Differential evolution for dynamic environments with unknown numbers of optima

This paper investigates optimization in dynamic environments where the numbers of optima are unknown or fluctuating. The authors present a novel algorithm, Dynamic Population Differential Evolution (DynPopDE), which is specifically designed for these problems. DynPopDE is a Differential Evolution based multi-population algorithm that dynamically spawns and removes populations as required. The new algorithm is evaluated on an extension of the Moving Peaks Benchmark. Comparisons with other state-of-the-art algorithms indicate that DynPopDE is an effective approach to use when the number of optima in a dynamic problem space is unknown or changing over time.     

Mathematical modelling in university education. An experiment at the University of Oldenburg

This paper suggests that mathematics teacher educators should listen carefully to what their students are saying. More specifically, it demonstrates how from one pre-teacher's non-traditional geometric representation of a unit fraction, a variety of learning environments that lead to the enrichment of mathematics for teaching can be developed. The paper shows how new knowledge may be generated through an attempt to validate an intuitive idea; in other words, how the quest for rigour may serve as a catalyst for the growth of mathematical concepts in the context of K-16 mathematics.     

Synthesis of β-aminoethanesulfonyl fluorides or 2-substituted taurine sulfonyl fluorides as potential protease inhibitors

Substituted taurine sulfonyl fluorides derived from taurine or protected amino acids are conveniently synthesized from β-aminoethanesulfonyl chlorides using KF/18-crown-6 or from β-aminoethanesulfonates using DAST.     

Note on the size of binary Armstrong codes

We show for binary Armstrong codes Arm(2, k, n) that asymptotically n/k ≤ 1.224, while such a code is shown to exist whenever n/k ≤ 1.12. We also construct an Arm(2, n ? 2, n) and Arm(2, n ? 3, n) for all admissible n.     

The detection of electrons in pulse irradiated liquid hydrocarbons by microwave absorption

An apparatus for studying the absorption of microwave energy by electrons in pulse irradiated liquid hydrocarbons on a nanosecond timescale is described. The used of the technique is illustrated by results obtained in liquid iso-octane. Rate constants for the reaction of electrons with biphenyl and TMPD in iso-octane have been determined to be (1.5 ± 0.3) × 10¹³ M^?1 sec^?1, respectively.     

Charge separation in the excited state electron donor—acceptor compounds containing the piperazine moiety

Three bridged electron donor—acceptor systems are investigated containing a 4-cyano-1-ethenylnaphthalene electron-acceptor and piperidine (compound 1), phenylpiperazine (2) and 4-methoxyphenylpiperazine (3) electron-donating groups. In the intramolecular charge-transfer states of 1 and 2, the extent of charge separation is similar, but in compound 3 the positive charge is shifted towards the more powerful arylamine donor site, which results in a significantly greater dipole moment. Optical absorption spectra of model radical cations demonstrate that the predominant charge localization on the trialkyl nitrogen in 2 and on the aryl nitrogen in 3 are a consequence of the bistable nature of the piperazine donors.     

Comparison between electrochemistry/mass spectrometry and cytochrome P450 catalyzed oxidation reactions

The extent to which electrochemistry on-line with electrospray mass spectrometry can be used to mimic cytochrome P450 catalyzed oxidations has been investigated. Comparisons on the mechanistic level have been made for most reactions in an effort to explain why certain reactions can, and some cannot, be mimicked by electrochemical oxidations. The EC/MS/MS system used successfully mimics in cases where the P450 catalyzed reactions are supposed to proceed via a mechanism initiated by a one-electron oxidation, such as N-dealkylation, S-oxidation, P-oxidation, alcohol oxidation and dehydrogenation. The P450 catalyzed reactions initiated via direct hydrogen atom abstraction, such as O-dealkylation and hydroxylation of unsubstituted aromatic rings, generally had a too high oxidation potential to be electrochemically oxidized below the oxidation potential limit of water, and were not mimicked by the EC/MS/MS system. Even though the EC/MS/MS system is not able to mimic all oxidations performed by cytochrome P450, valuable information can be obtained concerning the sensitivity of the substrate towards oxidation and in which position of the molecule oxidations are likely to take place. For small-scale electrochemical synthesis of metabolites, starting from the drug, the EC/MS/MS system should be very useful for quick optimization of the electrochemical conditions. The simplicity of the system, and the ease and speed with which it can be applied to a large number of compounds, make it a useful tool in drug metabolism research.     

Alpha 1-acid glycoprotein high-performance liquid chromatography column (EnantioPAC) as a screening tool for protein binding

An attempt was made to correlate retention behavior on a high-performance liquid chromatographic (HPLC) system employing an immobilized alpha 1-acid glycoprotein (AAG) column with AAG binding behavior for various compounds. Protein binding was assessed by propranolol displacement studies in an equilibrium dialysis system using isolated AAG. HPLC retention behavior poorly correlated with propranolol displacement from AAG. This system is not suitable for use as a screening tool for AAG affinity.     

Automated determination of pyrethroid insecticides in surface water by column liquid chromatography with diode array UV detection, using on-line micelle-mediated sample preparation

A liquid chromatographic method using gradient elution and diode array UV detection for the trace level determination of seven synthetic pyrethroids is described. The procedure involves automated on-line preconcentration on precolumns containing octadecylbonded silica using a Prospekt. Although the analytes display a mixed hydrophobic/hydrophilic behaviour, both breakthrough on the precolumn and adsorption to inner walls and surfaces can be prevented by adding Brij-35, a neutral surfactant, to the aqueous sample. The procedure has been tested for the analysis of surface water; detection limits typically are at the sub-g/l level and repeatability is excellent. The automated system is robust and there are no maintenance problems.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday