Cun、Agn和Aun(n≤9)团簇的静电极化率

The static polarizabilities and polarizability anisotropies of Cun,Agn and Aun (n≤9)clusters have been calculated by the B3LYP density functional method,which is a three parameter mixture of density functional and"exact" Hartree Fock exchange. The calculated results are compared with experimental polarizabilities of sodium clusters. It is shown that the size dependency of the static polarizabilities per atom of Cun,and Agn clusters possesses the same trend as that observed in sodium clusters exception of the Aunclusters while the polarizability of Au atom is much smaller than these of Cu and Ag.The(α-)of Au atom is the smallest and the(α-)per atom of Au approach to the values of Cu from the dimmer to the hexamer. It indicates that in Au clusters the electrons are more strongly attracted by the nuclei because of the more electrons. However,the absolute polarizabilities of the noble mental clusters are considerably smaller than those of the sodium clusters and the electronic structures of the noblemental are much more compact.     

Thermodynamics of dissolving and solvation processes for benzoic acid and the toluic acids in aqueous solution

Experimental data are presented for the solubility in water of benzoic and toluic acids from 5° to 65°C. From the solubility the molality of the monomeric form of the acid is calculated using literature data for both ionization and dimerization of the acid. These data for the monomer combined with data from the literature for vaporization of the solid and ionization in both the gas phase and the aqueous phase yield entropy and enthalpy changes for the solvation of molecular and anionic forms of the acid. A similar procedure is also applied to literature data for the solubility of benzene in water. It is shown that the hydration entropies of the monomeric forms are a linear function of their partial molar volumes. It is concluded that hydration of the undissociated o-toluic acid may be crucial to the increased acidity of that acid compared to benzoic acid.     

New aspects of migration and flame retardancy in polymer nanocomposites

Annealing of pristine polypropylene blended with the organomontmorillonite (OMMT) at temperatures of 180-340 °C under a stream of nitrogen and of nitrogen-air mixtures is investigated. The oxidative annealing brings about the dispersion of the OMMT in the polypropylene and the formation of a nanocomposite structure. This is evidenced by the increase in the interlayer distance ‘d’ as measured by small angle XRD, with time of annealing and with the weight percent of air. This indicates progressive intercalation of the polymeric matrix into the clay gallery and subsequently exfoliation. The degree of exfoliation is estimated by the extent of migration determined spectroscopically on the surface of the annealed sample. The accumulated clay on the surface due to migration hinders the penetration of the oxygen into the annealing melt as expressed by the decrease in the rate of migration with the increase in the air concentration. This indicates the increase in ageing and storage stability of nanocomposites with increase in the extent of migration. The extent of migration is proportional to the polar carbonyl groups formed on the matrix. The energy of activation of the migration was found to be 37.82 kJ/mol indicating that the rate-determining step of migration is diffusion controlled reaction. The penetration of oxygen into the melt is the first of five steps, followed by oxidation, intercalation, exfoliation and migration. Monitoring the migration with increase in the temperature enables the observation at 275 °C of the transition of the nanocomposite structure to noncolloidal microcomposite. Increasing the annealing temperature above 300 °C brings about a slow, low-temperature combustion and formation of a new kind of char on the surface of the sample.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

TiO2膜光催化剂的改进及表征

提出用粉末-溶胶法制备TiO2薄膜型光催化剂,介绍了粉溶法的制备工艺及改变pH值对催化活性的影响.研究结果表明, 利用粉溶法或添加浓HNO3后制备的TiO2薄膜光催化剂表现出了较高的光催化活性.结合结构表征详细分析了其中的原因.认为粉溶法制备的催化剂表面更粗糙,比表面积增大,膜厚度减小,这些都可能是其催化活性提高的原因.而加酸后膜催化活性提高主要是因为酸性条件下表面几乎没有Ti3+表面态,利于光生电子与光生空穴的分离.     

A study of the ageing of the gel structure in a nonionic O/W cream by X-ray diffraction,differential scanning calorimetry and spin-lattice relaxation measurements

The time dependent changes of the lamellar gel structure in a nonionic O/W cream were studied. It appeared that the changes were connected with alterations in the hydrophilic layers of this lamellar gel structure. The structure of the hydrocarbon layers did not change. The alterations were induced by an increasing hydration of the surfactant molecules on cooling from the preparation temperature to room temperature. Ageing of the cream involves a decrease of the thickness of the hydrophilic layers and a change of the distribution of the surfactant molecules, resulting in, among other things, a decrease of the release rate of a hydrophilic drug. Ageing of the cream can be prevented by using the appropriate amount of starting materials or by the use of polymerizable surfactants. In the former case a cream, from which a drug is slowly released, is obtained. On the other hand, creams containing polymerized surfactants can release drugs at a relatively high rate.     

锌试剂与壳聚糖的结合反应机理的研究

为从分子水平认识多糖分子与小分子之间相互作用的机理,应用光谱法研究了壳聚糖(CTS)与锌试剂(ZCN)的相互作用机理;测得ZCN-CTS复合物吸收光谱出现新的吸收峰所需的临界ZCN/CTS摩尔比为2.67×103, CTS对ZCN的最大结合数为6.93×103,实验值与理论值相吻合,证明了多糖与生物探针相互作用理论模型的可靠性;探讨了ZCN与CTS相互作用产生变色反应的机理,认为其是在ZCN与CTS大分子间发生静电相互作用的基础上,主要由ZCN与CTS大分子间的疏水相互作用所引起.     

Thermophysical Properties of Granules of Instant Drinks in the Process of Structuring

In this article the research of the thermophysical properties of the material depending on its moisture content been represented. The interrelation of various physical properties with the content of moisture in the mass were detected. In addition, their dependence on the quantitative ratio and the properties of structural carcass and pore spaces were proved. The need to consider the volume phase composition of the mixture was justified. A formula to calculate the thermal conductivity coefficient of the product molded from disperse materials was obtained on the basis of Lykov criterion defining the property of drying material and volume phase concentrations. It is proved that the use of volume phase characteristics of disperse systems opens new possibilities for improving the methodologies for determining the those thermophysical properties of dry and wet dispersion materials, allows increasing the reliability results of these definitions, revealing the mechanism of anomalous heat conductivity of wet material.     

反相微乳液模板原位聚合制备纳米氯化银/聚甲基丙烯酸甲酯及其结构表征

用甲基丙烯酸甲酯(MMA)作油相,反相胶束微乳液作为模板,制备了纳米氯化银(AgCl)粒子,再进行原位聚合制备了纳米氯化银/聚甲基丙烯酸甲酯(AgCl/PMMA)复合材料.透射电镜(TEM)分析表明,纳米AgCl的尺寸为20～80 nm.扫描电镜(SEM)测试表明纳米AgCl粒子均匀地存在于PMMA基材中.红外分析证明,胶束中水和表面活性剂AOT的羰基在MMA聚合后微观环境发生变化,纳米粒子同聚合物之间有吸附行为.动态力学(DMTA)分析复合材料,发现纳米AgCl粒子与聚合物之间存在强烈相互作用,形成了中间相层(interphase layer),改变了聚合物的动态力学性能.     

Polymorphism and Conformational Equilibrium of Nitro-Acetophenone in Solid State and under Matrix Conditions

Conformational and polymorphic states in the nitro-derivative of o-hydroxy acetophenone have been studied by experimental and theoretical methods. The potential energy curves for the rotation of the nitro group and isomerization of the hydroxyl group have been calculated by density functional theory (DFT) to estimate the barriers of the conformational changes. Two polymorphic forms of the studied compound were obtained by the slow and fast evaporation of polar and non-polar solutions, respectively. Both of the polymorphs were investigated by Infrared-Red (IR) and Raman spectroscopy, Incoherent Inelastic Neutron Scattering (IINS), X-ray diffraction, nuclear quadrupole resonance spectroscopy (NQR), differential scanning calorimetry (DSC) and density functional theory (DFT) methods. In one of the polymorphs, the existence of a phase transition was shown. The position of the nitro group and its impact on the crystal cell of the studied compound were analyzed. The conformational equilibrium determined by the reorientation of the hydroxyl group was observed under argon matrix isolation. An analysis of vibrational spectra was achieved for the interpretation of conformational equilibrium. The infrared spectra were measured in a wide temperature range to reveal the spectral bands that were the most sensitive to the phase transition and conformational equilibrium. The results showed the interrelations between intramolecular processes and macroscopic phenomena in the studied compound.     

INFLUENCE OF THERMAL AND NON-THERMAL EFFECTS OF ULTRASOUND ON ISOTHERMS OF PHENOL ON NKA II RESIN*

1.INTRODUCTIONUltrasoundhasproventobeaveryusefultoolinenhancingthereactionratesinavarietyofreactingsystems.Ithassuccessfullyincreasedtheconversion,improvedtheyield,changedthereactionpathwayand/orinitiatedthereactioninbiological,chemicalandelectrochemicalsystem[1,2].Recentyears,thestudyofultrasonicsandsonochemistryhasexpandedconsiderably.Arapidlygrowingareaisthatof"environmentalsonochemistry",whichmainlydealswithdestructionoforganicsinaqueoussolution.Inaddition,theuseofultrasoundtoenhanced…     

Theoretical study of dielectric behavior of microcapsule suspensions with distributed drug release rate

Theoretical consideration is made concerning the dielectric behavior of aqueous suspensions of W/O-type microcapsules containing aqueous electrolyte solutions, especially concerning distribution effects of the electrolyte release rate on the dielectric behavior.It is shown at first that the distribution of the release rate causes electrical conductivity of the capsule interior. Next, it is deduced, in the light of a theory of the interfacial polarization, that the distribution characteristics of the capsule interior's electrical conductivity are closely related to those of the relaxation time for a dielectric relaxation exhibited by the suspensions. Several formulas are derived to describe the relation between the distribution characteristics of the release rate and those of the relaxation time.     

Effect of Ag on the Grain Growth and Dielectric Properties of PbTiO3

A series of Ag-PbTiO3 composites were synthesized, and the effects of silver on the morphological development of hydrothermal synthesized PbTiO3 particles and dielectric properties of PbTiO3 ceramic were investigated. Results show that the introduction of Ag benefits the crystal growth of PbTiO3. The diffusion of Ag+ into the perovskite accelerates the crystal growth of PbTiO3 and leads to large fine PbTiO3 crystal. Furthermore, the dielectric constant of PbTiO3-based ceramic was enhanced greatly by the percolation effect of inner Ag clusters.     

Antibacterial mechanism of chitosan microspheres in a solid dispersing system against E. coli

In this study, we investigated the antibacterial mechanism through the interfacial contacting inhibition behaviors of chitosan antimicrobials against Escherichia coli in solid dispersing state. Chitosan microspheres (CMs) were prepared by emulsification cross-linking reaction, and oleoyl-CMs (OCMs) were obtained by introduction of oleoyl groups to the chitosan. The CMs were with smooth surface and spherical shape of diameter of about 124 microm. The antibacterial activity was directly proportional to the concentration and the hydrophobic property of CMs. The fluorescence experiments indicated CMs had influenced the structure of membrane, especially the OCMs were speculated to interact with proteins on the cell membrane. SEM photographs showed E. coli adhered to the surface of the CMs and provided evidences for the disruption of the cells, while the bacterium conglomerated on the surface of the OCMs. The CMs changed the permeability of membrane and caused cellular leakage that correlated with the hydrophobic interaction between CMs and cytoplasmic membrane phospholipids of Gram-negative bacteria. Solid dispersing system makes the antibacterial activities of CMs counted as a sequent event-driven to study the antibacterial mechanism of chitosan originally.     

水蒸气对煤热转化过程中钠析出特性影响研究

在不同水蒸气体积分数及温度条件下制备了相同焦产率的NaCl浸渍煤的煤焦样品,并利用电感耦合等离子体质谱仪分析了不同煤焦中钠的赋存形态及含量,研究了水蒸气及温度对煤热转化过程中钠迁徙转化的影响。结果表明,水蒸气体积分数的增加,一方面,增强了煤热转化过程中水溶态钠的释放;另一方面,也促进了水溶态钠向醋酸铵溶态、盐酸溶态以及不溶态钠的转化,使得钠的释放受到一定程度抑制。煤焦结构演化对碱金属钠释放具有重要影响。水蒸气的气化反应引起煤焦缩聚程度增加,小芳香环缩聚形成大芳香环结构时会对钠起到一定的包裹作用,使得钠的释放受到抑制;同时,气化反应产生的煤焦比表面积越大,越有利于钠直接释放。提高反应温度一方面会促进水溶态钠的释放;同时也会促进水溶态钠向其他溶态形式钠的转化,使得钠析出率随反应温度上升而增加的趋势逐渐变缓。     

Chemical heterogeneity in emulsion copolymers of carboxylic monomers

Copolymer latices of butylacrylate (BA) with acrylic and methacrylic acid (AA and MAA) were prepared by batch type emulsion polymerization, and, for comparison, copolymers with identical monomer composition were prepared by batch type solution polymerization.The distribution of the carboxylic monomers in the latex particles and the serum was studied by density gradient and sedimentation experiments with the analytical ultracentrifuge. Dynamic mechanical measurements of films of these copolymers were used to determine the storage and loss moduli as a function of temperature. From these measurements the position and extension of the glass transition range on the temperature scale is obtained. For heterogeneous emulsion copolymers with two glass transition temperatures the distribution of the carboxylic monomer units in the different copolymer phases can be determined. Electron microscopy of ultra thin cross-sections of stained films gave further insight into the film morphology.The combination of the results obtained with the different methods gives rise to the following clues: In the BA/AA latices about 40% (by weight) of the total AA used in the recipe are found in the serum as a water soluble polymer, about 50% are found to increase the glass transition temperatureT _g of the bulk of the BA copolymer and, therefore, are thought to be incorporated into the interior of the latex particles, and the remaining 10% are, conclusively, located on the particle surface.In the BA/MAA latices no water soluble copolymer could be detected in the serum, about 90% of the MAA used is found in the bulk of the copolymer, and about 10% form a second hard phase on the surface of the latex particles.Dynamic mechanical measurements on the copolymer latex films show at least two phases with different glass transition temperatures: the bulk of the copolymer with a relatively low content of (M)AA units and a glass transition range at low temperatures, and a second (M)AA rich phase with a highT _g.The latter phase forms a honeycomb-like structure surrounding the packed latex particles. That results in a three-dimensional network of polymer with a highT _g extending throughout the latex film. In spite of the fact that this phase is built from a small fraction of the total copolymer only, it has a very pronounced influence on the performance behaviour of latex films.Dedicated to Professor Dr. R. Manecke on the occasion of his 70th birthday.     

Population Balance Model for Batch Gravity Separation of Crude Oil and Water Emulsions. Part I: Model Formulation

A population balance model for the separation of emulsions in a batch gravity settler is presented. Within the context of the model development, possible methodologies were elucidated for incorporating a) the physical properties of the bulk liquids, b) the physical properties of the phase interface, and c) the presence and functioning of interfacially active compounds. The model presented explicitly accounts for interfacial coalescence and the deformation of the emulsion zone due to the dynamic growth of the resolved dispersed phase; interfacial coalescence is modeled in terms of physically meaningful film drainage models and an approach for incorporating the accumulated buoyancy force in the dense packed layer is also discussed. Hydrodynamically hindered sedimentation is also considered in the model. The model is well suited to predict experimental batch settling data, especially data obtained from low-frequency NMR measurements of emulsion destabilization. The model predicts the evolution of the volume fraction of the dispersed phase at any axial position and time in the separator. Furthermore, the model predicts the location of the resolved dispersed phase interface as a function of time. Additionally, for any axial position and time in the settler, the model predicts the evolution of the average number density of droplets, the average volume/radius of droplets, the standard deviation of the droplet volume/radius, and the rate of growth of the droplets. The model is compared directly with experimental data for crude oil separations in Part II of this article.     

Morphology of homogeneous copolymers of ethene and 1-octene. I. Influence of thermal history on morphology

The morphology of homogeneous copolymers of ethene and 1-octene synthesized using a V-based Ziegler-Natta catalyst was studied as a function of the short chain branching content (SCBC) and the molar mass. Linear polyethylenes (LPE) were used as reference material. For the linear samples an increase in molar mass results in an increase of the long period and the crystalline lamella thickness. A decrease of cooling rate results in an increase of the melting temperature, the long period and the crystalline lamella thickness and an evolution from spherulitic structures to perfectly stacked lamellae. For the branched samples, increasing the SCBC results in a decrease of the melting and the crystallization temperature, crystallinity, spherulite radius, the long period, and the crystalline lamella thickness. The two latter tend to a limiting value on reaching a SCBC of 20CH₃/1000C. On the other hand, an increase of the a axis and to a lesser extent the b axis of the unit cell is observed. Decreasing the cooling rate affects only the crystallinity of the least branched samples. Furthermore decreasing the cooling rate results in smaller spherulites, has a minor influence on the lamellar parameters and reduces the dimensions of the basal plane of the unit cell. Increasing the molar mass of the branched samples results in a drop of the crystallinity, a deterioration of the superstructure, enlarges the amorphous layer thickness and the dimensions of the basal plane. All these observations can be accounted for by the different crystallization regimes being applicable when different molar masses, SCBC and cooling rates are used. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2689–2713, 1997     

Influence of nozzle geometry on polystyrene degradation in convergent flow

Polymer degradation is readily observed in flows where the extensional component surpasses the rotational component of the velocity gradient. This type of flow is conveniently obtained by pushing a liquid into a convergent channel across an orifice. Kinetics of chain scission is sensitive to subtle modification of the coil conformation, which in turn depends on the details of the pervading flow field. By changing the orifice diameter and the conical angle of the inlet, it is possible to modify the spatial distribution of the velocity gradient, and hence, the residence time of a fluid element in the high strain-rate region. Degradation yields, measured under -conditions in decalin by Gel Permeation Chromatography, showed a strong dependence on the fluid velocity at the orifice, but not on the magnitude of the strain-rate. This result is contrary to the common belief that assumes viscous friction, proportional to the strain-rate, is the determining factor for the scission rate of a bond under stress. Rather, experimental findings tend to indicate that the driving force for chain scission was provided by the energy accumulated in the coil during the flow-induced deformation process. The sharp propensity for mid-chain scission was maintained regardless of the nozzle geometry.Dedicated to Prof. W. R. Pechhold on the occasion of his 60th birthday     

Semiquantitative analysis of isomeric oligosaccharides by negative-ion mode UV-MALDI TOF postsource decay mass spectrometry and their fragmentation mechanism study at N-acetyl hexosamine moiety

Postsource decay (PSD) spectra of isomeric neutral lactooligosaccharide mixtures were measured from the chlorinated molecules [M + Cl]- by negative-ion mode ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI TOF MS) to estimate quantitatively the mixing ratios in their mixtures. The PSD ions specific to each isomeric structure were used to distinguish the linkage and branching isomers, and the molar ratios of the isomers were estimated from their ion abundances. The relative ion abundances changed linearly in the PSD spectra of the mixtures of the isomers as their molar ratio was varied in the analyte solutions. Therefore, the molar ratios of the isomers in the analyte mixtures could be estimated semiquantitatively. In addition, we studied their fragmentation mechanisms in N-acetyl hexosamines such as GlcNAc, which enabled us to quantitatively analyze the structures of the isomers of lactooligosaccharides. The conjugated systems elongate in the chemical species of the Z-type fragmentation on the 3-linked GlcNAc owing to the acetoamido groups at the C-2 positions, which made the chemical species of the Z-type ions stable. The glycosyl bonds of the front of GlcNAc cleaved easily as a C-type fragmentation because the negative charge at the anomeric position could be delocalized to the carbonyl oxygen atom at the acetoamido group of GlcNAc. These factors caused the stabilization of the chemical species of the C/Z fragment ions produced by the double cleavage around GlcNAc.