Synthesis of Multicomponent Oxide Low-Dimensional Systems on the Surface of Porous Silicon Dioxide Using the Molecular Layering Method

Reflecting the research in the field of the surface chemistry of solids over the last 25-30 years, the results related to the application of the molecular layering method for the synthesis of surface low-dimensional structures of complex composition are presented. The regularities of formation of multicomponent mono-, multilayers on the surface of solid-phase matrices are studied on examples of chemical interactions, by a preset program, of chlorides and oxychlorides of titanium, vanadium, phosphorus, chromium, zinc, and iron with hydroxy and secondary functional groups of porous silicon dioxide. On the basis of chemical-analytical and spectroscopic data, structural schemes of synthesized products are proposed and functional interactions in multicomponent monolayers on the surface are considered. The reactivity of the element chlorides and oxychlorides as a function of the chemical composition of surface functional groups of silica and on synthesis conditions is estimated. In view of the revealed regularities of formation of complex low-dimensional systems on silica surface, prospects of application of the resulting data are considered for elaboration of scientific foundations of the chemical nanotechnology of production of solid-phase materials of various functional use, based on the molecular layering method.     

Rheological and electrical characteristics of carbon black dispersions in apolar dielectric medium

Results of the study of the rheological characteristics, as well as of the electrical resistance and capacity of vaseline oil suspensions of carbon blacks with different degrees of oxidation under the action of shear and vibration are reported. Possible mechanisms of suspension conductivity as a function of the regime of dynamic loading are considered. The reasons for the appearance and displacement of dilatant peaks in vaseline oil suspensions of carbon black are proposed as being dependent on the content of particles of solid phase and the degree of surface oxidation.     

Lipids of the oils of the fruit and leaves ofHoppophaë rhamnoides

The analysis of some lipids of four forms of the common sea buckthorn has shown that they all differ with respect to the composition of the fatty acids of the triacylglycerols of the leaves. One of the forms is characterized by an infringement of the specificity of the composition of the fatty acids in positions 2 of the triacylglycerols of the oils of the seeds and the leaves.     

Porous Phosphates of Trivalent Metals: Problems of Their Synthesis and Application

Abstract

Porous phosphates are compounds with a branched system of pores, such as X-ray amorphous xerogels of metalphosphates and crystalline phosphates of zeolite type. Having generalized extensive experimental data about the conditions of Al-, Fe-, Cr-, Ga-, In-, Y-phosphate hydrogels synthesis we found the influence of a number of factors on the rates of their formation, stability of structures and the porosity character of xerogels. The mechanism of porous structure formation of xerogels of metalphosphates has been proposed. The problems connected with the regulation of porous structure of xerogels have been discussed. The formation of porous crystalline aluminophosphates of zeolite type has been accomplished through a number of stages. The nature of alkyl ammonium bases influences the direction of the crystallization process and the type of the structure. It was noted that the stoppind of crystallization on different stages of synthesis gives the possibility to obtain new molecular sieves. Thermal changes and sorption properties of aluminopnosphates of zeolite type have been studied. During the process of removing organic cations the formation of secondary porosity was established. The effectiveness of applying porous metalphosphates in catalysis and adsorption processes has been showed.     

Development of methods for synthesis of surface-modified fluoropolymer-containing composite materials

The results of studies into development of methods for synthesizing new modified fluoropolymer-containing composite materials were summarized. The issues covered include: new modes and initiation methods of graft polymerization of fluoromonomers onto the surface of items of various nature and dispersity without homopolymer formation; nature of the surface active centers of the modified material and how it affects the kinetics and mechanism of both postradiation graft polymerization of tetrafluoroethylene and the subsequent chemical modification of the graft-polymer; major mechanisms and methods of blocking the terminal radicals of the grafted fluoropolymer layer, including those based on reaction with some perfluoroolefins at their double bond, yielding stable long-lived radicals, which allows controlling the physicochemical properties of composite materials; and new methods of synthesis of selective biocompatible sorbents with specific adsorption properties. Accelerating effect of oxygen on polymerization was analyzed, and the phenomenon of ozone initiation of low-temperature polymerization of tetrafluoroethylene was revealed and examined; a new class of high-performance polymerization initiators, namely, perflouroolefin ozonides, was synthesized; and new methods of initiation of polymerization and copolymerization of fluoromonomers, as well as of some other monomers with their use were developed.     

The current state and development of perspectives of application of synthetic antimicrobial agents

The review presents data regarding the main classes of substances applied in pharmaceutics for long-term control of pathogenic microflora. The problems of application of these substances caused by the resistance of pathogenic microflora to the main classes of the biocides are discussed. Mechanisms of action of antimicrobial agents and possible mechanisms of adaptation of pathogenic microflora to these substances are considered. Guanidine-containing cationic polyelectrolytes with different structures affecting their features, as well as the main stages of their mechanism of action, are described. Comparative information on the range of antimicrobial action of representatives of this class based on the results of studies conducted in different periods of time is presented. Analysis of the literature data demonstrated that branched oligohexamethyleneguanidine hydrochloride is a promising compound for the development of pharmaceutical substance.     

等物质的量定律及其应用

本文指出了滴定计算中等物质的量规则的缺陷,并提出了等物质的量定律,将这个反映化学反应客观规律的定律定义为:在氧化还原反应体系中氧化剂与还原剂得与失电子的物质的量相等;在酸碱反应体系中酸与碱得与失质子的物质的量相等;在沉淀反应中阳离子与阴离子所具有电荷的物质的量相等;在络合滴定中金属离子与氨羧络合剂的物质的量相等。等物质的量定律可用下式表达:(i=k)∑(i=1)△n(1/z_Ai)Ai=(i=P)∑(i=1)△n(1/z_Bi)Bi。这个定律及其表达式能使复杂的滴定分析计算简单化、规范化。     

Electro-optics of solutions of biopolymers and their complexes

The review summarizes the results of electric-birefringence studies of the molecular properties of biopolymers and their complexes. The application of alternating electric fields makes it possible to study the kinetics of orientation of DNA, RNA, and polypeptide molecules in diluted solutions. An analysis of molecular-mass dependences of relaxation times of biopolymer molecules in terms of the rotational friction theory is used to determine the equilibrium rigidity of macromolecules characterized by Kuhn segment length A. For DNA molecules in buffer solutions with a low ionic strength, the value of A derived from electro-optical measurements is 114 nm. The high sensitivity of electric birefringence to changes in the secondary and tertiary structures of biopolymers ensures its use for the analysis of sequence curvature in short fragments of DNA and for investigation of transitions between different tertiary structures of RNA. The study of electro-optical birefringence in solutions of complexes of DNA and polypeptides with oppositely charged ions of surfactants makes it possible to gain insight into their conformational properties in organic solvents. The stoichiometric complexes of DNA in chloroform occur in the compact globular state, whereas the conformation of complexes formed by various polypeptides depends on their composition and may vary from rodlike to coiled. Electric birefringence in solutions of biopolymer complexes is associated with the orientation of molecules that is due to the external-field-induced dipole moment that appears as a result of a small displacement of ions along the contour of polyion chains. The time of reaching the induced dipole moment is equal to or greater than the time of orientational relaxation of the complex as a whole.     

Effects of the degree of dispersion and the morphology of zinc powder on the thermodynamics of its interaction with polystyrene in solution and in composite films

The adsorption of block PS on the surface of spherical, round, and flaky particles of highly dispersed Zn powders with dimensions of 3.5–23 μm and the interaction of the polymer with the surface of Zn powders in the composite films are studied by refractometry and isothermal calorimetry. During establishment of adsorption equilibrium, the concentration of PS in the bulk of solution increases, while, near the surface of Zn particles, the concentration of PS decreases, thus indicating the predominance of absorption from solution of the solvent o-xylene. With the use of the thermodynamic cycle, including processes of solution of the polymer and Zn-PS film composite and wetting of the Zn powder, the enthalpies of formation of PS-Zn composites are estimated. The enthalpies of mixing of filled compositions comprise two contributions of opposite signs: In the low-filling region, the negative contribution of adhesion interactions prevails, while in the region of high-filled compositions, a positive structural contribution, which is associated with additional loosening of the glassy packing of PS near the filler surface, plays the decisive role. The contribution of adhesion interaction is largely determined by the dimensions of filler particles, while the structural contribution is controlled by their shape. The experimental evidence suggests that spherical particles possess the highest thermodynamic compatibility with the polymer matrix of the composite material.     

The effect of the diversity of molecules in sets and similarity of sets on the quality of prediction in QSAR studies

We report here: (a) formulas/procedures for calculating the similarity of molecules, considering their chemical structure, size, shape and hydrophilicity (b) a procedure for clusterization of the sets of molecules, according to similarity (c) formulas/procedures for calculating the diversity of molecules in clusterized sets as well as similarity of clusterized sets, based on Shannon Entropy formalism The paper analyses the influence of the diversity of molecules and similarity of calibration/prediction sets on the quality of prediction for prediction set molecules. The calculated influence of certain molecular feature (chemical structure, size, shape and hydrophilicity) on toxicity depends on the structure of the database, specifically the number of molecules and diversity of molecules having analyzed molecular feature. A QSAR analysis of 49 phenol derivatives revealed the effect of the diversity of molecules in sets and of the similarity of sets on the quality of prediction for prediction set molecules: (a) a direct correlation with the similarity of sets, regardless of analyzed molecular feature (b) an inverse correlation with the diversity of molecules in the calibration set, from the point of view of chemical structure, size and shape (c) a direct correlation with the diversity of molecules in calibration set, from the point of view of hydrophilicity (d) a direct correlation with the diversity of molecules in prediction set, regardless of analyzed feature.     

Stoichiography and present-day analytical chemistry of solid inorganic substances and materials

The article covers factors that determine fundamental difficulties of chemical phase analysis of a mixture of solid phases of inorganic compounds. Stoichiographic principles and methods, novel for analytical chemistry and leading to the efficient solution of the problems of phase analysis, are discussed. Conditions of the selective separation of mixtures of multiphase multielement solid compounds and principles of the new method, fan-like separation, ensuring the extraction of individual phases from unseparated mixtures, are considered. An idea of a complex method of solving analytical problems by stoichiography methods in proposed. The problem of the multiplicity of objects of analysis is discussed and general principles of the efficient solution of problems of the detection and identification of components of complex mixtures of unknown chemical composition are considered.     

Quantitative X-ray fluorescence analysis of multielemental subjects of complex shape without implementation of reference standards

A theoretical dependence of the ratio of intensities of X-ray fluorescence lines of chemical elements on the ratio of their concentration in a sample is suggested. The effect of various experimental factors on parameters of the obtained model is considered. A method of quantitative X-ray fluorescence analysis of multielemental subjects using the suggested calibration dependence without the implementation of reference standards is described. The adequacy and analytical advantages of the developed approach are demonstrated for the determination of the elemental composition of a sample of a metal alloy of complex shape.     

Reasons for the effect of the amount of electrolyte on the performance of lithium–sulfur cells

As is known, the depth of the electrochemical reduction of sulfur and lithium polysulfides, the reduction rate, and the cycle life of lithium–sulfur cells decrease with the electrolyte content. The present paper studies the reasons for the effect of the amount of electrolyte on the depth of sulfur reduction and the cycle life of lithium–sulfur cells. The main reason for the effect of the amount of electrolyte on the depth of the electrochemical reduction of sulfur was shown to be the generation of solvate complexes of lithium polysulfides. The minimum amount of electrolyte required for complete reduction of sulfur during the discharge of lithium–sulfur cells is determined by the composition of the generated solvate complexes of lithium polysulfides. The solvate numbers of the lithium ion in the solvate complexes of lithium polysulfides generted in sulfolane electrolyte systems were evaluated from the experimental data. An analysis of the results shows that the minimum solvate number of lithium ions in the solvate complexes of lithium polysulfides with sulfolane is 1.     

Thermodynamic and Kinetic Foundations of the Micellization Theory: 5. Hierarchy of Kinetic Times

The characteristic kinetic times of micellization in the solution of a nonionic surfactant: the times of establishment of quasi-equilibrium concentrations of molecular aggregates in micellar, subcritical, and overcritical regions, times of establishment of quasi-equilibrium concentrations of molecular aggregates in the near-critical region of their sizes, the average time between two successive acts of emission of surfactant monomers by a micelle, the average value of micelle lifetime, the time of establishment of quasi-stationary mode of matter exchange between the solution and molecular aggregate, as well as the times of fast and slow relaxation in a solution were analyzed. The hierarchy of these times disclosing complex multistage kinetic process of micelle formation and decomposition and the establishment of equilibrium in the micellar solution was revealed. It was shown that this hierarchy is provided by the small parameters of the kinetic theory. The inverse problem of micellization kinetics was discussed; this problem allows us to find the characteristics of the formation work for micellar aggregate from the experimental data on the relaxation time of micellar solution.     

Synthesis of dispersed silicon, titanium, and zirconium dioxides by pyrolysis of cellulose inorganic composites

The method of the synthesis of dispersed powders of silicon, titanium, and zirconium dioxides was developed, including formation of cellulose inorganic composites by impregnation of pressed granules of powdered cellulose with solutions of tetraethoxysilane and tetrabutoxy zirconium, hydrolysis of the organometallic constituent of the composite, pyrolysis of the cellulose matrix of the composite, and burning of its carbon constituent.     

Electrohydraulic effect in heterodisperse water-plant systems. II. Chemical nature of the suspended particles

On the basis of the results of acid hydrolysis, chromatographic analysis of the hydrolysates, and a study of IR spectra, it has been established that the suspended particles liberated under the action of electrohydraulic shocks on heterodisperse water—plant systems consist of small fragments of the lignocarbohydrate complex of the plant tissue.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent. FAX (3712) 62 73 48. Division of Wood Chemistry, Irkutsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Institute of Solar and Terrestrial Physics, Siberian Division of the Russian Academy of Sciences, Irkutsk, FAX (395-3) 46 25 57. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 435–439, May–June, 1994.     

Lipids and lipopolysaccharides of the genusFlavobacterium

The fatty acid compositions of the free lipids of three strains and the monosaccharide compositions of the lipopolysaccharides of four strains of new species of microorganisms of the genusFlavobacterium have been studied. The acidic nature of the polysaccharides of the LPSs of the microorganisms studied has been shown.Pacific Ocean Institute of Bioorganic Chemistry of the Far Eastern Scientific Center of the USSR Academy of Sciences, Vladivostok, and Institute of Microbiology of the USSR Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 564–567, September–October, 1986.     

Rotating coiled columns in the speciation analysis of natural samples: Dynamic fractionation of element forms in soils,sludges, and bottom sediments

The potentials of dynamic extraction in rotating coiled columns (RCCs) for the speciation analysis of soils, sludges, and bottom sediments is discussed on an example of the fractionation of element forms. A comparative study of the results of the fractionation of the forms of heavy metals differing in physicochemical mobility and bioavailability (Zn, Cd, Pb, Cu, Ni, Cr), obtained using a number of procedures of sequential extraction, is performed. Particular attention is paid to mercury, which is quite different from other metals in biogeochemical properties. Conditions are described for the dynamic fractionation of arsenic species occurring in natural samples in anionic forms. It is revealed that, in contrast to batch extraction, the continuous renewal of the eluent in a rotating column eliminates the problem of readsorption and overlapping of isolated fractions and enables the correct assessment of the concentration of the most mobile and bioavailable forms of toxic elements. A hyphenated method for the fractionation and determination of certain forms of elements (based on the ICP-AES detection of elements in the column eluate in the on-line mode) is described, ensuring the processing and a real-time control of the dynamic extraction of the forms of elements. The kinetic aspects of selective leaching are considered. It is shown that a comparison of the elution curves of micro- and macrocomponents makes possible a judgment about the selectivity of the leaching reagent, optimization of the conditions for the isolation of each fraction, and the investigation of the features of the binding of heavy metals and matrix elements in soils and bottom sediments. Some recommendations are given for the dynamic fractionation of the forms of elements in soils, sludges, and bottom sediments in RCCs.     

Computer simulation of the structure formation and disruption processes in the solid-liquid disperse systems

Results of the computer simulation of solid-liquid disperse systems are reported. Main regularities of the formation and disruption of the internal structure of such systems are demonstrated under static and dynamic conditions (including the combination of shear and orthogonal vibrations). The effect of the character of the interaction of dispersed phase particles, as well as of a number of parameters concerning the type and intensity of external actions on the behavior of disperse systems is shown. The possibility of the regulation of the character of microstructure and rheological properties of disperse systems by the combination of shearing and orthogonal vibrations is illustrated.     

Molecular and electronic structures and magnetic properties of multilayer graphene nanoclusters and their changes under the influence of adsorbed molecules

The results of investigations of the structures and properties of multilayer graphene nano-clusters (nanographites), structural blocks of activated carbon fibers, and their changes under the influence of adsorbed molecules are presented. The presence of specific edge p-electron-ic states in the nanographites and a reversible decrease in their density at the Fermi level upon the interaction of the graphite nanoparticles with adsorbed molecules of oxygen, chlorine, and water were found. The explanation of the discovered effect was proposed in the terms of the model of spin splitting of edge p-electronic states initiated by the transfer of a small fraction of the electron density from the nanographites to adsorbed molecules. The change in the sign of the temperature coefficient of current carrier spin relaxation rate in the presence of adsorbates can be accounted for by their interaction with edge spin-split (magnetically ordered) states. The preservation of peripheral p-electronic states of the nanographites of free (dangling) s-orbitals of edge carbon atoms at saturation with chlorine was substantiated.