Structural, dielectric and electrical properties of Li2Pb2La2W2Ti4Nb4O30 ceramic

Li₂Pb₂La₂W₂Ti₄Nb₄O₃₀ complex ferroelectric oxide was prepared by using a high-temperature solid-state reaction method (calcination temperature, ~1100 °C and sintering temperature, ~1150 °C). Room temperature preliminary structural analysis shows formation of a single-phase compound. The nature of microstructure (i.e. grain distribution, presence of voids, grain size, etc) recorded using scanning electron microscope (SEM) clearly suggests the formation of high quality and density of pellet samples. Studies of temperature dependence of dielectric constant, tangent loss and polarization show the existence of ferroelectric phase transition in the material at high temperature (307 °C). Detailed studies of temperature dependence of electrical parameters (i.e. impedance (400?475 °C), modulus, conductivity, etc) of the material clearly suggest a strong correlation between its microstructure (i.e. bulk, grain boundary, etc) and electrical properties. The nature of temperature variation of d.c. conductivity showed an Arrhenius behaviour of the material. A signature of ionic conductivity in the material was observed in its a.c. conductivity spectrum. The nature of frequency dependence of a.c. conductivity of the material can be explained by Jonscher’s universal power law. Electrical transport properties of the material show existence of non-exponential type of conductivity relaxation.     

Phase behaviour and separation kinetics of polymer blends

The liquid–liquid phase separation kinetics and phase behaviour of hydrogenated polyethylene and deuterated polypropylene blends have been systematically studied by optical microscope. Phase diagram was constructed from the phase transition temperature. The hydrogenated polyethylene/deuterated polypropylene blend exhibits upper critical solution temperature in the melt. The time evolution of the characteristics morphology for liquid–liquid phase separation is determined for the hydrogenated polyethylene/deuterated polypropylene blend at various compositions and following a quench from initial homogenous melts at higher temperature to various lower temperatures. Liquid–liquid phase separation kinetics follows nucleation and growth mechanism. The experimental results from optical microscope measurement at various conditions are all consistent with the nucleation and growth mechanism.     

Spectral behaviour of salt-affected soils

For mapping and monitoring the spatial distribution of salt-alTected soils using remote sensing data, a thorough understanding of their spectral behaviour is of paramount importance. The spectral behaviour of a few typical salt-affected soils of the Indo-Gangetic alluvial plain was studied by taking ground-based spectral measurements with the Exotech radiometer (model 100 BX) and measurements made by the thematic mapper (TM) onboard Landsat-5. Salt-alTected soils, in general, showed relatively higher spectral response in the visible and near-infrared regions of the spectrum as compared to normal cultivated soils. Further, strongly saline-sodic soils were found to have higher spectral response as compared to moderately saline-sodic soils. The vegetation cover modifies the overall spectral response pattern of salt-affected soils especially in the green and red spectral bands. In addition, variation in the Sun elevation angle and moisture content were also found to modify the observed spectral response of salt-alTected soils. Methodology and results are discussed in detail.     

Zinc electrowinning from acidic sulfate solutions: Part I: Effects of sodium lauryl sulfate

The effects of sodium lauryl sulphate(SLS) in the presence and absence of antimony(iii) on the current efficiency, power consumption and polarization behaviour of zinc were determined. The surface morphologies and deposit crystallographic orientations were also evaluated. The results were compared with glue as the addition agent. The addition of sodium lauryl sulfate to the zinc sulfate solution increased current efficiency, reduced power consumption and improved the surface morphology. Maximum current efficiency and minimum power consumption were achieved on addition of 0.02mgdm–3 Sb with 1mgdm–3 sodium lauryl sulfate.     

An X-ray diffraction and Mossbauer study of nano-crystalline Fe2O3–Cr2O3 solid solutions

A series of gels with nominal composition Fe_2−xCr_xO₃ (x=0–2) was prepared at room temperature by an inorganic sol–gel route and studied by X-ray diffraction and Mossbauer spectroscopy. The gels dried at 105°C were found to be X-ray amorphous, but Mossbauer studies revealed the gels to be nano-crystalline solid-solution particles of the composition above, with super-paramagnetic properties. Further heating to 600°C gave crystalline X-ray patterns which allowed lattice parameter and crystallite size calculations to be made. It was found that lattice parameters and crystallite sizes decreased with increasing chromia content, and that at the higher chromia/iron ratios, a partially collapsed Mossbauer pattern results, indicating reductions in crystallite size and hyperfine field with increasing chromia content. This revised version was published online in November 2006 with corrections to the Cover Date.     

Dilatometric Sintering of Ti-2Al and Ti-5Al Elemental Powders

The effect of Al addition （2 and 5 at. pct） on sintering kinetics of Ti power were investigated. Al reduces the sintering rates, sinter density, increases activation energy of sintering and accelerates the grain growth. Sintering was controlled by mixed mode, i.e. transient liquid phase sintering, formation of intermetallics, and Ti grain boundary diffusion in TiAl2 and other intermetallics.     

Polycarboxylate derivative of <Emphasis Type="Italic">α</Emphasis>-amino acid as growth modifier of sulphide minerals

Construction of modified inorganic mineral with controlled mineralization analogues of those produced by nature is now of current interest for understanding the mechanism of the in vivo biomineralization processes, as well as looking for fresh industrial and technological applications. Low-molecular-weight chiral polycarboxylate ligands derived from naturally occurring L-α-amino acids have been used as model systems to study the effect of small organic matrix on crystal growth modification. The sulphide minerals are characterized by PXRD, FT–IR and SEM. Furthermore, the optical properties of these minerals have been characterized by UV-Vis and photoluminescence (PL) spectra.     

New approach for solving intuitionistic fuzzy multi-objective transportation problem

Multi-objective transportation problem (MOTP) under intuitionistic fuzzy (IF) environment is analysed in this paper. Due to the fluctuation of market scenario, we assume that the transportation cost, the supply and the demand parameters are not always precise. Hence, the parameters are imprecise, i.e., they are IF numbers. Considering the specific cut interval, the IF transportation cost matrix is converted to interval cost matrix in our proposed problem. Again, using the same concept, the IF supply and the IF demand of the MOTP are reduced to the interval form. Then the proposed MOTP is changed into the deterministic MOTP, which includes interval form of the objective functions. Two approaches, namely intuitionistic fuzzy programming and goal programming, are used to derive the optimal solutions of our proposed problem, and then the optimal solutions are compared. A numerical example is included to illustrate the feasibility and the applicability of the proposed problem. Finally, we present the conclusions with the future scopes of our study.     

Impact of physico‐chemical parameters on the microbial population and its nature in a major retting zone of Kerala

As part of an environmental abatement programme, through the application of bioremediation in the retting zones of Kerala, a microbiological survey was conducted during March 1999 in the Kadinamkulam kayal, a major retting zone in Kerala. Some selected physico‐chemical parameters were also analysed to assess the water quality in the context of retting activity. Comparatively low dissolved oxygen content coupled with high hydrogen sulphide observed at Stations 1 and 2 can be attributed to retting. Salinity distribution is of the mixohaline nature. Pseudomonas sp., E. coli and other coliform groups were found to be present in the area. Of these the most dominant was Pseudomonas sp. and hence its nature and plasmid profile were also studied. The study indicates an environmental degradation in the area, and the possibility of hotspots of pollution in the backwater biotopes in the State.     

DOUBLE-HEADED TRYPSIN/CHYMOTRYPSIN INHIBITORS FROM HORSE GRAM (DOLICHOS BIFLORUS): PURIFICATION, MOLECULAR AND KINETIC PROPERTIES

Four proteinase inhibitors were purified to homogeneity from horse gram (Dolichos biflorus). These inhibitors are double-headed and inhibit trypsin and chymotrypsin simultaneously and independently. Dissociation constants range between 0.87 and 4.6 × 10^?7 M. Each of the four isoinhibitors possesses a crucial lysine residue at the trypsin reactive site. These inhibitors have molecular masses of 8.5 kDa and isoelectric points of 4.6 to 5.6. They exist mainly as dimers under physiological conditions. Amino acid analysis revealed high levels of half-cystine, serine, aspartate and proline but low levels of methionine and aromatic amino acids. Amino-terminal sequence analysis revealed that each of the four isoinhibitors have a conserved core sequence but are divergent at the N-terminal end. These inhibitors belong to the Bowman-Birk (BBI) family of proteinase inhibitors as reflected by their inhibitory properties, amino acid composition and homology to other BBIs.