Structural changes of flavylium salts

A general discussion is presented of the effects of hydroxylation pattern upon the structural changes of flavylium salts and their stability at different pH levels. The discussion is based upon the results of spectrometric and polarographic investigations of flavylium salts and incorporates hitherto unpublished data for the anthocyanidin, cyanidin chloride.     

Investigation of fibres based on rigid-chain polyamides by the wide-line nmr and ultrasonic acoustics

Conclusions -- A dependence of the second moment of the NMR line on the angle between the fibre axis and the magnetic field has been given; the structural coefficient C ₀, C ₂, and C ₄ have been calculated for fibres based on poly-p-phenyleneterephthalamide and poly-p-benzamide at temperatures of –196 and +20°C and for Kevlar-49, from –196 to +400°C.-- The intramolecular structural coefficients C ₀ ^im, C ₂ ^im, and C ₄ ^im have been calculated theoretically, and the orientation parameters and and the acoustic orientation factor f have been obtained, values for which indicate a high degree of orientation of the macromolecules in fibres.-- The smaller values of the second moment of the NMR line for PABI as compared with fibres based on PPTA in the temperature region 250–380°C indicate a more mobile structure for the PABI.-- In the range from –196 to +20°C thermal action leads to a more important change in the coefficient C ₀ for Kevlar-29 and Kevlar-49 as compared with PABI; this is apparently connected with thermal expansion in planes having a predominant concentration of van der Waals bonds for Kevlar-29 and Kevlar-49.Translated from Khimicheskie Volokna, No. 4, pp. 23–26, July–August, 1990.     

Anionic polymerization of styrene in 2-methyltetrahydrofuran: temperature dependence of the field effect

Kinetics of living anionic polymerizations of styrene was investigated for lithium, sodium, and potassium salts in 2-methyltetrahydrofuran at 35, 25, 0, and ?70°C in the presence and absence of a high intensity electric field. At 35 and 25°C, a field acceleration effect was observed whereas no effect was found at 0 and ?70°C. The propagation rate constant of ion pairs was almost independent of gegen ions and their temperature dependence was smaller than that of free anions. The free ions seem to be more strongly solvated as the temperature decreases.     

Friction factors in pulsed turbulent flow

An apparatus for investigating pulsed turbulent liquid flow in a 2 in. diameter, 80 ft. pipeline is described. The pulsation unit was powered by compressed air with a consumption of up to 2.7 std. cu.ft./min. at 35 lb/in² gauge. The pressure drop for water flowing at mean velocities of 7.66 to 12.28 ft./sec. has been measured, both for steady flow and for pulsed flow, at frequencies between 0.48 and 0.82 Hz. The experimentally measured pressure versus time curves for pulsed flow can be matched fairly closely by a solution of Euler's equation employing the friction factors measured under steady flow conditions.     

Properties and structure of welded joints of high-strength steel after zonal heat treatment by electron beam

Conclusion Zonal electron-beam heat treatment in vacuum of welded joints of high-strength steel, produced by electron-beam welding, brings about a troostomartensitic and a martensitic-sorbitic structure in the welded joint and equalization of the properties over the section of the welded joint: impact toughness of the welding seam and of the weld-affected zone is practically the same, viz., 30 J/m².Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 7–8, March, 1991.     

Production and properties of zirconia ceramics

Conclusions A study was made of the effect of preliminary milling and the process temperature of a mixture of zirconium and yttrium hydroxides on the technical aspects of preparing large articles from partially stabilized zirconia.A procedure was developed for making such items from tetragonal zirconia, both by monoaxial pressing and by slip casting in gypsum molds. The main physicochemical and frictional properties of the materials were investigated.The material has been tested for pushers, piston units, inserts and gaskets, friction pairs of the gas distribution tract in internal combustion engines, and the axles of shafts for pumps handling corrosive media. The tests confirmed the workability of the material in friction pairs.Translated from Ogneupory, No. 2, pp. 6–9, February, 1991.     

Application of scanning tunnelling microscopy to the quality control of tungsten carbide (WC-Co) ball bearings

Scanning tunnelling microscopy (STM) has been applied to the topographical study of tungsten carbide (with 6% Co) ball bearings in air. It is shown that, for this material, scanning tunnelling microscopy can provide not only general topographical information on the surface microtexture with a resolution of nearly 0.1 nm if required, but also quantitative information for the measurement of surface roughness. Thus, scanning tunnelling microscopy has utility as a quality control tool of particular relevance in the submicron range. The STM topographical results from specific tungsten carbide ball bearings are presented, and the limitations and applicability of the STM technique when used as a quality control tool are discussed.