Space-time chaos in reactions of NADH with atmospheric oxygen in the presence of copper(II) complexes

In the oxidation of aqueous solutions of NADH by atmospheric oxygen in the presence of certain copper(II) compounds, an irregularly oscillating timewise change has been observed in the potential of a point platinum electrode (PPE), relative to either a silver chloride electrode or a second PPE located in the same solution. Phase portraits have been constructed on the basis of experimental data for all of the systems that have been investigated. It has been shown that the existence of chaotic oscillations, and also the form of the phase portrait of the systems, depend on the magnitude of the redox potential of the CuL²⁺/CuL⁺ pair. For compounds with E₀=0.60–0.64 V, the phase portrait has the form of a screw-type chaos, which then changes over to Lorentz-type chaos. Only for this group of complexes is chaotic behavior observed when the solution is stirred. For compounds with E₀=0.15–0.41 V, screw-type chaos is observed; and for compounds with E₀<0, no chaotic behavior has been detected.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 26, No. 2, pp. 175–184, March–April, 1990.     

Deterministic chaos in chemistry

The characteristics of chaotic processes in chemical systems and the manner in which these processes differ from other irregularly oscillatory phenomena, in particular, stochastic noise, are studied. The basic definitions and concepts employed for describing chaotic states are given, and quantitative characteristics of deterministic chaos are examined. Most redox reactions occurring in solutions in the chaotic regime are analyzed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, Nos. 5–6, pp. 382–399, September–December, 1992.     

The effect of fractal dimension of porous catalysts on the activation energy of CO oxidation

An approach based on the interrelationship between the activation energy of the rate-limiting step of a heterogeneous catalytic reaction and the structure of the catalyst surface expressed in terms of fractal geometry is presented for the example of the oxidation of carbon monoxide. The activation energy of this reaction was shown to increase with increasing nonuniformity of the catalyst surface given by the fractal dimension D_F. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 43–46, January–February, 2007.     

Classical and quantum properties of a simple autocatalytic mechanism — The Lotka-Volterra system

A method is proposed for construction of simple models describing chaotic regimes in chemical reactions. Using the Hamiltonian structure of the Lotka-Volterra system, a quantum analog of a model is described, which explains the observed and experimental transitions between discrete states for chaotic regimes in CSTR during external periodic perturbation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 1, pp. 49–56, January–February, 1993.     

Colloidal Regularities of the Interaction between Uranium(VI) and the Cells of Metal-Resistant Bacillus cereus AUMC 4368 Bacterial Culture

Sorption of uranium(VI) by the cells of metal-resistant Bacillus cereus AUMC 4368 bacterium was studied in aqueous solutions as a function of pH, equilibrium concentration of metal, and the presence of co-ions with account of the changes in phase state of metals and biocolloids. Experimental data indicate that the sorption of uranium(VI) by negatively charged biocolloids is maximal at pH 4.2–4.5 (1.2 mM per 1g of dry biomass), when metal is present in the form of positively charged hydroxocomplexes. At pH 8, the interaction between uranium(VI) and the cells is inhibited due to the formation of negatively charged water-soluble hydroxocarbonate complexes and uranate ions. Co, Sr, Cu, Ca, Mg, and Zn ions do not influence the efficiency of sorption of uranium(VI) in a weakly acidic medium, but can cause inhibiting effect in neutral pH region. The most pronounced effect expressed in broadening of sorption range and in the heterocoagulation of uranyl is observed in the presence of Fe³⁺ ions. It was established that the binding of uranium(VI) occurs by the carboxyl surface groups of Bacillus cereuscell surface. Uranium(VI) is irreversibly bound by the carboxyl groups of cell surface and its efficient desorption is possible only during the interaction with citric acid or sodium hydrocarbonate with the formation of water-soluble complexes transferred to aqueous phase. It was shown that uranyl in the form of organocomplexes (citric, humatic, and fulvatic) is not sorbed by biocolloids.     

Conditions for Mixed Mode Oscillations and Deterministic Chaos in Nonlinear Chemical Systems

An approach has been proposed for finding the conditions for the existence of mixed-mode oscillations and deterministic chaos in a kinetic scheme after reduction to a simple system of equations. Analysis of the position and stability of the steady states of this system suggested simple conditions for the existence of mixed-mode oscillations and deterministic chaos. The boundaries for monostability, bistability, and oscillations were also found. The results obtained were completely confirmed by numerical modelling.     

Ignition of a floating droplet of organic coal–water fuel

The results of experimental investigations are presented for the ignition of droplets (particles) of organic coal–water fuels (OCWFs) floating in a flow of an oxidizer using a special combustion chamber from high-temperature quartz glass. The temperature and the velocity of motion of the oxidizer vary in the ranges of 500–900 K and 0.5–3 m/s. The initial sizes (radii) of fuel droplets amounted to 0.3–1.5 mm. As the basic OCWF components, particles (of 80–100 µm in size) of brown coal “B2,” water, mazut, and waste castor and compressor oils are used. With use of the system of high-velocity video registration, the conditions providing for floating of OCWF particles without initiation of burning and with the subsequent steady ignition are established. Four modes of OCWF-droplet ignition with different trajectories of their motion in the combustion chamber are singled out. The times of the OCWF-ignition delay in dependence on the size of fuel particles and oxidizer temperatures are determined. The deviations of the OCWF-ignition-delay times obtained under conditions of suspension of a droplet on the thermocouple junction and while floating in the oxidizer flow are established.