Electrocatalytic oxidation and highly selective voltammetric determination of L-cysteine at the surface of a 1-[4-(ferrocenyl ethynyl)phenyl]-1-ethanone modified carbon paste electrode.

A carbon paste electrode (CPE) chemically modified with 1-[4-(ferrocenyl ethynyl)phenyl]-1-ethanone (4-FEPEMCPE) was employed to study the electrocatalytic oxidation of L-cysteine using cyclic voltammetry, differential pulse voltammetry and double potential step chronoamperometry as diagnostic techniques. The diffusion coefficient (D = 7.863 x 10(-6) cm2 s(-1)) of L-cysteine was also estimated using chronoamperometry. The electron-transfer coefficient, alpha (= 0.40), for L-cysteine at the surface of 4-FEPEMCPE was determined using cyclic voltammetry technique. It was found that under an optimum pH (= 7.00), the oxidation of L-cysteine at the surface of such an electrode occurred at a potential of about 350 mV less positive than that of an unmodified CPE. The catalytic oxidation peak currents represented a linear dependence on the L-cysteine concentration. Linear analytical curves were obtained in the ranges of 9.0 x 10(-5) - 4.9 x 10(-3) M and 2.0 x 10(-5) - 2.8 x 10(-3) M of L-cysteine with correlation coefficients of 0.9981 and 0.9982 in cyclic voltammetry and differential pulse voltammetry, respectively. The detection limits (2 sigma) were determined to be 9.9 x 10(-6) M and 5 x 10(-6) M with cyclic voltammetry and differential pulse voltammetry, respectively. The influences of twenty other amino acids, such as glutamine, L-glutamic acid, L-glysine, L-histidine, L-isoleucine, L-leucine, L-arginine hydrochloride, L-aspargine, L-aspartic acid, S-carboxy methyl-L-cysteine, L-methionine, L-phenyl alanine, L-proline, L-serine, L-threonine, L-cystine, cysteamine and gluthathione, on the current response of the sensor were examined. The obtained results did not show any influence on the analytical signal of L-cysteine by these amino acids (except for cysteamine). The method was also used for the selective determination of L-cysteine in patient-blood plasma and some pharmaceutical preparations by using standard addition method.     

Structure-property relations in heat resistant polyesters with built-in ether and imide units

A new pyridine-based diacid containing ether and imide units was synthesized via reaction of 5-amino-1-naphthol with 2,6-dichloropyridine in the presence of potassium carbonate in N-methyl-2-pyrrolidone (NMP), and subsequent reaction of the obtained diamine with 2 mol of trimellitic anhydride. A series of poly(ether imide ester)s was synthesized by the polycondensation reactions of the prepared diacid with different diols via high temperature solution polycondensation reaction method. All the products were fully characterized by common spectroscopic methods. The polymers were examined by elemental analysis, IR and ¹H NMR spectra, inherent viscosity, X-ray diffraction, DSC, TGA and DMTA and their properties were studied. Polymers showed high thermal stability and good solubility in polar aprotic solvents. The Structure-property relations of the polymers were also studied.     

Rapid and Efficient Synthesis of Imidazolines and Bisimidazolines Under Microwave and Ultrasonic Irradiation

Small assemblies of 2-imidazolines and bisimidazolines from appropriate nitriles and ethylenediamine with catalytic amounts of P₂S₅ employing a microwave assisted protocol were prepared. Sonication of this system also led to successful synthesis of 2-imidazolines and bisimidazolines. Another advantage of these systems is the ability to carry out large scale reactions.     

Optimal piezoelectric actuator and sensor location for active vibration control, using genetic algorithm

This paper deals with the optimization of piezoelectric actuators and sensors locations for active vibration control. Two modified optimization criteria are used, ensuring good observability or controllability of the structure, and considering residual modes to limit the spillover effect. Two optimization variables are considered for each piezoelectric device: the location of its center and its orientation. Genetic algorithms are used to find the optimal configurations. Several simulations are presented for a simply supported plate.     

Efficacy of cones on topological vector spaces and application to common fixed points of multifunctions

Let (E, τ) be a topological vector space and P a cone in E. We shall define a topology τ _P on E so that (E, τ _P ) is a normable topological vector space and P is a normal cone with normal constant M = 1. Then by using the norm, we shall give some results about common fixed points of two multifunctions on cone metric spaces.     

Finding weak defining hyperplanes of PPS of the BCC model

Production possibility set (PPS) is intersection of the several halfspaces. Every halfspace corresponds with one strong or weak defining hyperplane (facet). This research proposes a method to find weak defining hyperplanes of PPS of BCC model. We state and prove some properties relative to our method. Numerical examples are provided for illustration.     

Generalizations of the Primitive and Normal Basis Theorems

Using a Zariski topology associated to a finite field extensions, we give new proofs and generalize the primitive and normal basis theorems.     

Photovoltaic cells technology: principles and recent developments

Solar energy is one of the renewable energy resources that can be changed to the electrical energy with photovoltaic cells. This article accomplishes a comprehensive review on the emersion, underlying principles, types and performance improvements of these cells. Although there are some different categorizations about the solar cells, but in general, all of them can be divided to crystalline silicon solar cells, thin film technology, III–V multijunction cells, dye-sensitized solar cells, polymer solar cells and quantum structured solar cells. Thin film technology is investigated in two non-crystalline silicon solar cells and chalcogenide cells. We present a complete categorization of solar cells and discuss the recent developments of different types of solar cells. Indeed, this paper covers almost all of the development processes of solar cells from their emersion in 1939 up to now. Also, due to substantial effects of the light trapping techniques on the improvements of the solar cells, a comprehensive study has been carried out.