生态实践中的传承与创新--中国城市科学研究会景观学与美丽中国建设专业委员会座谈会纪实

2018年1月21日,中国城市科学研究会景观学与美丽中国建设专业委员会座谈会于北京大学建筑与景观设计学院举办。来自景观、生态、水利、规划等领域的30余位学者、设计师、教育者及其他从业人士参加了会议,并围绕美丽中国建设、生态文明建设、景观设计学科建设、行业融合等议题展开讨论。座谈会最终达成共识,提出了跨界生态实践的迫切性和必要性,同时探讨了在教育和实践层面跨界的难点与问题——不同行业的优势、职责以及在"跨界"中的作用尚不明确,学科教育也未能很好地构建并明晰自身的核心竞争力——呼吁应积极促进学科与行业融合,使其适应当代需求。

Collective properties of neon isotopes investigated by projected shell model

Collective phenomenon in neon isotopes is an interesting topic.However,even the ground-state deformations cannot be well described by theories.Recently,QJ Zhi and ZZ Ren[Phys Lett B 638:166(2006)]have suggested an improved Nilsson potential,which can give a suitable description of ground-state properties in magnesium isotopes.In order to test the description of neon isotopes located around the‘‘island of inversion’’,we have used this potential to provide the deformed basis for the projectedshell-model calculations.The low-lying spectra and transition properties of neon isotopes can be reproduced reasonably.The gyromagnetic factors of neon isotopes have also been investigated.The structures of excited states along the yrast line are studied in the language of band diagrams.

Rapid generation of gene-targeted EPS-derived mouse models through tetraploid complementation

One major strategy to generate genetically modified mouse models is gene targeting in mouse embryonic stem(ES)cells,which is used to produce gene-targeted mice for wide applications in biomedicine.However,a major bottleneck in this approach is that the robustness of germiine transmission of gene-targeted ES cells can be significantly reduced by their genetic and epigenetic instability after long-term culturing,which impairs the efficiency and robustness of mouse model generation.Recently,we have established a new type of pluripotent cells termed extended pluripotent stem(EPS)cells,which have superior developmental potency and robust germline competence compared to conventional mouse ES cells.In this study,we demonstrate that mouse EPS cells well maintain developmental potency and genetic stability after long-term passage.Based on gene targeting in mouse EPS cells,we established a new approach to directly and rapidly generate gene-targeted mouse models through tetraploid complementation,Haibo Li and Chaoran Zhao contributed equally to this work.Electronic supplementary material The online version of this article(https://doi.org/10.1007/s13238-018-0556-1)contains supplementary material,which is available to authorized users.which could be accomplished in approximately 2 months.Importantly,using this approach,we successfully constructed mouse models in which the human interleukin 3(IL3)or interleukin 6(IL6)gene was knocked into its corresponding locus in the mouse genome.Our study demonstrates the feasibility of using mouse EPS cells to rapidly generate mouse models by gene targeting,which have great application potential in biomedical research.

An investigation of ab initio shell-model interactions derived by no-core shell model

The microscopic shell-model effective interactions are mainly based on the many-body perturbation theory(MBPT), the first work of which can be traced to Brown and Kuo's first attempt in 1966, derived from the Hamada-Johnston nucleon-nucleon potential.However, the convergence of the MBPT is still unclear. On the other hand, ab initio theories, such as Green's function Monte Carlo(GFMC), no-core shell model(NCSM), and coupled-cluster theory with single and double excitations(CCSD), have made many progress in recent years. However, due to the increasing demanding of computing resources, these ab initio applications are usually limited to nuclei with mass up to A = 16. Recently, people have realized the ab initio construction of valence-space effective interactions, which is obtained through a second-time renormalization, or to be more exactly, projecting the full-manybody Hamiltonian into core, one-body, and two-body cluster parts. In this paper, we present the investigation of such ab initio shell-model interactions, by the recent derived sd-shell effective interactions based on effective J-matrix Inverse Scattering Potential(JISP) and chiral effective-field theory(EFT) through NCSM. In this work, we have seen the similarity between the ab initio shellmodel interactions and the interactions obtained by MBPT or by empirical fitting. Without the inclusion of three-body(3-bd) force,the ab initio shell-model interactions still share similar defects with the microscopic interactions by MBPT, i.e., T = 1 channel is more attractive while T = 0 channel is more repulsive than empirical interactions. The progress to include more many-body correlations and 3-bd force is still badly needed, to see whether such efforts of ab initio shell-model interactions can reach similar precision as the interactions fitted to experimental data.

Influence of coalescence parameters on the production of protons and Helium-3 fragments

The time evolution of protons and 3He fragments from Au+Au/Pb+Pb reactions at 0.25, 2, and 20 Ge V/nucleon is investigated with the potential version of the Ultrarelativistic Quantum Molecular Dynamics（Ur QMD） model combined with the traditional coalescence afterburner. In the coalescence process, the relative distance R0 and relative momentum P0 are surveyed in the range of 3-4 fm and 0.25-0.35 Ge V/c, respectively. For both clusters, a strong reversed correlation between R0 and P0is seen and it is time-dependent as well. For protons, the accepted（R0, P0） bands lie in the time interval 30-60 fm/c, while for 3He, a longer time evolution（at about 60-90 fm/c） is needed. Otherwise, much smaller R0 and P0values should be chosen. If we further look at the rapidity distributions from both central and semi-central collisions, it is found that the accepted [tcut,（R0, P0）] assemble can provide consistent results for proton yield and collective flows especially at mid-rapdities, while for 3He, the consistency is destroyed at both middle and projectile-target rapidities.