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.     

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.     

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.     

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.     

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.     

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.     

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.     

叠氮二异丁基铝的构造及其缔合-解离平衡研究

叠氮二异丁基铝（DBAA）是一个新合成的化合物。通过相对分子质量的测定、氢－核磁共振谱和铝－核磁共振谱的测定,确定了DBAA三聚体的分子构造;在溶液中研究了DBAA的三聚体和单晶体之间的缔合－解离平衡。这个平衡受溶剂性质、温度的影响。借助铝－核磁共振谱和相对分子质量的测定计算了DBAA三聚体的解离平衡常数、解离焓和解离熵等热力学数据。     

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.     

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.     

云南松枝梢营养成分分析

对云南松健康树和纵坑切梢小蠹蛀害树枝梢营养成分进行了分析,在健康树和蛀害树松梢中分别检测出11种氨基酸和14种氨基酸。健康树松梢中元素含量变化趋势由高到低为Ca,Mg,Al,Mn,Fe,B,Zn,Sr,Ni,蛀害树松梢中无机元素含量变化趋势由高到低为Ca,Mg,Al,Fe,Mn,B,Zn,Sr,Ni,为查找纵坑切梢小蠹蛀害的原因提供依据和数据。     

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.     

A study of mica structure and strength properties of polymer materials based on it

The mica microstructure is studied, and its shape and particle sizes are found as dependent on coating technology. Using epoxy and organosilicon polymers, several lots of materials with different contents of mica are prepared and mechanical tests are performed. The optimal amounts of mica wherein the initial strength characteristics are preserved are found. The thicknesses of epoxy and organosilicon polymer wherein high optical decorative properties of mica are preserved are determined.     

封闭异氰酸酯几种反应的动力学

封闭异氰酸酯广泛地应用于各种单组分涂料、粉末涂料和胶粘剂中。近年来,随着人们对水性聚氨酯的重视和开发,封闭异氰酸酯的重视和使用程度进一步加大。本文对封闭异氰酸酯的相关反应的动力学进行了综述,对两种不同的反应机理及其动力学的影响因素作了介绍。     

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。     

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.     

Mechanisms of antioxidant action: Effect of processing on the transformation products of thiophosphoryl compounds in polyolefins

It is shown that low density polyethylene or polypropylene processed in the presence of thiophosphoryl disulphides or thiocarbamoyl disulphides in air or in the presence of hydroperoxides are much more photo-stable than analogous samples processed normally. This is found to be true when the additives are added at normal (low) concentration levels or as concentrates which are subsequently diluted in the polymer to normal levels. Among the products formed when bis dialkyl dithiophosphoryl disulphides are oxidatively processed in polyethylene are polymer-bound thiophosphoryl compounds which are believed to generate sulphur acids slowly in the polymer.     

Alternate multi-layered adsorption of macro-cations and -anions on the colloidal spheres. Influence of the deionization of the complexation mixtures with coexistence of the ion-exchange resins

The alternate multiple adsorption layers of macrocations and macroanions on the surfaces of colloidal spheres, in which the complexation mixtures are deionized with ion-exchange resins are studied with help of the electrophoretic light-scattering, dynamic light-scattering and transmitted electron-microscopy techniques. The results are compared with those without resins. Colloidal silica spheres (110 nm in diameter) and monodispersed polystyrene spheres (220 nm) are used as colloidal spheres. The macrocations used are poly (4-vinyl-N-n-butyl pyridinium bromide) and poly (allylamine hydrochloride). Sodium poly (styrene sulfonate) and sodium polyacrylate are used as macroanions. The macroion-colloid complexations are formed firmly when the complexation suspensions are deionized with the resins.     

The calculation of the elastic constants of nematics

A molecular model for nematics is proposed. Its elastic constants are calculated and the attendant approximations are discussed. The results are compared with those of existing models.