Effect of Mn substitution on the delicate balance between structure and properties of Gd1.4Ce0.6Sr2RuCu2O10

Some new members of a ruthenocuprate(2212) series have been synthesized by Mn substitution for Ru in Gd_1.4Ce_0.6Sr₂RuCu₂O₁₀. Characterization by x-ray diffraction (XRD) phase analysis has been carried out. Changes in structural features on substitution, including a significant change in lattice parameter for a very low substitution level, have been observed. Four-probe resistivity studies indicate the coexistence of superconductivity and magnetism for the pristine compound and a semiconductor-like upturn in resistivity and the absence of superconductivity even for very low levels of Mn substitution. AC susceptibility measurements show a progressive suppression of the magnetic transition temperature as well as a smearing of the magnetic transition as a function of Mn substitution. Possible reasons for the absence of superconductivity have been discussed.     

Establishing structure-property correlations and classification of base oils using statistical techniques and artificial neural networks

The present paper describes various classification techniques like cluster analysis, principal component (PC)/factor analysis to classify different types of base stocks. The API classification of base oils (Group I-III) has been compared to a more detailed NMR derived chemical compositional and molecular structural parameters based classification in order to point out the similarities of the base oils in the same group and the differences between the oils placed in different groups. The detailed compositional parameters have been generated using and nuclear magnetic resonance (NMR) spectroscopic methods. Further, oxidation stability, measured in terms of rotating bomb oxidation test (RBOT) life, of non-conventional base stocks and their blends with conventional base stocks, has been quantitatively correlated with their NMR and elemental (sulphur and nitrogen) data with the help of multiple linear regression (MLR) and artificial neural networks (ANN) techniques. The MLR based model developed using NMR and elemental data showed a high correlation between the ‘measured’ and ‘estimated’ RBOT values for both training (R=0.859) and validation (R=0.880) data sets. The ANN based model, developed using fewer number of input variables (only NMR data) also showed high correlation between the ‘measured’ and ‘estimated’ RBOT values for training (R=0.881), validation (R=0.860) and test (R=0.955) data sets.     

Spectrophotometric methods for the determination of tamoxifen citrate

Three simple and sensitive spectrophotometric methods for the determination of tamoxifen citrate have been developed. They are based on the formation of an ion-association complex between the drug and a dye, Erioglaucine A, which is extractable into chloroform and has an absorption maximum at 625 nm (method A), oxidation with excess potassium permanganate and the determination of unconsumed permanganate using Fast Green FCF (method B), or by the formation of a coloured cobalt thiocyante coordination complex which is extracted into benzene and measured at 635 nm (method C). Beer's law limits for methods A, B, and C are 0.5-3.0 mug ml(-1), 1.0-6.0 mug ml(-1) and 100-500 mug ml(-1), respectively. No interference was observed from tableting additives and the applicability of the methods was examined by analysing tablets containing tamoxifen. The quantities determined were 99.0-100.03% of the exptected values.     

Spectrophotometric estimation of ketotifen fumarate in pharmaceutical formulations

Four simple and sensitive spectrophotometric methods (A–D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, _max 520 nm) or by oxidizing it with excessN-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: _max 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: _max 720 nm) or by the formation of a chloroform-soluble, coloured ionassociation complex between the drug and Azocarmine G at pH 1.5 (method D: _max 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1–10, 2–12, 4–28 and 2.5–25 g/ml for methods A–D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within ±1.0%. Recoveries were 98.9–100.2%.     

Spectrophotometric determination of nicoumalone, acebutolol hydrochloride and procainamide hydrochloride

A sensitive spectrophotometric method is described for the determination of nicoumalone (NIC), acebutolol hydrochloride (ACBH) or procainamide hydrochloride (PAH) either in pure form or in pharmaceutical formulations. The method is based on the oxidative coupling reaction through the involvement of an aromatic primary amino group (released through reduction in NIC or hydrolysis in ACBH or existing free in PAH) in the drug with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ferric chloride [Fe(III)]. The resulting chromophores are measured at 620 nm for NIC and ACBH and 580 nm for PAH. The concentration measurements are reproducible within a relative standard deviation of 1%.     

Structure-energy relationships in curved polycyclic aromatic hydrocarbons: study of benzocorannulenes

B3LYP/6-31G* calculations indicate that sequential annelation of benzene rings to the rim of corannulene gradually flattens the skeleton. Pentabenzocorannulene is predicted to exhibit nearly barrierless flipping motion at room temperature. A mixed quartic-quadratic potential successfully explains the inversion barrier and curvature (given by the pi-orbital axis vector angle) relationship.     

Tegoprens in anaerobic digestion of a mixture of cheese whey,poultry waste,and cattle dung for improved biomethanation

To obtain enriched methane content and improve the anaerobic digestion of a mixture of cattle dung, poultry waste, and cheese whey, the effect of various doses of Tegoprens: T-3012, T-3022, T-5842, T-5843, T-5851, T-5852 has been studied, in bench-scale digesters. Among them, Tegoprens 3022 showed more than a 45% increase in gas production with higher methane content.     

Gold nanoparticle networks with photoresponsive interparticle spacings

Photoresponsive gold nanoparticle networks were prepared by functionalizing them with azobenzene derivatives. A network can be formed when a linker molecule constituting the azobenzene moiety suitably derivatized on either side with gold surface sensitive groups such as thiols and amines is added to the nanoparticle solution. It is shown that the interparticle spacing in the networks could be controlled by the reversible trans-cis isomerization of the azobenzene moiety induced by UV and visible light, respectively. The photoinduced variation in the interparticle spacings is inferred by the changes in the optical spectra of the gold nanoparticles which display a red or blue shift in the surface plasmon resonance peak depending on a decrease or increase in the interparticle spacing, respectively. Transmission electron microscopy images are in consonance with the evidence from the optical spectra.     

Extractive spectrophotometric determination of some fluoroquinolone derivatives in pure and dosage forms

Two simple and sensitive extractive spectrophotometric methods for the determination of some fluoroquinolone derivatives (norfloxacin, NRF; ciprofloxacin, CPF; ofloxacin, OFL; and enrofloxacin, ERF) with Supracene Violet 3B (SV 3B, method A) and tropaeolin 000 (TP 000, method B) are described. The methods are based on the formation of ion-association complexes of fluoroquinolones with these dyes, which are extracted into chloroform and have absorption maxima at 575 nm (SV 3B) and 485 nm (TP 000). The methods obey Beer's law and the precision and accuracy of the methods were checked by UV reference methods. The detection limits were 5.0 mug/ml for NRF and 2.5 mug/ml for CPF in method A and 2.5 mug/ml for OFL and ERF in methods A and B.