An Efficient Synthesis of 4H-Benzo[g]chromene-5,10-dione Derivatives through Triethylbenzylammonium Chloride Catalyzed Multicomponent Reaction under Solvent-free Conditions

A series of 4‐aryl‐5,10‐dihydro‐4H‐benzo[g]chromene‐5,10‐dione derivatives were synthesized by a three‐component reaction with aromatic aldehyde, 2‐hydroxy‐1,4‐dihydronaphthalene‐1,4‐dione, and malononitrile catalyzed by triethylbenzylammonium chloride under solvent‐free conditions. The novel efficient method has the advantages of environmental friendliness, high yield, simple work‐up and ease of operation.     

The interplay of inverted redox potentials and aromaticity in the oxidized states of new pi-electron donors: 9-(1,3-dithiol-2-ylidene)fluorene and 9-(1,3-dithiol-2-ylidene)thioxanthene derivatives

Derivatives of 9-(1,3-dithiol-2-ylidene)fluorene (9) and 9-(1,3-dithiol-2-ylidene)thioxanthene (10) have been synthesised using Horner-Wadsworth-Emmons reactions of (1,3-dithiol-2-yl)phosphonate reagents with fluorenone and thioxanthen-9-one. X-ray crystallography, solution electrochemistry, optical spectroscopy, spectroelectrochemistry and simultaneous electrochemistry and electron paramagnetic resonance (SEEPR), combined with theoretical calculations performed at the B3P86/6-31G** level, elucidate the interplay of the electronic and structural properties in these molecules. These compounds are strong two-electron donors, and the oxidation potentials depend on the electronic structure of the oxidised state. Two, single-electron oxidations (E(1)ox < E(1)ox) were observed for 9-(1,3-dithiol-2-ylidene)fluorene systems (9). In contrast, derivatives of 9-(1,3-dithiol-2-ylidene)thioxanthene (10) display the unusual phenomenon of inverted potentials (E(1)ox > E(1)ox) resulting in a single, two-electron oxidation process. The latter is due to the aromatic structure of the thioxanthenium cation (formed on the loss of a second electron), which stabilises the dication state (10(2+)) compared with the radical cation. This contrasts with the nonaromatic structure of the fluorenium cation of system 9. The two-electron oxidation wave in the thioxanthene derivatives is split into two separate one-electron waves in the corresponding sulfoxide and sulfone derivatives 27-29 owing to destabilisation of the dication state.     

Natural product diversification using a non-natural cofactor analogue of S-adenosyl-L-methionine

Adenosine analogues bearing either 5'-aziridine or 5'-N-mustard electrophiles are methyltransferase-dependent DNA alkylating agents. We present here a novel synthetic cofactor bearing a pendant 5'-amino acid N-mustard. Unlike previously studied synthetic cofactors, this material is very efficiently used by the natural product biosynthetic enzyme rebeccamycin methyltransferase (RebM) to generate a number of new rebeccamycin analogues. These data promote the notion that natural product methyltransferases can be used with non-natural cofactors to enhance the molecular diversity of natural product analogues for drug discovery. To our knowledge, this is the first documentation of a biological methyltransferase, other than DNA methyltransferases, that can exploit such synthetic cofactors.     

Rapid Evaluation of Individual Hydrogen Bonding Energies in Linear Water Chains

A model is proposed to rapidly evaluate the individual hydrogen bonding energies in linear water chains. We regarded the two O--H bonds of a water molecule as two dipoles. The magnitude of the O--H bond dipole mo- ment can be varied due to the other water molecules＇ presence. An analytic potential energy function, which explicitly contains the permanent dipole-dipole interactions, the polarization interactions, the van der Waals interactions and the covalent interactions, was therefore established. The individual hydrogen bonding energies in a series of linear water chains were evaluated via the analytic potential energy function and compared with those obtained from the CP-corrected MP2/aug-cc-pVTZ calculations. The results show that the analytic potential energy function not only can produce the individual hydrogen bonding energies as accurately as the CP-corrected MP2/aug-cc-pVTZ method, but is very efficient as well, demonstrating the model proposed is reasonable and useful. Based on the individual hy- drogen bonding energies obtained, the hydrogen bonding cooperativity in the linear water chains was explored and the natures of the hydrogen bonding in these water chains were discussed.     

Disturbance-observer-based robust synchronization control of uncertain chaotic systems

In this paper, a robust synchronization control scheme is proposed for chaotic systems in the presence of system uncertainties and unknown external disturbances. For the synchronization error system, the compound disturbance which is estimated using the disturbance observer cannot be directly measured. If the gain matrix is properly chosen, the disturbance observer can approximate the unknown compound disturbance well. And then, the constrained robust synchronization control scheme is presented for uncertain chaotic systems based on the output of disturbance observer. In the design of a robust synchronization control scheme, the effect of unknown control input constraint has been explicitly considered to guarantee the synchronization performance. Numerical simulation results are presented to illustrate the effectiveness of the proposed constrained synchronization control scheme for uncertain chaotic systems.     

Local Well-posedness and Blow Up Criterion for the Inviscid Boussinesq System in Hölder Spaces

We prove the local in time existence and a blow up criterion of solution in the Hölder spaces for the inviscid Boussinesq system in R^N, N≥ 2, under the assumptions that the initial values θ_0, μ_0∈C^r, with 1< r≠ 2.     

精氨酸侧链和核酸碱基间离子氢键作用强度分析

采用MP2/6-31+G(d,p)方法优化得到了22个由精氨酸侧链与碱基尿嘧啶、 胸腺嘧啶、 胞嘧啶、 鸟嘌呤及腺嘌呤形成的氢键复合物的气相稳定结构, 使用包含BSSE校正的MP2/aug-cc-pVTZ方法计算得到了复合物的气相结合能, 通过MP2/6-31+G(d,p)方法和PCM模型优化得到了复合物的水相稳定结构, 采用MP2/aug-cc-pVTZ方法和PCM模型计算得到了复合物的水相结合能. 研究发现, 精氨酸侧链与碱基间的离子氢键作用强度与单体间电荷转移量、 氢键临界点电子密度及二阶作用稳定化能密切相关. 与中性氢键相比, 离子氢键作用具有更显著的共价作用成分. 研究还发现, 精氨酸侧链和碱基间形成的氢键复合物的稳定性次序可以通过氢键受体碱基分子上氧原子和氮原子的质子化反应焓变进行预测, 质子化反应焓变越负, 形成的氢键复合物越稳定.     

Fabrication and cytocompatibility evaluation for blood‐compatible polyethersulfone membrane modified by a synthesized poly (vinyl pyrrolidone)‐block‐poly (acrylate‐graft‐poly(methyl methacrylate))‐block‐poly‐(vinyl pyrrolidone)

Polyethersulfone (PES) membrane, one of the most important polymeric materials because of its good chemical resistance, thermal stability, mechanical, and film‐forming properties, has already been used in hemodialysis, tissue engineering, and artificial organs. In order to improve the blood compatibility of PES membrane, many amphiphilic block copolymers have been synthesized and used as additives for surface modification. The object of this study is to develop a hydrophilic PES membrane by blending a comblike amphiphilic block copolymer poly (vinyl pyrrolidone)‐block‐poly [acrylate‐graft‐poly (methyl methacrylate)]‐block‐poly‐(vinyl pyrrolidone) [PVP‐b‐P (AE‐g‐PMMA)‐b‐PVP] synthesized by RAFT polymerization. The cytocompatibility performance of PVP‐b‐P (AE‐g‐PMMA)‐b‐PVP modified PES membrane was evaluated, which showed better cytocompatibility compared with that of pristine PES membrane. Endothelial cells cultured on the modified membranes present improved growth in terms of scanning electron microscope observation, MTT assay, and confocal laser scanning microscope observation. These results indicate that the modified membrane has great potential application in blood‐contact fields such as hemodialysis and bio‐artificial liver supports. Copyright © 2015 John Wiley & Sons, Ltd.     

Fabrication of Ag nanodot array over large area for surface-enhanced Raman scattering using hybrid nanoimprint mold made from AAO template

We demonstrated the fabrication of dense hexagonal arrays of Ag nanodots over a large area using a novel nanoimprint-based fabrication technique for surface-enhanced Raman spectroscopy. Flexible imprint molds with sub-10 nm features were duplicated from AAO templates using a novel hybrid mold technique. This method solves the nonflatness-induced defect issue in the conventional thermal nanoimprint technique, and allows high-quality duplications of nanometer features from rigid nonflat templates. Moreover, with the help of the excellent tunability of the size of nanoholes on AAO templates, we were able to tune the size of Ag nanodots, and consequently to tailor the resonance frequency of the Ag nanodot arrays. Finally, surface-enhanced Raman scattering of Rhodamine-123 on Ag nanodot arrays was measured, and large signal enhancement was observed on the 70 nm Ag nanodots. We numerically simulated the optical properties of those Ag nanodot arrays, and excellent agreement was found with the experimental results.     

光电子发射引起的柱腔内系统电磁脉冲的模拟

 用时域有限差分法结合PIC粒子模拟方法，对光电子发射引起的圆柱腔内电磁脉冲现象进行了模拟，并对单能电子发射时电场的空间分布和系统电磁脉冲波形特征进行了分析。利用粒子抽样和间隔时间粒子注入的方法，得到了特定电子发射谱下的计算结果，并与非抽样方法所得的结果进行了比较。计算结果显示，采用该方法后，噪声略有增加，但计算要求的条件大大降低，计算的粒子数有效地减少，适用于3维粒子模拟计算；计算结果还显示，发射电子能谱越高，注量越大，表面电场区与饱和电场区的长度越短。