Electrical and dielectric properties of rare earth oxides coated LiCoO2 particles

Pure and rare earth oxides (Sm₂O₃, La₂O₃) coated LiCoO₂ nanoparticles were prepared by acrylamide-assisted polymeric citrate and resin-coating processes, respectively. The prepared powders were characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and impedance spectroscopy. Powder X-ray diffraction patterns confirmed the formation of phase pure LiCoO₂ with nanocrystallite size. X-ray fluorescence spectra confirm the presence of Sm₂O₃ and La₂O₃ in coated samples. The conductivity, dielectric and electric modulus studies of the samples were carried out at room temperature. Dielectric spectra of the samples show the decrease in dielectric constant with an increase in frequency of the applied field. The modulus studies indicate the non-Debye behavior of the samples, which is due to long-time slow polarization and relaxation of hopping charges.     

Anisotropic Bianchi Type-I and Type-II Bulk Viscous String Cosmological Models Coupled with Zero Mass Scalar Field

The LRS Bianchi type-I and type-II string cosmological models are studied when the source for the energy momentum tensor is a bulk viscous stiff fluid containing one dimensional strings together with zero-mass scalar field. We have obtained the solutions of the field equations assuming a functional relationship between metric coefficients when the metric is Bianchi type-I and constant deceleration parameter in case of Bianchi type-II metric. The physical and kinematical properties of the models are discussed in each case. The effects of Viscosity on the physical and kinematical properties are also studied.     

Ultrasonic Studies on Molecular Interactions in Binary Mixtures of N-Methyl Aniline with Methyl Isobutylketone, +3-Pentanone, and +Cycloalkanones at 303.15 K

Densities, ρ, viscosities, η, and ultrasonic sound velocities u of pure methyl isobutylketone, diethylketone, cyclopentanone, cyclohexanone, 2-methyl cyclohexanone and those of their binary mixtures with N-methyl aniline were measured at 303.15 K over the entire composition range. These experimental data have been used to calculate the excess volume (V ^E), deviation in ultrasonic sound velocity (?u), isentropic compressibility (κ _s ), intermolecular free length (L _f), excess intermolecular free length ( $ L_{\text{f}}^{\text{E}} $ L f E ), acoustic impedance (Z), excess isentropic compressibility ( $ \kappa_S^{\text{E}} $ κ S E ), deviation in viscosity (?η) and excess Gibbs energy of activation of viscous flow (G ^*E). The viscosity data have been correlated using three equations proposed by Grunberg and Nissan, Katti and Chaudhri, and Hind et al. The excess/deviations have been fitted by Redlich–Kister equation and the results are discussed in terms of molecular interactions present in these mixtures.     

Preconcentration of Cu(II) and Ni(II) ions in edible fish organs by solid phase extraction using triton X-100 resin

An enrichment separation procedure for the atomic absorption spectrophotometric determinations of Cu(II) and Ni(II) ions in common edible fishes was established. The 2-[(2-hydroxynaphthalen-1-yl)diazenyl]-5-methylbenzene-1,3-diol (HNDMD) complexes of the analyte ions at pH 6.0 were adsorbed on the p-octylpolyethylene glycolphenylether (Triton X-100) column and then desorbed with 10 mL of acetone. Under optimized conditions, the recovery values were above 95%. The developed preconcentration methods were successfully applied to the determination of Cu(II) and Ni(II) ion concentrations in common edible fishes from the local market. The precision and accuracy of the method are very good.     

First Stereoselective and Concise Synthesis of Rhoiptelol C

The first concise stereoselective total synthesis of diarylheptanoid rhoiptelol C ( 1 ) was achieved from readily available vanillin. The synthesis involves Keck's asymmetric allylation, olefin cross metathesis, and Sharpless asymmetric dihydroxylation reaction as key steps.     

Spectral Investigations on Ho3+ Doped Mixed Alkali Chloroborate Glasses

The optical absorption and emission spectra of two different Ho³⁺ doped mixed alkali chloroborate glasses have been studied in the ultraviolet-visible near-infrared regions. Various spectroscopic parameters like Racah (E¹, E², and E³), spin orbit (ξ_4f), and configuration interaction (α) parameters have been calculated. From the measured spectral intensities of the various absorption bands of Ho³⁺ ion, the Judd–Ofelt intensity parameters (Ω₂, Ω₄, and Ω₆) have been evaluated and covalency was studied as a function of x in the glass matrices. Using these parameters, radiative transition probabilities, radiative lifetimes, branching ratios, and integrated absorption cross-sections have been calculated and reported for certain excited states of Ho³⁺ ion. From the emission spectra, stimulated emission cross-sections are determined for the emission transitions, ⁵F₄, ⁵S₂?→?⁵I₈, and ⁵F₅?→?⁵I₈ in these two mixed alkali chloroborate glasses. An attempt has been made to throw some light on the environment of Ho³⁺ ions in these glass systems by studying the variation in various spectroscopic parameters.     

Optical phase conjugation in nonresonant and saturable absorptive/resonant systems

Recent results obtained at Alabama A&M University on optical phase conjugation in electrically unpoled BaTiO₃, BANANA and SBN crystals are presented. The decay curves of the transient gratings and phase conjugation in these crystals indicate the involvement of more than one exponential process, possible reasons for which are indicated. Self induced gratings have been studied in electrically unpoled SBN crystal using a He−Ne Laser. The oscillations in a ring passive phase conjugator (RPPC) and in a unidirectional ring resonator using an electrically poled BaTiO₃ crystal have, been found to be bistable. It is also found that bistable oscillations are possible in a geometry in which the crystal is used simultaneously in a RPPC and as a linear passive phase conjugate (LPCC) mirror. The auxiliary oscillations pumped by the RPPC are bistable with the oscillations in LPCC. A brief review of the recent literature on phase conjugation in saturable absorptive/resonant systems along with the experiments planned to be undertaken by the authors on such systems are presented.