Physicochemical aspects of mechanochemical activation of glass powders

A variant of the physicochemical interpretation involving the principles of thermodynamically irreversible processes is suggested to account for the effect of mechanicochemical activation of glass powders on milling cullet in highly intensive (impact-repulsion etc.) mills Translated from Steklo i Keramika, No. 6, pp. 3–5, June, 1999.     

基于大环化合物主-客体作用的超分子聚合物凝胶材料研究进展

综述了近年来冠醚、环糊精、葫芦脲和柱芳烃等大环化合物的衍生物通过主-客体作用形成的超分子聚合物凝胶材料的研究情况。指出了该材料对温度、酸碱度、溶剂和客体分子等外界环境刺激敏感,在智能响应性方面表现出了优异的性质。对超分子聚合物凝胶材料未来的研究方向进行了展望。     

基于大环化合物主-客体作用的超分子聚合物凝胶材料研究进展

综述了近年来冠醚、环糊精、葫芦脲和柱芳烃等大环化合物的衍生物通过主-客体作用形成的超分子聚合物凝胶材料的研究情况。指出了该材料对温度、酸碱度、溶剂和客体分子等外界环境刺激敏感,在智能响应性方面表现出了优异的性质。对超分子聚合物凝胶材料未来的研究方向进行了展望。     

Physicochemical aspects of texturization: Fiber formation from globular proteins

The modification of proteins to produce fibrous or “fiber-like” textured products is a subject of unique importance and interest. Unfortunately, very little is known about the physicochemical properties of texturized “fibers”, the mechanisms that produce them, or the forces that hold the protein molecules in a given structure. This paper deals with the following topics: (a) methods for characterizing the physico-chemical properties of textured protein products; (b) the structures of naturally occurring fibrous proteins and synthetic polypeptides as possible models for texturized “fibers”; (c) the current understanding of the mechanisms and the forces required to form and stabilize fibrous protein structures; and (d) a brief and generalized survey of the presently available “fiber” forming processes.     

Theoretical aspects of bonding in silicon compounds

Ab initio-calculated bond dissociation energies of Si=Si and C=C are discussed by means of atomic ionization energies and p-p() AO overlap. At the same time ring strain energies of C- as well as Si-rings are estimated by homodesmic reactions where, according to Baeyer, the two-membered rings C=C and Si=Si are chosen to be the first members of the respective series. Thus, a better understanding of the double bonds can be gained. In addition, the exceptional structural and spectroscopic behavior of the five-membered Si-ring is discussed. Finally, the strikingly different results obtained in computational studies of the initial step for polymerization of the systems O=C=O and O=Si=O are discussed.     

1. Physicochemical aspects of the choice of silicon-bearing binders for production of refractories

The principles for selecting a silicon-bearing binder for refractory production are considered. The effect of the heat treatment temperature on the crystallization of SiO₂ gels with various prehistories is considered. It is shown that ethyl silicate binders have an advantage over other silicon-bearing binders that consists in that SiO₂ gel obtained from ethyl silicate éTS-32 can retain the amorphous state upon heating to over 1273 K. Translated from Ogneupory i Tekhnicheskaya Keramika, Nos. 1–2, pp. 8–11, January–February, 1999.     

Physicochemical aspects of graphite protection from oxidation in heat treatment of mixtures on ethyl silicate binder

Results of a study of the physicochemical processes that occur in heat treatment of graphite — ethyl silicate binder mixtures are presented. Diffusion “bridges” in plane 0001 of graphite between the latter and SiO₂ gel confirm diffusion matching of the ≡ Si — O — Si ≡ and ≡ C — C ≡ bonds in heat treatment of the mixtures at 1223 K with the formation of β-SiC, which diminishes the oxidation of graphite.     

New aspects in acceleration of glycidyl ether oligomerization by imidazole compounds

Summary Using simple model compounds the oligomerization of glycidyl ethers accelerated by imidazole and imidazole derivatives was investigated. The formation of oligomers depending on 1,3-diphenoxy-2-hydroxypropane as their starting compound was predominant.In the case of imidazole 1,2-dihydroxy-3-phenoxypropane and the resulting oligomers are further formed. It seems to be obvious that this reaction also occurs in the absence of water.An over-all reaction mechanism including both the main products of the glycidyl ether oligomerization formed and the different imidazole compounds investigated is proposed.     

Synthetic and mechanistic aspects of the electrochemical formation of polimeric alkyl-mercury compounds

The electrochemical reduction on mercury of a series of α, α-dibromoalkanes was studied at low cathodic potentials in aprotic media. 1,4-dibromobutane and 1,5-dibromopentane yielded solid alkyl-mercury compounds, the structures of which were established as being polymeric and of the general type R-Hg-(R-Hg)_n-R (R  alkyl). Proper adjustment of the electrochemical parameters allowed very high current efficiencies for the syntheses. The results obtained for 1,4-dibromobutane, combined with those already existing in the literature, permitted the formation of a general mechanism for the process.     

Technological aspects of preparation of high-purity compounds for sol-gel and pyrolytic synthesis methods

A number of aspects associated with the synthesis of high-purity compounds used in the gas-phase and sol-gel methods for preparing coatings and finely dispersed powders of oxides and oxide composites are considered.     

New dendrimer-peptide host-guest complexes: towards dendrimers as peptide carriers

Adamantyl urea and adamantyl thiourea modified poly(propylene imine) dendrimers act as hosts for N-terminal tert-butoxycarbonyl (Boc)-protected peptides and form chloroform-soluble complexes. Investigations with NMR spectroscopy show that the peptide is bound to the dendrimer by ionic interactions between the dendrimer outer shell tertiary amines and the C-terminal carboxylic acid of the peptide, and also through host-urea to peptide-amide hydrogen bonding. The hydrogen-bonding nature of the peptide-dendrimer interactions was further confirmed by using Fourier transform IR spectroscopy, for which the NH- and CO-stretch signals of the peptide amide moieties shift towards lower wavenumbers upon complexation with the dendrimer. Spatial analysis of the complexes with NOESY spectroscopy generally shows close proximity of the N-terminal Boc group of the peptide to the peripheral adamantyl groups on the dendrimer host. The influence of side-chain motif on interactions with the host is analyzed by using seven different N-Boc-protected tripeptides as guests for the dendrimer. Downfield shifts of up to 1.3 ppm were observed for the guest amide NH-proton signals. These shifts decreased with increasing 'bulkiness' of the amino acid side chains. Despite this, the dendrimer was capable of making multiple peptide-dendrimer complexes when presented with a library of seven peptides. The different peptides were all present in the host, which did not show specific preferences, and could be released under mild acidic conditions. These results show the general nature of the peptide-dendrimer interactions in the formation of either single- or multiple-peptide-dendrimer complexes.     

杯芳烃修饰主客体化学传感器研究——对甲酚的测定

以C—十一烷基间苯二酚杯 (6 )芳烃作为主体分子 ,修饰玻碳电极上制成的一种主客体化学传感器 ,并用其对溶液中的客体分子———对甲酚进行测定。该电极具有良好的选择性 ,对 5 .0× 10 -5～2 .0× 10 -3 mol/L的对甲酚具有很好的线性响应 ,检测下限为 3.0× 10 -5mol/L ,同时对修饰前后玻碳电极的表面状态进行了研究     

Physicochemical properties of fuel shales

Current economic conditions call for innovative products such as coke for the electrode industry, graphite, and fullerenes. To that end, the physicochemical properties of fuel shales must be determined. Attention focuses on shales from the Pribaltiisk Basin (Leningrad field). The goals of the experiment are to determine the physical properties of the shales (moisture content, ash content, actual and apparent density, porosity), the optimal briquetting conditions, and the calorific value of the briquets. The influence of the fractional composition and moisture content on briquet strength is studied. The influence of the heating conditions on the physicochemical properties in the shales is considered. The briquets are heated in pipe furnaces with uncontrolled and controlled atmospheres, in the temperature range 200–1000°C. It is found that the increasing the briquetting pressure (from 10 to 15 MPa) and moisture content (from 11.6 to 37%) improves the briquet strength, while adding coal fines (4 wt %) and reducing the moisture content (to 23%) improves the calorific value of the briquets. Semicoking begins at 400°C. Further heating increases the yield of gases and reduces the yield of semicoke. After pressing, the shale fines may expediently be processed by heat treatment to obtain a graphite material.