时代治乱与历史文献的散聚分合

历史文献在其积累和传承过程中 ,屡遭厄运 ,时代治乱和统治者的政治需求直接影响着历史文献的散聚分合 ,而历史文献的散聚分合往往成为时代治乱、国家盛衰的信号和象征。中国古代历史文献的发展经历了一个曲折反复的过程 ,其聚合、散分 ,又聚合、又散分 ,再到聚合的基本发展轨迹和基本特征无不打上了深深的时代印记。

Preparation and Characterization of Non-porous Superparamagnetic Microspheres with Epoxy Groups by Dispersion Polymerization

Non-porous superparamagnetic polymer microspheres with epoxy groups were prepared by dispersion polymerization of glycidyl methacrylate (GMA) in the presence of magnetic iron oxide (Fe3O4) nanoparticles coated with oleic acid. The polymerization was carried out in the ethanol/water medium using polyvinylpyrrolidone (PVP) and 2,2’-azobisisobutyronitrile (AIBN) as stabilizer and initiator, respectively. The magnetic microspheres obtained were characterized with scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) and Fourier transform infrared spectroscopy (FTIR). The results showed that the magnetic microspheres had an average size of-1μm with superparamagnetic characteristics. The saturation magnetization was found to be 4.5emu.g-1. There was abundance of epoxy groups with density of 0.028 mmol·g^-1 in microspheres. The magnetic PGMA microspheres have extensive potential uses in magnetic bioseparation and biotechnology.

Phase Transition of Poly（acrylic acid-co-N-isopropylacrylamide） Core-shell Nanogels

A series of poly（acrylic acid） macromolecular chain transfer agents with different molecular weights were synthesized by reversible addition-fragmentation chain transfer （RAFT） poly- merization and characterized by 1^H NMR and gel permeation chromatography. Multiresponsive core-shell nanogels were prepared by dispersion polymerization of N-isopropylacrylamide in water using these poly（potassium acrylate） macro-RAFT agents as the electrostcric stabilizer. The size of the nanogels decreases with the amount of the macro-RAFT agent, indicating that the surface area occupied by per polyelectrolyte group is a critical parameter for stabilizing the nanogels. The volume phase transition and the zeta potentials of the nanogels in aqueous solutions were studied by dynamic light scattering and zetasizer analyzer, respectively.

Influence of polymer dispersants on dispersion stability of nano-TiO_2 aqueous suspension and its application in inner wall latex paint

The effects of SN5040 and polyethylene glycol（PEG） individually and in combination on the dispersion stability of nano-TiO2 aqueous suspension were investigated by ultraviolet-visible absorption spectroscopy. The adsorption mechanism of these dispersants was detected by zeta potential, isothermal absorption and FTIR analysis. It is found that SN5040 is superior for stabilizing nano-TiO2 in aqueous suspension to PEG in basic region, and the optimum mass fraction of SN5040 addition is 3%. In the case of NaCl addition, the optimum value increases with .the increase of NaCl concentration in the solution. When the mixture of SN5040 and PEG is employed, the antagonism appears preponderant. When SN5040 and PEG are added sequentially, the synergistic reaction takes place. The synergistic reaction can be attributed to the mechanism that PEG adsorption decreases the electronic repulsion between SN5040 molecules, which results in the increase of SN5040 adsorption density. PEG is adsorbed by the interaction with the pre-adsorbed SN5040 layer. Furthermore, the modified inner wall latex paint with well dispersed nano-YiO2 suspension is endowed with excellent ultraviolet absorption and antibacterial properties.

A Population Balance Model for Disperse Systems:Particle Size Distribution in Suspension Polymerization

On the basis of population balance a mathematical model is developed to describe the formation of polymer particle in styrene suspension polymerization. The characteristics of coalescence and breakage of droplets and the gel effect are analyzed in particular. Parameters of the models are estimated by experimental data on reaction conversion and particle size distribution. The results show that the model is suitable for predicting polymerization processes.

Effect of the Molecular Structure of Polymer Dispersants on Limestone Suspension Properties in Fine Grinding

Polymer dispersants are widely used as grinding aids to reduce the viscosity of mineral particle suspensions and to improve energy efficiency during fine grinding. The authors studied here the effects of polymer dispersants of different molecular structure on limestone suspension properties in wet stirred media milling. The polymers differed in their molecular weight and PDI （polydispersity index）. Two traditionally fractionated polymer dispersants having a high PDI （over 2） and one made by controlled radical polymerization having a low PDI （1.2） were tested. It was noticed that these dispersants worked as electrosteric stabilizers and prevented the agglomeration of ground limestone particles. Their addition allowed increased solids concentrations to be used in the grinding experiments and at the same time lowered the particle size and specific energy consumption. The particle sizes obtained were about 1 μm regardless of the dispersant or its dose. The dispersant with a low PDI reduced the viscosity more than did the high PDI dispersants. The results indicate that higher solids concentrations can be used at the same dispersant dose when a low PDI dispersant is used, leading to energy savings via increased throughput. Alternatively, a lower dose of low PDI polymer dispersant than of a high PDI polymer dispersant can be used at the same solids concentration.

The Surface Properties of PAVAc Prepared by Dispersion Polymerization in ScCO_2

Dispersion copolymerization of acryionitrile-vinyi acetate （AN-VAc） has been successfully performed in supercriticai carbon dioxide （ScCO2） with a series of iipophilic/CO2-philic diblock copolymers, such as poly（ styrener-acrylonitrile）-b- poly （ 1, 1, 2, 2-tetrahydroperfluorooctyl methacrylate） （PSAN-b-PFOMA）, as steric stabilizers. The structure and the particle morphology of the product were characterised by FT-IR and SEM. In addition, the effects of the stabilizer on the surface properties of the products were investigated in detail. Results indicate that the surface free energy of the poly （AN-r-VAc） （PAVAc） film decreases dramatically because of the existence of the stabilizer. And, when the initial concentration of the monomer was 10% （the mass （g） of monomer to the volume （mL） of ScCO2 ） the optimal concentration of the stabilizer is about 5% （w/w% to monomers）.

Synthesis of crosslinked polystyrene particles by seeded batch polymerization with monomer absorption

A highly crosslinked, monodispersed polystyrene（PS） particle was prepared by a seeded batch dispersion polymerization with a monomer absorption method. Prior to polymerization, 1,9 lam monodispersed PS seed particles were treated under an optimum condition of monomer absorption. The effects of divinylbenzebe（DVB） concentration and polymerization temperature were examined for styrene（in PS seed）/styrene（in the second stage） mass ratio of 1：1 in the medium range of EtOH/water mass ratio of 100/0-80/20 and 2.3 μm uniform crosslinked PS particles containing 15%-20% （mass fraction） DVB were prepared at 60-70 ℃. The results show that monomer absorption before the second stage of polymerization is more effective to prepare highly crosslinked monodispersed PS particles.

PREPARATION OF POLYMER PARTICLES WITH HIGH CONTENT OF MAGNETIC MATERIAL

A method for preparing polymer microspheres with high magnetic content is introduced.First of all,the ferrofluid prepared by co precipitation was treated with ethanol.Then,in the presence of the treated Fe 3O 4 particles,the dispersion polymerization of acrylamide was performed using poly (ethylene glycol) (PEG) as dispersant,AIBN as initiator,and ethanol as dispersing medium.The effects of the dispersing medium,the agitation intensity,the amount and properties of magnetic particles on the polymerization and magnetic content in the polymer microspheres are discussed.Finally,polyacrylamide particles having as high as 32.2% (by weight) magnetic Fe 3O 4 particles were prepared.

浅谈中国画教学中“点”的艺术价值

点既是具象的又是抽象的,它可以起到虚隐实现的作用,还可以起连续和分合聚散作用。画面打点通过似节拍的转换形成了抑扬顿挫、轻重急缓特别能显示出音乐般节奏、旋律,力度变化的内在韵律感,有力地加强了画面情趣的感染力。

ZrO2/PMMA Nanocomposites： Preparation and Its Dispersion in Polymer Matrix

ZrO2/PMMA nanocomposite particles are synthesized through an in-situ free radical emulsion polymerization based on the silane coupling agent （Z-6030） modified ZrO2 nanoparticles, and the morphology, size and its distribution of nanocomposite particles are investigated. Scanning electron microscopy （SEM） images demonstrate that the methyl methacrylate （MMA） feeding rate has a significant effect on the particle size and morphology. When the MMA feeding rate decreases from 0.42 ml-min-1 to 0.08 ml. min-1, large particles （about 200-550.nm） will not form, and the size distribution become narrow （36-54 nm）. The average nanocomposite particles size increases from 34 nm to 55 nm, as the MMA/ZrO2 nanoparticles mass ratio increased from 4 ： 1 to 16 ： 1. Regular spherical ZrO2/PMMA nanocomposite particles are synthesized when the emulsifier OP-10 concentration is 2 mg.m1-1. The nanocomposite particles could be mixed with VAc-VeoVa10 polymer matrix just by magnetic stirring to prepare the ZrOE/PMMA/VAc-VeoVal0 hybrid coatings. SEM and atomic force microscopy （AFM） photos reveal that the distribution of the ZrO2/PMMA nanocomposite particles in the VAc-VeoVal0 polymer matrix is homogenous and stable. Here, the grafted-PMMA polymer on ZrO2 nanoparticles plays as a bridge which effectively connects the ZrO2 nanoparticles and the VAc-VeoVal0 polymer matrix with improved comparability. In consequence, the hybrid coating with good dispersion stability is obtained.

A novel group signature with one time secret key

A new group signature with one time secret key is proposed. The main merits are that it only needs the trusted center issuing the partial secret key one time for each group member; and that the group member can generate his different secret key each time when he wants to sign a message. The group public key is constant and the size of the signature is independent of the number of group members. The total computation cost of signature and verification requires only 8 modular exponentiations.

Measurement of refractive index modulation on PMMA/E49/TNF/ECZ polymer-dispersed liquid crystal by fiber F-P interferometer

The fiber Fabry-Perot interferometer used to measure the refractive index modulation of polymer-dispersed liquid crystal is introduced.From measuring the quantity of the interference fringe shift with a CCD based on the theory of isoclinal interference fringes formatting,the maximal refractive index modulation versus different external voltages,3.899×10-3 in the external voltage of 57.4 V/μm,and the dynamic refractive index modulation versus response time in the external voltage of 8 V/μm are found in our prepared 1.250 mm-thick PMMA/E49/TNF/ECZ polymer-dispersed liquid crystals.The experimental results will be helpful to understand the photoinduced reaction mechanism of the material and optimize the mixture ratio of each component.

Estimation of Separation of Electrolytes and Organic Compounds by Nanofiltration Membranes Using an Irreversible Thermodynamic Modei

Nanofiltration separation has become a popular technique for removing largeorganic molecules and inorganic substances from water. It is achieved by a combination of threemechanisms: electrostatic repulsion, sieving and diffusion. In the present work, a model based onirreversible thermodynamics is extended and used to estimate rejection of inorganic salts andorganic substances. Binary systems are modeled, where the feed contains an ion that is much lesspermeable to the membrane as compared with the other ion. The two model parameters are estimated byfitting the model to the experimental data. Variation of these parameters with the composition ofthe feed is described by an empirical correlation. This work attempts to describe transport throughthe nanofiltration membranes by a simple model.

Polymerization Kinetics and Stabilization Mechanism of the Monodisperse PMMA Microspheres

The effects of the concentration of monomer, crosslinking agent, initiator, stabilizer, and the polarity of medium on the polymerization kinetics were investigated. The results show that the rate of polymerization (Rp) and conversion increased with the increase of monomer concentration from 8% to 15% (total mass); the water content in dispersion medium and the initiator 2, 2′ -azobis (isobutyronitrile) (AIBN) concentration increased as well. Rp and conversion decreases with the increase of PVP when it is low, while it increases when it is high. Moreover, PVP plays an important role in microsphere stabilization. The stabilization mechanism was investigated primarily, which involves both adsorbing mechanism and graft mechanism. Within a certain range of crosslinking degree, Rp and conversion increased with the increase of the crosslinker concentration. The effect can be ignored when crosslinker concentration is above 0.3 % (total mass), and the reason was that the monomer can hardly be diffused into the microsphere phase with a certain degree of crosslinking.

Preparation of pH-and reductive-responsive prodrug nanoparticles via polymerization-induced self-assembly

pH-and reductive-responsive prodrug nanoparticles are constructed via a highly efficient strategy, polymerization-induced selfassembly(PISA). First, reversible addition-fragmentation chain transfer(RAFT) polymerization of 2-(diisopropylamino) ethyl methacrylate(DIPEMA) and camptothecin prodrug monomer(CPTM) using biocompatible poly(N-(2-hydroxypropyl) methacrylamide)(PHPMA-CPDB) as the macro RAFT agent is carried out, forming prodrug diblock copolymer PHPMA-P(DIPEMA-co-CPTM). Then, simultaneous fulfillment of polymerization, self-assembly, and drug encapsulation are achieved via RAFT dispersion polymerization of benzyl methacrylate(Bz MA) using the PHPMA-P(DIPEMA-co-CPTM) as the macro RAFT agent. The prodrug nanoparticles have three layers, the biocompatible shell(PHPMA), the drug-conjugated middle layer(P(DIPEMA-co-CPTM)) and the PBz MA core, and relatively high concentration(250 mg/g). The prodrug nanoparticles can respond to two stimuli(reductive and acidic conditions). Due to reductive microenvironment of cytosol, the cleavage of the conjugated camptothecin(CPT) within the prodrug nanoparticles could be effectively triggered. p H-Induced hydrophobic/hydrophilic transition of the PDIPEMA chains results in faster diffusion of GSH into the CPTM units, thus accelerated release of CPT is observed in mild acidic and reductive conditions. Cell viability assays show that the prodrug nanoparticles exhibit well performance of intracellular drug delivery and good anticancer activity.

Soft-to-hard templating to well-dispersed N-doped mesoporous carbon nanospheres via one-pot carbon/silica source copolymerization

Here we report a new approach referred as ＂soft- to-hard templating＂ strategy via the copolymerization of carbon source （dopamine） and silica source （tetraethyl orthosilicate） for the synthesis of well dispersed N-doped mesoporous carbon nanospheres （MCNs）, which exhibit high performance for electrochemical supercapacitor. This method overcomes the shortcoming of uncontrolled dis- persity and complicated procedures of soft- or hard-tem- plating methods, respectively. Moreover, the synthesized MCNs feature enriched heteroatom N-doping and easy functionalization by noble-metal nanoparticles during the one-pot synthesis. All the above characters make the as- prepared MCNs a promising platform in a variety of applications. To demonstrate the applicability of the syn- thesized nitrogen-doped MCNs, this material has been employed as an electrode for high-performance electro- chemical supercapacitor, which shows a capacitance of 223 and 140 F/g at current densities of 0.5 and 10 A/g in 1 mol/L KOH electrolyte, respectively.