The photodimerization of a cinnamoyl moiety derivative in dilute solution based on the intramolecular chain interaction of gemini surfactant

A Gemini surfactant, sodium N, N'-di(4-n-butyloxy cinnamoly)-L-cystine, containing a cinnamoyl moiety in the alkyl chains and disulfide bond in the spacer was designed and synthesized. The incorporation of a cinnamoyl moiety into the alkyl chains of Gemini surfactant makes it easy to probe the conformational information of the amphiphile molecule. The UV/vis absorption spectra and steady-state fluorescence were investigated at a concentration far below the critical micelle concentration (cmc). Both blue-shift of absorption and red-shift of fluorescence emission spectra indicate the existence of intramolecular interaction between the two alkyl chains in Gemini surfactant in the singly dispersed state. Results based on the breakdown of the disulfide bond by dithiotheritol (DTT) further confirmed the conclusion. Moreover, the characteristic of intramolecular chain interaction in Gemini surfactant improves the topochemical geometrical requirements of cinnamoyl moiety and increases the local concentration of reactant in dilute solution. Utilizing the incorporation of cinnamoyl moiety into the alkyl chains of Gemini surfactant, the cinnamoyl moiety upon irradiation undergoes dimerization in dilute aqueous solution with high yield of 78%.     

STRUCTURE AND MORPHOLOGY CHANGES OF HYDROBIOTITES MODIFIED BY CATIONIC SURFACTANTS

In this study, X-ray diffraction （XRD）, Fourier transform infrared spectrometer （FTIR） together with Scanning probe microscopy （SPM） were used to characterize the structure and morphology of the complexes, where the hydrobiotites （Xinfiang） were modified by single-chain surfactants octyltrimethylammonium bromide （OTMA） and octadecyltrimethylammonium bromide （ODTMA）. XRD patterns showed that the structure of complexes was significantly influenced by the surfactant concentration and the alkyl chain length, because obvious changes took place in the basal spacing. Furthermore, according to the XRD results, several arrangements of surfactant molecules within the hydrobiotite interlayer space were deduced. The FTIR spectrum indicated that the surfactant contents in complexes dramatically increased with the alkyl chain length. The SPM micrographs demonstrated that the surfaces of complexes prepared at lower surfactant concentration were relatively flat compared with that prepared at higher concentration, while those with higher surfactant concentration had much steeper surface due to the alkyl chain length. It was concluded that structure and morphology of surfactant/hydrobiotite complexes depend not only on the surfactant concentration, but also strongly on the surfactant species.     

茶叶中茶氨酸的快速测定

本文介绍用日立835-50型氨基酸分析仪测定茶氨酸的方法。本法简便快速,分离率高,重现性好,实际应用效果良好。     

Collagen-Immobilized Lipases Show Good Activity and Reusability for Butyl Butyrate Synthesis

Candida rugosa lipases were immobilized onto collagen fibers through glutaraldehyde cross-linking method. The immobilization process has been optimized. Under the optimal immobilization conditions, the activity of the collagen-immobilized lipase reached 340 U/g. The activity was recovered of 28.3 % by immobilization. The operational stability of the obtained collagen-immobilized lipase for hydrolysis of olive oil emulsion was determined. The collagen-immobilized lipase showed good tolerance to temperature and pH variations in comparison to free lipase. The collagen-immobilized lipase was also applied as biocatalyst for synthesis of butyl butyrate from butyric acid and 1-butanol in n-hexane. The conversion yield was 94 % at the optimal conditions. Of its initial activity, 64 % was retained after 5 cycles for synthesizing butyl butyrate in n-hexane.     

Black Phosphorus Quantum Dots

As a unique two‐dimensional nanomaterial, layered black phosphorus (BP) nanosheets have shown promising applications in electronics. Although mechanical exfoliation was successfully used to prepare BP nanosheets, it is still a challenge to produce novel BP nanostructures in high yield. A facile top‐down approach for preparation of black phosphorus quantum dots (BPQDs) in solution is presented. The obtained BPQDs have a lateral size of 4.9±1.6 nm and thickness of 1.9±0.9 nm (ca. 4±2 layers). As a proof‐of‐concept application, by using BPQDs mixed with polyvinylpyrrolidone as the active layer, a flexible memory device was successfully fabricated that exhibits a nonvolatile rewritable memory effect with a high ON/OFF current ratio and good stability.     

一类带拒绝的多种类服务系统的平稳分布

本文在文献[2]的基础上考虑了一类有拒绝的可批量到达的服务系统的平稳分布。文章首先给出了Q过程的常返性以及遍历性的充要条件，最后得出了系统的不变测度。     

Heat and spin transport in magnetic nanowires

Transport measurements are carried out in which temperature oscillation is applied to magnetic nanostructures. Using spin valves, this measurement reveals aspects of the spin transport in non-collinear configurations. In one implementation, an AC voltage is detected when a DC current is driven through the nanostructure under test and its temperature is made to oscillate by illuminating it with a laser diode. A simpler approach is presented that relies on Joule heating to generate the temperature oscillation, thus eliminating the need for any optical component.     

Phase shifting nano-moiré method with scanning tunneling microscope

In this paper, a new nano-moiré method using scanning tunneling microscope (STM) is proposed. This method is capable of measuring nanoscopic deformation of matter. The formation mechanism of the STM moiré fringe and the phase shifting technique used in STM moiré fringes are explained in details. Typical experiments are conducted with the crystal lattices of freshly cleaved highly oriented pyrolytic graphite, are used as specimen grating, to generate STM moiré fringe patterns. Phase shifting is realized in four steps from 0 to 2π by controlling the PZT in the STM system to shift the specimen in the vertical direction. This method provides a new way for disposal of moiré fringes pattern in the nano-moiré measurement.     

快速启动锥形节流制冷器的研制

介绍一种可实现快速启动的锥形节流制冷器,具有结构简单,体积小,重量轻,无运动部件,可实现快速启动的优点而广泛应用于制导导弹中用于红外凝视焦平面探测器的冷却.该制冷器采用双层管路绕制结构,具有高效的换热效率;与探测器杜瓦组件进行试验,结果表明充有压力45MPa氩气的100ml钢瓶作为气源,冷板内侧降温至100K所需时间≤2.3s,芯片降温至100K所需时间≤7.21s.     

氧缺位结构介孔二氧化钛/聚乙烯复合隔膜在锂硫电池中的应用

采用两步溶液法合成了一种具有高度氧缺位的黑色介孔二氧化钛, 并将其涂覆在隔膜表面作为锂硫电池复合隔膜, 研究了其在锂硫电池中的电化学性能. 结果表明, 氧缺位的黑色介孔二氧化钛材料不仅展现出良好的导电性, 还能加强对多硫化物的物理和化学吸附能力, 从而显著提高锂硫电池的放电比容量(0.1C倍率下首次放电比容量为1257 mA·h/g)和循环性能(循环100次后放电比容量为821 mA·h/g).