The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on20...The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on2022 July 27.In this paper,we introduce the design and on-ground test results of the LEIA instrument.Using stateof-the-art Micro-Pore Optics(MPO),a wide field of view of 346 square degrees(18.6°×18.6°)of the X-ray imager is realized.An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons,and four large-format complementary metal-oxide semiconductor(CMOS)sensors,each of size 6 cm×6 cm,are used as the focal plane detectors.The instrument has an angular resolution of 4’-8’(in terms of FWHM)for the central focal spot of the point-spread function,and an effective area of 2-3 cm^(2) at 1 keV in essentially all the directions within the field of view.The detection passband is 0.5-4 keV in soft X-rays and the sensitivity is2-3×10^(-11) erg s^(-1) cm^(-2)(about 1 milliCrab)with a 1000 s observation.The total weight of LEIA is 56 kg and the power is 85 W.The satellite,with a design lifetime of 2 yr,operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes.LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation,and by optimizing the working setups of the instrumental parameters.In addition,LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band,albeit with limited useful observing time available.展开更多
Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESⅢdetector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 fb^(-1),th...Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESⅢdetector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 fb^(-1),the process e^(+)e^(-)→pppñπ+c.c.is observed for the first time with a statistical significance of 11.5σ.The average Born cross sections in the energy ranges of(4.160,4.380)GeV,(4.400,4.600)GeV and(4.610,4.700)GeV are measured to be(21.5±5.7±1.2)fb,(46.3±10.6±2.5)fb and(59.0±9.4±3.2)fb,respectively,where the first uncertainties are statistical and the second are systematic.The line shapes of the pñ and ppπ^(-)invariant mass spectra are consistent with phase space distributions,indicating that no hexaquark or di-baryon state is observed.展开更多
Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb-1,collected by the BESⅢdetector in the energy region between 4599.53 MeV and 4698.82 MeV,we report the first obser...Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb-1,collected by the BESⅢdetector in the energy region between 4599.53 MeV and 4698.82 MeV,we report the first observations of the Cabibbo-suppressed decaysΛ_(c)^(+)→nπ^(+)π^(0),Λ_(c)^(+)→nπ^(+)π^(-)π^(+),and the Cabibbo-favored decayΛ_(c)^(+)→nK^(-)π^(+)π^(+)with statistical significances of 7.9σ,7.8σ,and>10σ,respectively.The branching fractions of these decays are measured to be B(Λ_(c)^(+)→nπ^(+)π^(0))=(0.64±0.09±0.02)%,B(Λ_(c)^(+)→nπ^(+)π^(-)π^(+))=(0.45±0.07±0.03)%,and B(Λ_(c)^(+)→nK^(-)π^(+)π^(+))=(1.90±0.08±0.09)%,where the first uncertainties are statistical and the second are systematic.We find that the branching fraction of the decayΛ_(c)^(+)→nπ^(+)π^(0)is about one order of magnitude higher than that ofΛ_(c)^(+)→nπ^(+).展开更多
Using(448.1±2.9)×10^(6)ψ(3686)for the weak baryonic decayψ(3686)→Λc+∑-+c.c..The analysis procedure is optimized using a blinded method.No significant signal is observed,and the upper limit on the branch...Using(448.1±2.9)×10^(6)ψ(3686)for the weak baryonic decayψ(3686)→Λc+∑-+c.c..The analysis procedure is optimized using a blinded method.No significant signal is observed,and the upper limit on the branching fraction(B)ofψ(3686)→Λc+∑-+c.c.is set as 1.4×10^(-5)at the 90%confidence level.展开更多
Using inclusive decays of J/ψ aprecise determination of the number of J/ψ events collected with the BESIII detector was performed.For the two data sets taken in 2009 and 2012,the numbers of J/ψ events were recalcul...Using inclusive decays of J/ψ aprecise determination of the number of J/ψ events collected with the BESIII detector was performed.For the two data sets taken in 2009 and 2012,the numbers of J/ψ events were recalculated to be(224.0±1.3)×10^(6) and(1088.5±4.4)×10^(6),respectively;these numbers are in good agreement with the previous measurements. For the J/ψ sample taken in 2017-2019,the number of events was determined to be(8774.0±39.4)×10^(6).The total number of J/ψ events collected with the BESIII detector was determined to be(10087±44)×10^(6),where the uncertainty is dominated by systematic effects,and the statistical uncertainty is negligible.展开更多
The cross sections of e^(+)e^(-)→K^(+)K^(-)J/Ψat center-of-mass energies from 4.127 to 4.600 GeV are measured based on 15.6 fb-1data collected with the BESⅢ detector operating at the BEPCⅡ storage ring.Two resonan...The cross sections of e^(+)e^(-)→K^(+)K^(-)J/Ψat center-of-mass energies from 4.127 to 4.600 GeV are measured based on 15.6 fb-1data collected with the BESⅢ detector operating at the BEPCⅡ storage ring.Two resonant structures are observed in the line shape of the cross sections.The mass and width of the first structure are measured to be(4225.3±2.3±21.5)MeV and(72.9±6.1±30.8)MeV,respectively.They are consistent with those of the established Y(4230).The second structure is observed for the first time with a statistical significance greater than 8σ,denoted as Y(4500).Its mass and width are determined to be(4484.7±13.3±24.1)MeV and(111.1±30.1±15.2)MeV,respectively.The first presented uncertainties are statistical and the second ones are systematic.The product of the electronic partial width with the decay branching fractionΓ(Y(4230)→e^(+)e^(−))B(Y(4230)→K^(+)K^(−)J/Ψ)is reported.展开更多
The integrated luminosities of data samples collected in the BESⅢ experiment in 2016-2017 at centerof-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhab...The integrated luminosities of data samples collected in the BESⅢ experiment in 2016-2017 at centerof-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events.The integrated luminosities of old datasets collected in 2010-2014 are updated by considering corrections related to detector performance,offsetting the effect of newly discovered readout errors in the electromagnetic calorimeter,which can haphazardly occur.展开更多
From December 2019 to June 2021,the BESⅢ experiment collected approximately 5.85 fb^(−1) of data at center-of-mass energies between 4.61 and 4.95 GeV.This is the highest collision energy BEPCⅡ has reached to date.Th...From December 2019 to June 2021,the BESⅢ experiment collected approximately 5.85 fb^(−1) of data at center-of-mass energies between 4.61 and 4.95 GeV.This is the highest collision energy BEPCⅡ has reached to date.The accumulated e^(+)e^(−) annihilation data samples are useful for studying charmonium(-like)states and charmed-hadron decays.By adopting a novel method of analyzing the production of A_(c)^(+)A_(c)^(-) pairs in e^(+)e^(−) annihilation,the center-of-mass energies are measured with a precision of 0.6 MeV.Integrated luminosities are measured with a precision of better than 1% by analyzing the events of large-angle Bhabha scattering.These measurements provide important inputs to analyses based on these data samples.展开更多
The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by ...The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.展开更多
During the 2016-17 and 2018-19 running periods,the BESIII experiment collected 7.5 fb of e^(+)e^(-)collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV.These data samples are primarily used for the ...During the 2016-17 and 2018-19 running periods,the BESIII experiment collected 7.5 fb of e^(+)e^(-)collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV.These data samples are primarily used for the study of excited charmonium and charmoniumlike states.By analyzing the di-muon process e^(+)e^(-)→(γISR=FSR)μ^(+)μ^(-),we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV.Through a run-by-run study,we find that the center-of-mass energies were stable throughout most of the data-collection period.展开更多
Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying.Herein,we found that the oxidation resistance of active metal Ce can be significantly impr...Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying.Herein,we found that the oxidation resistance of active metal Ce can be significantly improved by the addition of 20 at.%Ga.Focused ion beam lift-out technique and scanning transmission electron microscopy analysis disclosed that a discontinuous Ga-rich layer was generated beneath the oxide layer in the coarse-grained Ce-Ga alloy.The Ga-rich layer formed by selective oxidation of Ce acts as a diffusion barrier for Ce outward diffusion and ceases the O/M interfacial reaction when a critical concentration of Ga(75 at.%)is reached.After nanocrystallization,uniform distribution of Ga was achieved.After oxidation,a relatively continuous Ga-rich layer was formed which further enhanced the oxidation resistance.The introduction of noble elements combining with nanocrystallization may provide a novel strategy for the protection of metals with high activity and poor oxidation resistance.展开更多
Recently,Quantitative Biology(QB)held a discussion on"Al(artificial intelligence)for Life Science"among editorial board members and interested scholars in anticipation of rapid development of this growing ar...Recently,Quantitative Biology(QB)held a discussion on"Al(artificial intelligence)for Life Science"among editorial board members and interested scholars in anticipation of rapid development of this growing area after AlphaGo and ChatGPT mania.Many young people tend to get confused between facts and fictions;heated debates are unavoidable even among their mentors.When deep learning as represented by convolutional neural networks and LSTM(long shortterm memory)was made available for bioinformatics students,many of them rushed into this research field and tried to adopt these methods in all their projects without knowing the history that these tools were becoming successful consistently with Moore's Law(relating to rapid computer technology advances)展开更多
Basalt discriminant diagrams have been used to identify the tectonic setting of basaltic magmatism since the 1970s and have played an important role in reconstructing paleotectonic environments.However,the significant...Basalt discriminant diagrams have been used to identify the tectonic setting of basaltic magmatism since the 1970s and have played an important role in reconstructing paleotectonic environments.However,the significant increase in the availability of geochemical data has led to a reassessment of these diagrams,suggesting that some of the tectonic settings indicated by these diagrams are not accurate.Here,we use a database of global ocean island basalt(OIB),mid-ocean ridge basalt(MORB),and island arc basalt(IAB)geochemistry to propose a series of new tectonic discriminant diagrams based on the ratios of large-ion lithophile elements(LILEs)to high field strength elements(HFSEs).These new diagrams indicate that the LILE can be used to differentiate OIB,MORB,and IAB samples,meaning that LILE/HFSE ratios can discriminate between these basalts that form in different tectonic settings.Our new diagrams can correctly assign samples to OIB,MORB,and IAB categories more than 85%of the time,with the discrimination between OIB and MORB having an accuracy of slightly less than 85%.展开更多
The Brazilian test is a widely used method for determining the tensile strength of rocks and for calibrating parameters in bondedparticle models（BPMs）. In previous studies, the Brazilian disc has typically been trim...The Brazilian test is a widely used method for determining the tensile strength of rocks and for calibrating parameters in bondedparticle models（BPMs）. In previous studies, the Brazilian disc has typically been trimmed from a compacted rectangular specimen. The present study shows that different tensile strength values are obtained depending on the compressive loading direction. Several measures are proposed to reduce the anisotropy of the disc. The results reveal that the anisotropy of the disc is significantly influenced by the compactibility of the specimen from which it is trimmed. A new method is proposed in which the Brazilian disc is directly generated with a particle boundary, effectively reducing the anisotropy. The stiffness（particle and bond） and strength（bond） of the boundary are set at less than and greater than those of the disc assembly, respectively,which significantly decreases the stress concentration at the boundary contacts and prevents breakage of the boundary particle bonds. This leads to a significant reduction in the anisotropy of the disc and the discreteness of the tensile strength. This method is more suitable for carrying out a realistic Brazilian test for homogeneous rock-like material in the BPM.展开更多
Super-enhancers(SEs)comprise large clusters of enhancers,which are co-occupied by multiple lineage-specific and master tran-scription factors,and play pivotal roles in regulating gene expression and cell fate determin...Super-enhancers(SEs)comprise large clusters of enhancers,which are co-occupied by multiple lineage-specific and master tran-scription factors,and play pivotal roles in regulating gene expression and cell fate determination.However,it is still largely un-known whether and how SEs are regulated by the noncoding portion of the genome.Here,through genome-wide analysis,wefound that tpng noncoding RNA(IncRNA)genes preferentially lie next to SEs.In mouse embryonic stem cells(mESCs),depletionof$E-associated IlncRNA transcripts dysregulated the activity of their nearby SEs.Specifically,we revealed a critical regulatoryrole of the IncRNA gene Platr22 in modulating the activity of a nearby SE and the expression of the nearby pluripotency regulatorZFP281.Through these regulatory events,Platr22 contributes to pluripotency maintenance and proper differentiation of mESCs.Mechanistically,Platr22 transcripts coat chromatin near the SE region and interact with DDX5 and hnRNP-L.DDX5 further recruitsp300 and other factors related to active transcription.We propose that these factors assemble into a transcription hub,thus pro-moting an open and active epigenetic chromatin state.0ur study highlights an unanticipated role for a class of lncRNAs in epige-netically controlling the activity and vulnerability to perturbation of nearby SEs for cell fate determination.展开更多
We review some recent progress in the exploration of pseudospin-1 physics using dielectric photonic crystals(PCs).We show some physical implications of the PCs exhibiting an accidental degeneracy induced conical dispe...We review some recent progress in the exploration of pseudospin-1 physics using dielectric photonic crystals(PCs).We show some physical implications of the PCs exhibiting an accidental degeneracy induced conical dispersion at theΓpoint,such as the realization of zero refractive index medium and the zero Berry phase of a loop around the nodal point.Te photonic states of such PCs near the Dirac-like point can be described by an efective spin-orbit Hamiltonian of pseudospin-1.Te wave propagation in the positive,negative,and zero index media can be unifed within a framework of pseudospin-1 description.A scale change in PCs results in a rigid band shif of the Dirac-like cone,allowing for the manipulation of waves in pseudospin-1 systems in much the same way as applying a gate voltage in pseudospin-1/2 graphene.Te transport of waves in pseudospin-1 systems exhibits many interesting phenomena,including super Klein tunneling,robust supercollimation,and unconventional Anderson localization.Te transport properties of pseudospin-1 systems are distinct from their counterparts in pseudospin-1/2 systems,which will also be presented for comparison.展开更多
A model for describing the adsorption process of hydrogen on surface of tungsten oxide was proposed based on the first-principle calculations. Multiple factors such as type of active surface, adsorption site and distr...A model for describing the adsorption process of hydrogen on surface of tungsten oxide was proposed based on the first-principle calculations. Multiple factors such as type of active surface, adsorption site and distribution of oxygen vacancies were considered to evaluate the hydrogen adsorption capability of tungsten oxide. The adsorption Gibbs free energies, electronic structures and bonding characteristics under various conditions were examined to reveal the influence of oxygen vacancies on the surface. It is found that the capability of hydrogen adsorption of tungsten oxide can be significantly enhanced by adjusting the oxygen vacancy on the outermost layer of certain active surfaces. The modeling predicts that the surface structure stability and gas adsorption ability of tungsten oxide can be simultaneously improved through the formation of W–H bonds. The proposed strategy for moderating surface provides a new approach to obtain excellent gas-sensitive metal oxide materials.展开更多
Atherosclerotic cardiovascular disease resulting from dysregulated lipid metabolism is the leading cause of morbidity and mortality worldwide.Apolipoprotein E(ApoE)plays a critical role in cholesterol metabolism.Knock...Atherosclerotic cardiovascular disease resulting from dysregulated lipid metabolism is the leading cause of morbidity and mortality worldwide.Apolipoprotein E(ApoE)plays a critical role in cholesterol metabolism.Knockouts in lipid-metabolizing proteins including ApoE in multiple model organisms such as mice and rats exhibiting elevated levels of cholesterol have been widely used for dissecting the pathology of atherosclerosis,but few of these animal models exhibit advanced atherosclerotic plaques leading to ischemia-induced clinical symptoms,limiting their use for translational studies.Here we report hypercholesterolemia and severe atherosclerosis characterized by stenosis and occlusion of arteries,together with clinical manifestations of stroke and gangrene,in ApoE knockout dogs generated by CRISPR/Cas9 and cloned by somatic cell nuclear transfer technologies.Importantly,the hypercholesterolemia and atherosclerotic complications in F0 mutants are recapitulated in their offspring.As the ApoE-associated atherosclerosis and clinical manifestations in mutant dogs are more similar to that in human patients compared with those in other animal models,these mutant dogs will be invaluable in developing and evaluating new therapies,including endovascular procedures,against atherosclerosis and related disorders.展开更多
It is well known that spatial symmetry in a photonic crystal(PhC)slab is capable of creating bound states in the continuum(BICs),which can be characterized by topological charges of polarization vortices.Here,we show ...It is well known that spatial symmetry in a photonic crystal(PhC)slab is capable of creating bound states in the continuum(BICs),which can be characterized by topological charges of polarization vortices.Here,we show that when a PT-symmetric perturbation is introduced into the PhC slab,a new type of BICs(pt-BICs)will arise from each ordinary BIC together with the creation of rings of lasing threshold modes with pt-BICs embedded in these rings.Different from ordinary BICs,the Q-factor divergence rate of a pt-BIC is reduced and anisotropic in momentum space.Also,pt-BICs can even appear at off-high symmetry lines of the Brillouin zone.The pt-BICs also carry topological charges and can be created or annihilated with the total charge conserved.A unified picture on pt-BICs and the associated lasing threshold modes is given based on the temporal coupled mode theory.Our findings reveal the new physics arising from the interplay between PT symmetry and BIC in PhC slabs.展开更多
基金supported by the Einstein Probe project,a mission in the Strategic Priority Program on Space Science of CAS(grant Nos.XDA15310000,XDA15052100)in part been supported by the European Union’s Horizon 2020 Program under the AHEAD2020 project(grant No.871158).
文摘The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on2022 July 27.In this paper,we introduce the design and on-ground test results of the LEIA instrument.Using stateof-the-art Micro-Pore Optics(MPO),a wide field of view of 346 square degrees(18.6°×18.6°)of the X-ray imager is realized.An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons,and four large-format complementary metal-oxide semiconductor(CMOS)sensors,each of size 6 cm×6 cm,are used as the focal plane detectors.The instrument has an angular resolution of 4’-8’(in terms of FWHM)for the central focal spot of the point-spread function,and an effective area of 2-3 cm^(2) at 1 keV in essentially all the directions within the field of view.The detection passband is 0.5-4 keV in soft X-rays and the sensitivity is2-3×10^(-11) erg s^(-1) cm^(-2)(about 1 milliCrab)with a 1000 s observation.The total weight of LEIA is 56 kg and the power is 85 W.The satellite,with a design lifetime of 2 yr,operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes.LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation,and by optimizing the working setups of the instrumental parameters.In addition,LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band,albeit with limited useful observing time available.
基金Supported in part by National Key R&D Program of China under Contracts Nos.Supported in part by National Key R&D Program of China(2020YFA0406300,2020YFA0406400)National Natural Science Foundation of China(NSFC)(11975118,11625523,11635010,11735014,11822506,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12061131003,12075252,12192260,12192261,12192262,12192263,12192264,12192265)+19 种基金the Natural Science Foundation of Hunan Province of China(2019JJ30019)the Science and Technology Innovation Program of Hunan Province(2020RC3054)the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1732263,U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH040)100 Talents Program of CASINPAC and Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)European Union Horizon 2020 research and innovation programme under Contract No.Marie Sklodowska-Curie grant agreement(894790)German Research Foundation DFG(43159800)Collaborative Research Center CRC 1044,FOR 2359,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundOlle Engkvist Foundation(200-0605)STFC(United Kingdom)The Knut and Alice Wallenberg Foundation(Sweden)(2016.0157)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374,DE-SC-0012069)。
文摘Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESⅢdetector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 fb^(-1),the process e^(+)e^(-)→pppñπ+c.c.is observed for the first time with a statistical significance of 11.5σ.The average Born cross sections in the energy ranges of(4.160,4.380)GeV,(4.400,4.600)GeV and(4.610,4.700)GeV are measured to be(21.5±5.7±1.2)fb,(46.3±10.6±2.5)fb and(59.0±9.4±3.2)fb,respectively,where the first uncertainties are statistical and the second are systematic.The line shapes of the pñ and ppπ^(-)invariant mass spectra are consistent with phase space distributions,indicating that no hexaquark or di-baryon state is observed.
基金Supported in part by National Key R&D Program of China(2020YFA0406400,2020YFA0406300)National Natural Science Foundation of China(NSFC)(11635010,11735014,11805086,11835012,11935015,11935016,11935018,11975011,11961141012,12022510,12025502,12035009,12035013,12192260,12192261,12192262,12192263,12192264,12192265)+20 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)the CAS Center for Excellence in Particle Physics(CCEPP)100 Talents Program of CASFundamental Research Funds for the Central Universities,Lanzhou University,University of Chinese Academy of SciencesThe Institute of Nuclear and Particle Physics(INPAC)Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)German Research Foundation DFG(443159800)Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation(B16F640076STFC)(United Kingdom)Suranaree University of Technology(SUT)Thailand Science Research and Innovation(TSRI)National Science Research and Innovation Fund(NSRF)(160355)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DEFG02-05ER41374)。
文摘Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb-1,collected by the BESⅢdetector in the energy region between 4599.53 MeV and 4698.82 MeV,we report the first observations of the Cabibbo-suppressed decaysΛ_(c)^(+)→nπ^(+)π^(0),Λ_(c)^(+)→nπ^(+)π^(-)π^(+),and the Cabibbo-favored decayΛ_(c)^(+)→nK^(-)π^(+)π^(+)with statistical significances of 7.9σ,7.8σ,and>10σ,respectively.The branching fractions of these decays are measured to be B(Λ_(c)^(+)→nπ^(+)π^(0))=(0.64±0.09±0.02)%,B(Λ_(c)^(+)→nπ^(+)π^(-)π^(+))=(0.45±0.07±0.03)%,and B(Λ_(c)^(+)→nK^(-)π^(+)π^(+))=(1.90±0.08±0.09)%,where the first uncertainties are statistical and the second are systematic.We find that the branching fraction of the decayΛ_(c)^(+)→nπ^(+)π^(0)is about one order of magnitude higher than that ofΛ_(c)^(+)→nπ^(+).
基金supported in part by National Key Research and Development Program of China(2020YFA0406400,2020YFA0406300)National Natural Science Foundation of China(NSFC,11975118,11635010,11735014,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12192260,12192261,12192262,12192263,12192264,12192265,12061131003)+18 种基金the Natural Science Foundation of Hunan Province of China(2019JJ30019)the Science and Technology Innovation Program of Hunan Province(2020RC3054)the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH040)100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and Cosmology,ERC(758462)European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement(894790)German Research Foundation DFG(443159800)Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources and Institutional Development,Research and Innovation(B16F640076)STFC(United Kingdom)Suranaree University of Technology(SUT),Thailand Science Research and Innovation(TSRI),and National Science Research and Innovation Fund(NSRF,160355)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374)。
文摘Using(448.1±2.9)×10^(6)ψ(3686)for the weak baryonic decayψ(3686)→Λc+∑-+c.c..The analysis procedure is optimized using a blinded method.No significant signal is observed,and the upper limit on the branching fraction(B)ofψ(3686)→Λc+∑-+c.c.is set as 1.4×10^(-5)at the 90%confidence level.
基金Supported in part by National Key R&D Program of China(2020YFA0406300, 2020YFA0406400)National Natural Science Foundation of China(NSFC)(11625523, 11635010, 11735014, 11822506, 11835012, 11935015, 11935016, 11935018, 11961141012, 12022510, 12025502, 12035009, 12035013,12061131003,12075252)+16 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1732263, U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH040)100 Talents Program of CASINPAC and Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)European Union Horizon 2020 research and innovation programme Marie Sklodowska-Curie grant agreement(894790)German Research Foundation DFG(443159800), Collaborative Research Center CRC 1044, FOR 2359, GRK 214Istituto Nazionale di Fisica Nucleare, ItalyMinistry of Development of Turkey under Contract No. DPT2006K-120470National Science and Technology fundOlle Engkvist Foundation(200-0605)STFC(United Kingdom)The Knut and Alice Wallenberg Foundation(Sweden)(2016.0157)The Royal Society, UK(DH140054, DH160214)The Swedish Research CouncilU. S. Department of Energy(DE-FG02-05ER41374, DE-SC-0012069)
文摘Using inclusive decays of J/ψ aprecise determination of the number of J/ψ events collected with the BESIII detector was performed.For the two data sets taken in 2009 and 2012,the numbers of J/ψ events were recalculated to be(224.0±1.3)×10^(6) and(1088.5±4.4)×10^(6),respectively;these numbers are in good agreement with the previous measurements. For the J/ψ sample taken in 2017-2019,the number of events was determined to be(8774.0±39.4)×10^(6).The total number of J/ψ events collected with the BESIII detector was determined to be(10087±44)×10^(6),where the uncertainty is dominated by systematic effects,and the statistical uncertainty is negligible.
基金Supported in part by National Key R&D Program of China(2020YFA0406300,2020YFA0406400)National Natural Science Foundation of China(NSFC)under Contracts Nos.(11625523,11635010,11735014,11822506,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12061131003)+16 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts Nos.(U1732263,U1832207)CAS Key Research Program of Frontier Sciences under Contract No.(QYZDJ-SSW-SLH040)100 Talents Program of CASINPAC and Shanghai Key Laboratory for Particle Physics and CosmologyERC under Contract No.(758462)European Union Horizon 2020 research and innovation programme under Contract No.Marie Sklodowska-Curie grant agreement No(894790)German Research Foundation DFG under Contracts Nos.(443159800),Collaborative Research Center CRC 1044,FOR 2359,GRK 214Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey under Contract No.(DPT2006K-120470)National Science and Technology fundOlle Engkvist Foundation under Contract No.(200-0605)STFC(United Kingdom)The Knut and Alice Wallenberg Foundation(Sweden)under Contract No.(2016.0157)The Royal Society,UK under Contracts Nos.(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy under Contracts Nos.(DE-FG02-05ER41374,DE-SC-001206)。
文摘The cross sections of e^(+)e^(-)→K^(+)K^(-)J/Ψat center-of-mass energies from 4.127 to 4.600 GeV are measured based on 15.6 fb-1data collected with the BESⅢ detector operating at the BEPCⅡ storage ring.Two resonant structures are observed in the line shape of the cross sections.The mass and width of the first structure are measured to be(4225.3±2.3±21.5)MeV and(72.9±6.1±30.8)MeV,respectively.They are consistent with those of the established Y(4230).The second structure is observed for the first time with a statistical significance greater than 8σ,denoted as Y(4500).Its mass and width are determined to be(4484.7±13.3±24.1)MeV and(111.1±30.1±15.2)MeV,respectively.The first presented uncertainties are statistical and the second ones are systematic.The product of the electronic partial width with the decay branching fractionΓ(Y(4230)→e^(+)e^(−))B(Y(4230)→K^(+)K^(−)J/Ψ)is reported.
基金Supported in part by National Key R&D Program of China(2020YFA0406300,2020YFA0406400)National Natural Science Foundation of China(NSFC)(11625523,11635010,11735014,11822506,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12061131003)+16 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1732263,U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH040)100 Talents Program of CASINPAC and Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)European Union Horizon 2020 research and innovation programme(Marie Sklodowska-Curie grant agreement No 894790)German Research Foundation DFG(443159800),Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundOlle Engkvist Foundation(200-0605)STFC(United Kingdom)The Knut and Alice Wallenberg Foundation(Sweden)(2016.0157)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374,DE-SC-0012069)。
文摘The integrated luminosities of data samples collected in the BESⅢ experiment in 2016-2017 at centerof-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events.The integrated luminosities of old datasets collected in 2010-2014 are updated by considering corrections related to detector performance,offsetting the effect of newly discovered readout errors in the electromagnetic calorimeter,which can haphazardly occur.
基金Supported in part by National Key R&D Program of China(2020YFA0406400,2020YFA0406300)National Natural Science Foundation of China(NSFC)(11635010,11735014,11805086,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12192260,12192261,12192262,12192263,12192264,12192265)+17 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH040)100 Talents Program of CASFundamental Research Funds for the Central Universities,Lanzhou University,University of Chinese Academy of SciencesThe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement(894790)German Research Foundation DFG(443159800),Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation(B16F640076)STFC(United Kingdom)Suranaree University of Technology(SUT),Thailand Science Research and Innovation(TSRI),and National Science Research and Innovation Fund(NSRF)(160355)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374)。
文摘From December 2019 to June 2021,the BESⅢ experiment collected approximately 5.85 fb^(−1) of data at center-of-mass energies between 4.61 and 4.95 GeV.This is the highest collision energy BEPCⅡ has reached to date.The accumulated e^(+)e^(−) annihilation data samples are useful for studying charmonium(-like)states and charmed-hadron decays.By adopting a novel method of analyzing the production of A_(c)^(+)A_(c)^(-) pairs in e^(+)e^(−) annihilation,the center-of-mass energies are measured with a precision of 0.6 MeV.Integrated luminosities are measured with a precision of better than 1% by analyzing the events of large-angle Bhabha scattering.These measurements provide important inputs to analyses based on these data samples.
基金Supported in part by the Ministry of Science and Technology of Chinathe U.S.Department of Energy,the Chinese Academy of Sciences,the CAS Center for Excellence in Particle Physics,the National Natural Science Foundation of China+3 种基金the Guangdong provincial governmentthe Shenzhen municipal government,the China General Nuclear Power Group,the Research Grants Council of the Hong Kong Special Administrative Region of China,the Ministry of Education in TWthe U.S.National Science Foundation,the Ministry of Education,Youth,and Sports of the Czech Republic,the Charles University Research Centre UNCE,the Joint Institute of Nuclear Research in Dubna,Russiathe National Commission of Scientific and Technological Research of Chile。
文摘The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.
基金Supported in part by National Key Research and Development Program of China(2020YFA0406300,2020YFA0406400)National Natural Science Foundation of China(NSFC)(11625523,11635010,11735014,11822506,11835012,11935015,11935016,11935018,11961141012)+12 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1732263,U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH003,QYZDJ-SSW-SLH040)100 Talents Program of CAS,INPAC and Shanghai Key Laboratory for Particle Physics and Cosmology,ERC(758462)European Union Horizon 2020 research and innovation programme(Marie Sklodowska-Curie grant agreement No 894790)German Research Foundation DFG(443159800)Collaborative Research Center CRC 1044,FOR 2359,FOR 2359,GRK 214Istituto Nazionale di Fisica Nucleare,Italy,Ministry of Development of Turkey(DPT2006K-120470)National Science and Technology fund,Olle Engkvist Foundation(200-0605)STFC(United Kingdom)The Knut and Alice Wallenberg Foundation(Sweden)(2016.0157)The Royal Society,UK(DH140054,DH160214)The Swedish Research Council,U.S.Department of Energy(DE-FG02-05ER41374,DE-SC-0012069)。
文摘During the 2016-17 and 2018-19 running periods,the BESIII experiment collected 7.5 fb of e^(+)e^(-)collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV.These data samples are primarily used for the study of excited charmonium and charmoniumlike states.By analyzing the di-muon process e^(+)e^(-)→(γISR=FSR)μ^(+)μ^(-),we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV.Through a run-by-run study,we find that the center-of-mass energies were stable throughout most of the data-collection period.
基金supported by the National Natural Science Foundation of China(No.52101107)the China Postdoctoral Science Foundation(No.2021M703274)CNNC’s 2021 young talents scientific research project(No.75)。
文摘Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying.Herein,we found that the oxidation resistance of active metal Ce can be significantly improved by the addition of 20 at.%Ga.Focused ion beam lift-out technique and scanning transmission electron microscopy analysis disclosed that a discontinuous Ga-rich layer was generated beneath the oxide layer in the coarse-grained Ce-Ga alloy.The Ga-rich layer formed by selective oxidation of Ce acts as a diffusion barrier for Ce outward diffusion and ceases the O/M interfacial reaction when a critical concentration of Ga(75 at.%)is reached.After nanocrystallization,uniform distribution of Ga was achieved.After oxidation,a relatively continuous Ga-rich layer was formed which further enhanced the oxidation resistance.The introduction of noble elements combining with nanocrystallization may provide a novel strategy for the protection of metals with high activity and poor oxidation resistance.
文摘Recently,Quantitative Biology(QB)held a discussion on"Al(artificial intelligence)for Life Science"among editorial board members and interested scholars in anticipation of rapid development of this growing area after AlphaGo and ChatGPT mania.Many young people tend to get confused between facts and fictions;heated debates are unavoidable even among their mentors.When deep learning as represented by convolutional neural networks and LSTM(long shortterm memory)was made available for bioinformatics students,many of them rushed into this research field and tried to adopt these methods in all their projects without knowing the history that these tools were becoming successful consistently with Moore's Law(relating to rapid computer technology advances)
基金Technological Leading Talents Program of Yunnan Province[grant number 2013HA001]the National Natural Science Foundation of China[grant number 41502076]+1 种基金the State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences program[grant number 81300001]the China Geological Survey[grant number 12120114013701].
文摘Basalt discriminant diagrams have been used to identify the tectonic setting of basaltic magmatism since the 1970s and have played an important role in reconstructing paleotectonic environments.However,the significant increase in the availability of geochemical data has led to a reassessment of these diagrams,suggesting that some of the tectonic settings indicated by these diagrams are not accurate.Here,we use a database of global ocean island basalt(OIB),mid-ocean ridge basalt(MORB),and island arc basalt(IAB)geochemistry to propose a series of new tectonic discriminant diagrams based on the ratios of large-ion lithophile elements(LILEs)to high field strength elements(HFSEs).These new diagrams indicate that the LILE can be used to differentiate OIB,MORB,and IAB samples,meaning that LILE/HFSE ratios can discriminate between these basalts that form in different tectonic settings.Our new diagrams can correctly assign samples to OIB,MORB,and IAB categories more than 85%of the time,with the discrimination between OIB and MORB having an accuracy of slightly less than 85%.
基金Support provided by the National Basic Research Program of China (2015CB258500, 2015CB058102, 2014CB046904)
文摘The Brazilian test is a widely used method for determining the tensile strength of rocks and for calibrating parameters in bondedparticle models（BPMs）. In previous studies, the Brazilian disc has typically been trimmed from a compacted rectangular specimen. The present study shows that different tensile strength values are obtained depending on the compressive loading direction. Several measures are proposed to reduce the anisotropy of the disc. The results reveal that the anisotropy of the disc is significantly influenced by the compactibility of the specimen from which it is trimmed. A new method is proposed in which the Brazilian disc is directly generated with a particle boundary, effectively reducing the anisotropy. The stiffness（particle and bond） and strength（bond） of the boundary are set at less than and greater than those of the disc assembly, respectively,which significantly decreases the stress concentration at the boundary contacts and prevents breakage of the boundary particle bonds. This leads to a significant reduction in the anisotropy of the disc and the discreteness of the tensile strength. This method is more suitable for carrying out a realistic Brazilian test for homogeneous rock-like material in the BPM.
基金Grant support is from the National Basic Research Program of China(2017YFA050420A and 2018YFA0107604)the National Natural Science Foundation of China(31630095 and 31925015)+1 种基金the Center for Life Science at Tsinghua UniversityWe thank J.Wang,X.Fu,B.Zhou,and Shen laboratory members for insightful discussion and suggestions.
文摘Super-enhancers(SEs)comprise large clusters of enhancers,which are co-occupied by multiple lineage-specific and master tran-scription factors,and play pivotal roles in regulating gene expression and cell fate determination.However,it is still largely un-known whether and how SEs are regulated by the noncoding portion of the genome.Here,through genome-wide analysis,wefound that tpng noncoding RNA(IncRNA)genes preferentially lie next to SEs.In mouse embryonic stem cells(mESCs),depletionof$E-associated IlncRNA transcripts dysregulated the activity of their nearby SEs.Specifically,we revealed a critical regulatoryrole of the IncRNA gene Platr22 in modulating the activity of a nearby SE and the expression of the nearby pluripotency regulatorZFP281.Through these regulatory events,Platr22 contributes to pluripotency maintenance and proper differentiation of mESCs.Mechanistically,Platr22 transcripts coat chromatin near the SE region and interact with DDX5 and hnRNP-L.DDX5 further recruitsp300 and other factors related to active transcription.We propose that these factors assemble into a transcription hub,thus pro-moting an open and active epigenetic chromatin state.0ur study highlights an unanticipated role for a class of lncRNAs in epige-netically controlling the activity and vulnerability to perturbation of nearby SEs for cell fate determination.
基金This work was supported by a grant from the Research Grants Council of the Hong Kong(Project No.AoE/P-02/12)S.G.L.also acknowledges support by the National Science Foundation under Grant No.DMR-1508412.
文摘We review some recent progress in the exploration of pseudospin-1 physics using dielectric photonic crystals(PCs).We show some physical implications of the PCs exhibiting an accidental degeneracy induced conical dispersion at theΓpoint,such as the realization of zero refractive index medium and the zero Berry phase of a loop around the nodal point.Te photonic states of such PCs near the Dirac-like point can be described by an efective spin-orbit Hamiltonian of pseudospin-1.Te wave propagation in the positive,negative,and zero index media can be unifed within a framework of pseudospin-1 description.A scale change in PCs results in a rigid band shif of the Dirac-like cone,allowing for the manipulation of waves in pseudospin-1 systems in much the same way as applying a gate voltage in pseudospin-1/2 graphene.Te transport of waves in pseudospin-1 systems exhibits many interesting phenomena,including super Klein tunneling,robust supercollimation,and unconventional Anderson localization.Te transport properties of pseudospin-1 systems are distinct from their counterparts in pseudospin-1/2 systems,which will also be presented for comparison.
基金supported by the National Key Program of Research and Development (2021YFB3501502, 2021YFB3501504)the National Natural Science Foundation of China (51631002, 92163107)the Beijing Natural Science Foundation (2214067)
文摘A model for describing the adsorption process of hydrogen on surface of tungsten oxide was proposed based on the first-principle calculations. Multiple factors such as type of active surface, adsorption site and distribution of oxygen vacancies were considered to evaluate the hydrogen adsorption capability of tungsten oxide. The adsorption Gibbs free energies, electronic structures and bonding characteristics under various conditions were examined to reveal the influence of oxygen vacancies on the surface. It is found that the capability of hydrogen adsorption of tungsten oxide can be significantly enhanced by adjusting the oxygen vacancy on the outermost layer of certain active surfaces. The modeling predicts that the surface structure stability and gas adsorption ability of tungsten oxide can be simultaneously improved through the formation of W–H bonds. The proposed strategy for moderating surface provides a new approach to obtain excellent gas-sensitive metal oxide materials.
基金supported by the National Natural Science Foundation of China(NSFC,81620108011)the Ministry of Science and Technology of China(MOST,2017YFC1308401)+3 种基金supported by NSFC(31830036 and 31921002)the Beijing Municipal Science&Technology Commission(Z181100001518001)MOST(2019YFA0707100)the Chinese Academy of Sciences(XDBS1020100)。
文摘Atherosclerotic cardiovascular disease resulting from dysregulated lipid metabolism is the leading cause of morbidity and mortality worldwide.Apolipoprotein E(ApoE)plays a critical role in cholesterol metabolism.Knockouts in lipid-metabolizing proteins including ApoE in multiple model organisms such as mice and rats exhibiting elevated levels of cholesterol have been widely used for dissecting the pathology of atherosclerosis,but few of these animal models exhibit advanced atherosclerotic plaques leading to ischemia-induced clinical symptoms,limiting their use for translational studies.Here we report hypercholesterolemia and severe atherosclerosis characterized by stenosis and occlusion of arteries,together with clinical manifestations of stroke and gangrene,in ApoE knockout dogs generated by CRISPR/Cas9 and cloned by somatic cell nuclear transfer technologies.Importantly,the hypercholesterolemia and atherosclerotic complications in F0 mutants are recapitulated in their offspring.As the ApoE-associated atherosclerosis and clinical manifestations in mutant dogs are more similar to that in human patients compared with those in other animal models,these mutant dogs will be invaluable in developing and evaluating new therapies,including endovascular procedures,against atherosclerosis and related disorders.
基金the National Natural Science Foundation of China(Grant Nos.12074049,11727811,and 12047564)the Hong Kong Research Grants Council(Grant Nos.Ao E/P-02/12,16303119,and N HKUST608/17)the Fundamental Research Funds for the Central Universities(Grant Nos.2020CDJQY-Z006 and 2020CDJQY-Z003)。
文摘It is well known that spatial symmetry in a photonic crystal(PhC)slab is capable of creating bound states in the continuum(BICs),which can be characterized by topological charges of polarization vortices.Here,we show that when a PT-symmetric perturbation is introduced into the PhC slab,a new type of BICs(pt-BICs)will arise from each ordinary BIC together with the creation of rings of lasing threshold modes with pt-BICs embedded in these rings.Different from ordinary BICs,the Q-factor divergence rate of a pt-BIC is reduced and anisotropic in momentum space.Also,pt-BICs can even appear at off-high symmetry lines of the Brillouin zone.The pt-BICs also carry topological charges and can be created or annihilated with the total charge conserved.A unified picture on pt-BICs and the associated lasing threshold modes is given based on the temporal coupled mode theory.Our findings reveal the new physics arising from the interplay between PT symmetry and BIC in PhC slabs.
