A NEW EXTENSION OF THE HIGH-ORDER VIRASORO ALGEBRA

1 IntroductionVirasoro algebra and W algebra have been widely investigated by both physicists andmahematicians. Virasoro algebra can be thought of as the central extended algebra Of diffeOmorphisms Di$S') on the circle S1. In Ref[1], ftaPpat et al. extended the notion ofloop algebra g(S') to algebra g(M), M being a closed surface with dim M > 1, and gave thefolowing commutation relations:c,[Lk,l, L.,.] = [mp(k -- T) -- ftO(l -- 8)]Lk .,l , ti ll ghO(k -- j) -- fl0(l -- j)lok .,O8l ,,…     

A Novel Route to the Preparation of Poly(N‐isopropylacrylamide) Microgels by Using Inorganic Clay as a Cross‐Linker

Adopting inorganic clay (hectorite) and MBA as physical and chemical cross‐linking agents, respectively, PNIPAM microgels were synthesized by SFEP. The chemical structure and morphology of the microgels were confirmed by FTIR, WXRD, and SEM. The temperature‐sensitivity of the microgels was investigated by DLS and UV spectrophotometers. The results inferred that clay platelets dispersed in an aqueous medium were fully exfoliated and could act as a kind of multifunctional cross‐linking agent and significantly reduced the hydrodynamic diameters of the microgels. In fact, the hydrodynamic diameters of the PNIPAM microgels with clay as cross‐linker ranged from 154 to 322 nm which was much smaller than that using MBA as chemical cross‐linker, the later was in the range of 284–808 nm on heating from 5 to 50 °C.

     

Mechanical Properties of Machined Nanostructures

"Three-dimensional molecular dynamics simulations have been carried out to predict the mechanical properties of a single crystalline copper with different scratching depths and no defects by embedded-atom method potential respectively. The mechanical properties for nanostructure with no defects and machined groove are investigated by various strain rates, scratched depths and scratching directions. Through the visualization technique of atomic coordination number, the onset and movement of defects in workpiece such as dislocations are analyzed under tensile loads. Work-harden formation, recrystallization behavior and the properties of rupturing process of nanostructure are exhibited at the atomic view. The relation between stress and the onset and evolvement of defects in specimen is analyzed for fundamental understanding the mechanical properties of nanostructure."     

季铵盐参与的直接化学选择性O-和N-烷基化反应

将羧酸或胺类化合物与季铵盐进行简单的混合加热,便可直接得到O-或N-烷基化产物。季铵盐中烷基的转移具有较好的选择性,其优先顺序为：苄基〉伯烷基〉仲烷基。     

甲醇水蒸汽催化转化制氢研究进展

氢气是石油炼制和化学工业的重要原料 .传统的大规模制氢 ,大多采用天然气、轻油、煤焦为原料造气 ,再用深冷或吸收吸附法提取氢气 ,工艺复杂 ,投资大 ,能耗高 .中小规模制氢 .一般采用电解水法 ,缺点是电耗大 .近年来 ,也采用变压吸附技术 ( PSA)从石化过程产生的含氢气体中回收氢气 ,但受具体条件的限制[1 ] .与上述方法相比 ,甲醇 -水蒸汽转化制氢具有独特的优势 .与大规模制氢相比 ,该方法工艺流程短 ,设备简单 ,投资和能耗低 ;与电解水制氢相比 ,甲醇 -水蒸汽转化制氢可降低电耗 90 %以上 ,成本降低 30 %～ 50 % ,甲醇 -水蒸汽制氢成…     

相转移法制备Cu-Mn合成气一步法合成甲酸甲酯催化剂

采用月桂酸作表面活性剂相转移制备了Ｃｕ－Ｍｎ合成甲酸甲酯催化剂,结果发现相转移法制得的催化剂粒径比采用共沉淀法要小得多,已经达到了纳米超细粒子水平。同时,比表面积也显著增大,用于由合成气一步法合成甲酸甲酯的活性显著高于共沉淀法及浸渍法制得的催化剂。     

萜烯低聚物与马来酸酐的加成反应及其制备环氧树脂的研究

松节油经阳离子聚合反应可生成聚萜烯。其中分子量较大 ,软化点在 80℃以上部分称为萜烯树脂 ,广泛用作热熔胶、压敏胶的增粘剂。而分子量较小 ,常温下为液体的部分称萜烯低聚物 ,由于其软化点低 ,一般不适合作增粘剂使用。迄今为止 ,萜烯低聚物作为一种工业副产品 ,国内外尚未见有效的利用。目前 ,我国萜烯树脂年生产能力近 2 0 0 0 0吨 ,其中每年副产萜烯低聚物 30 0 0多吨 ,均用作燃料使用。如能将这部分产品进行化学改性 ,制备出适合于工业用途的精细化学品 ,将会大大提高其价值。萜烯低聚物的成分比较复杂 ,主要是三萜和二萜聚合物 ,其…     

A quantum chemistry study on C–H homolytic bond dissociation enthalpies of five-membered and six-membered heterocyclic compounds

The C–H homolytic bond dissociation enthalpies (BDEs) of 27 heterocyclic compounds of small systems (less than 8 non-hydrogen atoms) were evaluated by the composite ab initio methods of G4 and CBS-Q. In addition, the C–H BDEs of an extended database including 60 heterocyclic compounds were assessed by 16 DFT functionals. The correlation between the theoretical and experimental values reveals that the BMK functional provided the lowest root mean square error (RMSE) of 10.2 kJ/mol, and the correlation coefficient (R²) was 0.955. The mean deviation (MD), mean absolute deviation (MAD) of BMK are 0.1 kJ/mol and 7.9 kJ/mol separately. Therefore, we utilized BMK to research C–H BDEs together with the substituent effects of five-membered and six-membered heterocyclic compounds including large systems. The nature of C–H BDE change pattern was analyzed by the natural bond orbital (NBO).     

A Porous 4d–4f Heterometallic Coordination Polymer: Synthesis,Crystal Structure and Physical Properties

A 4d–4f heterometallic coordination polymer, [AgLa(pydc)₂]·3H₂O ( 1 ) (H₂pydc = pyridine‐3,4‐dicarboxylic acid), has been synthesized under hydrothermal conditions, and further characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and single‐crystal X‐ray diffraction. Complex 1 features a three‐dimensional (3D) framework containing one‐dimensional (1D) channels occupied by free water molecules, which is constructed from 1D inorganic heterometallic chains and linear pydc linkers. To the best of our knowledge, complex 1 represents a rare example of 3D open‐framework 4d–4f heterometallic coordination polymer. Moreover, after removal of the water molecules from complex 1 , the remaining material has high thermal stability and good adsorption behavior towards nitrogen gas.     

E-CUSP scheme for the equations of ideal magnetohydrodynamics with high order WENO Scheme

An E-CUSP (energy-convective upwind and split pressure) scheme is developed to solve the equations of magnetohydrodynamics. Fifth order WENO reconstructions are employed to calculate the fluxes in order to achieve high order spacial accuracy. A characteristic speed of sound by averaging the fast wave speed and the acoustic speed of sound is suggested to evaluate the Mach number, which will yield robust and accurate solutions. The numerical experiments have demonstrated the accuracy and the capability of the new scheme to capture complex interactions of multiple shocks and vortices.