Analytical applications of ternary complexes-VII Elucidation of mode of formation of sensitized metal-chelate systems and determination of molybdenum and antimony

The ternary complexes which are formed when surface-active agents are added to various metal-dyestuff chelate systems are shown to be dependent on the formation of micelles. Spectrophotometric measurements indicate that true ternary complexes are formed with well defined structures and that the changes in absorption spectra produced are not due to simple adsorption of the binary metal-dye complex onto micellar aggregates. Some suggestions are made to account for the nature of the observed changes. The analytical potentialities of this type of system are illustrated by the formation of such complexes between molybdenum or antimony, Catechol Violet and cetyltrimethylammonium bromide, yielding molar absorptivities of 4.6 × 10⁴ and 3.0 × 10⁴ respectively.     

Extension of semiempirical methods to simulation of surfaces

Various approaches for surface simulation are described. They are based on free, saturated, and embedded clusters, as well as periodic models. The features of semiempirical methods are reviewed and ideas for their improvement are discussed. Special features of the structure and stability of clusters are presented which are suitable for the transition to the solid state. Linear and nonlinear relationships for binding energies and bond lengths in dependence of the average coordination number are discussed. Finally, a systematic way for the simulation of adsorption at ion crystal surfaces by model clusters is suggested. © 1996 John Wiley & Sons, Inc.     

Development of a new generation of drug dosage forms by construction of liposomal nanocontainers

Various methods of construction of liposomal nanocontainers are studied. Parameters of liposomes are determined. Advantages of phase transformation method are demonstrated. The routes of liposome delivery to the organism are determined.     

A perturbative calculation of the rovibrational energy levels of methane

The rovibrational energy levels of methane are determined from a quartic ab initio potential energy force field where the expansion coordinates are the Morse coordinates for the stretches and extension coordinates for the bends. Energies are calculated using canonical Van Vleck perturbation theory. Results are obtained for both rotation-vibration Hamiltonians expressed as functions of curvilinear and rectilinear normal coordinates. Second, fourth, and sixth order curvilinear results are compared with experimental results, and fourth order results for the rectilinear and curvilinear Hamiltonian are compared to each other. The calculated rovibrational levels are in good agreement with the experimental values for low J levels. The calculated rotational level splittings are in even better agreement with the experiment. In particular, the ground state tetrahedral splittings, which are as small as 10(-4) cm(-1), are well reproduced by our calculations at sixth order.     

Characteristics of interfacial layers of polymer composite materials

Design diagrams are given based on which engineering models are developed allowing one to calculate the characteristics of interfacial layers of polymer composite materials are given. Theoretical and experimental investigations of interfacial layer thicknesses are comparatively evaluated.     

Densities,speeds of sound,excess volumes and viscosities of binary mixtures of mtbe with tetralin and decalin at 303.15 k

Measurements of densities, speeds of sound, excess volumes and viscosities of binary mixture of methyl tert-butyl ether with tetralin and decalin are reported at 303.15?K over the entire range of composition. Excess volumes are measured using batch dilatometer technique. Sound speeds are obtained using ultrasonic interferometer. Densities are computed from excess volume data. Isentropic compressibilities are derived from density and sound speed data. Speeds of sound are evaluated on the basis of Jacobson's free length theory and Schaff's collision factor theory. The predicted values are in good agreement with the experimental results. The viscosity data are analysed on the basis of corresponding states approach. Excess volumes and deviation in isentropic compressibilities are negative and deviation in viscosities are positive over the entire composition range. The experimental results are discussed in terms of possible molecular interactions between unlike molecules.     

Review of chemical methods for the determination of penicillin

The published methods for the analysis of penicillin are classified according to whether they are intended a) to differentiate between types of penicillin, or b) to determine the total penicillins present in a given sample.The limitations of many of these methods are indicated, and those which are attractive for possible routine application are discussed in detail.     

Improvement of the Composition of Detergent Solutions for the Removal of Deposits on the Axial-Compressor Blades of Gas-Turbine Units

During the operation of gas-turbine units deposits, which have the form of a conglomerate of hydraulic oil and contaminations from atmosphere air, are accumulated on the axial-compressor blades. Deposits are occasionally removed using solid abrasive or detergent solutions. Only detergent solutions are employed on modern units, because abrasive substances damage the protective sputtering of blades. The detergent solutions that are used have a high cost and are unsafe in use. In this work, a high-performance detergent solution is suggested, which is able to dissolve deposits on the axial-compressor blades of gas-turbine units.     

The Application of NMR Spectroscopy and Chemometrics in Authentication of Spices

Spices and herbs are among the most commonly adulterated food types. This is because spices are widely used to process food. Spices not only enhance the flavor and taste of food, but they are also sources of numerous bioactive compounds that are significantly beneficial for health. The healing effects of spices are connected with their antimicrobial, anti-inflammatory and carminative properties. However, regular consumption of adulterated spices may cause fatal damage to our system because adulterants in most cases are unhealthy. For that reason, the appropriate analytical methods are necessary for quality assurance and to ensure the authenticity of spices. Spectroscopic methods are gaining interest as they are fast, require little or no sample preparation, and provide rich structural information. This review provides an overview of the application of NMR spectroscopy combined with chemometric analysis to determine the quality and adulteration of spices.     

Photometric complex-formation titration of submicromolar amounts of zirconium

Even in strongly acidic solution Zr(IV) forms polynuclear hydroxide complexes. In these compounds tetrameric units play a dominant role. When the Zr atoms in these units are interconnected through double OH-bridges (olated bonds) quantitative formation of Zr-EDTA is possible at room temperature. When the double OH-bridges are replaced by single oxygen-atom bridges (oxolated bonds) the units are less reactive. The oxolated tetramers are still capable of reacting quantitatively with EDTA if heated to about 100 degrees ; higher oxolated polymers are not. When these higher polymers are formed during the initial adjustment of conditions for a titration, large errors will be observed. By suitable treatment of the solutions oxolation can be restricted sufficiently to permit titrations with an error of less than 1%. Semi-Xylenol Orange has been found to be a suitable indicator for direct titrations; back-titrations are performed with Bi(3+), with PAR as indicator.     

Ionisation Energies and the Electronic Structures of the N-oxides of diazabenzenes

The ionisation energies and the HeI photoelectron spectra of the N-oxides of diazabenzenes are presented. The valence electronic structures of the N-oxides are discussed in view of the ionisation energies, and the profiles, of the bands. The interpreted data are compared to calculations which are in good agreement. The results are correlated to the physicochemical studies, and particularly to the electronic absorption spectroscopy, of the N-oxides. The assignment of the photoelectron spectra of the azabenzenes are considered with reference to the spectra of their N-oxides.     

Stabilization of isopropanol dispersions of nanosized powders of yttrium oxide-stabilized zirconium dioxide

The properties of dispersions of nanosized powders of yttrium oxide-stabilized cubic zirconium dioxide (YSZ) are studied. The sizes of YSZ aggregates are determined under different conditions. Dispersants for dispersions of YSZ nanosized powders in isopropanol are obtained through partial esterification of poly(acrylic acid) with triethyl orthoformate. The composition and structure of the dispersants are optimized.     

大面积功率器件软钎料的焊接失效分析

针对大面积功率器件软钎料的失效问题,运用扫描电子显微镜(SEM)分析了SnPb软钎料的微观结构并运用能谱仪对其进行成分分析,找出了失效的主要原因:对软钎料进行刚玉抛光后,未能将残留在软钎料内的Al2O3成分完全去除,以至于器件的可焊性变差.根据分析提出了改进意见,较好地解决了SnPb软钎料的失效问题.     

Synthesis,Redox and Spectroscopic Properties of Pterin of Molybdenum Cofactors

Pterins are bicyclic heterocycles that are found widely across Nature and are involved in a variety of biological functions. Notably, pterins are found at the core of molybdenum cofactor (Moco) containing enzymes in the molybdopterin (MPT) ligand that coordinates molybdenum and facilitates cofactor activity. Pterins are diverse and can be widely functionalized to tune their properties. Herein, the general methods of synthesis, redox and spectroscopic properties of pterin are discussed to provide more insight into pterin chemistry and their importance to biological systems.     

煤微组分结构的X-射线实验研究

本文介绍用X-射线研究烟煤的壳质组、镜质组和惰质组三种煤微组分的结构。结果表明,不同微组分的结构存在差异,这是由于其化学组成不同而决定的。     

Importance of the catalytic effect of the substrate in the functionality of lubricant additives: the case of molybdenum dithiocarbamates

Molybdenum dithiocarbamates (MoDTCs) are lubricant additives very efficient in reducing the friction of steel, and they are used in a number of industrial applications. The functionality of these additives is ruled by the chemical interactions occurring at the buried sliding interface, which are of key importance for the improvement of the lubrication performance. Yet, these tribochemical processes are very difficult to monitor in real time. Ab initio molecular dynamics simulations are the ideal tool to shed light on such a complicated reactivity. In this work, we perform ab initio simulations, both in static and tribological conditions, to understand the effect of surface oxidation on the tribochemical reactivity of MoDTC, and we find that when the surfaces are covered by oxygen, the first dissociative steps of the additives are significantly hindered. Our preliminary tribological tests on oxidized steel discs support these results. Bare metallic surfaces are necessary for a stable adsorption of the additives, their quick decomposition, and the formation of a durable MoS₂ tribolayer. This work demonstrates the importance of the catalytic role of the substrate and confirms the full capability of the computational protocol in the pursuit of materials and compounds more efficient in reducing friction.     

Synthesis and investigation of the efficiency of cationic aminopolymer resin

Experimental results of synthesis and investigation of the efficiency of a cationic aminopolymer resin are presented. The monomers are characterized, the synthesis conditions are considered, and the technical characteristics of the resin are given. It is shown that the resin facilitates the acceleration of dehydration of repulped stock, significantly reduces the cationic need, increasing the retention of anionic contaminations, and decreases the content of suspended substances in recycled water. The data on pilot tests of the resin are presented that demonstrate its high efficiency.     

The development of the fundamental concepts of surface thermodynamics

Author’s results concerning the most fundamental problems of the thermodynamics of surface phenomena are reviewed. The generalized Laplace-Young-Kelvin equation, phase rules, and Gibbs adsorption equations are presented. Analogs of Konovalov’s laws are describes as applied to surface phenomena. The surface tension dualism, the Gibbs equation for adsorption on solid surfaces, and the phase equilibrium condition for a soluble nanoparticle are explained. The general mechanochemical approach, chemical affinity tensor, and the discovery of the mechanochemical dissolution effect are characterized. A novel approach to the monolayer state equation is formulated based on an excluded area. The problems of nucleation and the theory of surface separation are reperted.     

Elastic constants of nematic solutions of rod-like and semi-flexible polymers

Analytical expressions for the elastic constants of nematic polymer solutions are derived when the macromolecules are monodisperse rod-like, bidisperse rodlike or semi-flexible. These expressions are derived in the gaussian approximation so that they constitute exact leading terms of a general asymptotic expansion for high degree of nematic ordering although the results are justifiable only within the range of validity of the second virial approximation. The limiting forms are in complete agreement with recent numerical work for monodisperse rods.