Investigation of the role of the C-PCM solvent effect in reactivity indices

It has been shown recently, how the coupling between electronic degrees of freedom and vibrational modes is reflected in the properties of molecules. The necessary derivatives have been analyzed and their thermodynamic relations were demonstrated. This present work is focused on the analysis of a molecular system, under the influence of C-PCM induced solvent effect. The analysis is based on reactivity indices derived from DFT. The shift of frequency for diatomic molecules has been obtained. It has been identified as chemical force effect. The role of nuclear reactivity indices has been emphasized. This concept has been extended to obtain regional chemical potential values within C-PCM model for polyatomic molecules.     

Transient nutation and molecular echoes in microwave double resonance experiments

Transient phenomena occurring in time resolved microwave-microwave double resonance experiments when the pump power is switched on and off have been investigated both theoretically and experimentally. Special attention has been paid to the case when both fields are saturating and exactly resonant. A calculation using the evolution operator formalism has been carried out to explain the experimental results. Transient nutations similar to those observed by the Stark modulation method have been observed and theoretically explained. A new phenomenon, the driven induction decay, has also been observed when the pump power is switched on. Moreover, double resonance photon echoes have also been exhibited. The application of these methods to relaxation studies is discussed.     

Enhancement of the reducing properties of metallic mercury in presence of complex forming ions

The reducing properties of metallic mercury in solutions containing ions forming precipitates or complexes with mercuric or mercurous ions have been studied.The reducing power of mercury in the presence of thiocyanate is greatly enhanced, and it is similar to that in the presence of hydrochloric acid. The effects of the thiocyanate and ferric concentrations have been examined. To reduce a 0.01 M solution of ferric ion without forming a precipitate of mercurous thiocyanate, a concentration of thiocyanate of at least 0.05 M is required. The action of mercurythiocyanate system on some oxidising substances has been studied. The most important reaction is the reduction of ferric ions. The method has been applied to the determination of iron on macro and semimicroscale and good results have been obtained.The reducing power of metallic mercury in the presence of cyanide has also been examined. In general it acts as a strong reducer in alkaline medium. Atmospheric oxygen is reduced partially to water and hydrogen peroxide. Ferricyanide is reduced quantitatively to ferrocyanide. The action of metallic mercury in the presence of cyanide on other oxidising substances has also been examined.     

THE EFFECT OF SLNGLE AND MIXED MICELLES OF SURFACTANTS ON POLYMERIZATION OF ACRYLAMIDE

Acrylamide is conveniendy polymerized in aqueous solution lo a water soluble polymer. The measurements of kinetic parameters of polymerization of acrylamide, in aqueous and micellar solution, have been earned out by conduction calorimeter. The polymerization is initiated by sodium sulfite and sulfite-persulfate redox system. The effect of initiator and monomer concentration as well as temperature and surfactants on polymerization rale constant has been investigated. The analog thermogram method has been employed to calculate the rate constants. The activation energy is calculated from Arrhenius relationship and molecular weights are determined by viscometry. Rate equations have been derived and reaction mechanism hove been suggested. The rate of reaction is found to increase with temperature and monomer concentration.     

Interaction between polyelectrolyte gels and surfactants of opposite charge

Investigations dealing with fundamental aspects of the interaction between covalently cross-linked polyelectrolyte gels and oppositely charged surfactants are reviewed. For reference, a brief summary of results from recent studies of associative phase separation in linear polyelectrolyte/surfactant mixtures is also included. It is found that great progress has been made in several sub-areas since the first reports appeared in the early 1990's. The frequently observed surfactant-induced volume transition has been studied in detail. Its relation to associative phase separation in solutions and the important role of polyion-mediated micelle–micelle attractions have been clarified. Phase separation in gels, in particular core/shell structures, has been studied in great detail. The importance of network mediated elastic forces between two phases coexisting in the same gel has been demonstrated and some of their consequences have been clarified. Hydrophobic interactions between polyion and micelle have been found to have strong effects on both binding and swelling isotherms. The effect of salt, which has been found to sometimes disfavor, sometimes promote surfactant binding, is quite well understood. The microstructure of gels in the collapsed state has been studied in great detail and is often found to be highly ordered, resembling liquid crystalline phases common to surfactant/water systems. The kinetics of surfactant binding and the associated volume change has been investigated to some extent. Progress has been made for gels displaying phase separation during the volume transition.     

Iodometric determination of ascorbic acid by controlled potential coulometry

An iodometric method for the determination of ascorbic acid has been devised. The method is based on previously developed coulometric instrumentation. The stability of different ascorbic acid solutions has been studied and the best conditions have been established. Ascorbic acid has been determined in different kinds of samples but with the main interest on pharmaceutical preparations. Speqial regard has also been paid to the other constituents in such samples, with respect to possible interferences. The error of the coulometric method is about 0·1% and the time of an analysis is in the range 2–6 min.     

Ionization probability of the hydrogen atom suddenly released from confinement

The problem of the stability of a confined atom when it is extracted from the confining cavity has been investigated, modeled by a spherical hard wall potential. The ionization probability when the atom is released from confinement has been obtained. The dependence of the ionization probability on the confinement radius and on the quantum numbers of the initial confined state has been studied. The probability density function of the ionization energy of the ejected electron has been obtained for the different cases considered. The oscillatory structure of this distribution function, with a principal maximum located in the neighborhood of the energy of the initial state and minima very close to zero has been elucidated. The sudden approximation has been applied and the analytic continuation method has been used to calculate the different stationary states.     

Dynamic and thermodynamic properties of clathrate hydrates

Vibrational spectra and thermodynamic properties of ices and the cubic structure I (CS-I) clathrate hydrate have been studied by the lattice dynamics method. The phonon density of states for the empty hydrate framework and for xenon hydrate have been determined; the vibrational frequencies of the guest molecules in large and small cavities have been found. The stability of the hydrate with respect to the external pressure at low temperatures and its thermodynamic stability at temperatures around 0°C have been studied. It has been found that the empty hydrate framework is unstable in certain temperature and pressure regions. A definite degree of occupation of the large cavities by the guest molecules is necessary for the hydrate to become stable. It has been found that there is a maximum of the critical temperature at which the hydrate exists, which is a function of the external pressure.Dedicated to Dr. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.     

2-氨基-5巯基-1,3,4-噻二唑异构化反应机理的量子化学研究

用密度泛函理论(DFT)中的B3LYP方法,采取6-31+G* *基组对2-氨基-5巯基-1,3,4-噻二唑(简称AMT)的异构化反应机理进行了量子化学研究,全参数优化了异构化过程中反应物、产物的几何构型,找出了异构化途径中的过渡态,并通过振动分析加以确认,同时进行零点能校正.研究结果表明,异构化过程存在六种不同的异构化通道,有六个过渡态,相对而言, A→C之间的异构化反应最易发生,C是最稳定的异构化产物.     

Limited configuration interaction calculation of the optical spectrum for the permanganate ion

A series of limited configuration interaction calculations based upon an extended basis set is presented for the permanganate ion. The configurations have been selected so that they describe initial and final states equally well, and the size of the expansion has been increased until a reasonable convergence in the results has been assured. Both singlet and triplet states have been treated. Electron density changes occurring at the so-called charge-transfer transitions have been studied, and relaxation turns out to play an important role. The agreement with experimental spectra is satisfactory.     

立方面心C60晶体晶格振动的研究

采用C60分子之间相互作用势的Kihra形式,研究了立方面心C60晶体的晶格振动问题,得到了质心振动沿[111]、[110]及[100]方向的声子散射圆频率分布曲线及C60晶格振动频率的态密度分布.采用所得到的C60晶格振动频率的态密度分布,计算了晶体C60在298 K时的等压热容,所得数值与实验值相符.     

Linear sweep voltammetry at the tubular graphite electrode: Part II. Totally irreversible processes

The theory of linear sweep voltammetry at the tubular graphite electrode has been developed for irreversible processes. The convective diffusion differential equations have been transformed into an integral equation which is solved numerically. The current-potential curves have been calculated theoretically and verified experimentally. The dependence of the current-potential curves on velocity has been studied. A procedure for the determination of kinetic parameters, i.e. standard rate constant and transfer coefficient, is presented.     

The precipitation of bismuth basic acetate from homogeneous solution

Precipitation from homogeneous solution by urea hydrolysis has been used to investigate the conditions affecting the precipitation of bismuth basic acetate. Evidence has been found that indicates that acetate complexes may be formed. The method has been tested for the determination of bismuth, but is not suitable if lead is present.     

量子控制论在化学中的应用

控制量子现象是化学研究中的一个重要目标,量子控制论对实现该目标具有积极的指导意义.本文综述了量子控制论在化学中的应用及其进展,重点分析了量子相干控制、量子优化控制、闭环学习控制和能控性观念在化学研究中的应用,介绍了它们的研究现状,并对其未来研究进行了展望.     

照相明胶荧光特性的研究

利用荧光分析法研究了照像明胶的荧光特性,结果表明,除了公认的苯丙氨酸和酪氨酸两种荧光物质外,还存在一种未知的荧光杂质,其最大激发峰为240 nm,荧光峰为395 nm,性能试验表明,该荧光杂质可能为卟啉类络合物或某种色素物质。     

A study of the effect of network angle of fabrics on kinetics of impregnation upon molding of articles made from carbon plastics

The permittivity coefficient, volume, and porosity of an elementary cell of fabric filler have been calculated. Two types of fabric structures have been considered using the example of carbon fabric: standard, in which filament yarn is cylindrical, and spread, it which it has a rectangular shape. A reflector of a mirror space antenna has been considered characterized by the presence of doubly curved surfaces is used as the object of study. Modeling of the kinetics of impregnation of reflector for two types of fabric structures has been carried out using the RAM–RTM program. In the work, the effect of the network angle on the duration of impregnation process has also been investigated. Based on the results of calculation, reflector samples have been made and their quality has been evaluated. Theoretical and experimental results have been compared.     

Application of the photoionization detector for the determination of ethanol in aqueous solutions and human breath

A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3delta-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results.     

Jahn－Teller畸变后D_（2h） C_（60）~－的电子结构和光谱

用ＩＮＤＯ系列方法对Ｃ_（６０）自由基负离子进行了几何构型优化，得到Ｄ_（２ｈ）对称性的构型，表明Ｃ_（６０）~－确实发生了Ｊａｈｎ－Ｔｅｌｌｅｒ畸变，导致单键变短，双键变长，形成１５种键，９种不等同碳原子，其额外负电荷主要分布在赤道附近。以此构型为基础，计算了Ｃ_（６０）~－的电子光谱，与实验值吻合，在对光谱进行理论指认的同时讨论了光谱红移的原因。     

Jahn-Teller畸变后D2h C60--的电子结构和光谱

用INDO系列方法对C60自由基负离子进行了几何构型优化,得到D2h对称性的构型,表明C60--确实发生了Jahn-Teller畸变,导致单键变短,双键变长,形成15种键,9种不等同碳原子,其额外负电荷主要分布在赤道附近。以此构型为基础,计算了C60--的电子光谱,与实验值吻合,在对光谱进行理论指认的同时讨论了光谱红移的原因。     

Charge storage performance of doped carbons prepared from polyaniline for supercapacitors

Doped carbons have been prepared from polyaniline for supercapacitors. The morphology of samples has been characterized by scanning electron microscope, the surface chemical composition of samples has been investigated by X-ray photoelectron spectroscopy, and the surface area of samples has been calculated by Brunauer–Emmett–Teller measurement. Electrochemical properties have been studied by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6 mol L⁻¹ potassium hydroxide. Their charge storage performance has been evaluated, and the effect of nitrogen atomic functionalities on the pseudocapacitive property has been studied. The experimental results have proved two mechanisms of energy storage in doped carbons: double-layer formation and pseudocapacitance. The overall specific capacitance of doped unactivated carbon is mainly attributed to pseudocapacitance, that of doped activated carbon prepared by physical activation is attributed to the synergic effect of pseudocapacitance and double-layer capacitance, but that of doped activated carbon prepared by chemical activation is mainly attributed to double-layer capacitance.