The synthesis and characterisation of ferromagnetic CaMn2O4 nanowires.

The synthesis of marokite CaMn(2)O(4) nanowires using a hydrothermal method is reported. Transmission electron microscopy and electron diffraction measurements show that the nanowires are polycrystalline in nature with diameters between 10 and 20 nm and lengths ranging from approximately 100 to 500 nm. Most interestingly, in contrast with the bulk material, magnetization measurements show that these nanowires exhibit ferromagnetic ordering with a Curie temperature (T(C)) of approximately 40 K.     

Initiation of polymerization of alkyl 2-cyanoacrylates in aqueous solutions of glycine and its derivatives

The polymerization of methyl 2-cyanoacrylate and heptyl 2-cyanoacrylate was carried out with the use of aqueous solutions of ¹⁴C-tagged glycine, methyl glycine, and acetyl glycine as initiators. When glycine and methyl glycine were used, radioactive polymers were formed. When acetyl glycine was used, the polymer formed was not radioactive. The data seem to indicate that free NH₂ groups appear to be necessary for the incorporation of the glycine initiator in the polymer. A possible mechanism for the polymerization is presented.     

An unusual electron-transfer behavior of ferrocene in aqueous microemulsion systems

The electrochemical behavior of ferrocene in an aqueous microemulsion (pentan-1-ol/sodium dodecyl sulfate (SDS)/aq. H₂SO₄) has been studied using an ultramicroelectrode. Contrary to the generally expected reversible peak, the experiments show the presence of a second oxidation peak during the reverse scan at low scan rates where the peak corresponding to ferricinium ion reduction is nearly absent along with the unanticipated appearance of a current dip. These observations are rationalized using a novel type of coupling between heterogeneous (electrochemical) and homogeneous (chemical) electron transfer processes. The composition of the medium, especially the acid concentration, affects the electron transfer of the solubilized probe and there exists a threshold acid concentration for achieving maximum anodic peak current.     

Molecular electrostatic potentials as input for the alignment of HIV-1 integrase inhibitors in 3D QSAR

Comparative molecular similarity indices analysis (CoMSIA), a three-dimensional quantitative structure activity relationship (3D QSAR) paradigm, was used to examine the correlations between the calculated physicochemical properties and the in vitro activities (3'-processing and 3'-strand transfer inhibition) of a series of human immunodeficiency virus type 1 (HIV-1) integrase inhibitors. The training set consisted of 34 molecules from five structurally diverse classes: salicylpyrazolinones, dioxepinones, coumarins, quinones, and benzoic hydrazides. The data set was aligned using extrema of molecular electrostatic potentials (MEPs). The predictive ability of the resultant model was evaluated using a test set comprised of 7 molecules belonging to a different structural class of thiazepinediones. A CoMSIA model using an MEP-based alignment showed considerable internal as well external predictive ability (r2(cv) = 0.821, r2(pred) = 0.608 for 3'-processing; and r2(cv) = 0.759, r2(pred.) = 0.660 for 3'-strand transfer).     

Determination of palladium in synthetic nuclear wastes by differential pulse voltammetry

A novel method for the determination of palladium in synthetic nuclear waste samples has been developed using a computerized voltammetric analyzer. The electrode system consists of hanging mercury drop electrode (HMDE)/glassy carbon/Ag-AgCl electrode. Various experimental conditions including electrolyte type, pH and concentration have been optimized, leading to a detection limit of 40 ng/ml. The mixture of 4^.10^-3M citric acid + 2^.10^-2M ammonia-ammonium chloride buffer + 4^.10^-3M EDTA was used as a supporting electrolyte at pH 9.0. Standard addition method was employed to determine the concentration of palladium present in the nuclear waste sample. The relative standard deviation of the proposed method was found to be 8% at 40 ng/ml of palladium content. The method is direct, simple, rapid and free from any possible interference.     

Transport of liquids using superhydrophobic aerogels

The experimental results of the studies on the transportation of water droplets on a superhydrophobic silica aerogel-powder-coated surface are reported. The superhydrophobic silica aerogels were prepared using sol-gel processing of methyltrimethoxysilane (MTMS) precursor, methanol (MeOH) solvent, and base (NH4OH)-catalyzed water followed by supercritical drying using methanol solvent. The molar ratio of NH4OH/MTMS, H2O/MTMS, and MeOH/MTMS were varied from 1.7x10(-1) to 3.5x10(-1), 2 to 8, and 1.7 to 14, respectively, to find out the best-quality aerogels in terms of higher hydrophobicity and high droplet velocity. A specially built device was used for the measurement of velocity of water droplet of size 2.8 mm (+/-0.2 mm) on an inclined surface coated with superhydrophobic aerogel powder. Liquid marbles were prepared by rolling water droplets on aerogel powder and the marble(s) velocities on a noncoated inclined surface were compared with that of the water droplets. It was observed that the microstructure of the aerogel affects the droplet as well as marble velocities considerably. For an aerogel with uniform and smaller particles, the water droplet and marble velocities were observed to be maximum, i.e., 144 and 123 cm/s, respectively, whereas for the aerogels with bigger and nonuniform particles, the water droplet and marble velocities were observed to be minimum, i.e., 92 and 82 cm/s, respectively. The results have been discussed by taking into account the contact angles and microstructural observations.     

Isometric graphing and multidimensional scaling for reaction-diffusion modeling on regular and fractal surfaces with spatiotemporal pattern recognition

Heterogeneous surface reactions exhibiting complex spatiotemporal dynamics and patterns can be studied as processes involving reaction-diffusion mechanisms. In many realistic situations, the surface has fractal characteristics. This situation is studied by isometric graphing and multidimensional scaling (IGMDS) of fractal surfaces for extracting geodesic distances (i.e., shortest scaled distances that obtain edges of neighboring surface nodes and their interconnections) and the results obtained used to model effects of surface diffusion with nonlinear reactions. Further analysis of evolved spatiotemporal patterns may be carried out by IGMDS because high-dimensional snapshot data can be efficiently projected to a transformed subspace with reduced dimensions. Validation of the IGMDS methodology is carried out by comparing results with reduction capabilities of conventional principal component analysis for simple situations of reaction and diffusion on surfaces. The usefulness of the IGMDS methodology is shown for analysis of complex patterns formed on both regular and fractal surfaces, and using generic nonlinear reaction-diffusion systems following FitzHugh Nagumo and cubic reaction kinetics. The studies of these systems with nonlinear kinetics and noise show that effects of surface disorder due to fractality can become very relevant. The relevance is shown by studying properties of dynamical invariants in IGMDS component space, viz., the Lyapunov exponents and the KS entropy for interesting situations of spiral formation and turbulent patterns.     

Creation of acid sites by La-ions in L zeolite

The creation of strong acid sites in alkaline K-L-zeolites on ion-exchanging with La-ions is reported. Acidity measurements have been carried out by temperature programmed desorption of adsorbed ammonia. Reaction data which confirm the creation of acid sites are also reported.

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