Preparation and Characterization of Cyclohexyl Moiety Toughened POSS-Reinforced Epoxy Nanocomposites

Polyhedral oligomeric silsesquioxane (POSS)-reinforced epoxy nanocomposites were prepared by reacting commercially available diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl diamino diphenyl methane (TGDDM) epoxy resins with 1,1-bis(3-methyl-4-glycidyloxyphenyl)cyclohexane (Cy-Ep) separately and reinforced with POSS nanocluster. POSS (OAPS)-reinforced hybrid Cy-Ep-epoxy resin castings were characterized for their mechanical and morphological properties. The data obtained from mechanical studies indicated that the incorporation of nano OAPS into Cy-Ep modified hybrid systems results in improved stability. Among the epoxy systems studied, the TGDDM-based hybrid epoxy system exhibited higher values of tensile and flexural properties than that of the DGEBA hybrid epoxy system, whereas the impact strength of the DGEBA system was higher than that of the TGDDM system. The dispersion of POSS was confirmed by scanning electron microscopy and visual observation studies.     

An analytical method for cyclosporine using liquid chromatography–mass spectrometry

A liquid chromatographic mass spectrometric (LC‐MS) assay has been developed for cyclosporine A (CyA) in rat plasma using amiodarone as internal standard (IS). Rat plasma (100 µL) containing drug and IS were extracted using liquid–liquid extraction with 4 mL of 95:5 ether:methanol. After evaporation of the organic layer the residue was reconstituted with 500 µL of water. Then the aqueous layer was transferred to LC‐MS sample vials. A 10 µL volume was injected. The analysis was performed on a C₈ column 3.5 µm (2.1 × 50 mm) heated to 60°C with a mobile phase consisting of acetonitrile:methanol:0.2% NH₄OH (60:20:20) at an isocratic flow‐rate of 0.2 mL/min. The ions used for quantitation of CyA and IS were m/z 1202.8 and 645.9, with retention times of 3.35 and 4.72 min, respectively. Linear relationships (r² > 0.99) were achieved between plasma or blood concentration and peak height ratios (drug:IS) over the concentration range 50–5000 ng/mL. The CV% and mean error were <19%. Based on validation data, the lower limit of quantification for the assay was 50 ng/mL. The reported assay method displayed high measures of linearity, sensitivity, reliability and precision, allowing its applicability in pharmacokinetic studies in rat. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and improved electrochemical performance of LiCo1‐xSnxO2 (x= 0 to 0.1) powders

Layered intercalation compounds LiCo_1‐xSn_xO₂ (x= 0 to 0.1) have been prepared using a simple combustion route method. X‐ray diffraction patterns and Laser Raman spectrum suggest that the synthesized materials had the R‐3m structure. Scanning electron images show that particles are well‐crystallized with a size distribution in the range of 50‐100 nm. The room temperature electrical conductivity of the sample increased with Sn content. For LiCo_1‐xSn_xO₂(x = 0, 0.01, 0.03, 0.05 and 0.1), the first discharge capacity increased with increase in Sn content. Among these samples, LiCo_0.95Sn_0.05O₂had produced the best performance of all others with a stable reversible capacity of 186 mAhg^‐1 after 30 cycles. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Inelasticity effects inππ production inγγ collisions

The inelasticity effects in the production of pion pairs in the processγγ→ππ for real photons are investigated using the partial wave dispersion relations. The total cross sections for different photon helicities are calculated. It is observed that this process is dominated by theππ final state interaction. A prediction for S* (997) →γγ decay width is also made. Work supported financially by CSIR, New Delhi     

Minimization of wafer bowing in GaN-based vertical light-emitting diodes by selective area growth using metal-organic chemical vapor deposition

The effect of selective area growth (SAG) on wafer bowing of GaN-based light-emitting diodes (LEDs) is investigated. The SAG of LED structures was carried out on a silicon dioxide (SiO₂) mask pattern with periodic 1000×1000 μm openings, along the sapphire 〈1?1 0 0〉 and 〈?1?1 2 0〉 directions. The morphology of a selectively-grown n-GaN epilayer was examined in relation to various growth parameters such as temperature, pressure, and V/III ratio. Under optimized growth conditions, formation of a ridge-shaped epilayer with a v-pit free smooth surface was realized. Furthermore, the ridge-shaped vertical LED structure, after the removal of the sapphire substrate by laser lift-off (LLO) showed less wafer bowing compared with conventional vertical LED structures. This is attributed to the suppression of lateral strain and dislocations during the site-selective growth process, due to a reduction in the lateral dimensions.     

Effect of Fe-ion implantation doping on structural and optical properties of CdS thin films

We report on effects of Fe implantation doping-induced changes in structural, optical, morphological, and vibrational properties of cadmium sulfide thin films. Films were implanted with 90 keV Fe⁺ ions at room temperature for a wide range of fluences from 0.1×10¹⁶ to 3.6×10¹⁶ ions cm⁻² (corresponding to 0.38–12.03 at.% of Fe). Glancing angle X-ray diffraction analysis revealed that the implanted Fe atoms tend to supersaturate by occupying the substitutional cationic sites rather than forming metallic clusters or secondary phase precipitates. In addition, Fe doping does not lead to any structural phase transformation although it induces structural disorder and lattice contraction. Optical absorption studies show a reduction in the optical band gap from 2.39 to 2.17 eV with increasing Fe concentration. This is attributed to disorder-induced band tailing in semiconductors and ion-beam-induced grain growth. The strain associated with a lattice contraction is deduced from micro-Raman scattering measurements and is found that size and shape fluctuations of grains, at higher fluences, give rise to inhomogeneity in strain.     

Synthesis,crystal growth and properties of the charge transfer complex adduct of 2‐nitro aniline with picric acid – An organic non‐linear optical material

The organic NLO material 2‐nitro aniline and picric acid (2NAP) was synthesized, needle shaped single crystals of dimension 10 × 1 × 0.8 mm^‐3 were grown by slow evaporation solution growth technique from the saturated solution of the title compound in chloroform at ambient temperature. The material was characterized through elemental analysis, powder XRD, ¹H NMR, ¹³C NMR and FTIR techniques. The various planes of reflection have been identified from the XRD powder pattern. The formation of the charge transfer complex was confirmed by UV‐VIS spectroscopy. The thermal stability of the crystals was investigated using TG/DTA analyses techniques. The second harmonic generation (SHG) efficiency of the material was estimated using Nd: YAG laser as source. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical analysis on flow and performance characteristics of a small-scale solar updraft tower (SUT) with horizontal absorber plate and collector glass

Journal of Thermal Analysis and Calorimetry - A numerical analysis has been performed to examine and assess the flow and performance characteristics of the solar updraft tower (SUT) power plant. A...     

A liquid chromatography-mass spectrometry assay method for simultaneous determination of amiodarone and desethylamiodarone in rat specimens

A liquid chromatographic-mass spectrometry (LC/MS) assay method was developed for the determination of amiodarone and desethylamiodarone in rat specimens. Analytes were extracted using liquid-liquid extraction in hexane. The LC/MS system consisted of a Waters Micromass ZQtrade mark 4000 spectrometer with an autosampler and pump. A C(18) 3.5 microm (2.1 x 50 mm) column heated to 45 degrees C was used for separation. The mobile phase consisted of methanol and 0.2% aqueous formic acid pumped at 0.2 mL/min as a linear gradient. Components eluted within 12 min. The concentrations of ethopropazine (internal standard), desethylamiodarone and amiodarone were monitored for m/z of 313.10, combination of 546.9 and 617.73, and 645.83, respectively. In plasma (0.1 mL), linearity was achieved between the peak area ratios and concentrations over the range of 2.5-1000 ng/mL for both amiodarone and desethylamiodarone (r(2) > 0.999). The intraday and interday CV were equal or less than 18%, and mean error was <12%. Similarly, in homogenates containing 0.1 g of rat tissue, linearity was observed in standards ranging from 5 to 5000 ng/g. The method was successfully used to measure tissue and plasma concentrations of drug. The validated lower limit of quantitation was 2.5 ng/mL for drug and metabolite, based on 0.1 mL of plasma.