The properties and structures of the mono- and the di- vacancy in Cu crystal

The structures and energies of formation and migration of the mono- and di-vacancy in Cu crystal have been described and calculated with modified analytical embedded atom method (MAEAM). The lattice relaxation is considered with molecular dynamics (MD) method at T=0 K. The results show the FN di-vacancy is the most stable and likely occurs in practice from the energy minimization. Compared with the mono-vacancy, the formation energy of the FN di-vacancy is higher than that of a mono-vacancy, but lower than that of two isolated mono-vacancy. The preferred migration mechanism of the FN di-vacancy is multi-jump of either vacancy (rotating the di-vacancy). The calculated migration energy of the FN di-vacancy is lower than that of a mono-vacancy, so the FN di-vacancy is easier to migrate. All of the calculated results are in good agreement with the experimental values.     

重视反馈的逆向教学设计:以质谱课程的教学为例*

基于逆向教学设计的特点及实践,分析了传统逆向教学设计的课堂实现中存在的关于预期评估与实际评估脱节的问题,阐述了教学反馈的重要性。从而提出了一种重视反馈的逆向教学设计方法。这种方法将评估预判和反馈策略充分结合到逆向教学设计中,在评估和反馈之间进行了有效关联,很好地解决了以上问题。结合笔者在质谱课程中的实践经验,对相应的教学设计的过程进行了举例说明。     

碳纳米管束中的正电子理论

采用中性原子叠加模型和有限差分方法(SNA-FD)计算了大范围内不同管径的单壁碳纳米管束中的正电子情况，发现对于单壁碳纳米管束，正电子的主要湮没区域，湮没对象和正电子寿命随碳纳米管管径的不同而发生规律性变化.计算得到管径范围在0.8—1.6nm的碳纳米管束的正电子寿命范围为332—470ps，与实验测得的394ps符合较好.     

An RNA polymerase I-driven human respiratory syncytial virus minigenome as a tool for quantifying virus titers and screening antiviral drug

Human respiratory syncytial virus(RSV) is an important pediatric pathogen of lower respiratory tract worldwide. No vaccines and antiviral drugs are available. Herein the use of an RNA polymerase I-driven RSV minigenome for analyzing RSV replication and screening anti-RSV drugs was investigated. The RNA polymerase I(Pol I) was used to transcribe RSV minigenome from the constructed plasmid, designated p HM-RSV-Gluc, of minigenome c DNA which comprised trailer region, gene start sequence(GS), reverse complementary copy of Gaussia luciferase(Gluc) gene, gene end sequence(GE), and leader region in the direction of 5'–3'end and was flanked by promoter and terminator of Pol I. The expression of Gluc was confirmed in p HM-RSV-Gluc transfected HEp-2 cells following RSV infection and had the characteristics of dose-dependent, which provided a rapid, sensitive, and quantitative method for quantifying virus titers and screening antiviral drugs.     

Structure of Pro4H+ investigated by infrared photodissociation（IRPD） spectroscopy and theoretical calculations

Combining with electrospray ionization(ESI)mass spectrometry,infrared photodissociation(IRPD)spectroscopy is a powerful method to study structures of cluster ions in the gas phase.In this paper,infrared photodissociation spectrum of Pro_4H~+in the range of 2700–3600 cm 1was obtained experimentally.Both theoretically predicted spectra of the two most stable isomers of Pro4~(-1) and Pro4~(-2) obtained at the level of M062X/6-31+G(d,p)are in good consistent with the experimental results.The two isomers have similar structures and close energies.Both of them only consist of zwitterionic units,indicating the strong salt-bridged interactions inside the clusters.And the calculated collision cross section(ccs)of Pro4-1 is found to be very close to the experimental result previously reported.     

Gain-of-function mutational activation of human tRNA synthetase procytokine

Disease-causing mutations occur in genes for aminoacyl tRNA synthetases. That some mutations are dominant suggests a gain of function. Native tRNA synthetases, such as tyrosyl-tRNA synthetase (TyrRS) and tryptophanyl-tRNA synthetase, catalyze aminoacylation and are also procytokines that are activated by natural fragmentation. In principle, however, gain-of-function phenotypes could arise from mutational activation of synthetase procytokines. From crystal structure analysis, we hypothesized that a steric block of a critical Glu-Leu-Arg (ELR) motif in full-length TyrRS suppresses the cytokine activity of a natural fragment. To test this hypothesis, we attempted to uncover ELR in the procytokine by mutating a conserved tyrosine (Y341) that tethers ELR. Site-specific proteolytic cleavage and small-angle X-ray scattering established subtle opening of the structure by the mutation. Strikingly, four different assays demonstrated mutational activation of cytokine functions. The results prove the possibilities for constitutive gain-of-function mutations in tRNA synthetases.     

元素周期表中元素单晶基于局域密度理论的正电子寿命计算

在局域密度近似理论（LDA）的基础上用中性原子叠加模型和有限插分方法（SNA-FD）计算了元素周期表中各种元素单晶的正电子体寿命和单空位寿命.分析了不同结构的单晶中自由正电子的分布信息和湮没信息.元素单晶的正电子寿命计算值与文献中的实验测量值相符合,表明LDA基础上的SNA-FD方法可以作为单晶中正电子湮没理论计算的有效研究手段. 关键词： 局域密度近似理论 正电子寿命     

团簇增强的纳秒激光电离产生Xez+(z≤20)高价离子

利用功率密度为1011—1012W·cm-2的1064nm纳秒激光电离氙原子团簇，在飞行时间质谱中观察到电离态高达+20的高价离子.不同脉冲束位置实验表明，仅当激光作用于分子束的中段时，才能观察到高价离子，且高价离子的强度随束源压力的增加而迅速增强.实验结果表明束中大尺寸团簇的存在与高价离子的形成密切相关.讨论了高价离子产生的可能机理. 关键词： 氙 纳秒激光 高价离子 飞行时间质谱     

Relationship between positron bulk lifetime and lattice constants-research on NaCl-type crystals

The positron lifetimes of some compounds with NaCl-type crystal structure are calculated with the method of atomic superposition approximation (ATSUP) based on the theories of local-density-approximation (LDA) and generalgradient-approximation (GGA).The systematical results are fitted to a curve as a function of lattice constants.The positron bulk lifetimes of some other compounds with NaCl-type crystal structure,which are deduced from the systematical results,are in agreement with the experimental results given in other literature.