The Nuclotron-based Ion Collider fAcility(NICA),currently under construction at JINR,is expected to conduct its first beam tests in the second half of 2025.The NICA project is designed to provide colliding beams for i...The Nuclotron-based Ion Collider fAcility(NICA),currently under construction at JINR,is expected to conduct its first beam tests in the second half of 2025.The NICA project is designed to provide colliding beams for investigating heavy stripped ion collisions at energies of 4.5 GeV/u.The NICA accelerator complex comprises several components:the operational heavy ion linac HILAC with an energy of 3.2 MeV/u,superconducting Booster synchrotron with a maximum energy of 600 MeV/u,superconducting Nuclotron synchrotron capable of accelerating gold ions to 3.9 GeV/u,and two storage rings with two interaction points currently under installation.The system includes two electron cooling units-one in the Booster synchrotron with a maximum electron energy of 60 keV,and another in the Collider with two electron beams,each with a maximum energy of 2.5 MeV.Additionally,two stochastic cooling systems are integrated into the setup.The status of the NICA accelerator complex,including its cooling systems,is presented.Experimental results from electron cooling studies conducted during the commissioning of the injection complex are reported.Plans for the further development and application of the electron and stochastic cooling systems are also described.展开更多
Molecular weight（Mw） is a fundamental property of humic acids（HAs）, which considerably affect the mobility and speciation of heavy metals in the environment. In this study, soil humic acid（HA） extracted from Jin...Molecular weight（Mw） is a fundamental property of humic acids（HAs）, which considerably affect the mobility and speciation of heavy metals in the environment. In this study, soil humic acid（HA） extracted from Jinyun Mountain, Chongqing was ultra-filtered into four fractions according to the molecular weight, and their properties were characterized.Complexation of cadmium was investigated by titration experiments. For the first time,Langmuir and non-ideal competitive adsorption-Donna（NICA-Donnan） models combined with fluorescence excitation-emission matrix（EEM） quenching were employed to elucidate the binding characteristics of individual Mw fractions of HA. The results showed that the concentration of acidic functional groups decreased with increasing Mw, especially the phenolic groups. The humification degree and aliphaticity increased with increasing Mw as indicated by elemental composition analysis and FT-IR spectra. The binding capacity of Cd2＋ to Mw fractions of HA followed the order UF1（〈 5 kDa） 〉 UF2（5–10 kDa） 〉 UF4（〉 30 kDa） 〉 UF3（10–30 kDa）. Moreover, the distribution of cadmium speciation indicated that the phenolic groups were responsible for the variations in binding of Cd2＋ among different Mw fractions. The results of fluorescence quenching illustrated that the binding capacity of Cd2＋ to Mw fractions was controlled by the content of functional groups, while the binding affinity was largely influenced by structural factors. The results provide a better understanding of the roles that different HA Mw fractions play in heavy metal binding,which has important implications in the control of heavy metal migration and bio-toxicity.展开更多
文摘The Nuclotron-based Ion Collider fAcility(NICA),currently under construction at JINR,is expected to conduct its first beam tests in the second half of 2025.The NICA project is designed to provide colliding beams for investigating heavy stripped ion collisions at energies of 4.5 GeV/u.The NICA accelerator complex comprises several components:the operational heavy ion linac HILAC with an energy of 3.2 MeV/u,superconducting Booster synchrotron with a maximum energy of 600 MeV/u,superconducting Nuclotron synchrotron capable of accelerating gold ions to 3.9 GeV/u,and two storage rings with two interaction points currently under installation.The system includes two electron cooling units-one in the Booster synchrotron with a maximum electron energy of 60 keV,and another in the Collider with two electron beams,each with a maximum energy of 2.5 MeV.Additionally,two stochastic cooling systems are integrated into the setup.The status of the NICA accelerator complex,including its cooling systems,is presented.Experimental results from electron cooling studies conducted during the commissioning of the injection complex are reported.Plans for the further development and application of the electron and stochastic cooling systems are also described.
基金supported by the National Natural Science Foundation of China(Nos.41771347 and 4177010514)
文摘Molecular weight（Mw） is a fundamental property of humic acids（HAs）, which considerably affect the mobility and speciation of heavy metals in the environment. In this study, soil humic acid（HA） extracted from Jinyun Mountain, Chongqing was ultra-filtered into four fractions according to the molecular weight, and their properties were characterized.Complexation of cadmium was investigated by titration experiments. For the first time,Langmuir and non-ideal competitive adsorption-Donna（NICA-Donnan） models combined with fluorescence excitation-emission matrix（EEM） quenching were employed to elucidate the binding characteristics of individual Mw fractions of HA. The results showed that the concentration of acidic functional groups decreased with increasing Mw, especially the phenolic groups. The humification degree and aliphaticity increased with increasing Mw as indicated by elemental composition analysis and FT-IR spectra. The binding capacity of Cd2＋ to Mw fractions of HA followed the order UF1（〈 5 kDa） 〉 UF2（5–10 kDa） 〉 UF4（〉 30 kDa） 〉 UF3（10–30 kDa）. Moreover, the distribution of cadmium speciation indicated that the phenolic groups were responsible for the variations in binding of Cd2＋ among different Mw fractions. The results of fluorescence quenching illustrated that the binding capacity of Cd2＋ to Mw fractions was controlled by the content of functional groups, while the binding affinity was largely influenced by structural factors. The results provide a better understanding of the roles that different HA Mw fractions play in heavy metal binding,which has important implications in the control of heavy metal migration and bio-toxicity.
