Simultaneous separation of 14 antiarrhythmic drugs and determination of mexiletine and flecainide by capillary zone electrophoresis

A method using capillary zone electrophoresis was developed for the simultaneous separation of 14 antiarrhythmic drugs belonging to various classes. The drugs are separated on a fused-silica capillary, 90 cm x 75 microm (72 cm effective length), with phosphate and acetate buffers as background electrolytes and UV detection at 217 nm. The effects of buffer pH, temperature, and applied voltage on the migration of the drugs were studied. The pH was found to be the most significant factor determining effective separation. The antiarrhythmic compounds are completely separated within a relatively short time (< 7 min) by using 70 mM phosphate buffer at pH 7.91, an applied voltage of 28 kV, and a temperature of 32 degrees C. Mexiletine (MEX) and flecainide (FLE) were quantified under conditions of the optimum separation. The calibration graphs were constructed over the concentration range of 4.0-14.0 microg/mL for both drugs with good correlation (r > or = 0.9999). Detection and quantitation limits were found to be 0.5 and 1.5 microg/mL for FLE and 0.7 and 2.1 microg/mL for MEX, respectively. The proposed method was used for the determination of both drugs in their commercial forms with satisfactory precision (relative standard deviations of 0.36-1.21% for FLE and 0.78-1.66% for MEX) and accuracy (relative standard errors of 0.13-1.17% for FLE and 0.35-1.18% for MEX).     

Luminescent chemical waves in the Cu(II)-catalyzed oscillatory oxidation of SCN- ions with hydrogen peroxide

The oscillatory oxidation of thiocyanate ions with hydrogen peroxide, catalyzed by Cu2+ ions in alkaline media, was so far observed as occurring simultaneously in the entire space of the batch or flow reactor. We performed this reaction for the first time in the thin-layer reactor and observed the spatiotemporal course of the above process, in the presence of luminol as the chemiluminescent indicator. A series of luminescent patterns periodically starting from the random reaction center and spreading throughout the entire solution layer was reported. For a batch-stirred system, the bursts of luminescence were found to correlate with the steep decreases of the oscillating Pt electrode potential. These novel results open possibilities for further experimental and theoretical investigations of those spatiotemporal patterns, including studies of the mechanism of this chemically complex process.     

A method for indefinite integration of oscillatory and singular functions

We propose a general method for computing indefinite integrals of the form

Assessment of predictive control performance using fractal measures

This paper presents novel approach to the task of control performance assessment. Proposed approach does not require any a priori knowledge on process model and uses control error time series data using nonlinear dynamical fractal persistence measures. Notion of the rescaled range R/S plots with estimation of Hurst exponent is applied. Crossover phenomenon is observed in data being investigated and discussed. Paper starts with industrial engineering rationale. Review of the control error histogram is followed by statistical analysis of probabilistic distribution functions (PDFs). Lévy \(\alpha \)-stable PDF parameters seem to be best fitted. They directly lead to the fractal analysis using Hurst exponents and R/S plot crossover points. The evaluation aims at performance of the generalized predictive control (GPC) and discusses freshly introduced loop performance quality sensitivity against design parameters of the GPC controller.     

Nonexistence of small,odd breathers for a class of nonlinear wave equations

In this note, we show that for a large class of nonlinear wave equations with odd nonlinearities, any globally defined odd solution which is small in the energy space decays to 0 in the local energy norm. In particular, this result shows nonexistence of small, odd breathers for some classical nonlinear Klein Gordon equations, such as the sine-Gordon equation and \(\phi ^4\) and \(\phi ^6\) models. It also partially answers a question of Soffer and Weinstein (Invent Math 136(1): 9–74, p 19 1999) about nonexistence of breathers for the cubic NLKG in dimension one.     

Refinement type equations and Grincevi?jus series

We consider L¹-solutions of the following refinement type equations

     

Equations of log del Pezzo surfaces of index ≤ 2

Del Pezzo surfaces over with log terminal singularities of index ≤ 2 were classified by Alekseev and Nikulin. In this paper, for each of these surfaces, we find an appropriate morphism to projective space. These morphisms enable us to describe equations of natural embeddings of log del Pezzo surfaces of index ≤ 2 in some weighted projective space. The results obtained give a completion of similar results of Du Val, Hidaka, and Watanabe, describing del Pezzo surfaces of index 1. The work was done during the authors’ stay at the University of Liverpool supported by the Marie Curie program in Autumn 2004.     

On-line arbitrarily vertex decomposable suns

We give a complete characterization of on-line arbitrarily vertex decomposable graphs in the family of unicycle graphs called suns. A sun is a graph with maximum degree three, such that deleting vertices of degree one results in a cycle. This result has already been used in another paper to prove some Ore-type conditions for on-line arbitrarily decomposable graphs.     

Absolutely summing multipliers on abstract Hardy spaces

We study summing multipliers from Banach spaces of analytic functions on the unit disc of the complex plane to the complex Banach sequence lattices. The domain spaces are abstract variants of the classical Hardy spaces generated by the complex symmetric spaces. Applying interpolation methods, we prove the Hausdorff Young and Hardy-Littlewood type theorems. We show applications of these results to study summing multipliers from the Hardy-Orlicz spaces to the Orlicz sequence lattices. The obtained results extend the well-known results for the Hp spaces.     

Heavy-tails and regime-switching in electricity prices

In this paper we first analyze the stylized facts of electricity prices, in particular, the extreme volatility and price spikes which lead to heavy-tailed distributions of price changes. Then we calibrate Markov regime-switching (MRS) models with heavy-tailed components and show that they adequately address the aforementioned characteristics. Contrary to the common belief that electricity price models ‘should be built on log-prices’, we find evidence that modeling the prices themselves is more beneficial and methodologically sound, at least in case of MRS models.