Kinetics and mechanism of (salen)MnIII–catalysed hydrogen peroxide oxidation of alkyl aryl sulphides

The kinetics of (salen)Mn^III complexes catalysed oxidation of aryl methyl and alkyl phenyl sulphides with hydrogen peroxide have been investigated at 25°C in 80% acetonitrile – 20% water spectrophotometrically. The reaction follows first‐order kinetics in (salen)Mn^III complex and zero‐order kinetics in hydrogen peroxide. The order of the reaction with respect to sulphide is fractional and saturation in reaction rate occurs at higher sulphide concentrations. The pseudo first‐order rate constants have been analysed as per Michaelis–Menten kinetics to obtain the values of k₂, the oxidant‐substrate complex decomposition rate constant, and K, the oxidant‐substrate complex formation constant. The effects of nitrogenous bases, free radical inhibitor and changes in solvent composition have also been studied. A suitable mechanism, supported by electronic‐oxidant and electronic‐substrate effect studies, involving a manganese(III)‐hydroperoxide complex as reactive species has been proposed. Copyright © 2007 John Wiley & Sons, Ltd.     

Tetracyclo[6.3.0.04,11.05,9]undecane-2,7-dione

The compound crystallizes in the triclinic space group, , witha=6.7702(4),b=7.0180(4),c=9.1960(7) Å, =92.457(6), =96.150(6), =93.444(5)°, andZ=2. The structure contains a rather short intramolecular H...H contact of 2.26(4) Å.     

Circularly polarized wave propagation in a class of bodies defined by a new class of implicit constitutive relations

In this paper, we show that circularly polarized transverse stress waves, standing shear stress waves, and oscillatory shear stress waves can propagate in a new class of viscoelastic solid bodies which are a subclass of bodies described by implicit constitutive theories. The class of models that is being considered includes as sub-classes, the classical Kelvin–Voigt model, the new models introduced by Rajagopal wherein the Cauchy–Green tensor is a non-linear function of the stress, and the Navier–Stokes fluid model. The solutions established in this paper are generalizations of solutions that have been established within the context of nonlinear elasticity by Carroll, and Destrade and Saccomandi, to the new class of elastic and viscoelastic bodies that are being considered.     

Interaction of low-frequency axisymmetric ultrasonic guided waves with bends in pipes of arbitrary bend angle and general bend radius

The use of ultrasonic guided waves for the inspection of pipes with elbow and U-type bends has received much attention in recent years, but studies for more general bend angles which may also occur commonly, for example in cross-country pipes, are limited. Here, we address this topic considering a general bend angle φ, a more general mean bend radius R in terms of the wavelength of the mode studied and pipe thickness b. We use 3D Finite Element (FE) simulation to understand the propagation of fundamental axisymmetric L(0, 2) mode across bends of different angles φ. The effect of the ratio of the mean bend radius to the wavelength of the mode studied, on the transmission and reflection of incident wave is also considered. The studies show that as the bend angle is reduced, a progressively larger extent of mode-conversion affects the transmission and velocity characteristics of the L(0, 2) mode. However the overall message on the potential of guided waves for inspection and monitoring of bent pipes remains positive, as bends seem to impact mode transmission only to the extent of 20% even at low bend angles. The conclusions seem to be valid for different typical pipe thicknesses b and bend radii. The modeling approach is validated by experiments and discussed in light of physics of guided waves.     

Identification and estimation of parameters defining a class of hybrid systems

In this paper, we consider the problem of parameter estimation in an air brake system. In an air brake system, the pressure of air in the brake chamber and the displacement of the pushrod and their derivatives form a set of states that characterize the system. The position of a valve or mass flow rate of air is an input and the pressure is the measured variable or the output. The pressure acting on the pushrod of the brake chamber causes motion, and the mode in which the system operates depends on the displacement of the pushrod. The mode-dependent nature of the system is a result of different sets of spring compliances associated with the piston in different ranges of its displacement. The mode to mode transition in the air brake system is governed by a parameter which is the clearance between the brake pads and the drum. The clearance between the brake pads and the drum can vary due to a variety of factors — for example, brake pad wear or brake fade. In these applications, characterizing the transition from one mode to another requires a lot of constitutive assumptions, and it can be difficult to calibrate the parameters associated with the constitutive assumptions. We therefore treat the air brake system as a system in which the parameter governing the transition from one mode to another (clearance between the brake pads and the drum) is not known exactly. Clearly, this parameter dictates the time delay and lag between the command and delivery of the brake torque at the wheels and affects the stopping distance of the vehicles considerably. The problem of identification considered in this paper is as follows. Suppose that the pressure of the fluid were to be measured and that the motion of the piston is not measured. Is it possible to estimate the final displacement of the piston without knowing the parameters that govern the system to transition from one mode to another?     

Response of an Elastic Body whose Heat Conduction Is Pressure Dependent

The properties of many real materials such as the viscosity, thermal and electrical conductivity, specific heat, relaxation time, as well as optical properties, depend upon the pressure to which the body is subject. For instance, the viscosity of fluids can vary by several orders of magnitude due to the variation in the pressure. In this paper we investigate the change in the response of an elastic solid due to the thermal conductivity being pressure dependent. It is well known that higher pressure leads to reduced molecular mobility, in rubber-like materials, leading in turn to higher cross-linking reaction rates. We find that the response of the solid is quite different from the classical response that is obtained by using Fourier??s law of heat conduction. The theoretical predictions according to the assumption that the thermal conductivity is pressure dependent, are in keeping with experimental results concerning the vulcanization of rubbers wherein one observes the conduction to be dependent on the pressure. To our knowledge, this is the first theoretical study that evaluates the response of non-linear elastic solids due the thermal conductivity depending on the pressure.     

Synthesis of α-carbolines via Pd-catalyzed amidation and Vilsmeier-Haack reaction of 3-acetyl-2-chloroindoles

A new class of α-carboline derivatives has been synthesized by Pd(2)(dba)(3)/BINAP catalyzed amidation of 3-acetyl-2-chloroindoles followed by a Vilsmeier-Haack reaction and is reported.     

Iron(III)–salen–H<Subscript>2</Subscript>O<Subscript>2</Subscript> as a peroxidase model: electron transfer reactions with anilines

Abstract  

Iron(III)–salen complexes catalyze the H₂O₂ oxidation of various ring-substituted anilines in MeCN have been studied, and [O=Fe^IV(salen)]^+· is proposed as the active species. Study of the kinetics of the reaction by spectrophotometry shows the emergence of a new peak at 445 nm in the spectrum which corresponds to azobenzene. Further oxidation of azobenzene by H₂O₂ leads to the formation of azoxybenzene. ESI–MS studies also support the formation of these products. The rate constants for the oxidation of meta- and para-substituted anilines were determined from the rate of decay of oxidant as well as the rate of formation of azobenzene, and the reaction follows Michaelis–Menten kinetics. The rate data show a linear relationship with the Hammett σ constants and yield a ρ value of −1.1 to −2.4 for substituent variation in the anilines. A reaction mechanism involving electron transfer from aniline to [O=Fe(salen)]^+· is proposed. The presence of axial ligands modulates the activity of the complex.     

Complete dynamical analysis of a neuron under magnetic flow effect

In the last decades, many studies have been done about nervous system from the mathematical and computational point of view. Many mathematical models have been proposed to describe neuron. Most of them have described the membrane potential of a neuron in terms of the leakage current and the synaptic inputs. Very recently, according to the Maxwell electromagnetic induction theorem, researchers proposed a new neuron model which considers inner magnetic fluctuation and external electromagnetic radiation as a significant missing part that can participate in neural activity. In this paper, dynamical properties of this new model, such as equilibria and its stability, phase portraits, bifurcation diagram, Lyapunov exponents, and basin of attraction, are investigated. Moreover, an implementation of electronic circuit and FPGA is also done to verify the feasibility of the theoretical model.