一例从保守向类耗散的过渡

建议研究一类特殊的分段连续力场中的受击转子.它在一个控制参数连续改变时可以演示从分段连续保守系统向类耗散系统的连续过渡，从而展现不连续边界像集随机网向一个瞬态随机网，以及网上的无边界混沌扩散运动向局域规则运动的转变.这种转变可能用瞬态随机网的分数维随控制参数的对数改变规律来描述，也可以用迭代在瞬态随机网中的平均生存时间随控制参数的指数改变规律来描述. 关键词： 受击转子 分段连续保守系统 类耗散系统 随机网     

Effects of Explicit and Implicit Solvent Models on the Hydrolysis Cleavage of N-Glycosidic Bond in 8-Oxo-7,8-dihydro-2?-deoxyguanosine

8-Oxoguanine(8-oxoG), a critical mutagenic DNA lesion induced by reactive oxygen species, gives rise to a G·C→T·A transversion during replication and thereby must be repaired. The effects of explicit and implicit solvent molecules on the hydrolysis cleavage of N-Glycosidic bond in 8-oxo-7,8-dihydro-2'-deoxyguanosine(8-oxo-dG) have been systematically clarified in the present work based upon two types of computational models. Detailed potential energy surface(PES) scans and full unconstraint optimizations for all the representative points on PESs were carried out at the B3LYP/6-31+G(d) level of theory. The effect of implicit solvent was tested by single-point calculation at the SCRF/IEF-PCM model. The results illustrate that the direct hydrolysis model involving one explicit water molecule can't provide a complete depiction of the hydrolysis process of 8-oxo-dG, attributed to the insufficiency of nucleophile activation and leaving group stabilization. The expansion hydrolysis model involving four explicit water molecules, however, facilitates discrete proton transfer and therefore produces smooth reaction surfaces for both the dissociative(SN1) and concerted(SN2) pathways. The presence of the implicit solvent substantially lowers all activation energies and the SN1 process is more favorable than the SN2 process. The data and insights present here agree well with the experimental results and have given out a baseline for the enzymatic deglycosylation reaction of 8-oxo-dG.     

Be2-非线性光学性质的从头算研究

采用MP2/6-31+G*水平的优化构型,对Be2-的非线性光学性质进行了从头算研究。用UHF方法对Be2-的(超)极化率计算进行了基组优化,排除了基组选择的偶然性。精确选择可以得到稳定(超)极化率的电场范围,用FF方法计算了Be2-的超极化率。得到了Be2-的UHF方法可靠的无微扰能量E和轴向极化率极限结果,报道的轴向超极化率也接近UHF极限。推荐基组39s16p4d1f的计算结果是：E=-29.1336456593,=439.6466994,= 。     

Prolongation structure of the variable coefficient KdV equation

The prolongation structure methodologies of Wahlquist--Estabrook [Wahlquist H D and Estabrook F B 1975 J. Math. Phys. 16 1] for nonlinear differential equations are applied to a variable-coefficient KdV equation. Based on the obtained prolongation structure, a Lie algebra with five parameters is constructed. Under certain conditions, a Lie algebra representation and three kinds of Lax pairs for the variable- coefficient KdV equation are derived.     

Robust Quantum Computing in Decoherence-Free Subspaces with Double-Dot Spin Qubits

We present a scheme for implementing robust quantum gates in decoherence-free subspaces （DFSs） with double-dot spin qubits. Through the resonator-assisted interaction, the controllable interqubit couplings can be achieved only by adjusting the qubit transition frequencies. We construct a set of logic gates on the DFS-encoded qubits to eliminate the collective noise effects, and thus the gate fidelities can be enhanced remarkably. This proposal may offer a potential approach to realize the robust quantum computing with spin qubits.     

Prolongation Structure of the Equation Studied by Qiao

The prolongation structure technique of Wahlquist andEstanbrook is improved and applied to a new equation proposed by Z.J. Qiao [J. Math. Phys.48(2007) 082701]. Two potentials and two pseudopotentials are obtained,from which a new type of inverse scattering problem, Lax equations, and infinite number of conservation laws are obtained.     

Transient Expression of Minimum Linear Gene Cassettes in Onion Epidermal Cells Via Direct Transformation

A new method without any special devices for direct transformation of linear gene cassettes was developed. Its feasibility was verified through 5′-fluorescent dye (fluorescein isothiocyanate, FITC)-labeled fluorescent tracing and transient expression of a gus reporter gene. Minimal linear gene cassettes, containing necessary regulation elements and a gus reporter gene, was prepared by polymerase chain reaction and dissolved in transformation buffer solution to 100 ng/mL. The basic transformation solution used was Murashige and Skoog basal salt mixture (MS) liquid medium. Hypertonic pretreatment of explants and transformation cofactors, including Ca²⁺, surfactant assistants, Agrobacterium LBA4404 cell culture on transformation efficiency were evaluated. Prior to the incubation of the explants and target linear cassette in each designed transformation solution for 3 h, the onion low epidermal explants were pre-cultured in darkness at 27 °C for 48 h and then transferred to MS solid media for 72 h. FITC-labeled linear DNA was used to trace the delivery of DNA entry into the cell and the nuclei. By GUS staining and flow-cytometry-mediated fluorescent detection, a significant increase of the ratios of fluorescent nuclei as well as expression of the gus reporter gene was observed by each designed transformation solution. This potent and feasible method showed prospective applications in plant transgenic research.     

Electron beam density imaging system at Beam study using a portable slit the Shanghai Electron Ion Trap

In this work, a portable slit imaging system is developed to study both the electron beam diameter and the profile of the newly developed Shanghai Electron Beam Ion Trap （Shanghai EBIT）. Images are detected by a charge coupled device （CCD） sensitive to both X rays and longer wavelength photons （up to visible）. Large scale ray tracings were conducted for correcting the image broadening effects caused by the finite slit width and the finite width of the CCD pixels. A numerical de-convolution method was developed to analyse and reconstruct the electron beam density distribution in the EBIT. As an example of the measured beam diameter and current density, the FWHM （full width at half maximum） diameter of the electron beam at 81 keV and 120 mA is found to be 76.2 μm and the density 2.00 × 10^3 A.cm-2, under a magnetic field of 3 T, including all corrections.     

在近平衡态QGP中费米子的分布函数

从QGP动力论出发,得到QGP在色场涨落扰动下偏离平衡态而处于近平衡时的分布函数, 进而分析了决定偏离因子的物理因素.并分别讨论了在高温低密和低温高密区偏离因子特征.     

基于一维金属光子晶体平凹镜的柱矢量光束亚波长聚焦

柱矢量光束具有柱对称性的偏振分布,其独特的光场分布和聚焦特性被广泛应用于光学微操纵及光学成像等领域,并迅速向亚波长尺度拓展.通常,亚波长尺度聚焦采用等离激元透镜实现,但存在光场调控的偏振态局限性.而借助光子晶体的负折射效应,不仅能够实现亚波长聚焦或成像,而且应对正交偏振态同时有效.采用对电磁波具有更强调控能力的一维金属光子晶体结构,计算得到的能带结构和等频曲线表明其负折射效应在特定波段对正交偏振态同时有效.在此基础上设计出一维金属光子晶体柱对称平凹镜结构,通过有限元算法模拟显示了可见光波段的径向和旋向偏振光的同时亚波长聚焦行为.进一步的结果表明,改变柱矢量光束的偏振组分能够直接有效地调节焦场空间分布及偏振分布特性.所提出的平凹镜结构能够实现对任意偏振组分的柱矢量光束的亚波长尺度聚焦,且该结构的设计对于各波段情况均有参考意义.该研究结果对小尺度粒子的光学微操纵、超分辨率成像等相关领域具有潜在的应用价值.