Synthesis,characterization and gas sensitivity of MoO<Subscript>3</Subscript> nanoparticles

Nanoparticles of molybdenum oxide were synthesized using the citrate sol-gel method and characterized using scanning electron microscopy and X-ray diffraction techniques. The sensitivity of the material to the presence of various gases was analysed and the particles showed higher sensitivity towards NO₂ gas.     

Rheological properties of boehmite sols during ageing at room temperature (30 ±1°C) under closed condition

Boehmite sols were obtained by peptizing boehmite precipitates with glacial acetic acid. The sols were aged at room temperature (30 ±1°C) under closed condition. Rheological properties of the sols were studied at different ageing times. The sol characteristics were interpreted by measuring their viscosity, areas of hysteresis of the flow curves and yield stress (τ_y). Viscosity and the area of hysteresis of the flow curves increased with increasing ageing time of the sols. A sharp change of yield stress was observed during the ageing period from 15 to 36 days. The change in viscous to elastic nature and the appearance of gel point of the sol was observed by studying their oscillatory flow behaviour, i.e. by measuring loss modulus(G″), elastic modulus (G′), and loss tangent (tan δ) of the sols. Gel point of boehmite sol was found at 36 days of ageing under closed condition at room temperature (30 ±1°C).     

Effect of Ca doping on the structural and superconducting properties of EuBaSrCu3O7−δ

The effect of Ca doping in EuBaSrCu₃O_7?δ has been investigated by X-ray diffraction, ac susceptibility, and electrical resistivity measurements. X-Ray diffraction analyses of the samples showed that up to 30 at.% Ca can be substituted for Sr in EuBaSrCu₃O_7?δ, which has orthorhombic symmetry. The orthorhombicity decreases with increase inx, in EuBaSr_1?xCa_x Cu₃O_7?δ, the material becoming tetragonal atx=0.2. Ac susceptibility and dc electrical resistivity measurements as function of temperature from 10 to 300 K showed that the superconducting transition temperatureT _c decreases monotonically from 84 to 75K as the Ca concentrationx increases from 0.0 to 0.3 The decrease inT _c can be attributed to the structural change taking place in EuBaSrCu₃O₇ as a consequence of replacement of Sr by Ca.     

Molecular motions within the pore of voltage-dependent sodium channels

The pores of ion channel proteins are often modeled as static structures. In this view, selectivity reflects rigidly constrained backbone orientations. Such a picture is at variance with the generalization that biological proteins are flexible, capable of major internal motions on biologically relevant time scales. We tested for motions in the sodium channel pore by systematically introducing pairs of cysteine residues throughout the pore-lining segments. Two distinct pairs of residues spontaneously formed disulfide bonds bridging domains I and II. Nine other permutations, involving all four domains, were capable of disulfide bonding in the presence of a redox catalyst. The results are inconsistent with a single fixed backbone structure for the pore; instead, the segments that line the permeation pathway appear capable of sizable motions.     

Curing kinetics of epoxy-anhydride systems using quaternary ammonium guar and hydroxyethyl guar as catalysts

The kinetic parameters for the curing reactions of initially uncured and partly cured samples of the diglycidyl ether of bisphenol-A (DGEBA) with phthalic anhydride and quaternary ammonium compounds of guar gum or quaternary ammonium compounds of hydroxyethyl guar gum as catalyst, with or without n-butanol as diluent, were determined using the differential scanning calorimetry technique with a dynamic scan. To evaluate the kinetic parameters, four different computational methods were applied. The reaction was found to be first-order, with activation energy in the range 65-96 kJ mol^?1.     

A structural study of chemical stability of (Y1−x Ca x)(Ba2−x La x )Cu3O7−δ(x= 0.0, 0.2, and 0.4)

Neutron structural studies are made on (Y_1?x Ca _x)(Ba_2?x La _x )Cu₃O_7?δ for compositions corresponding to x=0.0, 0.2, and 0.4 in order to evaluate any correlation between the remarkably high chemical stability of the cosubstituted samples (x=0.2 and 0.4) and the structural parameters. It is suggested that the increased chemical stability is caused by a decrease in the puckering of the Cu-O planes with increase inx, causing them to flatten, which leads to a reduction in the internal stresses existing in the perovskite lattice of this technologically important material.     

Renal handling of Ca2+ in diabetes

Transient activation of COS-1 cell phospholipase-D (PLD) in response to the protein kinase C (PKC) agonist tetradecanoyl phorbol acetate (TPA) was demonstrated by monitoring the ethanol-dependent accumulation of phosphatidylethanol (PtdEth). Transfection of COS-1 cells with PKC-alpha (wild type and constitutively activated mutants) produced no detectable ptdEth on incubation of transfected cells in the presence of ethanol. However, the response of transfected cells to subsequent TPA stimulation was inhibited, consistent with a role for the PKC-alpha in the suppression of PLD activity.