Complex mixed-mode periodic and chaotic oscillations in a simple three-variable model of nonlinear system

A detailed study of a generic model exhibiting new type of mixed-mode oscillations is presented. Period doubling and various period adding sequences of bifurcations are observed. New type of a family of 1D (one-dimensional) return maps is found. The maps are discontinuous at three points and consist of four branches. They are not invertible. The model describes in a qualitative way mixed-mode oscillations with two types of small amplitude oscillations at local maxima and local minima of large amplitude oscillations, which have been observed recently in the Belousov-Zhabotinsky system. (c) 2000 American Institute of Physics.     

Ignition of polymeric material with single hot metallic and nonmetallic particles under diffusive-convective heat and mass transfer in an oxidizing medium

A mathematical model of the gas-phase ignition of a typical polymeric material by a single hot particle of parallelepiped shape with consideration for the associated physicochemical processes (conductive heat transfer and thermal degradation in the condensed phase, diffusive-convective heat and mass transfer and oxidation in the gas phase) is developed. Based on numerical simulations, the dependence of the delay time of the ignition of the polymer, the main integrated characteristic of the process, on the initial temperature of the source of the limited energy capacity are determined. A number of modes of ignition differing in the location the leading oxidation reaction in the gas phase are identified.     

Limited transverse sizes of a droplet cloud under disintegration of a water mass during its fall from a great height

The main stages of the formation of a droplet cloud during the disintegration of water masses (with an initial volume of 0.05–1 L) during their free fall from a great height (up to 15 m) have been determined. High-speed (up to 6 × 10⁵ frames per second) video cameras were used to perform 3D video recording of the transformation and destruction of water mass with the formation of a droplet cloud. It is found that the transverse sizes of the newly formed droplet cloud rapidly increase when the mass passes the first few (up to 10) meters from the onset of falling. It is shown that the maximum cross-sectional areas of the water mass change only slightly with an increase in the discharge height at heights above 10 m. A model of limited growth of the transverse sizes of droplet cloud is developed for the first time based on the results of large-scale experiments.     

Antiozonant activity of the silica modified with 3d metal complexes

Criteria for preliminary selection of the antiozonants based on the silica modified with the complexes of 3d metal were proposed and the activity of the antiozonants as a dependence on the nature of the ligands (Schiff bases, Cl^?, NO ₃ ^? ) and metal ions [Cu(II), Co(II), Mn(II)] was established. We found that advantageous were complexes MnL₂/ $\overline {Si} $ , where L denotes a Schiff base of phenol or quinoline series, whose kinetic and specific stoichiometric energy parameters of the reaction were the largest because of the formation during the reaction of the manganese oxide form which performs the catalytic decomposition of ozone.     

Numerical solution to the plane heat-mass transfer problem in a system of focused radiation flux-liquid condensed substance film-oxidizer

The plane problem of heat and mass transfer in a focused radiation flux-liquid condensed substance film-oxidizer system is numerically solved. Peculiarities of heat and mass transfer at radiation energy absorption by a vapor-gas mixture near the liquid surface are analyzed. The influence of the radiation density distribution in a flux and the liquid and oxidizer parameters on the conditions of heat and mass transfer is assessed.     

Numerical simulation of solid-phase ignition of metallized condensed matter by a particle heated to a high temperature

Numerical simulation of the ignition of a composite propellant by a single “hot” particle of metal is carried out in the framework of the solid-phase model of ignition. The dependences of the ignition lag time for a metallized condensed matter on the initial temperature of a local energy source are determined. Close agreement of the obtained theoretical results with the known experimental data is found.     

Effect of the means of preparation of nanodispersed CuO/MgO catalysts on their activity in the oxidation of CO

A method is proposed for obtaining copper-containing catalysts by means of mechanical mixing of previously formed monodispersed CuO nanoparticles (mean particle diameter 12 nm) with MgO. Higher activity was found for these catalysts in the oxidation of carbon monoxide than for the analogous copper-containing systems prepared by impregnation and deposition of cupric oxide nanoparticles from colloidal solution. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 165–169, May–June, 2008.     

Design,Synthesis, and Application of an Optimized Monofluorinated Aliphatic Label for Peptide Studies by Solid‐State 19F NMR Spectroscopy

A conformationally restricted monofluorinated α‐amino acid, (3‐fluorobicyclo[1.1.1]pentyl)glycine (F‐Bpg), was designed as a label for the structural analysis of membrane‐bound peptides by solid‐state ¹⁹F NMR spectroscopy. The compound was synthesized and validated as a ¹⁹F label for replacing natural aliphatic α‐amino acids. Calculations suggested that F‐Bpg is similar to Leu/Ile in terms of size and lipophilicity. The ¹⁹F NMR label was incorporated into the membrane‐active antimicrobial peptide PGLa and provided information on the structure of the peptide in a lipid bilayer.