Optical absorption and EPR spectral studies of vauquelinite

Vauquelinite ‐ a mineral ‐ was investigated by EPR, NIR and optical spectroscopic techniques. EPR studies on powder sample confirm the presence of Cu(II) and Fe(III) impurity in the mineral. Optical absorption spectrum also indicates that Cu(II) impurity is present in rhombically distorted octahedral structure and Fe(III) in octahedral structure. NIR results are due to water fundamentals and phosphate combination tone. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Concurrent determination of olanzapine,risperidone and 9‐hydroxyrisperidone in human plasma by ultra performance liquid chromatography with diode array detection method: application to pharmacokinetic study

A simple and sensitive ultra‐performance liquid chromatography (UPLC) method has been developed and validated for simultaneous estimation of olanzapine (OLZ), risperidone (RIS) and 9‐hydroxyrisperidone (9‐OHRIS) in human plasma in vitro. The sample preparation was performed by simple liquid–liquid extraction technique. The analytes were chromatographed on a Waters Acquity H class UPLC system using isocratic mobile phase conditions at a flow rate of 0.3 mL/min and Acquity UPLC BEH shield RP₁₈ column maintained at 40°C. Quantification was performed on a photodiode array detector set at 277 nm and clozapine was used as internal standard (IS). OLZ, RIS, 9‐OHRIS and IS retention times were found to be 0.9, 1.4, .1.8 and 3.1 min, respectively, and the total run time was 4 min. The method was validated for selectivity, specificity, recovery, linearity, accuracy, precision and sample stability. The calibration curve was linear over the concentration range 1–100 ng/mL for OLZ, RIS and 9‐OHRIS. Intra‐ and inter‐day precisions for OLZ, RIS and 9‐OHRIS were found to be good with the coefficient of variation <6.96%, and the accuracy ranging from 97.55 to 105.41%, in human plasma. The validated UPLC method was successfully applied to the pharmacokinetic study of RIS and 9‐OHRIS in human plasma. Copyright © 2015 John Wiley & Sons, Ltd.     

Hydrodechlorination of chlorobenzene over supported metal catalysts

The use of supported Pd catalysts, with low and high metal content, for the hydrodechlorination of chlorobenzene is presented in this article. Application of microwave irradiation during preparation of catalysts resulted in the synthesis of large Pd particles at moderate temperatures. The nature of the support played a key role in the formation of cationic Pd species. The extent of interaction of the Pd species with the support, the nature of metal precursor, particularly the residual chlorine on the surface were found to significantly affect the activity of the catalysts. In the case of bimetallic catalysts also microwave heating resulted in creation of bigger particles of Pd compared to those observed in conventionally heated catalysts. Besides, it minimized alloy formation as a result of which the activity of the catalysts in hydrodechlorination was found to be higher compared to that observed on conventionally prepared catalysts. Contrary to the general observation that low dispersed Pd catalysts are preferable for high stability, by means of the deposition-precipitation method adopted for catalyst preparation it was demonstrated that even highly dispersed (low Pd containing) catalysts can exhibit comparable activity and stability. An analysis of the nature of Pd species and its role in the stability of the catalysts is presented.IICT communication No. 051224     

Aggregation behavior of single-walled carbon nanotubes in dilute aqueous suspension

The aggregation behavior of colloidal single-walled carbon nanotubes (SWNT) in dilute aqueous suspensions was investigated using a novel light scattering measurement technique. The aggregation of SWNT in three suspensions was examined: (1) nanotubes after acid treatment; (2) as-received nanotubes stabilized by a nonionic surfactant; and (3) acid-treated nanotubes with nonionic surfactant. Continuous light scattering measurements of the SWNT suspensions (probing the 38-436 nm length scale) made over two weeks showed that the nanotubes in each sample formed networks with fractal-like structures. The as-received nanotubes were stable over the measurement period, while the acid-treated nanotube suspension showed greater dispersion variability over time, yielding looser structures at large length scales and more compact structures at smaller length scales. The addition of surfactant to the acid-treated suspension significantly enhanced nanotube dispersion.     

An organo-catalytic approach to the enantioselective synthesis of (R)-selegiline

An efficient enantioselective synthesis of (R)-selegiline has been achieved by two routes, via proline-catalyzed α-aminooxylation as well as α-amination of phenylpropanaldehyde as the key step.     

I–V characteristics and break down studies of Sb2O3 structures

I–V characteristics of sandwiched Al–Sb₂O₃–Al structures have been studied for different thicknesses. The current-voltage curves in general exhibit three regions, ohmic, non ohmic and breakdown regions. The breakdown voltage increases whereas the dielectric strength decreases with increase in Sb₂O₃ film thickness. The electrical breakdown studies have been done for dc and ac voltages and optical photomicrographs of breakdown patterns during different stages of voltage have been taken and the results are explained.     

Rotation implementation of a circular cylinder in incompressible flow via staggered grid approach

In this paper, we present a finite difference method for the implementation of the rotation of a circular cylinder in the incompressible flow field by solving the two-dimensional unsteady Navier-Stokes equations. The approach is to use staggered grid method so that the accuracy and order of convergence of the associated algorithms can be maintained. The proposed method is easy to be implemented and is effective. A set of simulations for the flow dynamics is provided to show the computational results.     

A study on the inclusion complexation of 3,4,5-trihydroxybenzoic acid with β-cyclodextrin at different pH

Effect of β-cyclodextrin (β-CD) on the absorption and fluorescence spectra of 3,4,5-trihydroxybenzoic acid (THB) have been studied buffer solutions of different pHs (pH ~1, pH ~7 and pH ~10). The study reveals that in all the above pHs THB forms 1:1 inclusion complex. The hydroxyl groups are present in the interior part of the β-CD cavity and carboxyl group is present in the hydrophilic part of the β-CD cavity. Dual luminescence is observed at pH ~1 and pH ~7 solutions which shows that intramolecular charge transfer present at these pH. The broad spectral maximum at pH ~10 indicates that intramolecular proton transfer is present in THB.