Hamiltonian graphs of given order and minimum algebraic connectivity

In this paper, we study the algebraic connectivity of a Hamiltonian graph, and determine all Hamiltonian graphs whose algebraic connectivity attain the minimum among all Hamiltonian graphs on n vertices.     

First total synthesis of isoquinolinone alkaloid marinamide and its methyl ester

The first total synthesis of isoquinolinone alkaloid marinamide 1 and its methyl ester 2 was described. The key steps involved a regioselective Frieclel-Crafts reaction of 1-benzyl-1H-pyrrole to form the intermediate 8.     

二维拓扑绝缘体退相干效应研究

拓扑绝缘体是当前凝聚态物理研究的热点.退相干效应对该体系的影响的研究不仅有重要的理论意义,而且也是实现未来量子器件的不可或缺的前期工作.文章作者从理论上研究了退相干对二维拓扑绝缘体特别是量子自旋霍尔效应的影响.研究结果表明,作为量子自旋霍尔效应的标志的量子化纵向电阻平台对不破坏自旋记忆的退相干效应(普通退相干)不敏感,但却对破坏自旋记忆的退相干效应(自旋退相干)非常敏感.因此,该量子化平台只能在尺寸小于自旋退相干长度的介观样品中存在,从而解释了量子自旋霍尔效应实验中所观测到的结果(见Science,2007,318:766).同时,文章作者还定义了一个新的物理量,即自旋霍尔电阻,并发现该自旋霍尔电阻也有量子化平台.特别是该量子化平台对两种类型的退相干都不敏感.这说明在宏观样品中也能观测到自旋霍尔电阻的量子化平台,因此更能全面地反映量子自旋霍尔效应的拓扑特性.     

A New Microporous Hydrogen-Bonding Framework Constructed from 1-(4-Hydroxyphenyl)-5-Thioacetatetetrazole

Abstract  

The new complex with flexible heterocyclic carboxylate ligand, [Ba(HL⁻)₂(H₂O)₃]·H₂O (H₂L = 1-(4-Hydroxyphenyl)-5-thioacetatetetrazole), were synthesized and structurally determined by X-ray diffraction analysis. The complex belongs to the monoclinic system, space group C2/c. The center Ba(II) is nine-coordinated by six carboxylate oxygen atoms from four HL-ligands and three water molecules in a distorted monocapped square trans-prism geometry. The ligand serves as a bridge to link two adjacent Ba(II) atoms into a chain structure which are further assembled into the final three-dimensional supramolecular architecture with microporous open channel via hydrogen bonds.     

Describing spatiotemporal couplings in ultrashort pulses using coupling coefficients

Three coupling coefficients are defined to describe spatiotemporal coupling in ultrashort pulses. With these coupling coefficients, the first-order spatiotemporal couplings of Gaussian pulse and beam are described analytically. Also, the first-order and the second-order spatiotemporal couplings caused by angular dispersion elements are studied using these coupling coefficients. It can be shown that these coupling coefficients are dimensionless and normalized, and readily indicate the severity of spatiotemporal coupling.     

Polarisation-sensitive four-wave mixing and soliton self-frequency shift effect in the highly birefringent photonic crystal fibre

By adjusting the polarisation state of the pump at 805 nm parallel to slow (x) and fast (y) axes of the highly birefringent photonic crystal fibre with zero dispersion wavelengths 790 nm and 750 nm, this paper demonstrates the efficient polarisation-sensitive four wave mixing involved in pump, anti-Stokes and Stokes signals and soliton self-frequency shift effects induced by the phase-matching between red-shifted solitons and blue-shifted dispersive waves. If the reduction of coupling efficiency to the circular pump laser mode or other circular fibres due to asymmetry of the core is neglected, more than 98% of the total input power is kept in a single linear polarisation. Controlled dispersion characteristic of the doublet of fundamental guided-modes results in achieving light field strongly confined in principal axes of photonic crystal fibre, and enhancing the corresponding nonlinear-optical process through the remarkable nonlinear birefringence.     

荧光可逆调控研究CdTe量子点-吖啶橙-小牛胸腺DNA的相互作用及分析应用

水相合成了谷胱甘肽(GSH)修饰的CdTe 量子点(QDs). 在PH＝7.4的Tris-HCl缓冲溶液中, 吖啶橙(AO)通过静电引力吸附到GSH-CdTe QDs 的表面, 与GSH-CdTe QDs形成了基态复合物, 导致GSH-CdTe QDs的荧光猝灭. 在GSH-CdTe QDs-AO体系中加入小牛胸腺DNA (ctDNA), ctDNA诱导AO从GSH-CdTe QDs表面脱落嵌入其双螺旋结构中, 导致GSH-CdTe QDs的荧光恢复. 根据GSH-CdTe QDs荧光的猝灭和恢复, 实现了量子点荧光的可逆调控. ctDNA引起GSH-CdTe QDs-AO体系荧光恢复强度与ctDNA浓度成良好的线性关系, 检出限为0.13 ng•mL^－1, 据此提出了简便快捷、准确、高灵敏测定ctDNA的新方法. 还结合共振瑞利散射(RRS)光谱、吸收光谱和原子力显微镜照片研究了GSH-CdTe QDs-AO-ctDNA三者之间的相互作用, 对相互作用机理进行了讨论并提出了相应的作用模型.     

一步醇-水热法合成高效的F掺杂BiVO4光催化剂

以NH₄F为掺杂前体,采用简单的一步醇-水热法制备了F掺杂BiVO₄光催化剂。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-Vis）和光致发光光谱（PL）表征了这些光催化剂的物理化学性质。在少量H₂O₂存在条件下,以可见光照射下光催化降解苯酚的反应测定了这些光催化剂的催化活性。研究表明,相较于未掺杂的BiVO₄样品而言,F掺杂BiVO₄样品不仅仍保留了单斜结构,而且有更高的结晶度、表面氧空位密度和光生电荷载流子分离效率,更强的光吸收和更低的带隙能。在这些F掺杂BiVO₄样品中,以n_F/n_Bi的理论值为1.0且带隙能为2.43 eV的F掺杂BiVO₄样品的光催化活性最好（90 min内苯酚的降解率可达95%）。这一优良的光催化性能与其具有最高的结晶度、表面氧空位密度和光生电荷载流子分离效率,最强的光吸收和最低的带隙能有关。     

Mean-field approximations of fixation time distributions of evolutionary game dynamics on graphs

The mean fixation time is often not accurate for describing the timescales of fixation probabilities of evolutionary games taking place on complex networks. We simulate the game dynamics on top of complex network topologies and approximate the fixation time distributions using a mean-field approach. We assume that there are two absorbing states. Numerically, we show that the mean fixation time is sufficient in characterizing the evolutionary timescales when network structures are close to the well-mixing condition. In contrast, the mean fixation time shows large inaccuracies when networks become sparse. The approximation accuracy is determined by the network structure, and hence by the suitability of the mean-field approach. The numerical results show good agreement with the theoretical predictions.