分子模拟方法考察泡沫生成能力

采用分子模拟的方法研究表面活性剂的泡沫生成能力, 以界面形成能作为考察泡沫体系中液膜界面积的量化依据, 研究了泡沫液膜厚度、表面活性剂分子界面密度以及表面活性剂类型对泡沫液膜界面形成能计算的影响. 通过与实验结果相对应, 建立了界面形成能和泡沫生成能力之间的联系.     

不同添加物对表面活性剂溶液预胶束形成的影响

关于表面活性剂溶液中预胶束的形成问题已有不少报道［’－‘］．预胶束是表面活性剂溶液在浓度很稀时（远小于其临界胶束浓度（CMC》、表面活性分子所形成的一种集合体·由于一般的物理化学方法对其难于捡出，因此常被研究者忽略．文献间曾指出：预胶束形成的驱动力与胶束一样，也是疏水作用所致．因此表面活性分子的链长、头部极性、溶剂性质以及添加物的引入等因素必然会影响预胶束的形成．本工作是对添加物的引入问题所作的初步研究·。作中所研究的阴离子表面活性剂有十二烷基硫酸钠（sss）·＋”烷基；Iv酸钠（5％）和十六烷基硫酸…     

技能形成、技能形成体制及其经济社会学的研究展望

逆全球化回潮意味着全球生产价值链条秩序的重新洗牌,对于中国制造而言,依赖比较优势的传统发展模式面临着前所未有的挑战,其突出表现就是基于低技能、低成本的经济发展方式与社会平等之间的矛盾日益尖锐。在发达资本主义国家从劳动密集型迈向技术密集型发展方式的转型过程中,国家技能形成体制起到了最为核心的作用,成为其重要的比较制度优势。国家技能形成体制分为国家主义、市场主义、集体主义、以及分隔主义四种制度模式。这四种制度模式具有不同的制度特性,同时也会导致不同的经济社会后果。中国的国家技能形成体制呈现出明显的碎片化,其间的制度冲突已成为阻碍中国技能生产、劳工保护乃至国家制造业创新能力提升的深层制度根源。从人力资本形成走向技能形成、分析技术流动的社会断裂现象成为经济社会学相关领域研究的一个新增长点。     

On calculating a polymer's enthalpy of formation with quantum chemical methods

Calculating the enthalpy of formation of a polymer with ab initio methods requires two choices. The first decision is whether to use oligomeric extrapolation or periodic boundary conditions to model the extended system, and the second choice is between formation reactions to be modeled, for example, formation from atoms, formation from standard states, or formation from some set of molecular systems. Utilizing trans-polyacetylene and polyethylene as examples, the oligomeric and periodic techniques are contrasted, leading to a discussion of the larger than minimal unit cell required when frequency calculations only include in-phase vibrations, that is, only the k = 0 frequencies, in an enthalpy of formation calculation. The accuracy of calculating the enthalpy of formation, in light of density functional theory's increased error with larger systems and with respect to various reference states, is also discussed. The calculation of the enthalpy of formation for a polymer is most accurate when the reference states are chosen carefully and most efficient when using periodic boundary conditions.     

Kinetics of the formation of silver dimers: early stages in the formation of silver nanoparticles

Silver clusters too small to support a plasmon band possess interesting fluorescence properties as well as being a convenient route to studying the early stages of nanoparticle formation. Fluorescent silver clusters are synthesized in toluene solution, and the formation is monitored herein by laser flash photolysis (LFP). Kinetic analysis of the formation of the Ag clusters is consistent with the formation of the smallest possible clusters, silver dimers (Ag(2)), whereby a mechanism for the formation of these clusters is provided as well as the first reported extinction coefficient and association constant for Ag(0) to form Ag(2). The formation of Ag(2) clusters is contrasted with the formation of Ag nanoparticles in aqueous media, and the particular stability and selectivity toward Ag(2) in this system is also studied using LFP.     

Hydrothermal solidification of diatomaceous earth with analcime formation

Diatomaceous earth (DE) solidifies hydrothermally with analcime formation. With analcime formation, strength development was much greater than that with calcium silicate hydrate (CSH) formation. NaOH addition conditioned analcime formation because NaOH solution not only promoted dissolution of quartz and montmorillonite but also provided Na⁺ to form the analcime. Curing temperature and time affected analcime formation, and, in this study, over 6 h (at 200 °C) and 175 °C (for 12 h), analcime seemed to form readily. After hydrothermal treatment, the skeletons of diatoms can still be seen in the solid after analcime formation but can hardly be found after CSH formation.     

Formation and filtration characteristics of solids generated in a high level liquid waste treatment process

The solids formation behavior in a simulated high level liquid waste (HLLW) was experimentally examined, when the simulated HLLW was treated in the ordinary way of actual HLLW treatment process. Solids formation conditions and mechanism were closely discussed. The solids formation during a concentration step can be explained by considering the formation of zirconium phosphate, phosphomolybdic acid and precipitation of strontium and barium nitrates and their solubilities. For the solids formation during the denitration step, at least four courses were observed; formation of an undissolved material by a chemical reaction with each other of solute elements (zirconium, molybdenum, tellurium) precipitation by reduction (platinum group metals) formation of hydroxide or carbonate compounds (chromium, neodymium, iron nickel, strontium, barium) and a physical adsorption to stable solid such as zirconium molybdate (nickel, strontium, barium).     

热环合反应速率的量子理论

应用多声子无辐射跃迁理论研究热环合反应, 给出热环合反应速率的一般公式。在高温条件下得出反应速率和活化能公式。所得公式可适用于多个环合点的热环合反应。     

锂离子电池有机电解液成膜添加剂研究进展

综述了锂离子电池有机电解液成膜添加剂的作用原理，从气体、液体、固体成膜添加剂三个方面综述了目前成膜添加剂的研究现状。重点论述了每一种添加剂的作用原理以及在碳负极上的还原机理，同时对它们的优缺点也作了适当的评述。     

辽河渣油热转化和加氢裂化过程中生焦行为的研究

考察了辽河渣油热转化和浆液床催化加氢反应过程中生焦行为。研究生焦趋势与渣油物理化学组成的关系，初期生焦机制及其对后生焦的影响，并用高倍显微镜、傅立叶变换红外光谱技术对所生焦进行表征，结果发现，随加工苛刻度的增加，反应体系中生成的焦油细分散向簇状分散过渡、实姓焦对后期生焦有一定促进作用，在低压热转化过程中更为显著，生焦趋势不仅与反应条件有关而且与渣油物理化学性质相关，还与反应物系对生焦先躯物的胶溶能     

Impedance spectroscopy investigation of the water-in-oil microemulsions formation

In this work it was investigated the microemulsion formation using impedance spectroscopy analysis. The results indicated that the microemulsion formation is clearly observed on the impedance complex plane. The phase transition related with microemulsion formation is characterized by a time relaxation distribution. In the condition of the microemulsion formation, the impedance spectra are characterized by a single relaxation time.     

NaHY沸石中结构羟基与积碳的关系

Uylterhoevn和Ward等人已经证明了:1.NaHY沸石中的结构羟基,是NH₄NaY脱氨后余下的氢附连于邻近的骨架氧而形成的。对应红外光谱3643cm_-1吸收峰的结构羟基具有Brnsted酸性。     

Ab initio study on the kinetics and mechanisms of the formation of Agn (n = 2–6) clusters

The CCSD(T)/11e-RECP//MP2/11e-RECP method was used to explore the potential energy surfaces (PESs) of the formation of Ag_n (n = 2–6) clusters. Two kinds of reaction mechanisms were revealed in the formation of Ag_n clusters, the association mechanism for the formation of Ag₂, Ag₅, and Ag₆ clusters and the association–isomerization mechanism for the formation of Ag₃ and Ag₄ clusters. Based on the canonical transition state theory, the calculated rate constants of the formation of Ag_n clusters displayed an odd–even effect: the rate constants of formation of Ag_n clusters with odd number were larger than those with even number. The rate constant of formation of Ag₄ was the lowest, whereas that of Ag₅ was the highest among Ag_n (n = 2–6) clusters. The formation of Ag₄ was the most difficult step in the aggregation process of the silver clusters. The formation of Ag₄ may be related with the critical point in the silver aggregation process.     

Complex formation thermodynamics of some metal(II) phenyl-2-pyridylketoximates

The formation of phenyl-2-pyridylketoximates of nickel(II), zinc(II), cadmium-(II), mercury(II) and lead(II) was studied potentiometrically in a medium of 40% (w/w) acetone and 60% (w/w) water. The values of step formation constants, free energy, entropy and enthalpy of complex formation were calculated. The formation of the mercury chelate was found to be entropy driven. The formation of phenyl-2-pyridylketoximates of other metals of the first transitional series could not be studied owing to experimental difficulties.     

The spontaneous polymerization of methyl methacrylate-IV: Formation of cyclic dimers and linear trimers

The mechanism of the spontaneous polymerization of methyl methacrylate (MMA) is still unknown. We now present evidence for the formation of 1.1.2.2-tetrasubstituted cyclobutanes in a side-reaction confirming, by the kinetics of their formation, the postulated biradical mechanism of initiation. The structures and formation kinetics of linear trimers were determined thus verifying the en-enophil mechanism for the formation of unsaturated oligomers.     

End-to-end vs interior loop formation kinetics in unfolded polypeptide chains

The conformational search for favorable intramolecular interactions during protein folding is limited by intrachain diffusion processes. Recent studies on the dynamics of loop formation in unfolded polypeptide chains have focused on loops involving residues near the chain ends. During protein folding, however, most contacts are formed between residues in the interior of the chain. We compared the kinetics of end-to-end loop formation (type I loops) to the formation of end-to-interior (type II loops) and interior-to-interior loops (type III loops) using triplet-triplet energy transfer from xanthone to naphthylalanine. The results show that formation of type II and type III loops is slower compared to type I loops of the same size and amino acid sequence. The rate constant for type II loop formation decreases with increasing overall chain dimensions up to a limiting value, at which loop formation is about 2.5-fold slower for type II loops compared to type I loops. Comparing type II loops of different loop size and amino acid sequence shows that the ratio of loop dimension over total chain dimension determines the rate constant for loop formation. Formation of type III loops is 1.7-fold slower than formation of type II loops, indicating that local chain motions are strongly coupled to motions of other chain segments which leads to faster dynamics toward the chain ends. Our results show that differences in the kinetics of formation of type I, type II, and type III loops are mainly caused by differences in internal flexibility at the different positions in the polypeptide chain. Interactions of the polypeptide chain with the solvent contribute to the kinetics of loop formation, which are strongly viscosity-dependent. However, the observed differences in the kinetics of formation of type I, type II, and type III loops are not due to the increased number of peptide-solvent interactions in type II and type III loops compared to type I loops as indicated by identical viscosity dependencies for the kinetics of formation of the different types of loops.     

Ionic equilibria in alkaline aqueous solutions of metal complex salts

A thermodynamic analysis of the formation conditions of metal hydroxides was performed. The areas of stable formation of metal hydroxide precipitates in the coordinates pH-metal concentration, including also solutions containing various kinds of complexing agents, were evaluated. With the precipitation of cadmium hydroxide as example, X-ray phase analysis confirmed the formation of metal hydroxide in the chemical composition areas where its formation is predicted by a thermodynamic analysis.     

Unique organic-inorganic interactions leading to a structure-directed microporous aluminophosphate crystallization as observed with in situ Raman spectroscopy

We report on the direct observation of key organic template-framework interactions leading to the formation of specific aluminophosphate structures. In particular, we show how MeAPO-34 formation was governed by an interaction between the divalent framework substituted metal ion and the template conformation, while for AlPO-5 the structure formation was determined by the template conformation alone. Understanding such interactions therefore appears to be important for the rationalization of microporous material formation.     

过渡金属修饰对铜箔电催化还原CO2的性能影响

CO2还原是一种解决温室效应以及能源短缺问题的有效方式.目前对于水溶液体系中的CO2还原,主要有光催化、电催化以及光电催化等方法,其中还原CO2法可在室温下进行,并较易实现大规模应用.由于金属电极在CO2电催化还原过程中表现较高电流密度和催化性能,使得目前研究的热点集中于金属电极的修饰改性.金属Cu与H2, CO结合能力适中,并且对生成碳氢化合物具有较好的催化性能,因此其在催化CO2还原中具有较大潜力.以往对于Cu的研究主要集中在表面修饰、调控表面结构以及制备合金等方向,其中对金属进行氧化后再还原的处理也是提高其催化活性的一种有效手段.氧化后还原得到的铜具有较大的粗糙度,且暴露的活性位点更多,对CO2还原具有较好的催化活性.我们对铜箔在空气氛围下、300oC焙烧5 h,然后恒电位还原,再进行过渡金属Ni、Zn、Au的修饰,研究所得样品电催化还原CO2性能.电极的表面形貌用扫描电镜表征, CO2还原的液相和气相产物分别用核磁和在线气相色谱进行检测.
　　修饰后电极的形貌没有发生太大变化,仍具有十分粗糙的表面结构.通过线性扫描伏安曲线可以看出,修饰Zn、Au后电流密度较未修饰前有明显增加,但是由于CO2还原过程中不可避免地伴随析氢副反应,因此,我们通过计算产物的法拉第效率来表征修饰后的电极对产物选择性的改变：未修饰时,在?1.2至?1.6 V均可检测到甲酸的生成,电位负于?1.4 V时可以检测到乙醇和正丙醇. Ni的修饰明显提高了甲酸的法拉第效率,也促进了正丙醇的生成.?1.3 V时甲酸的法拉第效率为26.0%,?1.5 V时液相产物的法拉第效率为34.3%.在线气相色谱结果发现, Ni的修饰也明显提高了CO的法拉第效率,在?1.4 V下, CO的法拉第效率为44.6%.这可能是由于Ni (r =0.1246 nm)的原子半径比Cu (r =0.1278 nm)更小,因此Ni的修饰会使Cu发生晶格收缩、导致d带中心下移而降低了CO的结合能,从而更易生成CO和HCOOH;而修饰Ni后对CO2还原产物正丙醇的提高可能是由于Ni的引入促进了C–C键的形成.修饰Zn后,甲酸的产率明显下降,在?1.6 V下甲酸的法拉第效率只有14.8%,但是乙醇与正丙醇的法拉第效率分别为1.6%与2.0%,相较于未修饰的电极略有提高.修饰Au后,液相产物甲酸及醇类的法拉第效率明显下降,在?1.5 V下,甲酸的法拉第效率只有7.9%,且只检测到少量的乙醇,未检测到正丙醇的生成,这可能与Au修饰后的电极对CO2还原中间体CO的吸附较弱有关,生成的CO中间体更易从表面脱附,而难以被进一步还原.     

Features of the phase formation in the nanocomposites

Thermodynamic conditions of formation of critical nuclei in the composites that are the phase forming medium, a matrix with inclusions of nanoparticles of the other phase, are considered. It is shown that depending on the nature of the spatial distribution of nanoparticles in the matrix, critical nuclei of different shapes may appear at the phase formation. In some cases the formation and stable existence of metastable phases, including amorphous ones is possible. The conditions of formation in the nanocomposites of the critical nuclei of heterogeneous structure are determined. The experimental data on the phase formation in the nanocomposites ZrO₂-Al(OH)₃ and ZrO₂-SiO₂ were analyzed and the earlier described feature of formation of the new phase nuclei is confirmed theoretically.