An implementation of a reduced subgradient method via Luenberger-Mokhtar variant

We present an implementable algorithm for minimizing a convex function which is not necessarily differentiable subject to linear equality constraints and to nonnegativity bounds on the variables. The algorithm is based on extending the variant proposed by Luenberger to the nondifferentiable case and using the bundle techniques introduced by Lemaréchal to approximate the subdifferential of the objective function. In particular, at each iteration, we compute a search direction by solving a quadratic subproblem, and an inexact line search along this direction yields a decrease in the objective value. Under some assumptions, the convergence of the proposed algorithm is analysed. Finally, some numerical results are presented, which show that the algorithm performs efficiently.     

Determination of Esomeprazole on an Electropolymerized L‐arginine and β‐cyclodextrin Modified Screen Printed Carbon Electrode

The formation of an inclusion complex of the proton‐pump inhibitor (PPI) drug esomeprazole (ESO) with ß‐cyclodextrin (ß‐CD) has been investigated and proven by cyclic voltammetry (CV). The formation constant of the complex was determined. Thereafter, an electropolymerized β‐CD and L‐arginine (L‐arg) modified screen printed carbon electrode (P‐β‐CD‐L‐arg/SPCE) was developed for the determination of ESO using differential pulse adsorptive stripping voltammetry (DPAdSV). A significant enhancement of the peak current was observed when applying an accumulation step due to the effect of adsorption. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) further indicated that the polymer of β‐CD and L‐arg efficiently improved the electron transfer kinetic between analyte and electrode surface. Under the optimized conditions, the oxidation peak current was linearly proportional to the concentration of the drug in the range of 1.0×10^?8 to 1.0×10^?5 M. The DPAdSV method was successfully used to determine the concentrations of the drug in spiked human serum samples.     

Correlation between Electrochemical Impedance and Spectroscopic Measurements in Adsorbing Paraquat on Silver: Application in Underground Water Samples

The electrochemical impedance spectroscopy (EIS) has been used to study the interaction between paraquat and carbon modified by silver (Ag? CPE) and silver particles‐impregnated natural phosphate (Ag/NPh? CPE). This study was developed using spectrophotometry (UV? Vis) and infrared spectroscopy. The resulting interaction was controlled by adsorption at lower concentration (≤1.0×10^?5 mol L^?1) and by diffusion in the opposite case. Both electrodes are used to determining paraquat with a low detection limit (<1.0×10^?12 mol L^?1). The precision expressed as relative standard deviation RSD for the concentration level 1.0×10^?5 mol L^?1 of paraquat, (n=8) were 0.93 % and 1.1 % for Ag/NPh? CPE and Ag? CPE respectively.     

Computational Design,Synthesis and Application of a New Selective Molecularly Imprinted Polymer for Electrochemical Detection

A computational approach was developed to find a suitable functional monomer to design a new molecularly imprinted polymer (MIP), based on which methacyrlic acid (MAA) was selected as a functional monomer to synthesize the molecular imprinted and non‐imprinted polymers. All calculations were carried out using Gaussian 03 software based on the application of Hartree?Fock (HF) method with 6‐31G (d) basis set. The performance of the MIPs prepared with different ratios of MAA was then evaluated using equilibrium rebinding assays. The MIP with the highest binding capacity was chosen as recognition material for the fabrication of new PVC sensors and their responses were compared with each other and with previously reported modifiers in literature. The addition of the ionic surfactant (TFPB) was found to have a synergistic effect on the response mechanism of the electrodes. The results of the MIP modified sensors show that they provide an improved electrode slope, wider pH range and a highly extended life time reaching 7 months compared to 2–4 weeks in case of traditional ion‐exchangers reported in literature, besides, being successfully applied for measurements in biological samples.     

Synthesis and some transformations of 1-methyl-2-(thiophen-3-yl)-1<Emphasis Type="Italic">H</Emphasis>-benzimidazole

1-Methyl-2-(thiophen-3-yl)-1H-benzimidazole was synthesized by the Weidenhagen reaction, followed by N-methylation. Electrophilic substitution reactions of the title compound, in particular nitration, bromination, sulfonation, formylation, and acylation, were studied. The formylation and acylation in polyphosphoric acid afforded mixtures of 2- and 5-substituted isomers at the thiophene ring. The nitration of 1-methyl-2-(thiophen-3-yl)-1H-benzimidazole involved the thiophene ring or both thiophene and benzene fragments, depending on the conditions. Steric arrangement of the heterocycles in the 1-methyl-2-(thiophen-3-yl)-1H-benzimidazole molecule was analyzed by quantum chemical calculations.     

Merging Iron Catalysis and Biocatalysis—Iron Carbonyl Complexes as Efficient Hydrogen Autotransfer Catalysts in Dynamic Kinetic Resolutions

A dual catalytic iron/lipase system has been developed and applied in the dynamic kinetic resolution of benzylic and aliphatic secondary alcohols. A detailed study of the Knölker‐type iron complexes demonstrated the hydrogen autotransfer of alcohols to proceed under mild reaction conditions and allowed the combination with the enzymatic resolution. Different racemic alcohols were efficiently converted to chiral acetates in good yields and with excellent enantioselectivities.     

Two-step formation mechanism of<Emphasis Type="Italic"> Acetobacter</Emphasis> cellulosic biofilm: synthesis of sparse and compact cellulose

Classical studies concerning “Acetobacter xylinum” focus on bacterial cellulose “BC” yield and rate in broth, after a long period of incubation (7–14 days). Such observations do not highlight bacterial physiology in the first incubation hours and its impact on BC production. In this study, the growth of a wild strain of Acetobacter was monitored in the first incubation hours. We showed the presence of two different physiologies; the first extends from the incubation moment till the formation of a sparse BC. Sparse BC modifies surface viscosity, and stabilizes hydrodynamic conditions to initiate compact BC production that marks the second physiology. Two containers, of different shapes, were used to confirm our findings, one of which is a culture tube with high drift currents on the broth-air interface, and the other is a conical flask with more stable hydrodynamic conditions at the culture’s surface. We showed that Acetobacter always follows two physiologies independent of the container shape. Logistic model, FTIR, XRD and SEM analysis are used to confirm the results.     

Variation of student numerical and figural reasoning approaches by pattern generalization type,strategy use and grade level

This paper explored variation of student numerical and figural reasoning approaches across different pattern generalization types and across grade level. An instrument was designed for this purpose. The instrument was given to a sample of 1232 students from grades 4 to 11 from five schools in Lebanon. Analysis of data showed that the numerical reasoning approach seems to be more dominant than the figural reasoning approach for the near and far pattern generalization types but not for the immediate generalization type. The findings showed that for the recursive strategy, the numerical reasoning approach seems to be more dominant than the figural reasoning approach for each of the three pattern generalization types. However, the figural reasoning approach seems to be more dominant than the numerical reasoning approach for the functional strategy, for each generalization type. The findings also showed that the numerical reasoning was more dominant than the figural reasoning in lower grade levels (grades 4 and 5) for each generalization type. In contrast, the figural reasoning became more dominant than the numerical reasoning in the upper grade levels (grades 10 and 11).     

Use of microdevices to determine the diffusion coefficient of electrochemically generated species: application to binary solvent mixtures and micellar solutions

A new approach for the determination of diffusion coefficient, D, of redox species is presented. It is based on the use of a home-constructed twin electrode within a thin-layered cell (TETLC) filled with a solution of electroactive species. Values of D are readily calculated, provided that the time required for the electrochemically generated species (produced at the generator electrode) to reach the collector electrode and the distance between both electrodes are known. Other parameters typically required to calculate D, e.g., concentration of the redox species, area of the electrode, and number of electrons transferred, are not needed. Diffusion coefficients of Fe(CN)(6)(3-), Ru(NH3)(6)(2+), and quinone were determined in water and, for Fe(CN)(6)(4-), in binary mixtures with glycerol. The results obtained were in good agreement with literature values. Aqueous glycerol solutions are microheterogeneous, as shown by the dependence on medium composition of the empirical solvent polarity scale, ET(30), determined by the solvatochromic probe RB. The responses of RB and the electrochemically generated species (Fe(CN)(6)(4-)) to the composition of aqueous glycerol mixtures were found to be remarkably similar. Measurements of D of ferrocene in micellar solutions of the cationic surfactant CTABr were also performed. Values of D for ferrocene and the ferrocenium cation are very different, in agreement with the chemical affinity of both species for the cationic micelle.