Synthesis,crystal structures,and fluorescence properties of two dinuclear cadmium(II) complexes derived from <Emphasis Type="Italic">N</Emphasis>-isopropyl-<Emphasis Type="Italic">N</Emphasis>′-(1-pyridin-2-ylethylidene)ethane-1,2-diamine

A new tridentate pyridyl Schiff base, N-isopropyl-N′-(1-pyridin-2-ylethylidene)ethane-1,2-diamine (L), was used to synthesize two dinuclear cadmium(II) complexes, [Cd₂L₂(μ _1,1-N₃)₂(N₃)₂] (1) and [Cd₂L₂(μ _1,3-NCS)₂(NCS)₂] (2). X-ray single crystal structure determination reveals that in both centrosymmetric complexes, the Cd atom is in a distorted octahedral coordination. In the crystal structures of 1 and 2, the dinuclear cadmium(II) complex molecules are linked, respectively, through intermolecular N–H···N and N–H···S hydrogen bonds to form infinite 1D chains. The preliminary fluorescence properties of the complexes were investigated.     

A glucose biosensor based on chitosan-Prussian blue-multiwall carbon nanotubes-hollow PtCo nanochains formed by one-step electrodeposition

In this paper, a simple one-step electrodeposition method is described to fabricate chitosan-Prussian blue-multiwall carbon nanotubes-hollow PtCo nanochains (CS-PB-MWNTs-H-PtCo) film onto the gold electrode surface, then glucose oxidase (GOD) and Nafion were modified onto the film subsequently to fabricate a glucose biosensor. The morphologies and electrochemistry of the composite were investigated by using Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and electrochemical techniques including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. The performances of the biosensor have been investigated by chronoamperometry method under the optimized conditions. This biosensor showed a linear response to glucose range from 1.5 μM to 1.12 mM with a detection limit of 0.47 μM (S/N=3), a high sensitivity of 23.4 μA mM(-1) cm(-2), and a fast response time. The apparent Michaelis-Menten constant (K(M)(app)) was 1.89 mM. In addition, the biosensor also exhibited strong anti-interference ability, excellent stability and good reproducibility.     

Highly efficient and diastereoselective gold(I)-catalyzed synthesis of tertiary amines from secondary amines and alkynes: substrate scope and mechanistic insights

An efficient method for the synthesis of tertiary amines through a gold(I)‐catalyzed tandem reaction of alkynes with secondary amines has been developed. In the presence of ethyl Hantzsch ester and [{(tBu)₂(o‐biphenyl)P}AuCl]/AgBF₄ (2 mol %), a variety of secondary amines bearing electron‐deficient and electron‐rich substituents and a wide range of alkynes, including terminal and internal aryl alkynes, aliphatic alkynes, and electron‐deficient alkynes, underwent a tandem reaction to afford the corresponding tertiary amines in up to 99 % yield. For indolines bearing a preexisting chiral center, their reactions with alkynes in the presence of ethyl Hantzsch ester catalyzed by [{(tBu)₂(o‐biphenyl)P}AuCl]/AgBF₄ (2 mol %) afforded tertiary amines in excellent yields and with good to excellent diastereoselectivity. All of these organic transformations can be conducted as a one‐pot reaction from simple and readily available starting materials without the need of isolation of air/moisture‐sensitive enamine intermediates, and under mild reaction conditions (mostly room temperature and mild reducing agents). Mechanistic studies by NMR spectroscopy, ESI‐MS, isotope labeling studies, and DFT calculations on this gold(I)‐catalyzed tandem reaction reveal that the first step involving a monomeric cationic gold(I)–alkyne intermediate is more likely than a gold(I)–amine intermediate, a three‐coordinate gold(I) intermediate, or a dinuclear gold(I)–alkyne intermediate. These studies also support the proposed reaction pathway, which involves a gold(I)‐coordinated enamine complex as a key intermediate for the subsequent transfer hydrogenation with a hydride source, and reveal the intrinsic stereospecific nature of these transformations observed in the experiments.     

The impact of resale on entry in second price auctions

This paper investigates the effect of resale allowance on entry strategies in a second price auction with two bidders whose entries are sequential and costly. We first characterize the perfect Bayesian equilibrium in cutoff strategies. We then show that there exists a unique threshold such that if the reseller’s bargaining power is greater (less) than the threshold, resale allowance causes the leading bidder (the following bidder) to have a higher (lower) incentive on entry; i.e., the cutoff of entry becomes lower (higher). We also discuss asymmetric bidders and the original seller’s expected revenue.     

Forcing faces in plane bipartite graphs (II)

The concept of forcing faces of a plane bipartite graph was first introduced in Che and Chen (2008) [3] [Z. Che, Z. Chen, Forcing faces in plane bipartite graphs, Discrete Mathematics 308 (2008) 2427–2439], which is a natural generalization of the concept of forcing hexagons of a hexagonal system introduced in Che and Chen (2006) [2] [Z. Che and Z. Chen, Forcing hexagons in hexagonal systems, MATCH Commun. Math. Comput. Chem. 56 (2006) 649–668]. In this paper, we further extend this concept from finite faces to all faces (including the infinite face) as follows: A face $s$ (finite or infinite) of a 2-connected plane bipartite graph $G$ is called a forcing face if the subgraph $G?V\left(s\right)$ obtained by removing all vertices of $s$ together with their incident edges has exactly one perfect matching.For a plane elementary bipartite graph $G$ with more than two vertices, we give three necessary and sufficient conditions for $G$ to have all faces forcing. We also give a new necessary and sufficient condition for a finite face of $G$ to be forcing in terms of bridges in the $Z$-transformation graph $Z\left(G\right)$ of $G$. Moreover, for the graphs $G$ whose faces are all forcing, we obtain a characterization of forcing edges in $G$ by using the notion of $handle$, from which a simple counting formula for the number of forcing edges follows.     

电磁脉冲对数字信号处理器的干扰及其防护

为寻找有效的电磁脉冲防护加固措施,首先对电磁脉冲模拟器的干扰路径进行分析,包括数字信号处理器（DSP）与放电回路的共地耦合干扰及共网电耦合干扰,并将结构优化设计、硬件屏蔽加固措施与设置软件陷阱、开启看门狗等抗干扰措施相结合,对数字信号处理器（DSP）内核工作电压、输入/输出（I/O）端口以及显示屏等进行了干扰测试。实验结果表明,采用硬件与软件相结合的防护加固技术后,DSP主板的内核工作电压及I/O端口的干扰脉冲幅值减小,且干扰持续时间由2 s减少到400 ns,干扰脉冲获得了有效抑制。     

Fluorescence Quenching of 4-tert-Octylphenol by Room Temperature Ionic Liquids and its Application

The interactions between room temperature ionic liquids (RTILs) and weak fluorescent chemicals still remain unclear, which hinders the complete and efficient utilization of these “green” solvents in fluorescent analyses of organic chemicals. Herein, we reported the effects of four RTILs, [C₈MIM]BF_4, [C₁₄MIM]BF_4, [C₈MIM]PF₆ and [C₁₄MIM]PF₆, on fluorescence behavior of 4-tert-octylphenol (4-t-OP). In the fortified concentration range of 0.2–1.0 mM, the quenching effects were increased with increasing concentrations of RTILs. However, no obvious variation of peak shape of 4-t-OP was observed in the quenching process, suggesting no formation of ground-state complex between fluorophores in 4-t-OP and quencher (ionic liquids). As for anion effect, the fluorescence quenching efficiency of 4-t-OP by BF₄ ^- was greater than PF₆ ^-, but the carbon chain length on the imidazolium ring had no significant relationship with fluorescence intensity of 4-t-OP. Both Ksv values (>1.0?×?10³?L/mol.s) and the different temperature effects demonstrated that the quenching of 4-t-OP by four RTILs was the presence of dynamic and static quenching mechanism. The FI of dansyl chloride within [C₈MIM]BF₄ increased nearly 5-fold as compared to the control, showing a sensitizing effect on the strong fluorescent chemicals, while a quenching effect on 4-t-OP belonging to weak fluorescent chemicals. The fluorescence-enhanced amplitude of dansyl chloride in [C₈MIM]PF₆ was greater than [C₈MIM]BF_4. The fluorescence quenching of 4-t-OP by [C₈MIM]PF₆ did not belong to FRET phenomenon because of no overlap of emission spectrum of 4-t-OP and absorption spectrum of [C₈MIM]PF₆. When 0.6 mM [C₈MIM]PF₆ in acetonitrile was used as the solvent, the detection limit of 4-t-OP was 3.7 μg/L, and the linearity range was 0.01–0.8 mg/L (R²?=?0.9990). In summary, these results provide a theoretical foundation for the application of RTILs in weak fluorescent chemicals.     

Numerical study on heat transfer and resistance characteristics of supercritical water inside internally-ribbed tube

The effects of structural parameters for internally-ribbed tube on heat transfer and flow characteristics of supercritical water were studied numerically. The results show that the heat transfer and pressure loss increases with the increase of mass flow or heat flux. The Heat transfer and resistance coefficients of supercritical water increase with the spiral rising angle decrease or rib height increase, while rib width has a weak influence on heat transfer and pressure drop.     

Hydrothermal synthesis of graphitic carbon nitride–BiVO4 composites with enhanced visible light photocatalytic activities and the mechanism study

Novel graphitic carbon nitride (C₃N₄) and bismuth vanadate (BiVO₄) composite photocatalysts were successfully synthesized by a facile hydrothermal method. The scanning electron microscopy (SEM) revealed that an intimate interface between C₃N₄ and BiVO₄ formed in the composites. Compared with the pure C₃N₄ and BiVO₄, the C₃N₄–BiVO₄ photocatalysts showed remarkably the higher photocatalytic activities in degrading rhodamine B (Rh B). The best active heterojunction proportion was 0.5C₃N₄–0.5BiVO₄. Over this catalyst, the 100% degradation of Rh B (0.002 mmol L⁻¹) was obtained under visible light irradiation (λ>420 nm) for 40 min. The active species in Rh B degradation were examined by adding a series of scavengers. The study on photocatalytic mechanism revealed that the electrons injected directly from the conduction band of C₃N₄ to that of BiVO₄, resulting in the production of superoxide radical (O₂^•−) and hydroxyl radical (OH^•) in the conduction band of BiVO₄. Simultaneously, the rich holes in the valence band of g-C₃N₄ oxidized Rh B directly to promote the photocatalytic degradation reaction.     

量子点红外探测器在空间光电系统中的应用

为了更好地开发和利用空间资源,各国竞相通过向空间发射卫星、空间站、航天飞机等航天器来建立探测站点和通信网络以占据具有最大优势的位置,其中空间光电系统在探索新资源方面起到关键的作用.点对点的距离远、空间辐射强、温差较大等空间环境因素严重影响着光电系统性能的发挥,也向空间光电系统的稳定性和可靠性提出了挑战.本文提出将具有较高的探测灵敏度、工作温度、抗辐射能力和响应带宽的新型量子点红外探测器应用于空间光电系统,阐述了量子点红外探测器的基本工作原理和优点,并讨论了量子点红外探测器在空间应用的技术要求,分析了其在空间的激光雷达、卫星光通信和成像或者非成像系统中的应用.