Molecular polarizability of organic compounds and their complexes: LII. Molar volumes of polymeric compounds in solutions,extrapolated to infinite dilution,and steric structure of their molecules

The molar volumes in solutions at infinite dilution were determined for a series of vinyl, glycol, isoprene, and cyclopentadiene polymers and oligomers with various degrees of polymerization. An additive analysis of the molar volumes showed that molecules of vinyl, ethylene glycol, and isoprene polymers exist in solutions in elongated helical conformations. In the majority of polymer molecules, except polystyrenes, polyisoprenes, and polycyclopentadienes, there are randomly disordered regions creating additional volumes inaccessible to solvation with solvent molecules. Cyclopentadiene oligomers formed by the Diels-Alder reaction have in solution the conformation of corrugated bands. The additive scheme for calculating the molar volumes considerably simplifies the determination of the dipole moments and Kerr constants of the compounds for which this scheme has been constructed.     

Phenolic composition ofArtemisia laciniata

V. L. Komarov Botanical Institute, Academy of Sciences of the USSR, Leningrad. Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 115–117, January–February, 1990.     

Application of Chromium-Containing Silica for Synthesising Functional Glasslike Materials by the Sol–Gel Method

A new variant of the sol–gel method for synthesising silica glasses and optical composites containing nanoparticles of chromium oxide has been designed. Monolithic gels are produced by mixing preformed silica modified with chromium oxide (Cr₂O₃/SiO₂), with a sol–gel solution containing Si(OC₂H₅)₄, and gelation catalyst ((CH₂)₆N₄ or NH₃). Highly dispersed Cr₂O₃/SiO₂ samples were synthesised through a step-by-step controlled adsorption of vapours of CrO₂Cl₂ and C₆H₁₄ on the surface of fumed silica (A-300) and a subsequent thermal decomposition. With increasing chromium concentration in samples from 0.9 to 5.1 wt.%, the size of chromium oxide nanoparticles increases from 10 to 46 nm. XRD, DTA, TG, IR-spectroscopy and measurements of specific surface area have been used to investigate structural and physico-chemical properties of Cr₂O₃/SiO₂ and xerogels during the course of their thermal transformations up to formation of glasses. A study has also been carried out of optical properties of transparent samples (distribution of refractive index values through cross section of a preform). The glasses synthesised with the aid of Cr₂O₃/SiO₂ have a more uniform distribution of doping constituents and exhibit a larger refractive index in comparison to glasses synthesised through impregnation of silica matrices with a solution of (NH₄)₂Cr₂O₇.     

A method for the experimental determination of the viscoelastic properties of a cylindrical sample

Forced oscillations of a cylinder, clamped to a vibrating base and loaded on top with a certain mass, is considered using a two-dimensional deformation model. The boundary conditions are specified over the whole cylinder surface, and the equation of the balance of forces on its outer surface is used. An algorithm for solving the problem using the collocation method is proposed. It is shown that the accuracy with which the modulus of elasticity and the loss factor are determined is much higher than when using methods based on the one-dimensional model, since the proposed method does not require a knowledge of the dynamic form factor.     

Statistical analysis of the strength of ultra-oriented ultra-high-molecular-weight polyethylene film filaments in the framework of the Weibull model

A statistical analysis of the distribution of the tensile strength σ of ultra-oriented ultra-high-molecular-weight polyethylene (UHMWPE) film filaments has been performed in the framework of the Weibull model using the results obtained from a large number (50) of measurements. The UHMWPE film filaments have been produced by means of high-temperature multistage zone drawing of xerogels prepared from 1.5% UHMWPE solutions in decalin. The Weibull modulus has been determined for this type of materials. It has been shown that, for the ultimate draw ratio λ = 120, the average tensile strength is equal to 4.7 GPa, which is significantly higher than the tensile strength σ = 3.5 GPa for commercial gel-spun UHMWPE fibers manufactured by the DSM Company (The Netherlands) and the Honeywell International Incorporation (United States). It has been demonstrated that, for 20% of the specimens thus prepared, the tensile strength reaches record-high values σ = 5.2–5.9 GPa.     

Numerical spectral analysis of temporal stability of laminar duct flows with constant cross sections

Problems related to the temporal stability of laminar viscous incompressible flows in ducts with a constant cross section are formulated, justified, and numerically solved. For the systems of ordinary differential and algebraic equations obtained by a spatial approximation, a new dimension reduction technique is proposed and substantiated. The solutions to the reduced systems are decomposed over subspaces of modes, which considerably improves the computational stability of the method and reduces the computational costs as compared with the usual decompositions over individual modes. The optimal disturbance problem is considered as an example. Numerical results for Poiseuille flows in a square duct are presented and discussed.     

Preparation of N-phenyl-substituted quinolinium derivatives labeled with tritium by chemonuclear synthesis

A chemonuclear method of synthesis is proposed for obtaining difficultly available phenyl-substituted derivatives of quinoline labeled with tritium. The ion-molecule reaction of free phenyl cations, generated on β-decay of tritium, with the nucleophilic centers of heterocyclic compounds is the basis of the synthesis. The onium derivatives synthesized possess significant inhibitory antimicrobial activity and are promising for a detailed study of the reaction mechanisms and metabolic processes using radioactive indicators.     

MODIFICATION AND VERIFICATION OF NUMERICAL ALGORITHMS FOR DAM-BREAK FLOW OVER A HORIZONTAL BED

Journal of Applied Mechanics and Technical Physics - Numerical simulation of dam-break water flow over a horizontal dry bed has been performed. We have modified and verified computational...     

The infrared absorption spectra of finely divided manganese borate

Journal of Applied Spectroscopy -