Optimal configuration of microstructure in ferroelectric materials by stochastic optimization

An optimization procedure determining the ideal configuration at the microstructural level of ferroelectric (FE) materials is applied to maximize piezoelectricity. Piezoelectricity in ceramic FEs differ significantly from that of single crystals because of the presence of crystallites (grains) possessing crystallographic axes aligned imperfectly. The piezoelectric properties of a polycrystalline (ceramic) FE is inextricably related to the grain orientation distribution (texture). The set of combination of variables, known as solution space, which dictates the texture of a ceramic is unlimited and hence the choice of the optimal solution which maximizes the piezoelectricity is complicated. Thus a stochastic global optimization combined with homogenization is employed for the identification of the optimal granular configuration of the FE ceramic microstructure with optimum piezoelectric properties. The macroscopic equilibrium piezoelectric properties of polycrystalline FE is calculated using mathematical homogenization at each iteration step. The configuration of grains characterised by its orientations at each iteration is generated using a randomly selected set of orientation distribution parameters. Apparent enhancement of piezoelectric coefficient $d_{33}$ is observed in an optimally oriented BaTiO$_3$ single crystal. A configuration of crystallites, simultaneously constraining the orientation distribution of the c-axis (polar axis) while incorporating ab-plane randomness, which would multiply the overall piezoelectricity in ceramic BaTiO$_{3}$ is also identified. The orientation distribution of the c-axes is found to be a narrow Gaussian distribution centred around ${45^\circ}$. The piezoelectric coefficient in such a ceramic is found to be nearly three times as that of the single crystal.Comment: 11 pages, 7 figure

A SIMPLE RP-HPLC METHOD FOR SIMULTANEOUS ESTIMATION OF ORGANIC IMPURITIES, ENANTIOMER AND ASSAY OF DEXLANSOPRAZOLE

Objective: To develop a simple and accurate RP-HPLC method for simultaneous estimation of organic impurities, enantiomer and assay of Dexlansoprazole, proposed method was validated according to an International Conference on Harmonisation of technical requirements for registration of pharmaceuticals for human use (ICH) guidelines.Methods: Cellulose tris-(3,5-dichlorophenylcarbamate) bonded on silica gel (Chiralpak IC) were used as stationary phase. Acetonitrile (ACN) and 10 mM dibasic potassium phosphate buffer of pH 7.20, adjusted with dilute ortho phosphoric acid, were used as mobile phase in gradient composition at a flow rate of 1.0 ml/min. UV detection was made at 283 nm and run time was 27 min.Results: Limit of detection (LOD) and Limit of quantification (LOQ) was 42 and 126 ng/ml, respectively. Analytes response was studied from 0.25-1.50 µg/ml and r2 value of the calibration curve was>0.999. Accuracy was studied in three different concentrations, the mean recovery was observed between 93.8 and 102.5%. To the maximum of 0.01% impurity variation was observed between the results of inter and intra-day precision.Conclusion: Proposed method is specific, precise, sensitive, linear and accurate. As a significance of this proposed method, the listed known impurities of Lansoprazole monograph [United States, British and European pharmacopoeias (USP/BP/Ph. Eur.)] Were used in method development and separation was demonstrated. Apart from this, enantiomer resolution was achieved and the same chromatogram was used for assay calculation.Â

Mulch requirement of ginger (Zingiber officinale Rosc.) under shade

Field experiments conducted at Vellayani (Kerala, India) to study the mulch requirement of ginger (Zingiber officinale) under various shade levels indicated that under 25 per cent shade, one-fourth quantity (7.5 t/ha) of green leaf mulch could be saved. &nbsp

BIODEGRADATION OF TOLUENE HYDROCARBON BY A PSEUDOMONAS SP. ISOLATED FROM GASOLINE CONTAMINATED SOIL

ABSTRACT: In the present study efforts were made to isolate and characterize bacteria capable of aerobic biodegradation of toluene hydrocarbon from gasoline polluted soil. After initial screening, 28 different strains were isolated from soil samples and the most promising strain was selected for toluene degradation study. Biochemical and morphological characterization classified the bacterial strains selected as Pseudomonas sp. and was designated Pseudomonas sp. SBCT-17. The spectrophotometric determination of toluene monoxygenase activity, using horseradish preoxydase (HRP) assay showed 0.248 U/ml enzyme activity at 420 nm. The results obtained from enzyme assay and FT-IR degradation analysis in this study confirms that the Pseudomonas sp. SBCT-17 is an efficient strain capable of biodegrading toluene hydrocarbon

Small-angle neutron scattering studies on water soluble complexes of poly(ethylene glycol)-based cationic random copolymer and SDS

The interaction of cationic random copolymers of methoxy poly(ethylene glycol) monomethacrylate and (3-(methacryloylamino)propyl) trimethylammonium chloride with oppositely charged surfactant, sodium dodecyl sulphate, and the influence of surfactant association on the polymer conformation have been investigated by small-angle neutron scattering. SANS data showed a positive indication of the formation of RCPSDS complexes. Even though the complete structure of the polyion complexes could not be ascertained, the results obtained give us the information on the local structure in these polymer-surfactant systems. The data were analysed using the log-normal distribution of the polydispersed spherical aggregate model for the local structure in these complexes. For all the systems the median radius and the polydispersity were found to be in the range of 20 ± 2 Å and 0.6 ± 0.05, respectively

Characteristics of VHF radiowave scintillations over a solar cycle (1983?1993) at a low-latitude station: Waltair (17.7°N, 83.3°E)

International audienceThe characteristics of VHF radiowave scintillations at 244 MHz (FLEETSAT) during a complete solar cycle (1983?93) at a low-latitude station, Waltair (17.7°N, 83.3°E), are presented. The occurrence of night-time scintillations shows equinoctial maxima and summer minima in all the epochs of solar activity, and follows the solar activity. The daytime scintillation occurrence is negatively correlated with the solar activity and shows maximum occurrence during the summer months in a period of low solar activity. The occurrence of night-time scintillations is inhibited during disturbed days of high solar activity and enhanced during low solar activity

Enhancement of the electromechanical response in ferroelectric ceramics by design

It is demonstrated based on continuum mechanics modeling and simulation that it is possible to obtain polycrystalline ceramic ferroelectric materials which beggars single crystals in electromechanical properties. The local inhomogeneities at the ferroelectric domain-scale level due to spontaneous polarization and the underlying anisotropy are taken into consideration in the framework of mathematical homogenization of physical properties in ferroelectric materials. The intrinsic randomness of the spatial distribution of polarization is shown to be judiciously employed for the design of better polycrystalline ferroelectrics. The noncollinear rotation of the net polarization-vectors embedded in crystallites of the ceramic ferroelectrics is demonstrated to play the key role in the enhancement of physical properties.Comment: 7 fugure