EPR and optical absorption studies of Cr3+ doped lithium potassium sulphate single crystals

X-band electron paramagnetic resonance (EPR) studies of Cr³⁺ doped lithium potassium sulphate single crystals have been done at room temperature. The Cr³⁺ crystal field and spin Hamiltonian parameters have been evaluated by employing resonance line positions observed in the EPR spectra for different orientations of external magnetic field. The evaluated g, D and E values are: g_x = 2.0763 ± 0.0002, g_y = 1.9878 ± 0.0002, g_z = 1.8685 ± 0.0002 and D = 549 ± 2 × 10^?4 cm^?1, E = 183 ± 2 × 10^?4 cm^?1. Using EPR data the site symmetry of Cr³⁺ ion in the crystal is discussed. Cr³⁺ ion enters the lattice substitutionally replacing K⁺ site. The optical absorption study of the single crystal is also done in 195–925 nm wavelength range at room temperature. By correlating optical and EPR data the nature of bonding in the crystal is discussed. The calculated values of Racah parameters (B and C), crystal field parameter (D_q) and nephelauxetic parameters (h and k) are obtained as: B = 697, C = 3247, D_q = 2050 cm^?1, h = 1.146 and k = 0.21.     

Preparation and ac electrical characterizations of Cd doped SnO2 nanoparticles

Nanoparticles (NPs) of the Sn_1?xCd_xO₂ (0.0 ≤ x ≤ 0.04) were synthesized through soft chemistry method. These NPs were characterized for structural, morphological and electrical properties by X-ray diffraction, High resolution transmission electron microscopy and dielectric spectroscopy techniques respectively. Structural analysis confirms that all the NPs are having single phase rutile tetragonal structure. The NPs are of spherical shape and average size of these is found to decrease with Cd doping. Dielectric permittivity and AC conductivity of all the NPs were evaluated as a function of frequency and composition at room temperature. The frequency response of ε_r, ε_i, tan δ and σ _ac show that the dispersion is due to the interfacial polarization and these parameters decrease with doping of Cd in the SnO₂ matrix. The possible correlation between observed dielectric properties and size of NPs, and hence disorder in the system are explored.     

Synthesis of FePt nanorods and nanowires by a facile method

FePt nanorods and nanowires have been synthesized by the reduction of Pt(acac)(2) and the thermal decomposition of Fe(CO)(5) in the presence of solvents/surfactants by simply controlling the sequence of addition of surfactants. The as-synthesized FePt nanorods and nanowires have a face centered cubic structure with average diameter of 3?nm. Length of nanorods and nanowires can be adjusted in the range of 15-150?nm by varying reaction parameters. Nanocrystalline L1(0) FePt phase with coercivity up to 24?kOe was obtained after heat treatments.     

Comparison of Computer Models for Estimating Hydrology and Water Quality in an Agricultural Watershed

Various computer models, ranging from simple to complex, have been developed to simulate hydrology and water quality from field to watershed scales. However, many users are uncertain about which model to choose when estimating water quantity and quality conditions in a watershed. This study compared hydrologic/water quality models including Spreadsheet Tool for the Estimation of Pollutant Load (STEPL)-Purdue, Soil and Water Assessment Tool (SWAT), High Impact Targeting (HIT), Long-Term Hydrologic Impact Assessment (L-THIA), Pollutant Load (PLOAD), Spatially and Temporally Distributed Model for Phosphorus Management (STEM-P), Region 5, and ensemble modeling (using STEPL-Purdue, SWAT, L-THIA, PLOAD, and STEM-P). Model capabilities, inputs, and underlying methods to estimate streamflow, surface runoff, baseflow, nutrients, and sediment were examined. Uncalibrated, calibrated, and validated outputs of these models and uncalibrated ensemble modeling in estimating water quantity and quality for a 41.5 km² agricultural watershed in Northeastern Indiana were explored, and suggestions were provided on the selection and use of models. Models need to be selected carefully based on the simulation objectives, data availability, model characteristics, time constraints, and project budgets.

     

Kantowski-Sachs and Bianchi type models with a general non-canonical scalar field

The paper deals with spatially homogeneous and anisotropic Kantowski-Sachs and Bianchi universes with a general non-canonical scalar field with the Lagrangian L = F(X) ? Ω(?), where \(X = \frac{1}{2}{\phi _i}{\phi ^i}\). We discuss a general non-canonical scalar field in three different cosmologies: (i) cosmology with a constant potential, Ω(?) = Ω₀ = const, (ii) cosmology with a constant equation-of-state parameter, i.e., γ_? = const, and (iii) cosmology with a constant speed of sound, i.e., c _s ² = const. For a constant potential, we have shown that the k-essence Lagrangian and the Lagrangian of the present model are equivalent. Dissipation of anisotropy, when the universe is filled with a general non-canonical scalar field, is investigated. The existence of an average bounce in Kantowski-Sachs and locally rotationally symmetric Bianchi-I and Bianchi-III models is discussed in detail.     

Utilisation of nickel plant leach residue by sintering technique

This paper presents useful data on process parameters and experimental conditions for producing quality sinter based on laboratory scale experiments for sintering of a completely waste material, i.e., nickel plant leached residue for its effective utilization to extract nickel and chromium in the alloyed form by producing chromium based pig iron. Some attempts have also been made to evaluate the results obtained from several laboratory scale experiments for estimation of strength and productivity. It has been found that, by implementation of the process waste released from a nickel plant (based on reduction-roast-ammonia leaching) can be used to produce value added products thereby adding to the overall economics of the nickel production technology.     

Stable analogues of OSB-AMP: potent inhibitors of MenE, the o-succinylbenzoate-CoA synthetase from bacterial menaquinone biosynthesis

MenE, the o-succinylbenzoate (OSB)-CoA synthetase from bacterial menaquinone biosynthesis, is a promising new antibacterial target. Sulfonyladenosine analogues of the cognate reaction intermediate, OSB-AMP, have been developed as inhibitors of the MenE enzymes from Mycobacterium tuberculosis (mtMenE), Staphylococcus aureus (saMenE) and Escherichia coli (ecMenE). Both a free carboxylate and a ketone moiety on the OSB side chain are required for potent inhibitory activity. OSB-AMS (4) is a competitive inhibitor of mtMenE with respect to ATP (K(i) =5.4±0.1 nM) and a noncompetitive inhibitor with respect to OSB (K(i) =11.2±0.9 nM). These data are consistent with a Bi Uni Uni Bi Ping-Pong kinetic mechanism for these enzymes. In addition, OSB-AMS inhibits saMenE with K(i)(app) =22±8 nM and ecMenE with K(i)(OSB) =128±5 nM. Putative active-site residues, Arg222, which may interact with the OSB aromatic carboxylate, and Ser302, which may bind the OSB ketone oxygen, have been identified through computational docking of OSB-AMP with the unliganded crystal structure of saMenE. A pH-dependent interconversion of the free keto acid and lactol forms of the inhibitors is also described, along with implications for inhibitor design.     

Studies on relative catalytic efficiencies of zinc and aluminium on nucleation of dispersed bismuth droplets

In Zn-Bi and Al-Bi systems, both of which belong to monotectic class, dispersion of second phase particles within the matrix have been produced through rapid solidification processing (RSP) route. In order to understand relative catalytic efficiencies of Zn and Al matrices in catalyzing nucleation of Bi particles entrapped in the respective metal matrices, thermal analysis in constant program mode was performed. Thermal analyses revealed that Bi undercools by 132° in Zn matrix and by 157° in Al matrix. Thermodynamic barrier to nucleation (ΔG*) for Bi has also been calculated, which is 39·8 kcal/mole and 47·085 kcal/mole, in Zn and Al matrices, respectively at the maximum recorded undercoolings.