Perturbation theory for nematic liquid crystals of axially symmetric molecules: Numerical results at high pressures including second- and fourth rank orientational order parameters

A statistical mechanical perturbation theory is applied to study the thermo-dynamic properties of nematic liquid crystals at the nematic-isotropic (N-I) phase transition under pressure, retaining second- and fourth-rank long-range orientational order parameters. We report calculations for a hard ellipsoidal system superposed with an attractive interaction and subjected to different external pressures. The repulsive interaction is represented by a repulsion between hard ellipsoids characterized by a length-to-width ratio and the interaction arising from the dispersion interaction between two asymmetric molecules represents the attractive interaction. The inclusion of the fourth-rank order parameter in the effective one-body potential ψ(Ω) does not lead to a significant overall improvement. The influence of pressure on the stability, ordering and thermodynamic functions at the N-I transition is analysed. We find that our theoretical predictions are in accordance with experimental observations.     

Aryl-bis(thioaryl)sulfonium salts and their use for the preparation of S-aryl-episulfonium salts

A new method for the preparation of S-arylepisulfonium salts has been developed and several compounds of this type have been isolated.     

Biophysical,spectroscopic and biochemical investigation of DNA–Cu(II)-GSH interactions

The interaction of DNA with Copper(II)-Glutathione (CuGSH) has been investigated by various biophysical methods. The interaction ratio of DNA and Copper(II)-Glutathione in solution phase has been determined spectrophotometrically and found to be 0.25. EPR spectroscopy and UV–Vis findings suggest that Cu(II)-Glutathione neither bound to the DNA bases covalently nor intercalated, this has further been substantiated by the determination of intrinsic binding constant (2.1 × 10²). Viscometric measurements also support this type of binding to DNA by Cu(II)-Glutathione. EPR studies and visible d–d spectra of CuGSH after interaction with DNA, suggested that Copper remained in the Copper(II) state. DNA conformations after interaction with Cu(II)-Glutathione has been determined spectroscopically. Circular dichroism studies revealed that the B conformation of DNA is changed to A after interaction with Cu(II)-Glutathione. This has further been substantiated by thin film IR (Infrared) studies.     

Liquid Chromatography Tandem Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy of Magnesium (II) Gluconate Solution

Magnesium gluconate is a classical pharmaceutical compound used as a source of magnesium for the prevention and treatment of hypomagnesemia. To the best of our knowledge, a robust and reliable liquid chromatography tandem mass spectrometry technique has not yet been reported for the qualitative and quantitative analysis of magnesium gluconate. This study describes the method development for the LC–ESI–MS/MS analysis of magnesium gluconate using three different reversed-phase HPLC conditions (Method I–III) with comprehensive fragmentation pattern and the structural characterization by NMR spectroscopy. The LC–MS and NMR data were found in accordance with the structure of magnesium gluconate. When magnesium gluconate was dissolved in the acetonitrile and water–methanol solutions, it exists in situ in three different forms: magnesium gluconate itself, gluconic acid, and magnesium gluconate chelate with gluconic acid by a coordinate covalent bond. Method I exhibited pseudo-molecular ion peaks with more magnesium gluconate chelates with gluconic acid, while method II showed an adduct of magnesium gluconate with the solvent along with the molecular ion peak. There was no pseudo-molecular ion peaks found in method III. Thus, method III was found to be the more accurate, robust and reliable LC–MS method for the qualitative and quantitative analysis, structural characterization, and could also be suitable for the pharmacokinetic study of magnesium gluconate. The detailed fragmentation analysis might be useful for the structural characterization of unknown divalent organometallics.     

Effect of filter spacing on melody recognition: acoustic and electric hearing

This paper assesses the effect of filter spacing on melody recognition by normal-hearing (NH) and cochlear implant (CI) subjects. A new semitone filter spacing is proposed for music. The quality of melodies processed by the various filter spacings is also evaluated. Results from NH listeners showed nearly perfect melody recognition with only four channels of stimulation, and results from CI users indicated significantly higher scores with a 12-channel semitone spacing compared to the spacing used in their daily processor. The quality of melodies processed by the semitone filter spacing was preferred over melodies processed by the conventional logarithmic filter spacing.     

Kinetics of the oxidation of sulphite by tetrachloroaurate(III)

Summary The reaction between sulphite and gold(III) in hydrochloric acid medium has been studied; an initial complex is formed prior to electron transfer. The reaction rate is inversely proportional to the hydrogen ion concentration and the reaction appears to proceed through the intermediate formation of a free radical which reacts with gold(III) to give the products. Evidence for the formation of dithionate together with sulphate is presented.     

Separation of polar and steric effects in the oxidation of ortho-substituted benzaldehydes by N-bromobenzamide

The kinetics of the oxidation of twelve ortho-substituted benzaldehydes by N-bromobenzamide (NBB) to the corresponding benzoic acids have been studied. The reaction is first order with respect to NBB, the aldehyde and hydrogen ions. The addition of benzamide has no effect on the reaction rate. (PhCONH₂Br)⁺ has been postulated as the reactive oxidising species. The correlation of rates with the single substituent-parameter equations is poor. The correlation with Charton’s equation of inductive, resonance and steric parameters is satisfactory. However, excellent correlations were obtained, when Charton’s steric parameter was used along with Taft’s σ₁; andσ _R ⁺ substituent constants. The polar reaction constants have negative values. The reaction is subject to steric hindrance by the ortho-substituents.     

A novel biflavonyloxymethane from Pongamia pinnata and its radical quenching activity

The root bark of Pongamia pinnata Pierre (syn P. glabra Vent.) has afforded a new biflavonyloxymethane, pongabiflavone, along with a known furanoflavone, 3-methoxy-(7, 8, 2", 3") furanoflavone. The structure of this new compound was elucidated from extensive spectral studies, including 2D-NMR spectroscopic experiments. The antioxidant, radical quenching activity- superoxide and nitric oxide quenching activities of both pongabiflavone and previously isolated karanjabiflavone have been evaluated which can be a key to cure Psoriasis.     

Towards the synthesis of sugar amino acid containing antimicrobial noncytotoxic CAP conjugates with gold nanoparticles and a mechanistic study of cell disruption

Cationic antimicrobial peptides are potent inhibitors of growth of a broad spectrum of micro-organisms but often have large cytotoxic effects. We prepared some novel sugar amino acid containing cyclic cationic peptides and their Au nanoparticle attached counterparts and studied their antimicrobial activities and cytotoxic behaviour, including an investigation of the mechanism of the cytotoxicity.