Silica chloride catalyzed one-pot synthesis of fully substituted pyrazoles

Silica chloride catalysted one pot cyclocondensation of aldehydes,ethyl acetoacetate and phenyl hydrazine leading to substituted pyrazoles has been reported.     

A modified volumetric method for the estimation of streptomycin sulphate in pharmaceuticals

Summary A volumetric method for the estimation of streptomycin sulphate in pharmaceuticals is based on the quantitative discharge of the violet colour of the maltol-iron complex, produced when streptomycin is hydrolysed in alkaline medium and treated with ferric chloride, by potassium permanganate. It is simple, accurate and other antibiotics such as dihydrostreptomycin, sodium salt of benzyl penicillin, chloramphenicol do not interfere. Procain penicillin has to be separated by extractio with chloroform.

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Zusammenfassung Die beschriebene volumetrische Streptomycinbestimmung in Arzneimitteln beruht auf dem Abbau des Streptomycins in alkalischer Lösung zu Maltol, Bildung des Maltol-Eisen(III)-Komplexes und Titration mit Permanganat bis zur Entfärbung. Das Verfahren ist einfach auszuführen und gibt Werte von befriedigender Genauigkeit. Dihydrostreptomycin, Chloramphenicol sowie das Natriumsalz des Benzylpenicillins stören nicht. Procain-Penicillin muß vorher durch Extraktion mit Chloroform abgetrennt werden.

     

Some efficient methods to correct confocal images for easy interpretation

In this paper we have explained some efficient methods to correct artefacts in confocal laser beam scanning microscope (CLSM) images. The main aim is to enhance object features such that they become clearly visible for interactive evaluation and to reduce the overall noise so that the automatic segmentation and feature measurement can be done easily. A simple automatic-thresholding technique, and a straightforward method to restore the light intensity along the depth of the image stack are proposed. Another problem associated with the CLSM is the non-isotropic resolution. We have presented an interpolation technique based on XOR contouring and morphing to virtually insert the image slices in the image stack for improving the axial resolution. This interpolation technique has the merits of both contour- and intensity-based interpolations. Results of application of these methods on CLSM data are shown.     

Large near resonance third order nonlinearity in GaN

We have studied third order nonlinearities, including two-photon absorption coefficient and nonlinear refractive index n ₂, of GaN in below bandgap ultraviolet (UV) wavelength regime by using UV femtosecond pulses. Two-photon absorption was investigated by demonstrating femtosecond UV pulsewidth autocorrelation in a GaN thin film while femtosecond Z-scan measurements revealed information for both n ₂ and . The distribution of n ₂ versus wavelength was found to be consistent with a model described by the quadratic Stark effect, which is the dominant factor contributed to the nonlinear refractive index near the bandgap. Large on the order of 10 cm/GW and large negative n ₂ with a magnitude on the order of several 10^–12 cm²/W were obtained. The at near mid-gap infrared (IR) wavelength was also found to be on the order of several cm/GW by using two-photon-type autocorrelations in a GaN thin film. Taking advantage of the large two-photon absorption at mid-gap wavelengths, we have demonstrated excellent image quality on two-photon confocal microscopy, including two-photon-scanning-photoluminescence imaging and two-photon optical-beam-induced current microscopy, on a GaN Hall measurement sample and an InGaN green light emitting diode.     

Dicationic Ionic Liquid Mediated Synthesis of 5-Arylidine-2,4-thiazolidinediones

An efficient synthesis of 5‐arylidine‐2,4‐thiazolidinediones has been developed using dicationic ionic liquid as green medium and catalyst. This method performed well for the condensation of both aryl as well as heteryl aldehydes with 2,4‐thiazolidinedione and gave 5‐arylidine‐2,4‐thiazolidinediones with excellent yields.     

Fluorescence Quenching Studies of the Interaction Between Riboflavin and Norfloxacin and Analytical Application in the Determination of Vitamin B<Subscript>2</Subscript>

The binding of riboflavin (RBF) to norfloxacin (NF) was investigated by spectroscopic techniques. The results revealed that RBF caused the fluorescence quenching of NF by complex formation. The binding parameters and corresponding thermodynamic parameters ΔH, ΔG and ΔS at different temperatures were calculated. The negative enthalpy (ΔH) and positive entropy (ΔS) values indicated that both hydrogen bond and hydrophobic forces played major roles in the binding of RBF to NF. The distance r between donor (NF) and acceptor (RBF) was obtained according to the Forster’s theory of non-radiative energy transfer. The method of quenching was successfully applied for the determination of riboflavin from pharmaceutical samples.     

Chiral ligand derived from (1S,2R)-norephedrine as a catalyst for enantioselective prochiral ketone reduction

Chiral oxazaborolidines derived from (1S,2R)-(+)-norephedrine and substituted salicylaldehydes were employed in the asymmetric reduction of prochiral ketones using borane dimethyl sulfide as a reducing agent. The secondary alcohols were formed in excellent yields (45–99.8%) with enantioselectivities up to 99.8%. The effect of the substitution in the aromatic ring of the ligand was discussed with the enantioselectivity of the product.     

Thermal,physicochemical and spectroscopic studies on some novel organic complexes obtained by green synthesis

Journal of Thermal Analysis and Calorimetry - The solid–liquid equilibrium phase diagram and thermochemical studies on two binary organic systems involving N-methylurea (MU) with...     

Ferroelectric phase transitions in ultrathin films of BaTiO3

We present molecular dynamics simulations of a realistic model of an ultrathin film of BaTiO3 sandwiched between short-circuited electrodes to determine and understand effects of film thickness, epitaxial strain, and the nature of electrodes on its ferroelectric phase transitions as a function of temperature. We determine a full epitaxial strain-temperature phase diagram in the presence of perfect electrodes. Even with the vanishing depolarization field, we find that ferroelectric phase transitions to states with in-plane and out-of-plane components of polarization exhibit dependence on thickness; it arises from the interactions of local dipoles with their electrostatic images in the presence of electrodes. Secondly, in the presence of relatively bad metal electrodes which only partly compensate the surface charges and depolarization field, a qualitatively different phase with stripelike domains is stabilized at low temperature.