Superior refractive index tailoring properties in composite ZrO2/SiO2 thin film systems achieved through reactive electron beam codeposition process

Composite optical thin-film materials have received a significant amount of interest in order to relieve the material constraints on refractive indices as well as reducing the number of layers required in optical coating design. Amongst others binary zirconia-silica composite thin films have attracted considerable attentions due to their several favorable opto-mechanical properties. In the present studies such a composite system under certain compositional mixings displayed both refractive index and band gap supremacy over pure zirconia films violating the most popular Moss rule. This unexpected evolution has several practical applications one of which can be directly employed in extending the range of tunability of the refractive index. Besides, the probing of such a novel evolution through the analysis of ellipsometric refractive index modeling and morphological correlation functions has revealed several novel as well as superior microstructural properties in the composite thin film systems. All these characterization and analysis techniques distinctly indicate a strong interrelation between the microstructural ordering and superior optical properties of the present zirconia-silica codeposited composites.     

Critical points in the Bragg glass phase of a weakly pinned crystal of Ca3Rh4Sn13

New experimental data are presented on the scan rate dependence of the magnetization hysteresis width ΔM(H) (∞ critical current densityJ _c(H)) in isothermalMH scans in a weakly pinned single crystal of Ca₃Rh₄Sn₁₃, which displays second magnetization peak (SMP) anomaly as distinct from the peak effect (PE). We observe an interesting modulation in the field dependence of a parameter which purports to measure the dynamical annealing of the disordered bundles of vortices injected through the sample edges towards the destined equilibrium vortex state at a givenH. These data, in conjunction with the earlier observations made while studying the thermomagnetic history dependence inJ _c(H) in the tracing of the minor hysteresis loops, imply that the partially disordered state heals towards the more ordered state between the peak field of the SMP anomaly and the onset field of the PE. The vortex phase diagram in the given crystal of Ca₃Rh₄Sn₁₃ has been updated in the context of the notion of the phase coexistence of the ordered and disordered regions between the onset field of the SMP anomaly and the spinodal line located just prior to the irreversibility line. A multi-critical point and a critical point in the (H,T) region of the Bragg glass phase have been marked in this phase diagram and the observed behavior is discussed in the light of recent data on multi-critical point in the vortex phase diagram in a single crystal of Nb.     

Enzymatic polymerizations using surfactant microstructures and the preparation of polymer-ferrite composites

Applied Biochemistry and Biotechnology - Horseradish peroxidase has been used as a biocatalyst to synthesize a polymeric material from alkyl-substituted phenols. The synthesis is carried out in a...     

Thermal analysis and thermal expansion studies on high density YBa2−xLaxCu3O7−δ, 0x0.2

The compositions in the YBa_2−xLa_xCu₃O_7−δ (0x0.2) system were prepared by the solid state reaction, employing a novel high-temperature oxygen sintering route. The modified sintering route yields dense slab like microstructures with large grains. The decomposition (incongruent melting) temperature of the YBa₂Cu₃O_7−δ (Y-123) phase was found to shift to higher temperatures with increasing oxygen partial pressure and lanthanum content. Structure remained orthorhombic up to x=0.2 with a decrease in the orthorhombic strain ((b−a)/b). Iodometric titration indicated a systematic increase in the oxygen content with increasing lanthanum content. Thermo-gravimetric studies in various oxygen partial pressures revealed that the oxygen diffusion in to the YBa₂Cu₃O_7−δ (δ>0.5) lattice is an exothermic event and takes place at temperatures not less than 573 K. High-temperature thermal-expansion measurements in air indicated that the nonlinearity in thermal expansion behaviour was reduced by the substitution of lanthanum.     

A novel one-pot conversion of amines to homologated esters in poly(ethylene glycol)

The first deaminative homologation of amines (-CH₂NH₂) to esters (-CH₂CH₂COOEt) in one-pot is reported. The reaction proceeds through, formation of an aldehyde from an amine in the presence of Pd/C as catalyst followed by Wittig reaction and catalytic hydrogenation using poly(ethylene glycol) as the solvent in one-pot.     

Formulation–composition map of a lecithin-based emulsion

Formulation–composition map is an interesting tool to predict the nature of an emulsion, stability, viscosity and nevertheless to decide the mixing protocol of its ingredients. Information based on optimum formulation (environmental conditions at which the affinity of an emulsifier for oil and for aqueous phase is same), which is depicted through hydrophilic–lipophilic deviation (HLD) concept, is necessary to make a formulation–composition map of an emulsion. In order to apply this concept in food emulsions, it is necessary to determine characteristic constants of each component of the system, i.e. the aqueous phase, the oil phase and the emulsifier at equilibrium. In this work formulation–composition map of a sunflower oil–water–lecithin system, based on the knowledge of phase behavior of lecithin at equilibrium and emulsification, was made. The shape of inversion line on formulation–composition map was not the classical stair type rather an almost vertical inversion line at water-fraction (f_w) near 0.20 was observed. It was supposed to be linked to the viscosity of oil phase which was 50 times the viscosity of aqueous phase. Additionally, emulsions were of oil-in-water (O/W) type for f_w higher than 0.20, but their viscosity and the drop size behavior with respect to salt concentration as formulation variable did not show the existence of transitional inversion line on formulation–composition map. Such map in advance can certainly facilitate the guidelines for dynamic emulsification.     

Analysis of gamma-ray continuum spectra to determine the chemical composition

Neutron induced -ray spectra from various geological samples were analyzed to evaluate the usefulness of continuum spectra in deriving the chemical composition information. A fast Fourier transform technique has been used to estimate the signal content of selected energy bands of the continuum spectra. Monte Carlo calculations have been performed using the major -ray energy sources (due to Fe, Ca, Si and Al) to generate the corresponding detected -ray spectra. The experimental spectra are compared to the simulated spectra to check the consistency of the signal distribution between the peak and the continuum. The continuum above and below a chosen -ray line is calculated to find what fraction of the lower energy continuum is due to that line. The accuracy of the relative elemental concentrations determined by this method is confirmed through comparison with laboratory elemental analysis of the samples. It is found that using the continuum could greatly increase the sensitivity and precision of the measurement of elemental concentrations determined from -ray spectra of thick target sources, for spectra having peaks of poor statistical significance. However, for thin target sources or spectra with very good statistics in their peaks, this method may not be very advantageous.     

Extraction of ternary complexes of thorium(IV) with 3-phenyl-4-benzoyl-5-isoxazolone and neutral donors from nitric acid medium

The extraction behaviour of thorium(IV) from aqueous nitric acid employing 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) in the presence of tri-n-octyl phosphine oxide (TOPO) as well as tri-n-butyl phosphate (TBP) in xylene medium was investigated. The extraction constant (log k(ex)) for the binary organic phase species Th(PBI)(4) was determined to be 8.26 which is by far the largest amongst the corresponding values known for other beta-diketones. The overall extraction constant (log K) for the ternary species Th(PBI)(4) TBP and Th(PBI)(4).2TOPO were estimated to be 14.96 and 20.96 respectively. An inverse correlation of the adduct formation constant (log K(s)) with the pK(a) of the beta-diketones, 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and HPBI, was observed. The steric as well as the electronic effects of adduct formation have been discussed. Analytical application of HPBI for the separation of (234)Th radiotracer from natural uranium (99.3% (238)U) has been suggested.