development Program of China(No.2019YFA0210003)the National Natural Science Foundation of China(Nos.11775163 and 11875208)。
文摘In this paper, a series of Sb-doped and Bi-doped Cu_(2)Sn_(1-x)M_(x)Se_(3) samples(M = Sb, Bi) are prepared by vacuum melting combined with the spark plasma sintering process. The effects of different atomic doping amounts on their properties are discussed. Structural studies indicate that all obtained samples comprise a single Cu_(2)SnSe_(3) phase. Sb and Bi atoms are experimentally demonstrated to be efficient cation dopants for increasing the transport performance. Compared with that doping on the cation site,Bi doping is much more efficient in increasing the electron concentration of the Cu_(2)SnSe_(3) system. Ultimately, a high figure of merit of 0.36 is achieved in the Cu_(2)Sn_(0.94)Sb_(0.06) Se_(3) sample at 773 K due to the enhanced power factor and lowered lattice thermal conductivity,which are 1.73 times higher than those of the pure sample.Our results provide an efficient approach to enhance thermoelectric performance via other doping atoms, which could also be applied to copper-based chalcogenide materials.
基金Project(51635005)supported by the National Natural Science Foundation of China
文摘The annealing tests heated by pulsed current(PC)or furnace for AZ31B magnesium sheets were carried out,and the effects of PC on the microstructure and dislocation density of the alloy were analyzed.The results show that PC strengthens the migration of boundaries,and then the twin grains,most of which distribute in the coarse grains,“spheroidize”to equiaxed grains,thus separating the coarse grains and refining the microstructure.This process homogenizes the initial microstructure and eliminate the typically lamellar twin grains.Moreover,PC also strengthens the dislocation annihilation.When the specimens were annealed by PC at 300℃for 4 min,the dislocation density was even lower than that annealed by furnaces at 400℃for 3 h before deformation.Furthermore,dislocation annihilation is enhanced with the increase of peak current density and the decrease of pulsed frequency.
基金Supported by the National Natural Science Foundation of China under Grant No.29674020.
文摘Positron annihilation lifetime spectra measurements were performed on C_(60)-containing chitosan as a function of temperature ranging from 290 to 380K.Both the ortho-positronium annihilation lifetimeт_(3) and its intensity Is increase with increasing temperature,however,the values of I_(3) in C_(60)-containing chitosan are smaller than that in pure chitosan,and the slope ofт_(3) with temperature is also suppressed after C_(60) linked.The existing three models for positron annihilation in polymer have been compared to analyze the experiment result.It is realized that only the spur reaction model,combined with the free volume model,can explain it satisfactorily.The ortho-positronium lifetime and intensity were affected by the local physicochemical environment of material,i.e.,free-volume structure,electron scavenging and trapping sites,etc.The linked C_(60) that play a significant chemical inhibition and quenching role on positronium formation and annihilation isfirst observed.The microstructure change brought by C_(60) group has also been discussed.
文摘In this paper, the damage to methyl silicone rubber induced by irradiation with protons of 150 keV energy wasstudied. The surface morphology, tensile strength, Shore hardness, cross-linking density and glass transition temperaturewere examined. Positron annihilation lifetime spectrum analysis (PALS) was perfomed to reveal the damage mechanisms ofthe rubber. The results showed that tensile strength and Shore hardness of the rubber increased first and then decreased withincreasing irradiation fluence. The PALS characteristics τ_3 and I_3, as well as the free volume V_f, decreased with increasingirradiation fluence up to 10^(15) cm^(-2), and then increased slowly. It indicates that proton irradiation causes a decrease of freevolume in the methyl silicone rubber when the fluence is less than 10^(15)cm^(-2), while the free volume increases when thefluence is greater than 10^(15)cm^(-2). The results on cross-linking density indicate that the cross-linking induced by protonirradiation is dominant at smaller proton fluences, increasing the tensile strength and Shore hardness of the rubber, while thedegradation of rubber dominates at greater fluence, leading to a decrease of tensile strength and Shore hardness.
基金supported by the National Natural Science Foundation of China (Grant No 10574097)
文摘Taking two Laguerre-Gaussian beams with topological charge 1 = ±1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre-Gaussian beams with different phases, amplitudes, waist widths, off-axis distances, and their propagation in free space. It is shown by detailed numerical illustrative examples that the number and location of composite vortices at the waist plane are variable by varying the relative phase β, amplitude ratio η, waist width ratio ξ, or off-axis distance ratio μ. The net topological charge lnet is not always equal to the sum lsum of charges of the two component beams. The motion, creation and annihilation of composite vortices take place in the free-space propagation, and the net charge during the propagation remains unchanged and equals to the net charge at the waist plane.
基金financially supported by the National Natural Science Foundation of China(Nos.21877011,21576038,21421005)the Talent Fund of Shandong Collaborative Innovation Center of Eco-Chemical Engineering(No.XTCXYX03)
文摘Thermally activated delayed fluorescence(TADF)organic molecules feature with long-lived delayed fluorescence,because they can undergo not only efficient intersystem crossing(ISC),but also efficient reverse intersystem crossing(RISC)at room temperature.As a new type of luminescent molecules,they have exhibited successful applications in organic light emitting diodes(OLEDs).Aside from OLEDs,they are also found to have potential applications in time-resolved luminescence imaging based on long-lived fluorescence property.Meanwhile,due to their excited triplet characteristic originated from efficient ISC,they were found to be applied in triplet-triplet annihilation upconversion(TTA-UC),photodynamic therapy(PDT)and organic photocatalytic synthesis.This review briefly summarizes the characteristics and excellent photophysical properties of TADF organic compounds,then covers their applications to date aside from OLEDs based on their highly efficient ISC ability and RISC ability at room temperature.
基金Supported in part by the National Natural Science Foundation of China under Grant No 10421503, and the Key Grant Project of the Ministry of Education of China under Grant No 305001.
文摘We apply perturbative QCD to the radiative decays of charmonia J/ψ and χcJ into light mesons. We perform a complete numerical calculation for the quark-gluon loop diagrams involved in these processes. The calculated J/ψ decay branching ratios into p-wave mesons f2（1270） and f1（1285） fit the data well, while that of fo（980） （if treated as an ss meson） is predicted to be 1.6×10^-4, which implies that f0（1710） can not be the ss or （uu＋dd）/√2 meson. Decays of p-wave charmonia χcJ→ρ（ω;φ）γ （J = 0, 1, 2） are also studied, and the branching ratio of χc1→ργ is predicted to be 1.4×10^-5, which may be tested by CLEO-c collaboration and BESlg collaboration with future experiments.
