Landau theory description of observed isotropic to anisotropic phase transition in mixed clay gels

A characteristic new cooperative dehydration transition, in 1:1 Laponite-MMT cogel, was observed at T(c) ≈ 60 °C, a temperature at which the storage modulus (G(')) and depolarization ratio (D(p)) showed sharp increase, and the isotropic cogel turned into an anisotropic one. The dehydration dynamics could be described through power-law relations: G(') ～ (T(c)-T)(-γ) and D(p) ～ (T(c)-T)(-β) with γ ≈ β = 0.40 ± 0.05. The x-ray diffraction data revealed that the crystallite size decreased from 17 nm (at 20 °C) to 10 nm (at 80 °C) implying loss of free and inter-planar water. When this cogel was spontaneously cooled below T(c), it exhibited much larger storage modulii values which implied the existence of several metastable states in this system. This phase transition could be modeled through Landau theory, where the depolarization ratio was used as experimental order parameter (ψ). This parameter was found to scale with temperature, as ψ ～ (T(c)-T)(-α), with power-law exponent α = 0.40 ± 0.05; interestingly, we found α ≈ β ≈ γ.     

Microwave‐mediated synthesis and antibacterial activity of some novel 2‐(substituted biphenyl) benzimidazoles via Suzuki‐Miyaura cross coupling reaction and their N‐substituted derivatives

A series of some novel 2‐(substituted biphenyl) benzimidazoles and their N‐substituted derivatives were synthesized via microwave‐mediated Suzuki‐Miyaura coupling of 2‐(4‐iodophenyl)‐1H‐benzimidazole or 2‐(4‐iodophenyl)‐6‐amino‐1H‐benzimidazole and arylboronic acids. The method reported herein offers advantageous shorter reaction times, higher yields and is applicable to a large set of substrates. All the synthesized compounds were screened for their antibacterial activity against Staphylococcus aureus and Salmonella typhimurium bacterial species. J. Heterocyclic Chem., (2011).     

Validated High-Performance Thin-Layer Chromatographic Method for Quantitation of Fluvoxamine in the Presence of Degradation Products Formed under ICH Recommended Stress Conditions

JPC – Journal of Planar Chromatography – Modern TLC - This paper describes a sensitive, selective, precise, and stability-indicating high-performance thin-layer chromatographic method...     

Spectrum of L-fuzzy Prime Ideals of a Distributive Lattice

A topological space denoted by Fspec(D),called L-fuzzy prime spectrum of a bounded distributive lattice D is introduced.This space Fspec(D) is compact and it contains a subspace homeomorphic with the prime spectrum of D which is dense in it.The correspondence associating D to the topological space Fspec(D) is shown to define a contravarient functor from the category of bounded distributive lattices into the category of compact topological spaces.     

Blue and red dual emission nanophosphor CaMgSi2O6:Eun+; crystal structure and electronic configuration

Well dispersed Eu doped CaMgSi₂O₆ (CMS) nanoparticles of 12–19 nm average sizes were synthesized by the co-precipitation method using different ratios of water and ethanol mixture as a solvent and subsequent air annealing. While ethanol as solvent produced pure CMS in monoclinic phase, pure water produced Ca₂MgSi₂O₇ (C2MS) and CMS in the mixed phase. Apart from the composition of CMS and C2MS, concentration and ionization state of the activator depended strongly on the composition (effective dielectric constant) of the solvent. Both the blue and red emission bands could be revealed for the europium activated CMS nanoparticles using single europium precursor. Efficiency of blue and red emissions in the nanophosphors, controlled by the relative abundance of europium in Eu²⁺ and Eu³⁺ oxidation states, could be controlled by adjusting the water content in the solvent. The relative intensity of the red emission (615 nm) decreased with the increase of water content in the solvent.     

Growth of ZnO nanodisk, nanospindles and nanoflowers for gas sensor: pH dependency

Suitable morphology for fast electron transportation is a crucial requirement for the fabrication of gas sensor application. Highly oriented and well defined zinc oxide (ZnO) nano/micro-scale structures are grown on the glass substrates using aqueous chemical route. The grown nanostructures have been characterized by X-ray diffraction pattern (XRD), scanning electron microscope (SEM) and optical absorption techniques. The SEM micrographs revealed the formation of disk, rod, spindle and flower-like morphologies at different pH values ranging from 5 to 10. The grown nanostructures were employed for acetone gas-sensing measurement. It is observed that the sensors based on nanoflowers showed higher response (95%) for acetone gas at 325 °C. The high acetone gas sensitivity of ZnO nanoflowers can be attributed to the surface morphology. Moreover, nanoflower-like structure exhibits the fast response and recovery.     

Studies on convective heat transfer through helical coils

An experimental investigation on steady state convection heat transfer from vertical helical coiled tubes in water was performed for laminar flow regime. Three coils with curvature ratios as 0.0757, 0.064, 0.055 and range of Prandtl number from 3.81 to 4.8, Reynolds number from 3,166 to 9,658 were considered in this work. The heat transfer data were generated from 30 experiments conducted at constant water bath temperature (60 °C) for different cold water flow rates in helical coils. For the first time, an innovative approach of correlating Nusselt number with ‘M’ number is proposed which is not available in the literature and the developed correlations are found to be in good agreement with the work of earlier researchers. Thus, dimensionless number ‘M’ was found to be significant to characterize the hydrodynamics of fluid flow and heat transfer correlations in helical coils. Several other correlations based on experimental data are developed. To cover wide range of industrial applications, suitable generalized correlations based on extended parameters beyond the range of present experimental work are also developed. All these correlations are developed by using least-squares power law fit and multiple-regression analysis of MATLAB software. Correlations so developed were compared with published correlations and were found to be in good agreement. Comparison of heat transfer coefficients, friction factor and Nusselt number for different geometrical conditions is presented in this paper.     

Relaxation studies of spray deposited Bi2Co0.1V0.9O5.35 solid electrolyte thin films on stainless steel substrate

The room temperature-stabilized γ-phase ion conducting Bi₂Co_0.1V_0.9O_5.35 thin film was deposited by spray pyrolysis on stainless steel substrate. The intra-grain and grain interior charge transfer was confirmed in these films with impedance spectroscopic measurements done from 1 Hz to 10 MHz in the temperature range 550 K to 741 K. Impedance data further revealed non-Debye kind of relaxation dispersion in the film. The relaxation frequency ranges from 10 to 100 Hz, which predicts long range jumping of the oxygen ions with chemical diffusivity. The Arrhenius plots for relaxation frequency and grain boundary conductivity were found to have same activation energy revealing grain boundary dominant conduction. The effect of polycrystallinity on relaxation dispersion is investigated for the first time on Bi₂Co_0.1V_0.9O_5.35 thin films using impedance formalism.     

Ionic liquid promoted expeditious synthesis of flavones

A smooth conversion of substituted 1-(2-hydroxy phenyl)-3-phenyl-1,3-propane diones to flavones has been done using n-butyl-3-methyl-imidazolium tetrafluoroborate ionic liquid.