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.     

A theoretical study of the formation of the parent phosphinine C5H5P from the flash vacuum thermolysis of diallylvinylphosphine

The gas-phase decomposition of diallylvinylphosphine 1 into C5H5P 12 is studied by DFT/6-311+G(d,p) calculations with the B3LYP functional, followed by single-point energy-only calculations at the CCSD(T)/6-311+G(d,p) level. According to these calculations, the first step involves a retro-ene elimination that yields 3-phosphahexatrienes 2Z and 2E. Both compounds equilibrate through the formation of 1,2- and 3,4-dihydrophosphetes 3 and 4, and it is shown that the formation of 2Z is favored by the exothermic formation of the 3,4-dihydrophosphinine 5 through a 6pi-electrocyclization. Though 5 can easily isomerize into 2,3- (6) and 1,2-diyhydrophosphinines (7) by successive 1,5-hydrogen shifts, the formation of 12 from 5, 6, or 7 through an elimination of H2 is found to be a high energy process. It is also shown that the elimination of H2 from lambda5-phosphinine 8 following a C2v pathway is a symmetry-forbidden process. Finally, 1,4-dihydrophosphinine 9, which can be formed through a 1,4-hydrogen shift from lambda5-phosphinine 8, is found to be a convenient precursor of 12 through a 1,4-elimination of H2. The formation of 9 from 5 involves the intermediary formation of 3-phosphabicyclo[3.1.0]hex-2-ene 10. The mechanism eventually proposed for the formation of 12 from 2Z is given in Scheme 16 at the CCSD(T) level.     

Survival of the Fittest: Competitive Co‐crystal Reactions in the Ball Mill

The driving forces triggering the formation of co‐crystals under milling conditions were investigated by using a set of multicomponent competitive milling reactions. In these reactions, different active pharmaceutical ingredients were ground together with a further compound acting as coformer. The study was based on new co‐crystals including the coformer anthranilic acid. The results of the competitive milling reactions indicate that the formation of co‐crystals driven by intermolecular recognition are influenced and inhibited by kinetic aspects including the formation of intermediates and the stability of the reactants.     

Direct Observation of the Double-Stranded DNA Formation through Metal Ion-Mediated Base Pairing in the Nanoscale Structure

This work demonstrates single-molecule imaging of metal-ion induced double-stranded DNA formation in DNA nanostructures. The formation of the metal ion-mediated base pairing in a DNA origami frame was examined using C-Ag-C and T-Hg-T metallo-base pairs. The target DNA strands containing consecutive C or T were incorporated into the DNA frame, and the binding was controlled by the addition of metal ions. Double-stranded DNA formation was monitored by observing the structural changes in the incorporated DNA strands using high-speed atomic force microscopy (AFM). Using the T-Hg-T base pair, the dynamic formation of unique dsDNA and its dissociation were observed. The formation of an unusual shape of dsDNA with consecutive T-Hg-T base pairs was visualized in the designed nanoscale structure.     

On the time dependence of the formation of a condensed film in the adsorption of adenosine at the interface mercury/electrolyte

The formation of a condensed film in the adsorption of adenosine at the interface mercury/electrolyte was investigated by means of the differential capacity-time dependence combined with the potential-step method. A mathematical function is given which approximates the experimentally found time dependence of the film formation. This function can theoretically be derived with the assumption that the mechanism of the formation of the condensed film is similar to that of two-dimensional nucleation in the case of metal deposition. A possible molecular mechanism of film formation is discussed.     

22Cr双相不锈钢钝化膜组成及其半导体性能研究

借助于Mott-Schottky方程分析了成膜电位、成膜时间、成膜温度以及氯离子等因素对22Cr双相不锈钢在碳酸氢钠/碳酸钠缓冲溶液中所成钝化膜半导体性能的影响, 同时借助于X射线光电子能谱(XPS)技术分析了所成钝化膜的组成. 结果表明: 22Cr双相不锈钢在碳酸氢钠/碳酸钠缓冲溶液中所成钝化膜呈n-p型半导体结构, 钝化膜内施主/受主密度随成膜电位增加、成膜时间延长、成膜温度降低、以及介质中氯离子浓度的降低而减小, 同时膜对基体保护作用随这些因素变化而增强. 钝化膜的XPS分析表明, 钝化膜呈现双层结构, 外层膜主要由三价铁的氧化物(Fe2O3)组成, 内层膜主要由三价铬氧化物(Cr2O3)以及少量二价铁氧化物(FeO)组成.     

FT-IR and FT-raman spectroscopy study of the cyclic anhydride intermediates for the esterification of cellulose: III. Cyclic anhydrides formed by the isomers of cyclohexanedicarboxylic acid

Multifunctional carboxylic acids have been used as crosslinking agents for cotton and wood pulp cellulose. In our previous research, we found that a polycarboxylic acid esterifies cellulose through the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two carboxyl groups. In this research, we studied the formation of cyclic anhydride intermediates by different isomers of cyclohexanedicarboxylic acid (CHA) so that we can elucidate the effects of molecular structure on the formation of the anhydride intermediates. We found that both cis-and trans-1,2-CHA form 5-membered anhydride intermediates when temperature reaches their melting points and that cis-1,2-CHA forms the cyclic anhydride at temperatures lower than does trans-1,2-CHA. 1,3-CHA forms 6-membered cyclic anhydride at temperatures much higher than its melting point. The formation of a 5-membered cyclic anhydride intermediates takes place at temperatures lower than that of a 6-membered anhydride. This is probably the main reason why those polycarboxylic acids with their carboxylic acid groups bonded to the adjacent carbons of the molecular backbones are more effective crosslinking agents for cellulose than those with their carboxylic groups bonded to the alternative carbons. No formation of cyclic anhydride was found for 1,4-CHA. The formation of a five-membered cyclic anhydride was accelerated by monosodium phosphate, which is used as a catalyst for the esterification of cotton cellulose by polycarboxylic acids.     

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.     

Experimental study of the dynamics of front propagation in the Co(OH)2/NH4OH Liesegang system using spectrophotometry

In this paper we study the temporal dynamics of the Co(OH) 2/NH 4OH Liesegang system with redissolution by complex formation with ammonia using UV-vis spectrophotometry with a special setup. The formation of precipitate bands is accompanied with band redissolution at the top, and because of such precipitation-redissoultion dynamics, the bands appear as a propagating wave. The spectrophotometric technique developed in this study allows us to study at the kinetics of formation of the bands and their redissolution in great details. The formation, growth, and dissolution of multiple bands are monitored by the time evolution of the absorbance. It was found that the individual band formation is sudden and takes between 15 min to half an hour to form before the next band appears. The speed of formation of bands was different for different bands and the maxima of these speeds fit a Gaussian curve. The content of cobalt hydroxide in these bands was calculated and is shown to increase to a maximum away from the interface and then decreases. The bands later grow by further precipitation. This growth was demonstrated to be nonlinear in time. On the other hand, the dissolution of bands was shown to take place simultaneously and collectively among the multiple bands under study. The effect of the concentration of Co (+2) ions on the dynamics of band formation and dissolution was studied. A time law for this Liesegang system was also determined. The system was also found to be very sensitive to temperature fluctuations.     

Concerning the Solvent Effect on the Rate of the Reaction between Picryl Chloride and Diphenylphosphinic Hydrazide

The solvent effect on the rate constant of the reaction of picryl chloride with diphenylphosphinic hydrazide can be quantitatively described by a two-parameter equation considering the basicity and polarity of the medium. The reaction proceeds via formation of a charge-transfer complex between the reagents. Its nucleophilic solvation facilitates formation of the final products.     

Pulse-radiolytic studies of DNA and polynucleotides in aqueous solution in the presence of oxygen

The kinetic parameters of the formation of single-strand breaks (ssb) induced by OH radicals in presence of oxygen and that of the decay of peroxyl radicals of the polynucleotide have been found to be very similar. The conclusion that the decay of the peroxyl radicals is involved in the rate-determining step of ssb formation is confirmed for poly(U) by a study of the effect of ethanol on ssb formation under conditions of laser pulse excitation. The kinetics of the formation of ssb for poly(U) is complex but is consistent with a first order followed by more complex reactions. This kinetics is compatible with a pathway to ssb formation assuming H abstraction from the sugar moiety by base peroxyl radicals as the rate-determining step in the beginning of the overall reaction.     

Zn Doping Effect on the Performance of Fe-Based Catalysts for the Hydrogenation of CO2 to Light Hydrocarbons

In this work, we studied the role of zinc in the composition of supported iron-containing catalysts for the hydrogenation of CO₂. Various variants of incipient wetness impregnation of the support were tested to obtain catalyst samples. The best results are shown for samples synthesized by co-impregnation of the support with a common solution of iron and zinc precursors at the same molar ratio of iron and zinc. Catalyst samples were analyzed by various methods: Raman, DRIFT-CO, TPR-H₂, XPS, and UV/Vis. The introduction of zinc leads to the formation of a mixed ZnFe₂O₄ phase. In this case, the activation of the catalyst proceeds through the stage of formation of the metastable wustite phase FeO. The formation of this wustite phase promotes the formation of metallic iron in the composition of the catalyst under the reaction conditions. It is believed that the presence of metallic iron is a necessary step in the formation of iron carbides—that is, active centers for the formation and growth of chain in the hydrocarbons. This leads to an increase in the activity and selectivity of the formation of hydrocarbons in the process of CO₂ hydrogenation.     

Comparative computational and experimental study on the thermochemistry of the chloropyrimidines

The standard (p0 = 0.1 MPa) molar enthalpies of formation, Delta fH(0)(M), for liquid 2,4,6-trichloropyrimidine and for crystalline 2-chloropyrimidine, 2,4- and 4,6-dichloropyrimidine, and 2,4,5,6-tetrachloropyrimidine compounds were determined at T = 298.15 K by rotating-bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation, Delta (g)(cr,l) H(0)(M), of these compounds at T = 298.15 K were determined by Calvet microcalorimetry. The experimental standard molar enthalpies of formation of those compounds, in the gaseous state, at T = 298.15 K, were thus obtained by combining these two sets of results. The latter values have been employed in the calibration of the computational procedure, which has been used to estimate the gas-phase enthalpies of formation for the other chloropyrimidines that were not possible to obtain in a pure form for the experimental study. It is found that the exchange-correlation functional based on the local spin density approximation (LSDA) seems to be a cheap choice for the estimation of enthalpies of formation for heterocycles containing nitrogen atoms; the well-known B3LYP hybrid method yields larger differences, with respect to the experimental values, for 2,4,6-tri- and 2,4,5,6-tetrachloropyrimidines.     

Investigation into the Formation of Bubbles in Capillary Electrochromatography

The formation of bubbles in capillary electrochromatography (CEC) is well documented: possible origins include Joule heating and variations in EOF velocity on passing from the stationary phase through the frit and into the open tube. Methods for the prevention of bubble formation are discussed which are confirmed by experimental results. Using frit lengths varying from 1 mm to 6 mm it is shown how frit length is directly related to the likelihood of bubble formation and how this is affected by applied voltage. It is shown that the change in applied voltage across a capillary affects the formation of bubbles and also that rebonding octadecylsilane (ODS) onto the silica frit after formation of the frit can minimize the formation of bubbles and how this effects the chromatography. A method is also described for increasing the robustness of silica capillaries using a column coupler along with modifications made to conventional capillary electrophoresis equipment to cater for CEC.     

Classical trajectory study of the formation of XeH+ and XeCl+ in the Xe++HCl collision

The collision-induced reaction of Xe+ with HCl has been studied by use of classical dynamics procedures at collision energies 2-20 eV using empirical potential parameters. The principal reaction pathway on the potential energy surface is the formation of XeH+ with the maximum reaction cross section, 1.2 A2, occurring at E=9 eV. At lower energies, the cross section for the charge transfer process Xe++HCl-->Xe+HCl+ is comparable to that for XeH+ formation, but at higher energies, it is larger by a factor of 2. The cross section of the XeCl+ formation is an order of magnitude smaller than that of XeH+. For both XeH+ and XeCl+ formations, the reaction threshold is approximately 2 eV. The XeH+ formation takes place immediately following the turning point in a direct-mode mechanism, whereas an indirect-mode mechanism operates in the formation of XeCl+. Both XeH+ and XeCl+ formations come mainly from the perpendicular configuration, Xe+...HCl, at the turning point. Product vibrational excitation is found to be strong in both XeH+ and XeCl+.     

乙炔/空气预混火焰中CO添加对炭黑生成影响的数值分析(英文)

针对乙炔/空气预混火焰中CO添加对炭黑生成的影响进行了详细的数值模拟.通过对含有不同CO添加量的火焰的模拟结果比较,研究CO添加的温度和化学作用对于炭黑形成的影响.计算结果显示CO添加使炭黑的生成单调下降.炭黑体积分数和成核速率随着温度的升高而增加,到达一个阈值后,再随温度的升高而减少.从炭黑生成的H-萃取角度来看,由于反应OH+CO=CO2+H的向右速率增加,H原子增加以及OH自由基减少,CO添加会激发炭黑生成.从炭黑生成的C-添加机理来看,CO添加减小了C2H2的消耗速率,CO添加也有助于炭黑生成,但CO添加降低了燃料中C2H2的体积分数,使得炭黑表面增长速率降低.     

新型分子筛的生成焓计算

The enthalpies of formation of some compounds are not easy to be measured experimentally. This paper reports the calculated values of the heat of formation for some novel moleclar sieves by a method of consistant molecular mechanics force field. The enthalpies of formation of novel type molecular sieves: ZSM-48, ZSM-22, ZSM-23 and ZSM-18, have been calculated.     

Effect of nonionic emulsifier on the production of multihollow polymer particles by the stepwise acid/alkali method

The effects of nonionic emulsifier on the formation of multihollow structures formed within sub-micron-sized polymer particles by the “acid/alkali method” proposed by the authors were examined. The original acid-swellable particles were produced by seeded emulsion terpolymerization of styrene, butyl acrylate, and dimethylaminoethyl methacrylate. The results indicate that the nonionic emulsifier had a great effect on the formation of multihollow particles.     

Structure of the crystalline C60 photopolymer and the isolation of its cycloadduct components

We produced C60 photopolymer in gram quantity by a new monomer recycling method and extracted its soluble components. The most abundant components, the (2 + 2) cycloadduct dimer, C120, and several oligomers were isolated by high-performance liquid chromatography (HPLC). Three different C180 isomers were identified on the basis of their formation and decomposition reactions. The crystal structure of the insoluble photopolymer is face-centered cubic (fcc) with a contracted lattice parameter relative to the pristine C60. The lattice parameter and the amounts of soluble oligomers depend on the preparation temperature. We explain this variation with a topochemical model of photopolymerization: The geometrical conditions allow the formation of only linear or planar oligomers in the triangular or square sublattices. Competing reactions in the intersecting planes prevent the formation of large oligomers. The lattice contraction is proportional to the number of cycloadduct bonds.     

四氢化萘热解中甲基茚满生成机理的密度泛函计算

采用量子化学密度泛函方法对四氢化萘热解过程中甲基茚满的生成机理进行计算。结果表明,热解产物甲基茚满的主要存在形式是1-甲基茚满;其主要生成反应途径是,首先通过自由基和四氢化萘间的氢转移反应生成β-四氢化萘基,然后β-四氢化萘基上的氢化芳环经缩环反应生成1-甲基茚满。提高温度能促进1-甲基茚满生成反应的进行,但对其生成反应路径没有太大影响。