Impulsive control for a class of neural networks with bounded and unbounded delays

In this paper, we study the problem of global exponential stability for a class of impulsive neural networks with bounded and unbounded delays and fixed moments of impulsive effect. We establish stability criteria by employing Lyapunov functions and Razumikhin technique. An illustrative example is given to demonstrate the effectiveness of the obtained results.     

Rates of dediazoniations of arenediazonium ions complexed with 18-, 21- and 24-membered crown ethers

The evaluation of the kinetics of dediazoniation of benzenediazonium tetrafluoroborate and $\text{p}$-chlorobenzenediazonium tetrafluoroborate in 1,2-dichloroethane at 50°C in the presence of 18-crown-6, 21-crown-7 and dicyclohexano-24-crown-8 demonstrates that the rate constant for the dediazoniation within the complex is smallest, and the equilibrium constant for complex formation is largest for the complex with 21-crown-7.     

Center of Gravity (COG) Method as a Tool in Processing of Voltammetric Signals

The center of gravity method (COG) was applied (for the first time) in voltammetry (polarography) as a tool for very precise determination of peak potentials, and signal shifts. Basically, the adjustment of the method consists of finding the optimal fraction of the peak that contains information about peak position, either of original signal or of its 1^st or 2^nd derivatives, along with optimal selection of parameters for Savitzky? Golay smoothing of original curves and elimination of baseline influence. The principle of the method and its validation were demonstrated and checked on simulated differential pulse polarograms (DPP) representing a series of curves for the determination of stability constants of labile metal complexes (DeFord‐Hume method). It was shown that COG outperforms the classical “one‐point” method (OPM) in precision and accuracy, providing excellent results even if a very large step potential (e.g. 10 mV) was used. The problems of reduced accuracy and precision in case of curved (non‐ideal) baseline and asymmetric peaks were successfully overcome by applying COG on curves transformed by 1^st and/or 2^nd derivatives. The method was additionally examined in details on a simple experimental dataset of cadmium chloride complexes in 4 mol dm^?3 ionic strength solution and on a more complex dataset of uranyl selenate complexes in 3 mol dm^?3 ionic strength solution. Stability constants obtained by COG agree well with those in the literature with much better precision than the classical one‐point method (checked by standard error of the fit).     

Determination of metal traces in wine by argon stabilized d.c. arc

A spetroscopic method for the determination of metal traces (Mn, Cu, Fe) in wine has been developed based on argon stabilized d.c. arc plasma at atmospheric pressure. The experimental conditions were optimized using lateral distributions of spectral line intensities of the trace elements in aqueous and ethanol-aqueous solutions. The method was applied to the analysis of 6 wines from 3 Serbian wine-growing regions. Direct and standard addition methods were tested. The precision of the method is characterized by a relative standard deviation of 0.50– 3.00%. The accuracy of the method was assessed by flame AAS.     

Impulsive Reaction-Diffusion Delayed Models in Biology: Integral Manifolds Approach

In this paper we study an impulsive delayed reaction-diffusion model applied in biology. The introduced model generalizes existing reaction-diffusion delayed epidemic models to the impulsive case. The integral manifolds notion has been introduced to the model under consideration. This notion extends the single state notion and has important applications in the study of multi-stable systems. By means of an extension of the Lyapunov method integral manifolds’ existence, results are established. Based on the Lyapunov functions technique combined with a Poincarè-type inequality qualitative criteria related to boundedness, permanence, and stability of the integral manifolds are also presented. The application of the proposed impulsive control model is closely related to a most important problems in the mathematical biology—the problem of optimal control of epidemic models. The considered impulsive effects can be used by epidemiologists as a very effective therapy control strategy. In addition, since the integral manifolds approach is relevant in various contexts, our results can be applied in the qualitative investigations of many problems in the epidemiology of diverse interest.     

Micro‐Raman and infrared analysis of medieval pottery findings from Braničevo,Serbia

A selection of Byzantine table pottery (17 samples) dating from the period between the beginning of the 12th century and the first half of the 13th century, discovered at Braničevo in Serbia, were analysed by Fourier transform infrared, micro‐Raman and scanning electron microscopy with energy dispersive spectroscopy and petrography analysis. The aim of the investigation was to determine the chemical and mineralogical composition of the body and of the glaze and thus to determine the production technology. Fourier transform infrared spectroscopy provided data for estimating the firing temperature and the basic mineralogical composition, and micro‐Raman spectroscopy was applied to study and characterise both the glaze and the body of the analysed sherds. It was found that noncalcareous clays, characterised by a rich mineral assemblage, were fired at temperatures between 700 and 900 °C. Oxidizing atmosphere was applied in the production of the red colour pottery. The dark and grey coloured paste of one group of sherds was produced by firing organic matter‐rich clays in a reducing environment. The main type of transparent glaze was identified as lead‐rich, and two samples were alkali–lime glazed. Copyright © 2011 John Wiley & Sons, Ltd.     

Vector Lyapunov functions for practical stability of nonlinear impulsive functional differential equations

This paper studies the practical stability of the solutions of nonlinear impulsive functional differential equations. The obtained results are based on the method of vector Lyapunov functions and on differential inequalities for piecewise continuous functions. Examples are given to illustrate our results.     

Solid phase selective separation and preconcentration of Cu(II) by Cu(II)-imprinted polymethacrylic microbeads

Ion-imprinted polymer (IIP) particles are prepared by copolymerization of methacrylic acid as monomer, trimethylolpropane trimethacrylate as crosslinking agent and 2,2′-azo-bis-isobutyronitrile as initiator in the presence of Cu(II), a Cu(II)-4-(2-pyridylazo)resorcinol (Cu(II)-PAR) complex, and PAR only. A batch procedure is used for the determination of the characteristics of the Cu(II) solid phase extraction from the IIP produced. The results obtained show that the Cu(II)-PAR IIP has the greatest adsorption capacity (37.4 μmol g⁻¹ of dry copolymer) among the IIPs investigated. The optimal pH value for the quantitative preconcentration is 7, and full desorption is achieved by 1 M HNO₃. The selectivity coefficients (S_Cu/Me) for Me = Ni(II), Co(II) are 45.0 and 38.5, respectively. It is established that Cu(II)-PAR IIPs can be used repeatedly without a considerable adsorption capacity loss. The determination of Cu(II) ions in seawater shows that the interfering matrix does not influence the preconcentration and selectivity values of the Cu(II)-PAR IIPs. The detection and quantification limits are 0.001 μmol L⁻¹ (3σ) and 0.003 μmol L⁻¹ (6σ), respectively.