Highly dispersed zinc phosphate microdomains in mesoporous silica

In situ immobilization of crystalline zinc phosphate nuclei in the mesoporous silica material resulted in a highly ordered 2D-hexagonal mesoporous material with evenly dispersed crystalline NaZnPO₄ microdomains in its matrix using the self-assembly of cationic surfactant under hydrothermal synthesis condition. Four samples with different Si:Zn:P:Na mole ratios have been prepared. X-ray diffraction (XRD) patterns of the as-synthesized as well as template-free samples indicated the presence of mesophase in each case. N₂ adsorption data indicated mesoporosity in the samples together with the existence of crystalline NaZnPO₄ phase for the materials synthesized with Si/Zn mole ratio 5-12. ²⁹Si MAS NMR results showed high value of the Q⁴/Q³ ratio in these materials suggesting highly crosslinked structure.     

Mutational analysis of active site residues of human adenosine deaminase

Adenosine deaminase was overexpressed in a baculovirus system. The pure recombinant and native enzymes were identical in size, Zn2+ content, and activity. Five amino acids, in proximity to the active site, were replaced by mutagenesis. The altered enzymes were purified to homogeneity and compared to wild-type adenosine deaminase with respect to zinc content, enzymatic activity, and kinetic parameters. All but one of the alterations produced significant activity perturbations. Replacement of Cys262 produced a protein that retained at least 30-40% of wild-type activity. In contrast, replacements of His17, His214, His238, and Glu217 resulted in dramatic losses of enzyme activity. None of these mutants exhibited large variations in Km. The proteins produced from alterations of amino acids implicated in metal coordination were slightly activated by inclusion of Zn2+ throughout purification. These experiments confirm that in the active enzyme Zn2+ plays a critical role in catalysis, that a histidine or glutamate residue plays a mechanistic role in the hydrolytic deamination step, and that cysteine is not involved in the catalytic mechanism of adenosine deaminase. These data support the roles for these amino acid residues suggested from the x-ray structure of murine adenosine deaminase (Wilson, D. K., Rudolf, F. B., and Quicho, F. A. (1991) Science 252, 1278-1284).     

Effect of TiN addition on sintering behaviour and mechanical properties of WC-10Co hard metals containing Mo2C and Ni

The aim of the present work was to substitute a portion of WC in WC-10 wt% Co hard metal by TiN by modification of the binder phase, and to produce an equivalent grade of hard metal. Sintering studies were carried out in both H₂ and H₂-N₂ (5050) mixture. Introduction of TiN into WC-10Co hard metal resulted in a high sintered porosity, and as a consequence the mechanical properties deteriorated. Partial substitution of cobalt in WC-8.7TiN-12Co by nickel further increased the sintered porosity and led to a non-uniform microstructure. Incorporation of Mo₂C along with cobalt-nickel binder promoted a fine-grained structure, which resulted in better sintered properties than those of WC-8.7TiN-6Co-6Ni hard metal. However, hot isostatic pressing (HIP) treatment of the liquid-phase sintered alloys was effective in eliminating the large pores and thus greatly enhanced the mechanical properties. HIPed hard metal of WC-8.7TiNS-12Co composition showed properties almost equivalent to those of WC-10Co hard metal.     

Low temperature,efficient synthesis of new As(V)-silicate molecular sieves with MFI topology and their catalytic properties in oxidation reactions

New MFI type arseno-silicate molecular sieves (As(V)-MFI), synthesized for the first time, can be crystallized at lower temperature (70–90C) in 1–3 days under hydrothermal conditions. Interestingly, these As(V)-MFI molecular sieves can be synthesized even faster than the As-free silicalite-1 under identical conditions. Further, the crystallization becomes faster with the increase in As content of the reaction mixture, contrary to the observations made on all the other high silica molecular sieves, so far. These microporous As(V)-silicates exhibit significant catalytic activity in (i) phenol hydroxylation using 30% aq. H₂O₂ (ca. 55% H₂O₂ efficiency) and (ii) oxidative dehydrogenation of 2-butanol and benzyl alcohol using air under fixed bed vapor phase reaction conditions exhibiting ca. 75–85% selectivity towards 2-butanone and benzaldehyde+benzoic acid, respectively.     

Robust Ensemble Kalman Filter Based on Exponential Cost Function

This paper provides an alternative point of view to the robust estimation technique for nonlinear non Gaussian systems based on exponential quadratic cost function. The proposed method, named the risk sensitive ensemble Kalman filter (RSEnKF), is based on the ensemble Kalman filter (EnKF) which may be thought of as a Monte Carlo implementation of the Kalman filter for nonlinear estimation problems. The theory and formulation of the RSEnKF are presented in this paper. The proposed method is superior to the extended risk sensitive filter (ERSF) and the quadrature based risk sensitive filters in terms of estimation accuracy, and is faster than the risk sensitive particle filter (RSPF).     

Failure of a low pressure turbine rotor blade of an aeroengine

During a test run of an aeroengine, a low-pressure turbine rotor blade had failed. The turbine blades were made of Ni-base superalloy of CM 247 LC grade and fabricated by DS investment casting. The blades were coated with platinum aluminide. Investigation revealed that the blade had failed by fatigue. It was concluded that the coating on the blade had developed cracks due to excessive bending/vibration, which in turn propagated by fatigue leading to the failure.     

Optimization study of adsorption parameters for removal of fluoride using aluminium-impregnated potato plant ash by response surface methodology

High fluoride level is a major threat to drinking water availability in many countries worldwide. Therefore, knowledge of its removal, using the best technique with optimal efficiency, is needed. In the present study, aluminium-impregnated potato plant ash (Al-IPPA) was used for removal of fluoride from synthetic fluoride solution. The Al-IPPA has high specific area and strong affinity towards fluoride. Synthesized Al-IPPA was characterized by point of zero charge, Fourier Transform infrared, scanning electron micrograph and XRD (X-ray diffraction) studies. Adsorption kinetics indicated that the adsorption equilibrium was reached within 30 min and the adsorption process followed the pseudo second-order model better. The equilibrium data were analysed using Langmuir, Freundlich, D–R and Temkin isotherm models. The Langmuir and D–R isotherm models could fit the experimental data well. Thermodynamic parameters such as Gibbs free energy (?G°), enthalpy (?H°) and entropy (?S°) changes of sorption were also evaluated, which indicated that the adsorption process was spontaneous, feasible and endothermic in nature. Furthermore, the coexisting anions had significant effect on fluoride adsorption. Finally, process parameters were optimized using response surface methodology. The desirability study highlighted the optimized process parameters: initial concentration 94.02 mg/l; pH 4.64; adsorbent dose 2.8 g/l; and contact time 57.0 min. On the other hand, perturbation study revealed that the process parameters such as contact time and initial fluoride concentration are the dominating factors. The desorption study with Al-IPPA showed that nearly 99 % of fluoride could be leached out at pH 12. However, up to pH 8.5, there is no leaching of fluoride. The reusable properties of material supported the possibility of its commercial use.     

Multispectral and hyperspectral analysis and modelling of the absorbance characteristics of marine algal pigments

The techniques of remote sensing in spectral bands and hyperspectral remote sensing were modelled with laboratory experiments on marine algal pigments obtained from four species of green micro‐algae of the eastern coast of India. The spectral absorbance was measured within the visible range of wavelength for chlorophyll mixtures of different concentrations and also for chromatographically separated pigments. The intention was to simulate and compare the expected nature of results obtained with remote sensing in wavebands and hyperspectral sensing involving a fine resolution in wavelength. Therefore, the absorbance was measured both with filters of three different visible spectral bands, viz. blue, green, and red, and with a continuous scan of wavelength. The algal species were distinguishable with both types of measurements. However, the hyperspectral technique was found to be more suitable in revealing the individual contribution of pigments. Based on the experimental results, a computational model was developed with Gaussian variation of absorbance as a function of wavelength. The experimental results were simulated with that model explaining the comparative spectroscopic results obtained from band and hyperspectral sensing.     

Annealing behaviour of cold rolled aluminum alloy in a high magnetic field

The crystallographic texture evolution of cold rolled (71%) aluminum alloy 3103 was investigated during annealing at 290 °C in a magnetic field of 19 T. The analysis reveals that texture and microstructure evolution in this material can be affected by a magnetic field which manifests itself in enhanced recovery and an earlier start of subsequent primary recrystallization.     

Mesoporous hybrid zirconium oxophenylphosphate synthesized in absence of any structure directing agent

A new organic–inorganic hybrid mesoporous zirconium oxophenylphosphate (ZPP-1) has been synthesized hydrothermally at 443 K by using phenylphosphonic acid (PPA) as phosphorus source in absence of any structure directing agent. Powder XRD, TEM, FE SEM, N₂ sorption, CHN and ICP-AES chemical analyses, ¹³C CP/MAS and ³¹P MAS NMR, UV–visible and FT IR spectroscopic tools and thermal analysis were employed to characterize this novel material. XRD, N₂ sorption and TEM image analysis suggested the existence of multi-lamellar structure of the pore wall with large micropores and mesopores having peak maximums of ca. 1.5 and 5.0–6.0 nm, respectively in this ZPP-1 material. Interestingly, this hybrid material showed very high thermal stability together with retention of nanostructure and phenyl group when heated upto 723 K. ZPP-1 showed fairly high H₂ adsorption capacity under atmospheric pressure at 77 K. Possible templating role played by the framework phenyl groups has been discussed.