We present the results of computer simulation studies of SrTiO,. After deriving a reliable potential model, we concentrate on the properties of defects and dopants. Our calculations are used to propose a defect model that is consistent with experimental observations. For vacancy disorder, the calculations show that SrTiO, (Schottky) and SrO (Schottky-like) disorder have very similar energy, with a small tendency for the development of Sr deficiency at higher temperatures. All mono-and divalent cations prefer to substitute at strontium sites. For trivalent cations, three types of mechanism (Sr and Ti substitution and selfcompensation) are proposed, whereas for tetravalent cations substitution on both A and B sites may occur, depending on the ionic radius.

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Polyaniline (PANI)/Ag nanocomposites were prepared by separate synthesis of silver nanoparticles by inert gas condensation, incorporating in the 1-methyl-2-pyrrolidinone (NMP) solution of polyaniline emeraldine base (PANIEB) and then cast into films at 120 °C. X-ray diffraction confirmed the presence of ∼67 nm silver nanoparticles in the polyaniline matrix. From the thermogravimetric analysis it is observed that the nanocomposite films have a higher degradation temperature than the pure PANI film. Scanning electron microscopy showed a uniform distribution, with spherical and granular morphology for low concentration of Ag nanoparticles, whereas for higher concentration (1.0% Ag) nanorods are formed. The impedance spectroscopic studies of NMP plasticized nanocomposite films suggest microphase separation into reduced and oxidized repeat units. Incorporation of silver nanoparticles in PANI reduces the charge trapping centres and increases the conducting channels, which causes a tenfold decrease in the real part of impedance.

Cadmium usually hampers plant growth, but bacterial inoculation may improve stress tolerance in plants to Cd by involving various mechanisms. The objective was to characterize and identify bacteria that improve plant growth under Cd stress and reduce Cd uptake. Cadmium-tolerant bacteria were isolated from rhizosphere soil, which was irrigated with tannery effluent, and six strains were selected as highly tolerant to Cd, showing minimum inhibitory concentration as 500 mg L(-1) or 4.45 mmol L(-1). These strains were identified by 16S rRNA gene analysis and functional analysis in regard to plant growth promotion characteristics. To determine their effect on cereal growth under Cd stress, seeds were inoculated with these strains individually and grown in soil contaminated with three Cd levels (0, 40 and 80 mg kg(-1)). Biomass production, relative water content (RWC), electrolyte leakage (ELL) and tissue Cd concentration were measured. Biomass of both cereals was inhibited strongly when exposed to Cd; however, bacterial inoculation significantly reduced the suppressive effect of Cd on cereal growth and physiology. The bacterial isolates belonged to the genera Klebsiella, Stenotrophomonas, Bacillus and Serratia. Maize was more sensitive than wheat to Cd. Klebsiella sp. strain CIK-502 had the most pronounced effects in promoting maize and wheat growth and lowering Cd uptake under Cd stress.

X-ray absorption fine structure (XAFS) spectroscopy has been employed to investigate the cation distribution in nanocrystalline zinc ferrites (ZnFe(2)O(4)), synthesized in acidic and basic media at different temperatures. By using (Zn(1-x)Fe(x))[Ni(x)Fe(2-x)]O(4) as model compounds we have determined cation distribution in nanosize ZnFe(2)O(4). The cation distribution for samples synthesized at low temperature (400 °C) is (Zn(0.5)Fe(0.5))[Zn(0.5)Fe(1.5)]O(4) for urea- and (Zn(0.75)Fe(0.25))[Zn(0.25)Fe(1.75)]O(4) for citric-acid-based samples. These results show that samples synthesized at and above 600 °C have a local structural environment identical to that of bulk ZnFe(2)O(4).