Hydrolytic and transglycosylation reactions of N-acyl modified substrates catalysed by β-N-acetylhexosaminidases

The hydrolytic and transglycosylation capabilities of 35 fungal β-N-acetylhexosaminidases with p-nitrophenyl 2-amino-2-deoxy-β-d-glucopyranoside and its four N-acyl derivatives (CHO, COCH₂OH, COCH₂CH₃, COCF₃) as substrates were tested. The preparation of four novel p-nitrophenyl disaccharides from these unnatural substrates catalysed by enzymes from Aspergillus oryzae, Penicillium oxalicum and Talaromyces flavus represents a considerable extension of the synthetic potential of glycosidases.     

Applications of surfactant-modified clays to synthetic organic chemistry

Two triphase catalysts (SLL) have been developed for organic phase-aqueous phase reactions catalyzed by suitable modified clay (solid phase). These triphase catalysts have been applied to nucleophilic displacement on activated (benzylic) as well as unactivated organic halides and provide a convenient and effective method of preparation of the corresponding products. Other useful transformations to, which these triphase catalysts have been successfully applied are the synthesis of 9,9-dichloro bicyclo[6.1.0]nonane, O-alkylation and C-alkylation of β-naphthol.     

Multilayer films of cationic surfactants incorporating polyoxometalate on electrodes

A new kind of multilayer of didodecyldimethylammonium bromide (DDAB) and 1:12 phosphomolybdic anions (PMo₁₂) was achieved on the surface of a wax-impregnated graphite (WIG) electrode by ion exchange and electrostatic interaction. The characterization and electrochemical behavior of the multilayer films of DDAB/PMo₁₂ is described in detail. The chemically modified electrode was shown to exhibit an excellent electrocatalytic activity toward the reduction of BrO₃ ^– anion in 0.5 M H₂SO₄ and possesses several attractive features, such as simple preparation, fast response, good stability, etc. Electronic Publication     

四硝基酞菁合钴化学修饰电极的制备及对氧的电催化还原

合成了4,4′,4″,4″′—四硝基酞菁合钴(Ⅱ),并进行了表征,用不可逆吸附法制备了该化合物为修饰物的化学修饰电极,以光电子能谱法进行了表面表征。并研究了分子氧在该化学修饰电极上的电化学行为,发现该化学修饰电极对氧的还原有明显的电催化作用。     

修形ZI蜗轮滚刀齿形合格长度的研究

本文研究了修形ZI蜗轮滚刀齿形误差的计算方法,从理论上分析了滚刀设计参数和铲磨工艺参数对齿形误差的影响,提出了变砂轮中心高铲磨新工艺,为增加滚刀齿形合格长度开辟了新途径．     

硫酸钡改性新型甲基化环糊精毛细管色谱柱柱行为的研究

在硫酸钡微晶对毛细管内壁改性的基础上,系统制备了甲基环糊精与不同混合固定液的毛细管色谱柱,从柱的分离选择性,惰性,柱效和分析准确性等方面作了较为系统的研究,并对环糊精的分离机理作了初步探索。     

Coil-to-globule transitions of interfacial copolymers in better than theta-solvents

Experimental studies of the coil-to-globule transitions exhibited in better than -solvents by interfacial copolymers ofN-isopropylacrylamide and acrylamide imply that a lower bound for the value of n in then-clusters of poly(N-isopropylacrylamide) (PNIPAM) is 3. The corresponding upper bound is therefore likely to be 5 or 6. Statistical copolymers of PNIPAM containing upwards of 0.75 mole fraction of acrylamide (whose homopolymer does not itself displayn-clustering) exhibited this transition, which disappeared at higher mole fractions of acrylamide. Interfacial homopolymers ofN-ethylacrylamide and its statistical copolymers withN-isopropylacrylamide exhibitedn-clustering at all compositions.     

Limit cycle analysis of a class of strongly nonlinear oscillation equations

The limit cycle of a class of strongly nonlinear oscillation equations of the form % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiGc9yrFr0xXdbba91rFfpec8Eeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqGaaO% qaaiqadwhagaWaaiabgUcaRmXvP5wqonvsaeHbbjxAHXgiofMCY92D% aGqbciab-DgaNjab-HcaOiaadwhacqWFPaqkcqWF9aqpcqaH1oqzca% WGMbGaaiikaiaadwhacaGGSaGabmyDayaacaGaaiykaaaa!50B8!\[\ddot u + g(u) = \varepsilon f(u,\dot u)\] is investigated by means of a modified version of the KBM method, where is a positive small parameter. The advantage of our method is its straightforwardness and effectiveness, which is suitable for the above equation, where g(u) need not be restricted to an odd function of u, provided that the reduced equation, corresponding to =0, has a periodic solution. A specific example is presented to demonstrate the validity and accuracy of our 09 method by comparing our results with numerical ones, which are in good agreement with each other even for relatively large .     

二硫代氨基甲酸螯合树脂化学修饰电极的制备及银离子的测定

将纯石墨电极经三氧化二铝抛光与浓硝酸和浓硫酸(1+1)混合酸使其极性化,之后于1 g·L-1聚氯乙烯(PVC)环己酮溶液10μL中浸渍片刻,取出,用红外灯照射烘干30 min,冷却后,将电极置于含有哌嗪、K3PO4及二甲基甲酰胺(DMF)(2:1:8)的混合液中使其反应;最后在氢氧化钠存在下与二硫化碳反应,用水洗至中性,即制成修饰有二硫代氨基甲酸螯合树脂的石墨电极,将其用于银的测定。与未修饰的电极相比此电极具有较高的灵敏度和较好的选择性,在1．0×10-8～1．0×10-5mol·L-1范围内,峰电流与浓度呈线性关系,检出限为5．0×10-9mol·L-1。