Improvement in mechanical and optical properties of vapour chopped vacuum evaporated PANI/PMMA composite thin film

PANI/PMMA composite was synthesized by emulsion polymerization pathway and the composite thin film was obtained by vacuum evaporation. The effect of vapour chopping and varying PMMA concentration was also studied. The FTIR spectra showed that the PANI/PMMA composite thin film deposited as a short chain oligomers. Increase in transmittance and decrease in refractive index was obtained with increasing concentration of PMMA, which further increased the adhesion and decreased intrinsic stress. The vapour chopping improved its optical as well as mechanical properties and produced smoother surface morphology. Increase of PMMA made the film more amorphous and does not change its band gap.     

All Valence Electron Molecular Orbital Study of Electronic Strture and Spectra of the Three Isometric Xylenes

Abstract

The modified method of Del Bene and Jaffe' (CNDO-CI) has been applied to study the electronic structure and spectra of the three isomeric xylenes taking a three dimensional geometry for the CH₃ group. The spectral transition energies and the corresponding oscillator strengths have been computed and the results are compared with ?-electron calculations and experimental results. Quite satisfactory results have been obtained. Ionization potentials have also been computed by the INDO and extended Hückel methods.     

Use of quartz crystal nanobalance to study the binding and stabilization of albumin and doxycycline on a thin layer of hydroxyapatite

This study reports the use of quartz crystal nanobalance (QCN) to study the adsorption of two model molecules namely albumin and doxycycline by hydroxyapatite (HA). The work focuses on the deposition of a stable coating of HA on the quartz crystal, modification of the coating using doxycycline and its subsequent effects on albumin adsorption. The uniformity and thickness of the HA coating has been studied using atomic force microscopy (AFM). The functional groups to ascertain the presence of the selected moieties have been characterized by Raman spectroscopy. The results indicate that the mass of albumin deposited on the surface of the HA coated quartz crystal functionalized with doxycycline shows a substantial increase when compared to the standard HA coated quartz crystal. The adsorbed albumin has also been found to be retained for an enhanced period of time. This surface immobilization of doxycycline and subsequent albumin adsorption seem to be a promising approach to confer biomaterials with antithrombogenic and antibacterial surfaces.     

Hopping type of conduction in (Na0.5Bi0.5)ZrO3 ceramic

Polycrystalline sample with (Na_0.5Bi_0.5)ZrO₃ (NBZ) stoichiometry was prepared using a high-temperature solid-state reaction technique. X-ray diffraction (XRD) analyses indicate the formation of a single-phase perovskite-type orthorhombic structure. AC impedance plot is used as tool to analyse the electrical behaviour of the sample as a function of temperature at different frequency. The AC impedance studies revealed the presence of grain boundary effect and evidence of a negative temperature coefficient of resistance (NTCR) character. Pseudo Cole-Cole and complex electric modulus analyses indicated non-Debye-type dielectric relaxation. The AC conductivity obeys the universal power law. The pair approximation type correlated barrier hopping (CBH) model explains the universal behaviour of the s exponent. The apparent activation energy to the conduction process and minimum hopping distance are discussed.     

Vibrational Spectroscopic Investigation,First Hyper Polarizability and Homo–Lumo Analysis of Tetrahydroxy-1,4Quinone Hydrate Using Density Functional Theory and Hartree-Fock Method

The FTIR and FT-Raman spectra of tetrahydroxy-1,4quinone hydrate have been recorded in the regions 4000–400 and 3500–50 cm^–1 respectively. Using the observed Fourier-transform infrared spectroscopy (FTIR) and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound has been carried out. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by the density functional theory (DFT/B3LYP) and Hartree–Fock (HF) method with 6-311+G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamental vibrations is very small. A detailed interpretation of the infrared and Raman spectra of tetrahydroxy-1,4quinone hydrate is also reported. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule.     

Synthesis and characterization of LSMO manganite-based biocomposite

In this paper we study the structural, morphological and magnetic properties of La_0.67Sr_0.33MnO₃ (LSMO) manganite nanoparticles (NPs) and its biocomposite, obtained by mixing NPs of hydroxyapatite (HA). From the studies of X-ray diffraction and Fourier transmission of infrared spectroscopy it is evident that in the biocomposite sample both the individual phases are distinguishable from each other. The measurements of direct current (DC) magnetization and hysteresis loops reveal that the basic magnetic behaviour of LSMO–HA is similar to that of LSMO; however, the admixture of HA makes the sample magnetically softer. From the investigation of transmission electron microscopy it is observed that such a biocomposite is composed of the NPs of LSMO surrounded by HA particles, which can be found suitable for biomedical applications.     

Plane Symmetric Viscous Fluid Cosmological Models with Varying <Emphasis Type="Italic">Λ</Emphasis>-Term

Plane symmetric viscous fluid cosmological models of the universe with a variable cosmological term are investigated. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear viscosity is to be proportional to rate of expansion in the model. We have also obtained a special model in which the shear viscosity is assumed to be zero. The cosmological constant Λ is found to be a decreasing function of time and a positive which is supported by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed.