Determination of the diffusivity-mobility ratio in degenerate semiconductors from linewidth measurements in laser diodes

In the present communication, it is shown that the diffusivity-mobility ratio of the electrons in degenerate semiconductors can be determined from a simple measurement of the linewidth of spontaneous emission preceding laser action in semiconductor junction lasers.The authors are indebted to Professor J. N.Bhar for his keen interest in the work.     

Kinetics and mechanism of the reduction of gold(III) by glycine in acetate buffer

The kinetics of reduction of tetrachloroaurate(III) by glycine has been spectrophotometrically studied in NaOAc–AcOH buffer in the pH range 3.73–4.77. The reaction is first order with respect to both Au(III) and glycine. Both H⁺ and Cl⁻ ions have inhibiting effects on the reaction rate. The rate decreases with a decrease in the dielectric constant of the medium. AuCl₄⁻ and AuCl₃(OH)⁻ are presumed to be the predominant oxidizing species under the conditions of the experiment. The reaction of gold(III) and zwitterionic species of glycine proceeds with the intermediate formation of gold(I) and iminic cation and the latter subsequently hydrolyses in a fast step to produce formaldehyde and ammonium ion. Formaldehyde was identified as the only organic product by ¹H NMR spectroscopy.     

On the modularity of supersingular elliptic curves over certain totally real number fields

We study generalisations to totally real fields of the methods originating with Wiles and Taylor and Wiles [A. Wiles, Modular elliptic curves and Fermat's Last Theorem, Ann. of Math. 141 (1995) 443-551; R. Taylor, A. Wiles, Ring-theoretic properties of certain Hecke algebras, Ann. of Math. 141 (1995) 553-572]. In view of the results of Skinner and Wiles [C. Skinner, A. Wiles, Nearly ordinary deformations of irreducible residual representations, Ann. Fac. Sci. Toulouse Math. (6) 10 (2001) 185-215] on elliptic curves with ordinary reduction, we focus here on the case of supersingular reduction. Combining these, we then obtain some partial results on the modularity problem for semistable elliptic curves, and end by giving some applications of our results, for example proving the modularity of all semistable elliptic curves over .     

Novel and rapid palladium-assisted 6pi electrocyclic reaction affording 9,10-dihydrophenanthrene and its analogues

A novel methodology for the synthesis of 9,10-dihydrophenanthrene and its analogues has been developed via a palladium-assisted 6pi electrocyclic reaction followed by formaldehyde elimination.     

Observation of a Long-lived Electronic Coherence Modulated by Vibrational Dynamics in Molecular Nd3+-Complexes at Room Temperature

Temporally delayed, phase-locked coherent pairs of near IR femtosecond laser pulses were employed to study electronic coherences in molecular Nd³⁺-complexes at room temperature. Dissolved and solid complexes were studied under a confocal microscope set-up with fluorescence detection. The observed electronic coherence on a few hundred femtoseconds time scale is modulated by additional coherent wave packet dynamics, which we attribute mainly to be vibrational in nature. In future, the complexes may serve as prototypes for possible applications in quantum information technology.     

Micro-scale membrane extraction of glyphosate and aminomethylphosphonic acid in water followed by high-performance liquid chromatography and post-column derivatization with fluorescence detector

A carrier-mediated supported liquid membrane micro-extraction using single hollow fiber membrane suitable for the determination of the herbicide glyphosate and its main metabolite aminomethylphosphonic acid in water is reported. A solution of 0.20 M Aliquat-336, a cationic carrier, in di-n-hexyl ether was selected as the supported liquid. A 20 microL of 1.0 M potassium chloride as the acceptor phase was filled in the membrane lumen. The membrane was immersed in a 20 mL of pH 9.0 sample solution. After 60-min extraction, the acceptor phase was analyzed by high-performance liquid chromatography with post-column derivatization. The enrichment factors were found to be 853 and 136 for glyphosate and aminomethylphosphonic acid, respectively. The method detection limits are 0.22 microg/L for glyphosate and 3.40 microg/L for aminomethylphosphonic acid. The procedure was validated and showed good accuracy and precision over a large linear dynamic range. The validated method was tested for the analysis of both analytes in spiked groundwater with good success.     

Synthesis of azirines containing aldehyde functionality and their utilization as synthetic tools for five membered oxazoles and isoxazoles

A simple and useful procedure for the synthesis of azirines containing aldehyde functionality from open chain bromo/chloro‐aldehydes at room temperature is reported. The scope of the ring expansion reaction of a number of 3‐substituted‐2‐formyl‐azirines has been examined using different oraganometallic catalysts and a variety of Lewis acids.     

Green synthesis of silver chloride nanoparticles using Prunus persica L. outer peel extract and investigation of antibacterial,anticandidal, antioxidant potential

The present study was conducted to synthesize silver chloride nanoparticles using the aqueous extract of outer peel of peach fruit (Prunus persica L.) and to evaluate its antibacterial activity, synergistic antibacterial and anticandidal potential against five foodborne pathogenic bacteria and five pathogenic Candida species respectively along with its antioxidant potential. The synthesized silver chloride nanoparticles (PE-AgClNPs) were visually confirmed with surface plasmon resonance peak at 440?nm upon UV–Vis spectroscopy analysis. Furthermore, the morphology, elemental composition and crystallinity nature were also characterized. PE-AgClNPs displayed strong antibacterial potentials (9.01–10.83?mm inhibition zone) against foodborne pathogenic bacteria and increased synergistic effect with kanamycin and rifampicin. PE-AgClNPs also displayed strong anticandidal synergistic activity with standard amphotericin b (10.51–14.01?mm inhibition zones), along with strong free radical scavenging and reducing power. Based on strong antibacterial and antioxidant capacities, PE-AgClNPs are anticipated to have potential applications in the biomedical and food sector industries.     

Solid-phase extraction for multiresidue determination of sulfonamides, tetracyclines, and pyrimethamine in Bovine's milk

This paper describes a systematic approach to the development of a solid-phase extraction method for simultaneous extraction of 10 antibiotic residues in bovine milk, belonging to groups of sulfonamides, tetracyclines, and pyrimethamine. The sample preparation steps include acidic deproteinization of milk proteins followed by sample enrichment and cleanup using a polymer-based Oasis HLB solid-phase extraction cartridge. The analyses were carried out by using a method based on liquid chromatography-electrospray ionisation-mass spectrometry with positive ion mode. The parameters affecting the extraction efficiency such as sample loading pH, SPE wash solvent composition, and eluting solution pH were carefully investigated and optimized. The developed solid-phase extraction procedure coupled to multiresidue liquid chromatography-electrospray ionization-mass spectrometry method was applied for the analysis of 10 antibiotic residues in milk samples, and it proved to be simple, sensitive, and selective providing a recovery ranging from 70 to 106%.     

Novel synthetic approach toward (+/-)-beta-cuparenone via palladium-catalyzed tandem Heck cyclization of 1-bromo-5-methyl-1-aryl-hexa-1,5-dien-3-ol derivatives

A novel and convenient synthetic route toward (+/-)-beta-cuparenone and many other sesquiterpene natural product precursors has been developed via palladium-catalyzed tandem Heck cyclization of 1-bromo-5-methyl-1-aryl-hexa-1,5-dien-3-ols. [reaction: see text].