RAPID DETERMINA TION OF L—GLUTAMIC ACID WITH AN ENZYME REACTOR OFL—GLUTAMIC DECARBOXYLASE IMMOBILIZED ON ION EXCHANGE RESIN

The preparation and characterization of an immobilized L-glutamic decarboxylase(GDC) were studied.This work is to develop a sensitive method for the determination of L-glutamate using a new biosensor,which consists of an enzyme column reactor of GDC immobilized on a novel ion exchange resin(carboxymethyl-copolymer of allyl dextran and N.N‘-methylene-bisacrylamide CM-CADB) and ion analyzer coupled with a CO2 electrode.The conditions for the enzyme immobilization were optimized by the parameters:buffer composition and concentration,adsorption equilibration time,amount of enzyme,temperature,ionic strength and pH.The properties of the immobilized enzyme on CM-CADB were studied by investigating the initial ate of the enzyme reaction,the effect of various parameters on the immobilized GDC activity and its stability.An immobilized GDC enzyme column reactor matched with a flow injection system-ion analyzer coupled with CO2 electrode-data collection system made up the original form of the apparatus of biosensor for determining of L-glutamate acid.The limit of detection is 1.0×10^-5M.The linearity response is in the range of 5×10^-2-5×10^-5M.The equation of linear regression of the calibration curve is y=43.3x+181.6(y is the milli-volt of electrical potential response,x is the logarithm of the concentration of the substrate of L-glutamate acid).The correlation coefficient equals 0.99.The coefficient of varioation equals 2.7%.     

气相色谱法定量分析α－乙酰－γ－丁内酯

 ?Butyrolactone, α-acetyl-γ-butyrolactone and solvent in reaction mixtures from the preparation of α-acetyl-γ-butyrolactone were determined by gas chromatography.The analytes were separated at 190℃ on a 1m ×3mm stainless-steel column packed with silanized 102 white support coated with polydiethylene glycol succinate and monitored with a thermal conductivity detector. The relative error was less than 2.5%.     

MICROMOLDING ON CURVED SURFACES WITH THERMOPLASTICS

Microstructures were produced on curved surfaces and micro-protrusions by using direct micromolding with fourthermoplastic polymers. This method is simpler and more convenient than micromolding with liquid prepolymer or using theμTM method. By repeated molding, crossed structures were produced with a stamp prepared only with lines. The processingvariables including the softening temperature of the polymers and heating time were discussed. The result shows that theoptimal molding temperature is preferably slightly higher than the melting temperature of the thermoplastic polymers, atwhich polymers are in the critical states of being melted. This method can be applied to many polymers except those with high softening temperatures or high rate of shrinkage upon temperature change.     

聚乙烯吡咯烷酮稳定的钯纳米粒子催化加氢

Nanosized colloidal platinum was prepared by reduction of H2PtCl6 in methanol-water mixture by refluxing. The particle size and morphology were characterized by transmission electron microscopy and electron diffraction. The influence of polyvinylpyrrolidone (PVP) molecular mass (MM),PVP concentration,and reduction time on platinum particle size was investigated. Small (1-2 nm) Pt particles are formed in the case of PVP with MM=1.2×104. With increasing polymer MM and decreasing polymer concentration,large aggregates from small particles appear. High catalytic activity of the obtained colloidal platinum in hydrogenation of acetylene compounds is shown. The effect of Pt particle size on the catalytic activity was studied.     

Determination of Sulpiride by Linear Sweep Stripping Voltammetry at a Mercury Electrode

This paper reports the electrochemical properties of sulpiride at a mercury electrode,especially its adsorptive characteristic,Sulpiride dissolved in a supporting electrolyte of a McIlvaine buffer at pH 6.8 represents a sensitive and well defined reduction wave by linear sweep stripping voltammetry.This method is based on the pre-concentration and the reduction of sulpiride at a hung mercury drop electrode.The reduction peak potential is -1.72V(vs.Ag-AgCl) and the peak current is proportional to the concentration of sulpiride in the range of 0.1-0.6 μg/mL.The detection limit is 0.0250μg/mL obtained under the experimental conditions selected in this work.The electrochemical properties of this system were investigated.and the proposed method was applied to the determination of sulpiride in pharmaceutical tablets with satisfactory results,It was compared well with the UV spectrophotometric method,showing a superior sensitivity.     

Syntheses, Confirmation and Properties of Porphyrin Oligomers with Alkoxyl Linkages

A new and general synthesis of a porphyrinK( Ⅰ ) with two alkoxyl linkages is described. The synthesis involves the reaction of dibromopropane with phenolic porphyrin to form ω-bromopropylporphyrin ether. This ether then reacts with another phenolic porphyrin to give the target compounds. The properties of the target compounds were confirmed by means of elemental analysis, UV-Vis, IR, and ^1H NMR spectroscopies. Their spectral properties and thermal stability were also studied.     

STUDIES ON ULTRASONIC ABSORPTION AND VISCO-RELAXATION OF POLY (ETHYLENE GLYCOL) AQUEOUS SOLUTIONS

Ultrasonic absorption and velocity measurements were made on aqueous solutions of poly (ethylene glycol)(PEG)of different molecular weights and concentrations, using a pulse sender-receiver ultrasonic generator, Measurements were obtained at a frequency of 2MHz. , and a temperature of 293 K. The results show a linear increase of the Values of velocity, density and viscosity with increase of molecu lar weight and concentration of PEG. On the contrary, the attenuation values decreased with increase of molecular weight and concentration of PEG. A mathematical equation correlating relaxation amplitude and molecular weight of the polymer is suggested. This was applied to calculate the molecular weights of unknown samples of PEG from their measured relaxation amplitude. The results obtained were in good agreement with those obtained from osmometry.     

An efficient green synthesis of dispirohydroquinolines via a diastereoselective one-pot eight-component reaction

The one-pot eight-component reaction between Meldrum's acid, an aromatic aldehyde, and an aryl amine was achieved in the presence of citric acid catalyst. The corresponding dispirohydroquino-lines were obtained in good yields with excellent diastereoselectivity. This method is a combination of the Knoevenagel and Michael reactions.     

NEURAL NETWORK ANALYSIS APPLICATION TO PERMEABILITY DETERMINATION OF FIBERGLASS AND CARBON PREFORMS

Preform permeability is an important process parameter in liquid injection molding of composite parts.This parameter is currently determined with time consuming and expensive experimental procedures.This paper presents the application of a back-propagation neural network to predicting fiber bed permeability of three types of reinforcement mats. Resin flow experiments were performed to simulate the injection cycle of a resin transfer molding process.The results of these experiments were used to prepare a ...     

A New Approach to the Asymmetric Reaction of the Chiron 5－L－Menthyloxy－2（5H）－furanones with Horner－Emmons Reagent

The asymmetric reaction of the chiron 2(5H )-furanones (4a-4c) with the Horner-Emmons reagents (5a-5b) has been investigated. The newly chirai organophosphorus derivatives 6 and 7 were obtained using the phosphoryl-stabilized carbanion as a building block in DMSO under mild conditions. Through the asymmetric introduction, the Horner-Emmons reagent could be transformed to a chiral building block to afford the novel functionalized phosphorus derivatives. The structures of the synthesized compounds 6 and 7 were identified on the basis of their elementary and spectroscopic data, such as IR,^1H NMR, ^13C NMR, MS and X-ray crystallography. These resuits provided a valuable approach to the synthesis of potentially interesting chirai organophosphorus derivatives and probing their biological activities.     

Design and Synthesis of a Highly Stable Six-hydrogen-bonded Serfassembly Yellowish Green Electroluminescent Molecular Duplex

This paper describes the design, synthesis and characterization of a hydrogen-bonded molecular duplex with 1,8-naphthalimide fluorescent pendants. The two oligoamide molecular strands, with complementary hydrogen bond sequences of DDADAA and AADADD, can form an ultra stable self-assembly duplex. Its molecular structure was confu-med by ^1H NMR and ESI-MS, and its photoluminescence properties were determined. The resulting duplex exhibited a dramatically enhanced photoluminescence （PL） quantum efficiency of 63.7% compared to the corresponding 1,8-naphthalimide segment （32.4%）, suggesting that the formation of the duplex with larger molecular weight could successfully inhibit the quenching of the fluorescent pendant. This novel duplex is a prospective candidate for new electroluminescent emitter.     

PROPERTIES AND THERMODYNAMICS OF ADSORPTION OF BENZOIC ACID ONTO XAD-4 AND A WATER-COMPATIBLE HYPERCROSSLINKED ADSORBENT

The adsorption behavior of benzoic acid onto a water-compatible hypercrosslinked polymeric adsorbent NJ-8 wascompared with that onto macroporous Amberlite XAN-4. This paper focuses on the static equilibrium adsorption behaviors,the adsorption thermodynamics and the column dynamic adsorption profiles. Five isotherm models are used to fit the results.This shows that the Freundlich equation can give a perfect fit. The specific surface area of NJ-8 is about as high as that ofAmberlite XAD-4, but the adsorbing capacity for benzoic acid on NJ-8 is about 14.9%-64.8% higher than that on AmberliteXAD-4, which is attributed to its microporous mechanism and partial polarity. The negative values of the adsorptionenthalpy are indicative of an exothermic process. Both enthalpy and free energy changes of adsorption manifest a physicalsorption process. The negative values of the adsorption entropy indicate that adsorption is well consistent with the restrictedmobilities and the configurations of the adsorbed molecules on the surface of the studied adsorbents with superficialheterogeneity. Both adsorbents were used in mini-column experiments to demonstrate the higher breakthrough adsorbing capacity of the hypercrosslinked polymeric adsorbent NJ-8 to benzoic acid, as compared with that of Amberlite XAD-4.     

Surface Modification of Nano－SiO2 by Grafting PMMA／PBA

The surface of nano-SiO2 was modified by being encapsulated with hydroxy-propyl-methyl cellulose (HPMC), and then co-grafted with acrylates. The grafting conditions, such as pH of the medium, and initiator concentration have been studied. The modified nano-SiO2 particles were characterized by TEM, DSC and FT-IR spectra. TEM images show that the surface of the nano-particles has been successfully modified by a thick layer of film-like polymer in this way. The DSC results show that the decomposition temperature of modified nano-particles of SIO2 is 90 ℃ higher than that of grafted-on polymer. According to the FT-IR spectra, It is convinced that poly-methyl methacrylate ( PMMA ) and poly-acrylic butyl-ester ( PBA ) were co-grafted onto the surface of nano-SiO2.     

A pneumatic micromixer facilitating fluid mixing at a wide range flow rate for the preparation of quantum dots

A novel fluid micromixer based on pneumatic perturbation and passive structures was developed. This micromixer facilitates integration and is applicable to fluid mixing over a wide range of flow rates. The microfluidic mixing device consists of an S-shaped structure with two mixing chambers and two barriers, and two pneumatic chambers designed over the S-shaped channel. The performance of the micromixer for fluids with wide variation of flow rates was significantly improved owing to the integration of the pneumatic mixing components with the passive mixing structures. The mixing mechanism of the passive mixing structures was explored by numerical simulation, and the influencing factors on the mixing efficiency were investigated. The results showed that when using a gas pressure of 0.26 MPa and a 100 m-thick polydimethylsiloxane (PDMS) pneumatic diaphragm, the mixing of fluids with flow rates ranging from 1 to 650 L/min was achieved with a pumping frequency of 50 Hz. Fast synthesis of CdS quantum dots was realized using this device. Smaller particles were obtained, and the size distribution was greatly improved compared with those obtained using conventional methods.     

纳米氧化钴－氧化钌复合型超级电容器的研究

A novel type of composite electrode based on sheet like cobalt oxide particles has been used in supercapacitors. Cobalt oxide cathodically deposited from Co（NO3）2 solution with carbon nanotubes as matrix exhibited large pseudo-capacitance of 322 F·g^-1 in 6 mol·L^-1 KOH. A sol-gel process for the preparation of ultrafine RuO2 particles was developed to design electrodes with large surface area. The composite electrodes were developed by the deposition of RuO： on the surface of carbon nanotubes. A specific capacitance of 785 F·g^-1 can be achieved with the 20% carbon nanotubes loaded. To characterize the metal oxide nanocomposite electrode, a cyclic voltammetry and AC impedance test are executed. This study also reports a hybrid capacitor, which consists of cobalt oxide composite as a cathode and ruthenium oxide composite as an anode. The electrochemical performance of the hybrid capacitor is characterized by a dc charge/discharge test and cyclic voltammograms. The hybrid capacitor shows capacitor behavior with an extended operating voltage of 1.4 V. The maximum energy density and specific power density of the cell reach the value of 23.7 and 8.1 kW·g^-1 respectively. The hybrid capacitor exhibits high-energy density and stable power characteristics.     

Electrochemical Study on the Interaction of Protein with Bromothymol Blue and Its Analytical Application

The interaction of bromothymol blue（BB） with human serum albumin（HSA） was studied by electrochemical techniques and a sensitive method for proteins assay was developed. When BB interacted with HSA, the voltammetric peak current value of BB decreased linearly with the concentration of HSA in a range of 1.0--40.0 mg/L, and the peak potential shifted negatively. Based on the results, a sensitive assay method for proteins, such as HSA, bovine serum albumin（BSA）, and egg albumin etc. was established. This method was further applied to determining the HSA in healthy human blood samples, and the results are not significantly different from those obtained by the classic Coomassie Brilliant Blue G-250 spectrophotometic method. The detecting conditions of this method were optimized and the interaction mechanism was discussed. The results show that the electrochemical parameters（formal potential E^0, standard rate constant of the electrode reaction ks, parameter of kinetic nα） of BB have no obvious changes before and after the interaction, which indicate that BB can interact with HSA, forming an electrochemical non-active complex. The equilibrium constant（βs） and the binding ratio（m） for this complex were calculated. The m is 4 and βs is 1.41 × 10^19. This method is fast, simple, highly sensitive, and has good selectivity, which can be used in clinical measurements.     

SYNTHESIS, MOLECULAR STRUCTURE, SPECTRA AND ELECTROCHEMISTRY OF TWO GEOMETRIC ISOMERS OF TETRAKIS(2-ANILINOPYRIDINATO) DIRHODIUM*

Two gemetric isomers of new dirhodium complex, Rh_2(ap)_4(ap=2-anilinopyridinato),have been synthesixed and isolated. The isomers were characterized by a single-crystal X-ray diffraction analysis. They are 4,0 gemeter (compound 1) and 2,2 trans geometer (compound 2).The radical cations of 1and 2are ESR active. The ESR spectrum of 1+ions, reports that the order of g value is g_⊥>g_e>∥,and the value of g is split into doublet at 77K. This result is consistent with a calculation of the self-consistent-charge discrete variational method. It is shown conclusively that the odd electron is localized on one rhodium. ion with no bound axial ligand, thus giving the first example of true Rh(Ⅱ )—Rh(Ⅲ) complex. The ESR spectrum of 2+ shows g split into a 1:2:1 trilet .In addition, cyclic voltammetry and ESCA of two isomers were detrmined and analyxed. The results indicate that Rh_2(ap)_4 is not only chemically reactive but also sensitive to photochemical oxidation, thus having a wide application in future.     

Functionalizing ps microspheres by supercritical deposition of P(S-<Emphasis Type="Italic">b</Emphasis>-<Emphasis Type="Italic">t</Emphasis>BA) for diverse interfacial properties exemplified with biocidal ability

Polystyrene（PS） microspheres were functionalized with poly（styrene-b-tert-butyl acrylate）（P（S-b-tBA）） by adsorption from supercritical mixture of CO₂ and hexane.Supercritical deposition formed a shell-core structure that contained a shell of poly（tert-butyl acrylate）（PtBA） blocks and a core of the PS blocks entangling with the PS microspheres. The thickness of the PtBA layer and thereby the areal density of tert-butyl ester groups increased with the deposition pressure until plateau values attained at 20 MPa and higher.The tert-butyl ester groups were hydrolyzed to carboxyl groups for conjugation with tert-butylamine molecules via amide bonds that were further chlorinated into biocidal N-halamine moieties. The functionalization layer and its bonded N-halamine moieties were stable in flowing water and the chlorine could be regenerated upon eventual loss.This functionalization concept is applicable to polymers of any external and internal surfaces to achieve diverse surface properties by varying block copolymer and conjugated moieties.     

STUDY ON AB-CROSSLINKED POLYMERS Ⅰ. THE SYNTHESIS AND MECHANICAL PROPERTIES OF AB-CROSSLINKED POLYMERS BASED. ON PU/PS

The AB-crosslinked polymers (i.e. ABCP) with polystyrene as chain A and vinyl group blocked prepolymers of polyurethanes (PU) as chain B were synthesized and studied. The results of dynamic mechanical spectrometry (DMS) show that the compatibility between the components A and B can be improved greatly through chemical crosslinking during the formation of ABCPs. This effect is especially pronounced when short chain prepolymers is chosen as one of the components. It is apparent that the degree of crosslinking between the two components plays a major role in determining their compatibility. Copolymerizafion of styrene with maleic anhydride in chain A can improve the compatibility and broaden the damping temperature range. Mechanical properties of the sythesized ABCPs were also studied.     

The Thermal Decomposition of Calcium Carbonate

The thermal decomposition reaction of calcium carbonate is a typical thermal decompo- sition reaction of the solid state. A great deal of studies on this reaction have been performed by previous investigators. This paper reports a procedure for estimating the non-isothermal kinetic parameters and the reaction mechanism of calcium carbonate.TG-DTG experiments were carried out on a LCT-1 model thermobalance and a WF-1 model differentiator with a TG-DTA-DTG simultaneous device. The size of…