Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD cr...Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants(up to fourth order) of event-byevent net-proton(proxy for net-baryon), net-charge and netkaon(proxy for net-strangeness) multiplicity distributions Au+Au collisions at sNN^(1/2) 7:7; 11:5; 14:5; 19:6; 27;39; 62:4; 200 Ge V from the first phase of beam energy scan program at the relativistic heavy-ion collider(RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations, and the unified description of efficiency correction and error estimation.Based on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future secondphase of the beam energy scan(2019–2020) at RHIC will also be discussed.展开更多
High pure wurtzite structure GaN has been synthesized by gas reaction method.Its structure was determined by powder x-ray diffraction using the Rietveld technique.The heat capacity Cp was measured from 113 to 1073 K,w...High pure wurtzite structure GaN has been synthesized by gas reaction method.Its structure was determined by powder x-ray diffraction using the Rietveld technique.The heat capacity Cp was measured from 113 to 1073 K,which can be represented by Cp=0.362+3.010 × 10^(-4)T-3.411 × 10^(3)T-2-7.791 × 10^(-8)T^(2).No measurable phase transition was observed in this temperature range.展开更多
柬埔寨洞里萨湖(Tonle Sap Lake)位于湄公河下游盆地的中心地带,是汹涌的湄公河的缩影和“心脏”,也是湄公河三角洲复杂生态水文的重要组成部分。如今,生物多样性极为丰富的洪泛区是170万人口的家园,也是含有鱼类物种最多的地区之一,极...柬埔寨洞里萨湖(Tonle Sap Lake)位于湄公河下游盆地的中心地带,是汹涌的湄公河的缩影和“心脏”,也是湄公河三角洲复杂生态水文的重要组成部分。如今,生物多样性极为丰富的洪泛区是170万人口的家园,也是含有鱼类物种最多的地区之一,极易受水电、灌溉、防洪和供水等大型水利工程设施建设的影响。在森林砍伐、种植作物单一、人口增长、国际投资激增、大规模旅游等各种发展压力下,千百年来的人类聚落、多民族的生活和社会文化习俗均受到威胁。同时,受淤积、污染、野生动物(尤其是鱼类和鸟类)资源的过度开发及农林种植规模扩张的影响,湖泊的生态活力岌岌可危。柬埔寨动荡的历史与大幅度土地割据,对其水利基础设施产生了根本性的影响。揭示了人类通过工程建设和领地扩张强化自身影响的情况下,土壤、植被、地形和水等自然景观要素与人类主宰力之间的内在联系。早先人类聚落和生产性景观的形成得益于多种传统生态知识(traditional ecological knowledge,TEK),特别体现在保留至今的众多水上渔村和湖边高脚屋上。批判性地指出,在过去的2个世纪里,人类大规模地侵占自然环境开展工程建设所形成的景观,在某种程度上破坏了自然系统的稳定性,人与自然和谐共生的关系被打破。只有深刻理解区域景观生态内的复杂关系并致力于其恢复重建,才能实现人类与其他物种和谐共生的愿景。展开更多
By combining the Backlund transformations and the AKNS system[Study in Appl.Math.53(1974)249.]which is a linear eigenvalue problem of the corresponding evolution equation,a method to find new exact solutions from know...By combining the Backlund transformations and the AKNS system[Study in Appl.Math.53(1974)249.]which is a linear eigenvalue problem of the corresponding evolution equation,a method to find new exact solutions from known stationary solutions for nonlinear integrable equations is proposed.As an example,Korteweg de Vries(KdV)equation is used to illustrate this method,and a class of new exact solutions of KdV equation is obtained.展开更多
In this letter we report of A165Fe15Cu20 alloy by means of electron and X-ray diffractometry.A new crystalline phase of body-center-cubic structure with a lattice parameter a°=1.407nm was observed together with t...In this letter we report of A165Fe15Cu20 alloy by means of electron and X-ray diffractometry.A new crystalline phase of body-center-cubic structure with a lattice parameter a°=1.407nm was observed together with the icosahedral phase in the same sample.The new phase is supposed to be an isomorph of Mg32(A1,Zn)49(R phase)on the basis of structure factor calculation.展开更多
The dependence of giant magnetoresistance of sputtered granular type(Co-Ag)/Ag multilayers on the thickness of Ag layers and magnetic layers with varying Co content in the magnetic layers was studied.The magnetoresist...The dependence of giant magnetoresistance of sputtered granular type(Co-Ag)/Ag multilayers on the thickness of Ag layers and magnetic layers with varying Co content in the magnetic layers was studied.The magnetoresistance ratioΔR/R was found to be enhanced by 2-7 times comparing with the single layer granular films.The enhancement was explained by the antiferromagnetic coupling due to magnetostatic interaction between the Co clusters in neighboring magnetic layers.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
We report a search for a heavier partner of the recently observed Z_(cs)(3985)^(-) state,denoted as Z_(cs)^('-),in the process e^(+)e^(−)→K^(+)D_(s)^(∗−) D^(∗0 )+ c.c.,based on e^(*)e^(-)collision data collected ...We report a search for a heavier partner of the recently observed Z_(cs)(3985)^(-) state,denoted as Z_(cs)^('-),in the process e^(+)e^(−)→K^(+)D_(s)^(∗−) D^(∗0 )+ c.c.,based on e^(*)e^(-)collision data collected at the center-of-mass energies of √s=4.661,4.682 and 4.699 GeV with the BESIII detector.The Z_(cs)^('-) is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark.A partial-reconstruction technique is used to isolate K^(+)recoil-mass spectra,which are probed for a potential contribution from Z_(cs)^('-)→D_(s)^(∗−) D^(∗0 )+ c.c.We find an excess of Z_(cs)^('-)→D_(s)^(*-)-D^(*0)(c.c.)candidates with a significance of 2.1o,after considering systematic uncertainties,at a mass of(4123.5±0.7_(sat)±4.7_(syst.))MeV/c^(2).As the data set is limited in size,the upper limits are evaluated at the 90%confidence level on the product of the Born cross sections(σ^(Borm))and the branching fraction(B)of Z_(cs)^('-)→D_(s)^(*-)-D^(*0),under different assumptions of the Z_(cs)^('-) mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies.The upper limits of σ^(Born).B are found to be at the level of O(1)pb at each energy.Larger data samples are needed to confirm the Z_(cs)^('-) state and clarify its nature in the coming years.展开更多
基金supported in part by the Mo ST of China 973-Project(No.2015CB856901)the National Natural Science Foundation of China(No.11575069)
文摘Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants(up to fourth order) of event-byevent net-proton(proxy for net-baryon), net-charge and netkaon(proxy for net-strangeness) multiplicity distributions Au+Au collisions at sNN^(1/2) 7:7; 11:5; 14:5; 19:6; 27;39; 62:4; 200 Ge V from the first phase of beam energy scan program at the relativistic heavy-ion collider(RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations, and the unified description of efficiency correction and error estimation.Based on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future secondphase of the beam energy scan(2019–2020) at RHIC will also be discussed.
基金Supported by the Chinese Academy of Sciences under Contract No.KJ952-J1-411.
文摘High pure wurtzite structure GaN has been synthesized by gas reaction method.Its structure was determined by powder x-ray diffraction using the Rietveld technique.The heat capacity Cp was measured from 113 to 1073 K,which can be represented by Cp=0.362+3.010 × 10^(-4)T-3.411 × 10^(3)T-2-7.791 × 10^(-8)T^(2).No measurable phase transition was observed in this temperature range.
文摘柬埔寨洞里萨湖(Tonle Sap Lake)位于湄公河下游盆地的中心地带,是汹涌的湄公河的缩影和“心脏”,也是湄公河三角洲复杂生态水文的重要组成部分。如今,生物多样性极为丰富的洪泛区是170万人口的家园,也是含有鱼类物种最多的地区之一,极易受水电、灌溉、防洪和供水等大型水利工程设施建设的影响。在森林砍伐、种植作物单一、人口增长、国际投资激增、大规模旅游等各种发展压力下,千百年来的人类聚落、多民族的生活和社会文化习俗均受到威胁。同时,受淤积、污染、野生动物(尤其是鱼类和鸟类)资源的过度开发及农林种植规模扩张的影响,湖泊的生态活力岌岌可危。柬埔寨动荡的历史与大幅度土地割据,对其水利基础设施产生了根本性的影响。揭示了人类通过工程建设和领地扩张强化自身影响的情况下,土壤、植被、地形和水等自然景观要素与人类主宰力之间的内在联系。早先人类聚落和生产性景观的形成得益于多种传统生态知识(traditional ecological knowledge,TEK),特别体现在保留至今的众多水上渔村和湖边高脚屋上。批判性地指出,在过去的2个世纪里,人类大规模地侵占自然环境开展工程建设所形成的景观,在某种程度上破坏了自然系统的稳定性,人与自然和谐共生的关系被打破。只有深刻理解区域景观生态内的复杂关系并致力于其恢复重建,才能实现人类与其他物种和谐共生的愿景。
基金Supported by the National Natural Science Foundation of China under Grant No.19872044.
文摘By combining the Backlund transformations and the AKNS system[Study in Appl.Math.53(1974)249.]which is a linear eigenvalue problem of the corresponding evolution equation,a method to find new exact solutions from known stationary solutions for nonlinear integrable equations is proposed.As an example,Korteweg de Vries(KdV)equation is used to illustrate this method,and a class of new exact solutions of KdV equation is obtained.
基金Project supported by the National Science Foundation of China.
文摘In this letter we report of A165Fe15Cu20 alloy by means of electron and X-ray diffractometry.A new crystalline phase of body-center-cubic structure with a lattice parameter a°=1.407nm was observed together with the icosahedral phase in the same sample.The new phase is supposed to be an isomorph of Mg32(A1,Zn)49(R phase)on the basis of structure factor calculation.
基金Supported by the National Natural Science Foundation of China under Grant Nos.19754001 and 59392800,and Shanghai Research Center for Applied Physics.
文摘The dependence of giant magnetoresistance of sputtered granular type(Co-Ag)/Ag multilayers on the thickness of Ag layers and magnetic layers with varying Co content in the magnetic layers was studied.The magnetoresistance ratioΔR/R was found to be enhanced by 2-7 times comparing with the single layer granular films.The enhancement was explained by the antiferromagnetic coupling due to magnetostatic interaction between the Co clusters in neighboring magnetic layers.
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 R&D Program of China(Grant Nos.2020YFA0406400,2020YFA0406300)National Natural Science Foundation of China(NSFC)(Grant Nos.11635010,11735014,11805086,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12192260,12192261,12192262,12192263,12192264,12192265)+18 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(Grant No.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)and Shanghai Key Laboratory for Particle Physics and CosmologyERC(Grant No.758462)European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement(Grant No.894790)German Research Foundation DFG(Grant No.443159800),Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(Grant No.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(Grant No.B16F640076)Olle Engkvist Foundation(Grant No.200-0605)STFC(United Kingdom)Suranaree University of Technology(SUT),Thailand Science Research and Innovation(TSRI),and National Science Research and Innovation Fund(NSRF)(Grant No.160355)The Royal Society,UK(Grant Nos.DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(Grant No.DE-FG02-05ER41374)。
文摘We report a search for a heavier partner of the recently observed Z_(cs)(3985)^(-) state,denoted as Z_(cs)^('-),in the process e^(+)e^(−)→K^(+)D_(s)^(∗−) D^(∗0 )+ c.c.,based on e^(*)e^(-)collision data collected at the center-of-mass energies of √s=4.661,4.682 and 4.699 GeV with the BESIII detector.The Z_(cs)^('-) is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark.A partial-reconstruction technique is used to isolate K^(+)recoil-mass spectra,which are probed for a potential contribution from Z_(cs)^('-)→D_(s)^(∗−) D^(∗0 )+ c.c.We find an excess of Z_(cs)^('-)→D_(s)^(*-)-D^(*0)(c.c.)candidates with a significance of 2.1o,after considering systematic uncertainties,at a mass of(4123.5±0.7_(sat)±4.7_(syst.))MeV/c^(2).As the data set is limited in size,the upper limits are evaluated at the 90%confidence level on the product of the Born cross sections(σ^(Borm))and the branching fraction(B)of Z_(cs)^('-)→D_(s)^(*-)-D^(*0),under different assumptions of the Z_(cs)^('-) mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies.The upper limits of σ^(Born).B are found to be at the level of O(1)pb at each energy.Larger data samples are needed to confirm the Z_(cs)^('-) state and clarify its nature in the coming years.
