A NOVEL EOR POLYMER (Ⅱ)——INVESTIGATION ON IN-SITU GELATION OF SMRF SYSTEM IN BEREA CORE

In-situ gelation of aqueous sulfomethylated resorcinol formaldehyde (SMRF) system inBerea core has been investigated. Two sets of displacement experiments were conducted with thissystem (containing 5% NaCl, 0. 036% CaCl_2. 2H_2O). The brine permeabilities of the coreswere reduced significantly from about 600 to 0.1 md. The in-situ gelation in Berea core occurreda little bit earlier than gelation anticipated from bulk test in the experiments. The gel time waseasier to control at initial pH between 6 and 8. During injection of SMRF system, the apparentviscosity was less than 1 mPa·s at 41℃.     

THE STUDY OF ADAPTABILITY OF Drepanopus bispinosus TO TEMPERATURE AND SALINITY IN THE ANTARCTIC BURTON LAKE

The tolerance to temperautre and salinity of a Calanoida copepod: Drepanopus bispinosus from the Burton Lake in the Vestfold Hills, Antarctica, was tested in each season. The results obtained show that the copepod has a marked physiological property of tolerance to low temperature and high salinity, and this property could be strengthened after winter. The response to different temperature and salinity of the copepod evidently expressed the tardy characteristics contrasted with seasons. This means that for a long term in early winter(lower temperature and higher salinity) the animal still has higher tolerance to lower salinity and higher temperature; and it is opposite in early summer. These physiological features are possibly caused by natural acclimatization in the lake. The experimental data were processed and plotted by computer. The correlation of animal's survival rate with the changes of temperature and salinity presented an approximately smooth surface of a three-degree elliptic sphere.     

Solvent-induced molecular gel formation at room temperature and the preparation of related gel-emulsions

The gelation behaviors of four recently reported amphiphilic cholesteryl derivatives (1, 2, 3 and 4) have been evaluated. It was found that the gel formation process can be controlled by introduction of water at room temperature. Addition of water to an acetone solution of 4 immediately results in the system becoming turbid, and a gel subsequently forms within a few minutes. Interestingly, 4 is a super-gelator for a mixed solvent of acetone and water at room temperature, in particular when their volume ratio is close to 1:1 at which the critical gelation concentration (CGC) is 0.06% (w/v). It was found that the introduction of water favors the formation of gel networks, and the gel possesses smart and reversible thixotropic properties. FTIR and 1H NMR spectroscopy confirmed that hydrogen bonding is one of the main driving forces for the gelation of the solvents. XRD demonstrated that 4 self-assembled into a layered structure within the acetone-water mixed solvent gel. Furthermore, 1 and 2 can be used as excellent stabilizers for gel emulsions of alkanes and water. The maximum of the dispersed phase, water, in one of the gel-emulsions can be as high as 97% (v/v).     

Polyglutamic acid based polyanionic shielding system for polycationic gene carriers

For the purpose of increasing the in vivo stability of polycation gene carriers, we prepared a kind of p H-sensitive poly(ethylene glycol)-poly(γ-benzyl-L-glutamate-co-glutamic acid)(PEG-PGA(65), 65 denotes the molar ratio of glutamic acid in poly(γ-benzyl-L-glutamate-co-glutamic acid)). PEG-PGA(65) showed low cytotoxicity and could shield the positive charge of DNA/PEI(1:1) polyplexes efficiently. The transfection was enhanced due to the partially charge shielding in He La cell line at pH of 7.4. There was almost no transfection efficiency when the surface charge of the ternary particles turned to negative at p H of 7.4. However, the transfection efficiency recovered a lot by culturing at p H of 6.0 at the beginning of transfection. Confocal microscopic observation and flow cytometry results showed DNA/PEI polyplexes should be efficiently released and endocytosized at p H 6.0, because of the p H triggered deshielding action of PEG-PGA(65). Due to the good biocompatibility and suitable p H triggered shielding/deshielding property, PEG-PGA(65) could be a potential shielding system for polycationic gene carriers used in vivo.     

IMMOBILIZATION OF GLUCOSE OXIDASE AND CELLULASE BY CHITOSAN— POLYACRYLIC ACID COMPLEX

This study is concerned with chitosan-polyacrylic acid complex as a carrier to immobilize glucose oxidase (GOD)and cellulase. The optimum emperature of the immobilized GOD (IG) was determined to be 60℃which is higher than that of the native GOD about 40℃. The optimum temperature of the immobilized cellulase (IC) was determined to be about 30℃higher than that of native cellulase. Both of the optimum pH of IG and IC shifted one pH unit to acid. Immobilized enzyme may be used in more wide pH range. Their storage life are much longer compared with their native states. Both of them can be reused at least 12 times.     

Computer Simulation on Kinetics of Primary Processes in Photosynthesis Ⅰ——Mechanism of Exciton Annihilation of Excited State Decay in Phycobiliproteins

A discrete model was used for studying the effects of exciton annihilation on the decay behavior of the excited state in phycobiliprotein super-molecules. The simulation shows: The more the chromophores are and the higher the excitation beam intensity is, the more susceptible to annihilation is a system; annihilation starts to occur at 10~(13) photons/cm~2 and becomes saturated at about 10~(15)—10~(16) photons/cm~2 with the parameters used in the current work. Whether the exciton annihilation occurs or not should not be simply judged from whether the decaying data could be fitted with a mono-exponential function. The quantum yield of fluorescence decreases synchronously with the increase of exciton annihilation extent. The so called "safety intensity" has significance only in special cases. In fact, annihilation extent is dependent not only on the pulse intensity but also on the width of the pulse, the optical cross section of a chromophore as well as the light absorption coefficient of a system.     

Study of viscoelastic properties of white carbon black reinforced synthetic polyisoprene

The viscoelastic properties of synthetic polyisoprenes(PI) reinforced by white carbon black(WCB) have been investigated and compared with WCB reinforced natural rubber(NR), including cure characteristics, physio-mechanical and dynamic mechanical properties. Compared with NR, PI loaded with the same amount of WCB(PI/WCB) exhibited shorter scorch time and optimal cure time, indicating that WCB fillers are comparatively easier to conjugate with PI. The tensile strength and elongation at break decreased with WCB filling in both PI and NR vulcanizates. The hardness of the rubber vulcanizates increased with the WCB filling in the rubber matrix. PI/WCB blends exhibited smaller hardness data, lower tensile strength, as well as lower elongation at break and tensile stress. Increasing the amount of WCB in rubber matrix induced the Payne effect. However, the Payne effect is much more obvious for the PI/WCB system, and PI/WCB also displayed higher storage modulus whereas lower loss modulus and loss tangent than NR/WCB, which could all be attributed to the poor dispersibilities of WCB in the PI matrix.     

THE METHOD OF LASER LIGHT SCATTERING ON NETWORK COPOLYMERIZATIONS

Laser light scattering method introduced in this paper is a new method to study macromolecular gelation.The most prominent features of the methods are its high sensitivity and use of the scanning technique, whereupon the parameters describing the properties of reaction process at a macro level can be obtained. They are the speed and the point of gelation and the point of phase separation. The parameters describing the inhomogeneous changes in reaction systems at a sub-micro level can also be obtained. They include a (the correlation coefficient) and (the mean squared dilectric constant fluctuation). Thus, the tracks describing the inhomogeneous changes in reaction systems can be traced. The method presented here will provide a new approach to decpening understanding of the gelation process.     

MORPHOLOGY,INTERFACIAL INTERACTION AND PROPERTIES OF STYRENE-BUTADIENE RUBBER/MODIFIED HALLOYSITE NANOTUBE NANOCOMPOSITES

 A natural nanotubular material, halloysite nanotubes (HNTs), was introduced to prepare styrene-butadiene rubber/modified halloysite nanotube (SBR/m-HNT) nanocomposites. Complex of resorcinol and hexamethylenetetramine (RH) was used as the interfacial modifier. The structure, morphology and mechanical properties of SBR/m-HNT nanocomposites, especially the interfacial interactions, were investigated. SEM and TEM observations showed that RH can not only facilitate the dispersion and orientation of HNTs in SBR matrix at nanometer scale, but also enhance the interfacial combination between HNTs and rubber matrix. FTIR and XPS investigations confirmed that a number of hydrogen bonds were formed between the phenol hydroxyl groups in resorcinol-formaldehyde resin derived from RH and the oxygen atoms in Si―O bonds or hydroxyl groups on HNTs surfaces. The m-HNTs modified with RH have significant reinforcing effect on SBR vulcanizates. RH as a good interfacial modifier can remarkably improve mechanical properties of SBR/HNT composites. The substantial improvement of comprehensive properties for SBR/m-HNT nanocomposites can be attributed to good dispersion and orientation of HNTs in SBR matrix at nanometer scale and the enhanced interfacial interaction between HNTs and rubber matrix.     

Enantioselective epoxidation of nonfunctionalized alkenes catalyzed by recyclable new homochiral bis-diamine-bridged bi-Mn(salen) complexes

Three new homochiral bis-diamine-bridged bi-Mn(salen) complexes were synthesized. Their catalysis on asymmetric epoxidation of α-methylstyrene, styrene and indene was studied with NaClO and m-CPBA as oxidants respectively. This homogeneous catalyst exhibited comparable catalytic activity and enantioselectivity to the Jacobsen’s catalyst in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the catalyst could be conveniently recovered and reused at least five times without significant losses of both activity and enantioselectivity. Specially, it also could be efficiently used in large-scale reactions with superior catalytic disposition being maintained at the same level, which provided the potential for the applications in industry. The effect of axial bases, temperature and solvent on activity and enantioselectivity of the catalytic system were also studied.     

Synthesis and Properties of a Biodegradable Dendritic Magnetic Resonance Imaging Contrast Agent

Novel biodegradable dendritic contrast agents (DCAs) based on polyester dendrimers were synthesized and characterized.The DCAs were stable at acidic pH,but hydrolyzed rapidly at physiological pH,which rendered the DCA's long-term Gd3+ retention as low as that of small molecule CAs.Their longitudinal relaxivities of 10.2 to 17.5 L·mmol-1·s-1 were about 2.4 to 4.1 times higher than that of DTPA-Gd,indicating their superior contrast-enhancing capability to the clinically used contrast agent.The in vivo MRI study suggested that the DCA at lower generation (G2-DTPA-Gd) could effectively enhance the MRI of tumor,while the one at higher generation (G5-DTPA-Gd) showed more potential in liver imaging.     

Simultaneous laser-induced fluorescence and contactless-conductivity detection for microfluidic chip

A combined detection system involving simultaneous LIF and contacfless-conductometric measurements at the same place of the microfluidic chip was described. The LIF measurement was designed according to the confocal principle and a moveable contactless-conduetivity detector was used in C^4D. Both measurements were mutually independent and advantageous in analyses of mixtures. Various experimental parameters affecting the response were examined and optimized. The performances were demonstrated by simultaneous detection of Rhodamine B. And the results showed that the combined detection system could be used sensitively and reliably.     

四元交互体系Li^＋,K^＋／cL^—,CO^2—3—H2O在298K时相平？…

Zabuye Saline Lake, Tibet, China, is unrivalled in the world for its very high salinity, in particular, for the very high concentration of ions of lithium, potassium, and boron in the brine. It belongs to alkaline and carbonate-borate-type salt lake. As a part of the study on phase equilibrium of the 6component subsystem Li+, Na+, K+/C1-, CO2-3, B4O2-7-H2O of the brine system, a study on the reciprocal quaternary system Li+, K+/C1-, CO32-H2O at 298 K was done with isothermal dissolution equilibrium method in the present work. The phase equilibrium of the reciprocal quaternary system Li+,K+/C1, CO2-3-H2O at 298 K was studied with isothermal dissolution method in this work. The physicochemistry properties of the corresponding equilibrium solutions such as densities, viscosities, refractive index, conductivities and pH value were determined. The dried salt diagram of the system consists of four crystallization fields (KC1, Li2CO3, LiCI·H2O, K2CO3·3/2H2O) and five isothermal solubility curves.There are no double slat or solid solution found. Pitzer′s model of the electrolyte solution theory was used for parameterization from the results of solubility determination for subsystems and the prediction of solubilities for the reciprocal quaternary system was made. The solubility data of the experiment are in agreement with those calculated.     

Nanomechanical properties of polyaniline and azo polyelectrolyte multilayer films

<正>Nanomechanical properties of multilayer films constructed of polyaniline(PANI) and azobeneze-containing polyelectrolytes(PNACN and PPAPE) were studied by using nanoindentation method.The multilayer films were prepared by the electrostatic layer-by-layer self-assembly through alternately dipping in the polymer solutions.The multilayer films deposited onto the glass slides after proper dry were used for the nanomechanical property testing.The nanomechanical measurement indicated that the PANI/PNACN and PANI/PPAPE multilayers possessed the mean elastic modulus of 5.42 GPa and 4.35 GPa,and hardness of 0.26 GPa and 0.18 GPa,respectively.The nanoscratch properties of the PANI/PNACN and PANI/PPAPE multilayer films were also measured.The critical loads of PANI/PNACN and PANI/PPAPE films were 103.52 mN and 100.59 mN.The degree of electrostatic cross-linking in the multilayers could be altered by exposing the films to aqueous solutions with different pH values.As a result,the modulus and hardness of the multilayer films were changed through the solvent treatment.Both modulus and hardness of the PANI/PNACN films obviously increased after dipping the multilayer films in solutions with pH in a range from 9 to 11.     

Triple-transforming gel prepared byβ-cyclodextrin,diphenylamine and lithium chloride in N,N-dimethylacetamide

<正>This paper describes a triple-transforming gel system(gel-sol-gel') for the first time,which is a thermo-responsive and multicomponent organogel prepared byβ-cyclodextrin(β-CD),diphenylamine(DPA) and lithium chloride(LiCl) in N,N-dimethylacetamide (DMAC) in a suitable proportion based on the supramolecular interactions.In the triple-transforming gel system,a gel(gel A) could be formed byβ-CD,DPA and LiCl in DMAC at room temperature based on stirring,then the gel could transform into a clear solution based on heating,and then the other gel(gel B) can be formed at a relatively high temperature(T_(gel),the gelation temperature by heating).The two gel states in the triple-transforming gel system have different microstructures.This gel system was characterized by OM,SEM,IR and rheology.     

Dehydration of xylose to furfural over niobium phosphate catalyst in biphasic solvent system

Phosphoric acid treated niobic acid(NbP)was used for the dehydration of xylose to furfural in biphasic solvent system,which was found to exhibit the best performance among the tested catalysts.The excellent performance of NbP could be explained by the better synergistic cooperation between Bro¨nsted and Lewis acid sites.Moreover,NbP showed good stability and no obvious deactivation or leaching of Nb could be observed after six continuous recycles.     

Selective catalytic oxidation of NO with O2 over Ce-doped MnOx/TiO2 catalysts

A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=1/3 and calcined at 300°C shows a superior activity for NO oxidation to NO2. On Ce(1)Mn(3)Ti catalyst, 58% NO conversion was obtained at 200°C and 85% NO conversion at 250°C with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst (48% at 250°C). Characterization results implied that the higher activity of Ce(1)Mn(3)Ti could be attributed to the enrichment of well-dispersed MnOx on the surface and the abundance of Mn3+ and Ti3+ species. The addition of Ce into MnOx/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.     

Molecular Design of Trypsin Towards High Substrate Selectivity

Molecular design of trypsin mutants towards higher substrate specificity for arginine or ly-sine type substrates was studied. The difference in side chain pKa of arginine and lysine was utilized in redesigning trypsin. If the enzyme could react effectively at a pH higher than lysine's pKa but lower than that of arginine, it would react more selectively with arginine-type substrates, since in that pH range, the side chain of arginie remain protonated, while that of lysine is deprotonated. For trypsin. the change of histidine (57)'s pKa reflects the shift in reaction optimum pH. Electrostatic calculations showed that when surface positive residues were mutated into neutral or negative ones, the pKa of histidine(57) would be raised and those surface charges within a cone of 70 degree around histidine(57) have strong influence on its pKa. Several sites were suggested in rat trypsin which might serve as potential mutation locations to make trypsin active at a higher pH, thus more selective towards arginine t     

Phthalonitrile Resins Derived from Vanillin: Synthesis,Curing Behavior,and Thermal Properties

Vanillin was used as sustainable source for phthalonitrile monomer synthesis, and allyl/propargyl ether moieties were introduced to improve the processability at the minimal cost of thermal properties. The synthesis route was optimized to minimize side-reactions and simplify post-processing, and the monomers were obtained in high purity and good yields. The curing behavior, mechanism, and processability of the monomers were studied, and the thermal properties of cured polymers were evaluated. Of the two monomers, the allyl ether-containing one exhibited a wide processing window of 185 °C, and was mainly cured into phthalocyanine and linear aliphatic structures through self-catalytic curing process. Also, the glass transition temperature was higher than 500 °C. In contrast, the propargyl ether-containing monomer could only be partially cured, and heat resistance was found to be compromised. Compared with traditional petroleum-based phthalonitrile resins, the biobased monomers could be cured without the addition of catalysts, and improvement in processability was achieved at no cost of thermal performances.     

Kinetics of tautomerization of 1,3,4,7-tetramethylisoindole

The kinetics of transformation of 1,3,4,7-tetramethylisoindole(1)to 1,3,4,7-tetramethyl-1H-isoindole(2)in water or in deuterium oxide at various pH or pD at 25℃ were measuredspectrophotometricalty.The results indicated that the transformation of 1 to 2 could be promotedby acid and base.From the solvent isotope effects and the fact that the 1-position of isoindole nucleusis electron-rich,the mechanism of this transformation is suggested.