A comparative study of ruthenium(III) catalysed oxidation of L-leucine and L-isoleucine by alkaline permanganate. A kinetic and mechanistic approach

The kinetics of the Ru^III-catalysed oxidation of L-leucine and L-isoleucine by alkaline permanganate were studied and compared, spectrophotometrically using a rapid kinetic accessory. The reaction is first order with respect to [oxidant] and [catalyst] with an apparently less than unit order in [substrate] and [alkali] respectively. The results suggest the formation of a complex between the amino acid and the hydroxylated species of ruthenium(III). The complex reacts further with the alkaline permanganate species in a rate-determining step, resulting in the formation of a free radical, which again reacts with the alkaline permanganate species in a subsequent fast step to yield the products. The reaction constants involved in the mechanism were calculated. There is a good agreement between observed and calculated rate constants under different experimental conditions. The activation parameters with respect to the slow step of the mechanism for both the amino acids were calculated and discussed. Of the two amino acids, leucine is oxidised at a faster rate than isoleucine.     

FT-IR, FT-Raman spectra and ab initio DFT vibrational analysis of p-bromophenoxyacetic acid

The Fourier transform Raman and Fourier transform infrared spectra of p-bromophenoxyacetic acid were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by HF and DFT (B3LYP) method with the 6-31G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental ones. A detailed interpretation of the infrared and Raman spectra of p-bromophenoxyacetic acid is reported on the basis of the calculated potential energy distribution. The theoretical spectrograms for the IR spectrum of the title molecule have been constructed.     

Spectral,thermal, and electrical properties of poly(o- and m-toluidine)-polystyrene blends prepared by emulsion pathway

Conducting poly(o-toluidine) (POT) and poly(m-toluidine) (PMT) blends containing 10, 30, 50, 70, and 90 % wt/wt of polystyrene (PSt) were prepared by employing a two-step emulsion pathway. The bands characteristic of both polystyrene and POT/PMT are present in the IR spectra of POT–PSt and PMT–PSt blends. The UV-visible spectra of POT–PSt and PMT–PSt blends exhibit two bands around 313 and 610 nm, confirming that some amount of POT/PMT base is present in the blends. The EPR parameters such as line width and spin concentration reveal the presence of POT/PMT salt in the respective blends. The TGA, DTA, and DSC results suggest a higher thermal stability for the POT and PMT blends than that for the respective salts. The conductivity values of POT(70)–PSt(30) and POT(90)–PSt(10) blends are almost the same (1.1 × 10⁻² and 1.3 × 10⁻² S cm⁻¹, respectively) and these values are very close to that of pure POT salt, suggesting that POT can be blended with up to 30% wt/wt of PSt to improve its mechanical properties without a significant drop in its conductivity. The conductivity values of PMT–PSt blends are lower than those of the corresponding POT–PSt blends by two to three orders of magnitude, indicating that POT is a better system than PMT to prepare blends by this method. The dielectric constant and tan δ values of the blends increase with the amount POT/PMT and are greater than that of polystyrene. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2291–2299, 1998     

Migration of active filaments under Poiseuille flow in a microcapillary tube

The European Physical Journal E - The buckling and twisting of slender, elastic fibers is a deep and well-studied field. A slender elastic rod that is twisted with respect to a fixed end will...     

Non-linear response of a string to random excitation

The mean square deflection of a non-linear string subjected to nonplanar Gaussian white noise excitation is determined by the perturbation method. It is shown that increase in tension due to stretching, and transverse transverse mode coupling tend to reduce the mean square deflection; while longitudinal-transverse mode coupling tends to counter this effect to some extent. These results are in conformity with the trend observed in the case of periodic excitation.     

Advantages of endoscopic laser arytenoidectomy using yag laser scalpel

The surgical management of bilateral vocal cord paralysis has been performed through an endoscope in the past. The etiology of bilateral vocal cord paralysis is usually secondary to trauma; to secure an adequate airway, a tracheostomy is performed. Endoscopic laser arytenoidectomy offers a safe method of decannulating patients with maintenance of good voice quality and a rima glottidis of 4–6 mm posteriorly. Several wavelengths are available to carry out this procedure, and this article will focus on Nd:Yag laser scalpel applications. The advantage of this method is the preservation of good voice quality with an option of an external procedure, if the need arises. The laser application offers excellent hemostasis, and decreased edema and scar tissue formation. The results of our study on 10 patients appear encouraging and superior with respect to other available wavelengths.     

A tandem mass spectrometric approach to the identification of O‐glycosylated glargine glycoforms in active pharmaceutical ingredient expressed in Pichia pastoris

Glycoforms of glargine expressed in Pichia pastoris were isolated by high‐performance liquid chromatography and analyzed by a series of chemical and mass spectrometric methods for the identification of various glycoforms, glycosylation position, nature and structure of glycans. Reduction and alkylation, peptide mapping techniques were used to decipher the amino acid site at which glycosylation had taken place. Chemical methods were coupled with mass spectrometry techniques such as electrospray ionization and matrix‐assisted laser desorption/ionization for identification of the glycosylation site. Copyright © 2009 John Wiley & Sons, Ltd.     

Initiation of localized shear bands in plane strain

This study is concerned with the initiation of localized shear bands in plane-strain tension and compression. A theoretical framework which views the initiation of such shear bands as a bifurcation phenomenon from a homogeneous equilibrium field in an elastic-plastic body is first briefly reviewed, and then the predictions of the theory are compared with some experimental observations on an aged maraging steel. The experiments support the physical relevance of the theory within the framework of continuum mechanics.Specifically, the comparison between theory and experiment is concerned with the critical strains to localization and the orientation of the shear bands relative to the load axis. The theoretical predictions are only in qualitative agreement with the experimental observations. A better agreement is obtained with use of the constitutive equations corresponding to the classical deformation theory (a simple vertex model) than with use of the constitutive equations of the classical flow theory. It is concluded that better constitutive equations for elastic-plastic materials are needed before theoretical predictions can be obtained which might be expected to be in closer quantitative accord with experiment.     

Effect of annealing on structural and electrical properties of the Li–Mn–O thin films, prepared by high frequency RF magnetron sputtering

Li–Mn–O thin film cathode materials are prepared by high frequency (27.12 MHz) RF magnetron sputtering. The high RF frequency gives higher deposition rates without compromising on the quality of the films. This investigation focuses on the effects of post-annealing on the micro-structural, morphological and electrical properties of Li–Mn–O films. It is observed that with the increase of annealing temperature the crystallinity as well as the electrical conductivity of the films increases. The films annealed at 600–700 °C are found to have high structural perfection and good electrical properties.