Efficient and mild benzoin condensation reaction catalyzed by simple 1-N-alkyl-3-methylimidazolium salts

The benzoin reaction, catalyzed by simple 1-N-alkyl-3-methylimidazolium salt-based ionic liquid via carbene intermediate, to give the α-hydroxyl ketone proceeds in CH₂Cl₂ under mild conditions.     

C2对称的类卟啉手性双噁唑啉的合成及其应用

合成了6个具有C2对称性的类卟啉手性双(口恶)唑啉配体,将这些化合物与RuCl3配位,NaIO4作氧化剂,应用于反式1,2-二苯基乙烯的不对称环氧化反应,获得了较高的产率(46.0%),但ee值(6.3%)较低.     

DNA-PROTEIN CROSSLINKING IN NORMAL HUMAN SKIN FIBROBLASTS EXPOSED TO SOLAR ULTRAVIOLET WAVELENGTHS

Three normal human skin fibroblast cell lines were exposed to the simulated solar UV radiation produced by a fluorescent sunlamp under conditions in which the wavelength components shorter than either 295, 305 or 315 nm were excluded. The level of DNA-protein crosslinks (DPC) was then measured in those cells using the alkaline elution technique either immediately after irradiation or following a 24 h incubation. In each case, cells were exposed to fluences that induce similar levels of DPC. For cells exposed to 10 kJ m(-2) of sunlamp UV > 295 nm, the level of DPC exhibited a 2-5-fold increase following incubation. In contrast, 40-100% of the DPC were removed upon incubation of cells irradiated with either 100 kJ m(-2) of sunlamp UV > 305 nm or 150 kJ m(-2) of sunlamp UV > 315 nm. A major difference between the effects induced by these wavelength regions is that, in addition to DPC, a very high level of pyrimidine dimers is also produced by sunlamp UV > 295 nm, whereas much lower dimer yields result from treatment with either sunlamp UV > 305 nm or sunlamp UV > 315 nm. A potential role for type II DNA topoisomerase in the formation of these DPC resulting from either the change in conformational structure caused by the presence of a high level of dimers or an involvement of this enzyme in dimer excision repair is discussed.     

Synthesis, Structure and Characterization of [Cu(2,2'-bpy)2][{Cu(2,2'-bpy)2}2W12O40(H2)]·4H2O

An organic-inorganic compound [Cu(2,2'-bpy)2][{Cu(2,2'-bpy)2}2W12O4o(H2)]·4H2O (Mr = 4048.00) was prepared from the hydrothermal reaction of Na2WO4·2H2O, CuCl2·2H2O,2,2'-bipyridine (2,2'-bpy) and H2O at 160 ℃ for 4 days. The compound crystallizes in the monoclinic system, space group P21/n with a = 18.9196(8), b = 20.4212(8), c = 21.8129(9)(A), β=96.992(3)°, V= 8365.0(6) (A)3, Dc= 3.214 g/cm3, Z = 4,μ(MoKα) = 17.269 mm-1 and F(000) = 7324.Of the 119837 total reflections, 17315 were unique (Rint = 0.0489). The final R = 0.0385 and wR =0.0770 for 11142 observed reflections with I ＞ 2σ(I). Single-crystal X-ray diffraction reveals that the structure is composed of [{Cu(2,2'-bpy)2}2W12O40(H2)]2- anions, discrete [Cu(2,2'-bpy)2]2 cations and lattice water molecules, and the anion is made up of a {W12O40(H2)}6- α-Keggin core decorated with two {Cu(2,2'-bpy)2}2 groups through bridging oxygen atoms.     

CTAB-Ti-Co-β沸石的制备、表征及其对环己烯水合催化性能

用十六烷基三甲基溴化铵（CTAB）对Ti-Co-β沸石表面进行修饰,制得了两亲性CTAB-Ti-Co-β沸石。通过XRD、IR、DRS-UV-Vis、TG-DTA、SEM和XPS等技术对样品进行了表征。结果表明：所制得的CTAB-Ti-Co-β沸石具有BEA拓扑结构,很高的结晶度,Ti和Co两种杂原子已进入沸石骨架。CTAB-Ti-Co-β沸石同时具有亲水和亲油性,对环己烯水合反应具有较高的催化活性,环己烯的转化率和环己醇的选择性分别高达20.6%和99.7%。     

尼龙6微孔发泡材料的制备及泡孔形貌调控

本文利用共混改性方法得到高熔体强度尼龙6基体,通过探索不同的工艺条件,获得不同倍率的尼龙6发泡材料,系统研究不同离聚体改性剂比例下对其熔体强度的影响.通过热性能测试和流变测试推测了其中微交联结构的存在.通过调节发泡工艺制备不同发泡倍率的尼龙6发泡材料,用扫描电镜(SEM)观测泡孔形貌.结果 表明,离聚体的加入大大提升尼龙6基体的熔体强度,实现了尼龙6超临界二氧化碳发泡的可能性,并获得了较大倍率的尼龙发泡材料.     

应用镍超微电极的电化学表面增强拉曼光谱技术研究

镍（Ni）电极在电化学中应用广泛。原位表征Ni电极表面的吸附物种有益于帮助理解电极反应历程、指导发展高效电催化剂。应用超微电极作为工作电极的电化学表面增强拉曼光谱技术结合了超微电极表面的传质特性和分子水平的高灵敏度表征,是研究Ni电化学的有力手段。本文所述的研究工作通过在金（Au）超微电极表面电吸附具有SERS活性的Au纳米粒子并恒电流沉积金属Ni薄层,制备并表征了具有SERS活性的Ni超微电极。在氢氧化钠溶液中的循环伏安实验和以4-甲基苯硫酚分子作为探针分子的SERS实验结果表明,沉积速率和沉积电量是影响超微电极表面Ni的覆盖度和SERS活性的关键因素。在吸附了直径为55 nm Au纳米粒子的、直径为10 μm Au的超微电极表面,以100 μA·cm^-2电流密度电沉积厚度约为5个原子层Ni的条件下,可获得Ni覆盖完好的、具有最强SERS活性的Ni超微电极。     

Combined effects of bending and elongation on polymer optical fiber losses

The combined effects of bending and elongation on fiber losses as rays propagate along deformed polymer optical fibers (POFs) are investigated. The variations in power attenuation for various curvature radii and elongations are studied. The experimental results indicate that the combination of bending and elongation significantly affects the power loss of POF. From the results an equation is proposed to predict the power losses for different bent radii and elongations. The maximum difference between the proposed equation and the experimental results is less than 5%.     

Nonpolar a-plane light-emitting diode with an in-situ SiNx interlayer on r-plane sapphire grown by metal-organic chemical vapour deposition

We report on the growth and fabrication of nonpolar a-plane light emitting diodes with an in-situ SiN_x interlayer grown between the undoped a-plane GaN buffer and Si-doped GaN layer. X-ray diffraction shows that the crystalline quality of the GaN buffer layer is greatly improved with the introduction of the SiN_x interlayer. The electrical properties are also improved. For example, electron mobility and sheet resistance are reduced from high resistance to 31.6 cm²/(V·s) and 460 Ω/口 respectively. Owing to the significant effect of the SiN_x interlayer, a-plane LEDs are realized. Electroluminescence of a nonpolar a-plane light-emitting diode with a wavelength of 488nm is demonstrated. The emission peak remains constant when the injection current increases to over 20 mA.     

Simulation for light power distribution of 3D InGaN/GaN MQW LED with textured surface

In this paper, we introduce a full 3D simulation for light power distribution of an InGaN/GaN MQW LED with a textured surface. Device simulation was performed with the APSYS software to get power distribution of light sources inside the LED. Based on this, ray tracing simulation was carried out to get light power distribution outside the LED. During the process of ray tracing, the textured surface was treated as a special material interface whose reflectivity, transmittance and refraction angle are obtained with a Finite-Difference Time-Domain (FDTD) method instead of using the usual Fresnel formulas for normal material interfaces. By comparing the ray tracing results with and without the textured surface, we found that the textured surface yields a smoother transmitted power distribution and greatly improved power extraction efficiency, which are comparable to experiment. These effects may be further improved by optimizing the texture geometry.