Synthesis,structure, spectroscopic (FT-IR) and density functional modelling studies of 1-[(4-ethoxyphenylimino)methyl]napthalene-2-ol

Synthesis, crystallographic characterisation, spectroscopic (Fourier transform infrared spectroscopy [FT-IR]) and density functional modelling studies of the Schiff base 1-[(4-ethoxyphenylimino)methyl]napthalene-2-ol (C₁₉H₁₇NO₂) have been reported. The molecular structure obtained from X-ray single-crystal analysis of the investigated compound in the ground state has been compared using Hartree–Fock and density functional theory (DFT) with the 6-311++G(d,p) basis set. In addition to the optimised geometrical structures, atomic charges, molecular electrostatic potential, natural bond orbital, non-linear optical (NLO) effects and thermodynamic properties of the compound have been investigated by using DFT. The experimental (FT-IR) and calculated vibrational frequencies (using DFT) of the title compound have been compared. The solvent effect was also investigated for obtained molecular energies and the atomic charge distributions of the compound. There exists a good correlation between experimental and theoretical data for enol-imine form of the compound. The total molecular dipole moment (µ), linear polarisability (α), and the first-order hyperpolarisability (β) were predicted by the B3LYP method with different basis sets 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) 150 and 6-311++G(d,p) for investigating the effects of basis sets on the NLO properties. Our computational results yield that β_tot for the title compound is greater than those of urea.     

Reformulation of electromagnetic and gravito-electromagnetic equations for Lorentz system with octonion algebra

In this paper, the real, complex octonion algebra and their properties are defined. The electromagnetic and gravito-electromagnetic equations with monopoles in terms of S and $\hbox {S}^{\prime }$ reference systems are presented in vector notations. Additionally, the duality transformations of gravito-electromagnetic situation for two reference systems are also represented. Besides, it is explained that Maxwell-like equations for gravito-electromagnetism are also invariant under Lorentz transformations. By introducing complex octonionic differential operator, a new generalized complex octonionic field term consisting of electromagnetic and gravito-electromagnetic components has been firstly suggested for Lorentz system. Afterwards, a complex octonionic source equation is obtained as in basic way, more compact and elegant notation. By defining a new complex octonionic general potential term, the field equation is attained once again. The components of complex octonionic field and wave equations are written in detailed for S and $\hbox {S}^{\prime }$ reference systems.     

New Amperometric Cholesterol Biosensors Using Poly(ethyleneoxide) Conducting Polymers

Accumulation of cholesterol in human blood can cause several health problems such as heart disease, coronary artery disease, arteriosclerosis, hypertension, cerebral thrombosis, etc. Therefore, simple and fast cholesterol determination in blood is clinically important. In this study, two types of amperometric cholesterol biosensors were designed by physically entrapping cholesterol oxidase in conducting polymers; thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-co-p-vinyl benzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy). PEO-co-PPy and CP-co-PPy were synthesized electrochemically and cholesterol oxidase was immobilized by entrapment during electropolymerization. The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H₂O₂ at +0.7 V in the absence of a mediator. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. Km values were found as 1.47 and 5.16 mM for PEO-co-PPy and CP-co-PPy enzyme electrodes, respectively. By using these Km values, it can be observed that ChOx immobilized in PEO-co-PPy shows higher affinity towards the substrate.     

One-Pot Synthesis of Mannich Bases Under Solvent-Free Conditions

A mild and practically convenient one-pot procedure for the Mannich reaction via condensation of amines, aldehydes and malonates, β-ketoesters, or β-dicarbonyl compounds has been carried out without using any organic solvent, metallic catalyst, or Lewis acids or bases at room temperature. The present protocol offers several advantages, such as goods yields, simple procedure with easy workup, and the absence of any volatile, hazardous organic solvents and metallic catalyst.     

Paal–Knorr Pyrrole Synthesis in Water

Water was a suitable medium for Paal–Knorr pyrrole cyclocondensation. Hexa-2,5-dione was reacted with several aliphatic and aromatic primary amines, affording N-substituted 2,5-dimethyl pyrrole derivatives in good to excellent yields. An efficient, green method using water either as environmentally friendly solvent or catalyst was presented.     

Water Miscible Mono Alcohols’ Effect on the Proteolytic Performance of Bacillus clausii Serine Alkaline Protease

In this study, our investigations showed that the increasing concentrations of all examined mono alcohols caused a decrease in the V _m, k _cat and k _cat/K _m values of Bacillus clausii GMBE 42 serine alkaline protease for casein hydrolysis. However, the K _m value of the enzyme remained almost the same, which was an indicator of non-competitive inhibition. Whereas inhibition by methanol was partial non-competitive, inhibition by the rest of the alcohols tested was simple non-competitive. The inhibition constants (K _I) were in the range of 1.32–3.10 M, and the order of the inhibitory effect was 1-propanol>2-propanol>methanol>ethanol. The ΔG ^≠ and ΔG ^≠ _E???T values of the enzyme increased at increasing concentrations of all alcohols examined, but the ΔG ^≠ _ES value of the enzyme remained almost the same. The constant K _m and ΔG ^≠ _ES values in the presence and absence of mono alcohols indicated the existence of different binding sites for mono alcohols and casein on enzyme the molecule. The k _cat of the enzyme decreased linearly by increasing log P and decreasing dielectric constant (D) values, but the ΔG ^≠ and ΔG ^≠ _E???T values of the enzyme increased by increasing log P and decreasing D values of the reaction medium containing mono alcohols.     

Sensitive and selective determination of tolterodine tartrate and its electrochemical investigation on solid carbon based electrodes

Tolterodine tartrate, a muscarinic receptor antagonist, was oxidized in various buffer media with different pH values using cyclic, differential pulse, and square wave voltammetric techniques on glassy carbon and boron-doped diamond electrodes. Two irreversible anodic peaks were obtained. The oxidation process of tolterodine tartrate was diffusion controlled depending on pH for both electrodes. A detailed oxidation mechanism was proposed and discussed. The dependences of the peak current and peak potentials on pH, concentration, nature of the buffer, and scan rate were investigated. A linear response between the peak current and the tolterodine tartrate concentration was obtained using differential pulse and square wave voltammetric techniques in the range of 0.4–8.0 μM for the peak at lower potential in acetate buffer at pH 5.7 and 0.4–40.0 μM for the peak at higher potential in 0.1 M H₂SO₄ on glassy carbon electrode and in the range of 0.4–40.0 μM in Britton-Robinson buffer at pH 11.0 on boron-doped diamond electrode. Limit of detection values varied between 0.04 and 0.13 μM for both techniques and electrodes. The repeatability, reproducibility, precision, and accuracy of the proposed methods were investigated. The recovery studies were also achieved to check selectivity, precision, and accuracy of the methods. The proposed methods were successfully applied to determine tolterodine tartrate from pharmaceutical dosage forms without any interference from inactive excipients.     

A fiber optic spectrophotometric determination of urinary indoxyl sulfate (indican) after cloud point extraction

This work describes a new, simple, and sensitive colorimetric determination method for indoxyl sulfate (indican) by fiber optic UV-Vis spectrophotometry coupled to cloud point extraction as the separation-preconcentration method. This method is based on the diazotization of sulphanilic acid in acidic medium followed by its coupling with indoxyl sulfate (indican), which gives an azo product and extraction of the colored product using the cloud point extraction (CPE) technique. The optimal extraction and reaction conditions (e.g., acid and reagent concentrations, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor) were obtained. Linear response was achieved within 0.9–44 μg/mL and the detection limit was estimated as 0.6 μg/mL. The inter-day and intraday relative standard deviations were in the ranges 1.2–1.3% and 1.6–1.8% for indican. The method was applied to the determination of indican in human spiked urine samples; Recoveries within 96–99% were obtained.     

Production and Subcontracting Strategies for Manufacturers with Limited Capacity and Volatile Demand

We study a manufacturing firm that builds a product to stock to meet a random demand. If there is a positive surplus of finished goods, customers make their purchases without delay and leave. If there is a backlog, the customers are sensitive to the quoted lead time and some choose not to order if they feel that the lead time is excessive. A set of subcontractors, who have different costs and capacities, are available to supplement the firm's production capacity. We derive a feedback policy that determines the production rate and the rate at which the subcontractors are requested to deliver products. The performance of the system, when it is managed according to this policy, is evaluated.     

DFT Study of the 1-Octene Metathesis Reaction Mechanism with WCl(6)/C Catalytic System

A catalytic system consisting of tungsten carbene generated from WCl(6) and an atomic carbon is investigated theoretically for the metathesis of 1-octene at B3LYP/extended LANL2DZ level of DFT. The ground-state geometries and charge distributions of the structures belonging to the reaction mechanism are located. Energetics for the complete set of reactions, involving the formation of the tungsten carbene precatalyst, Cl(4)WCCl(2), the formation of tungsten methylidene and tungsten heptylidene with this precatalyst, and finally productive and degenerative metathesis steps with these alkylidene species are calculated in terms of total electronic energy and thermal energies. The free-energy (ΔG(298)) surfaces of the structures involved in the related reactions are constructed. In addition, solvent effects on the single point energies of the structures are investigated for two different solvents, namely, cyclohexane and chloroform. The results indicate that the formation of the catalytically active heptylidene is energetically favored in comparison to the formation of methylidene, while the degenerative and productive metathesis steps are competitive. In the catalytic cycle, the formation of ethylene is exothermic, while the formation of 7-tetradecene is endothermic. As expected, solvent effects on the metathesis reactions are minor and solvation does not cause any change in the directions of the overall metathesis reactions.