Simple, selective and sensitive spectrophotometric determination of fenitrothion using novel chromogenic reagent

A facile, rapid and sensitive spectrophotometric method was developed for the determination of fenitrothion in its formulations, water, food grain and agriculture soil samples with newly synthesised reagent. The method was based on the alkaline hydrolysis of fenitrothion pesticide and resultant hydrolysed product of fenitrothion was coupled with diazotised 4,4'-methylene-bis-(p-amino-3'-hydroxybenzanilide) in basic medium to give orange coloured product having lambdamax 480 nm. The formation of coloured derivatives with the coupling agent is instantaneous and stable for 48 h. Beer's law was obeyed in the concentration range of 0.1-19.0 microg ml(-1). The proposed method is sensitive, easy to operate and permitted the determination of fenitrothion with a detection limits of 0.085 microg ml(-1). The experimental results indicate that the procedure can eliminate the fundamental interferences caused by other pesticides and non-target ions, which made these methods more sensitive and selective. The method was applicable to the determination of fenitrothion residue in water, food grain and soil samples up to ng level.     

Spectrophotometric determination of V(V) in environmental, biological, pharmaceutical and alloy samples by novel oxidative coupling reactions

A Novel, rapid, sensitive and selective reactions are developed for spectrophotometric determination of trace amounts of vanadium (V) in environmental, biological, pharmaceutical and alloy samples was studied. The methods were based on interactions of 4-bromophenyl hydrazine (4-BPH) with N-(1-naphthyl ethylenediamine dihydrochloride (NEDA) in the presence of vanadium in acidic medium (acetate buffer of pH 3.0) to give violet colored derivative or on the oxidation of 4-bromophenyl hydrazine by vanadium in basic medium and coupling with chromotropic acid (CA) to yield red color derivative. The violet color derivative having an absorbance maximum at 570nm which is stable for 7 days and the red derivative with lambda(max) 495nm for 5 days. Beer's law was obeyed for vanadium in the concentration range of 0.5-6.0microgml(-1) (violet derivative) and 0.6-7.0microgml(-1) (red derivative), respectively. The optimum reaction conditions and other important analytical parameters were established to enhance the sensitivity of the proposed methods. Interference due to various non-target ions was also investigated. The proposed methods were applied to the analysis of vanadium (V) in environmental, biological, pharmaceutical and steel samples. The performance of proposed methods were evaluated in terms of Student's t-test and Variance ratio F-test that indicates the significance of proposed methods over reported method.     

Nano-porous surface states of Ti–Y–Al–Co phase separated metallic glass

A novel nano-porous state was fabricated at the surface of the Ti-based metallic glass by selective etching technique. By transforming the surface of the Ti₄₅Y₁₁Al₂₄Co₂₀ phase separated alloy from smooth towards rough with nano-pores in an oxidised state, the passivation behaviour of the glassy alloy in simulated body fluid condition was remarkably improved leading to corrosion resistance significantly higher than that of the Ti–6Al–4V alloy, one of the favourite candidate materials for implant applications.     

Thermal Performance Simulation of a Heat Pump Assisted Solar Desalination System for Kazakhstan Climatic Conditions

ABSTRACT

A numerical model has been proposed in this research work for predicting the energy performance of a heat pump assisted regenerative solar still using phase change heat storage materials such as paraffin wax and hydrate salt. The numerical model is based on energy and mass balance. The performance was simulated for Fort Sherchenko town in Kazakhstan. The performance comparison between the conventional solar still and heat pump assisted regenerative solar still with and without phase change materials are presented. Moreover, the influence of two different phase change materials on thermal performance of a heat pump assisted regenerative solar still are described. The numerical simulation results showed that heat pump assisted regenerative solar still is more energy efficient and produces better productivity when compared to the conventional simple solar still. The use of hydrate salt phase change heat storage material was found to be a good option for enhancing the performance of a heat pump assisted regenerative solar still.     

A twin unidirectional impulse turbine topology for OWC based wave energy plants – Experimental validation and scaling

The twin unidirectional turbine topology was recently proposed with the promise of very significant improvements in the energy capture in Oscillating Water Column (OWC) based wave energy plants. Here, we present the initial results of the experimental validation of the twin unidirectional impulse turbine topology. A scale model of the concept was built and tested using simulated bidirectional flow. The model consists of two 165 mm impulse turbines each individually coupled to 375 W grid connected induction machines. An oscillatory flow test rig was used to simulate bidirectional flow to test the model. The results of the experiments validate the concept of the twin turbine configuration. The proposed topology utilizes no moving parts and achieves more than 50% efficiency over a broad range of flow coefficients. A comparison with other competing turbines (viz, a twin Wells’ turbine, a linked guide vane impulse turbine and a fixed guide vane impulse turbine) is done, based on actual measurements in the Indian wave energy plant. The results from the experiments are scaled to evaluate the design features of a 50 GWh wave energy plant.     

STUDIES OF TRANSESTERIFICATION OF KARANJA (Pongamia pinnata) OIL IN A PACKED BED REACTOR

Studies were made to determine the influence of different reaction temperatures and residence times on biodiesel yield by transesterification of karanja oil (Pongamia pinnata) in the presence of methanol using a solid acid heterogeneous catalyst in a continuous process. Recycle runs were conducted by further transesterification of the organic phases (first run mixture of methyl ester and unconverted oil) in the presence of methanol under similar conditions. High-pressure liquid chromatography (HPLC) reveals poor biodiesel yield even with an increase in the reaction temperature and residence time in the first run. Biodiesel yield obtained from the recycle runs, however, was greatly increased over that of the first-run biodiesel yield. Recycle transesterification at a reaction temperature of 240°C and residence time of 50 min gives a maximum yield value of 97.74%. Consequently, irrespective of the presence of high free fatty acids and other impurities in karanja oil, recycling the organic phase of the first run significantly enhances the biodiesel yield.     

WEDM of Mg/CRT/BN composites: Effect of materials and machining parameters

The current work presents a detailed exploration on real-time wire electric discharge machining (WEDM) experiments and grey relational analysis (GRA)–based multi-criteria optimization of material and machining characteristics for lowered surface roughness (R_a) and improvised material removal rate (MRR) of the newly developed magnesium/boron nitride/cathode ray tube (Mg/BN/CRT) hybrid metal matrix composites (MMCs). The composites were fabricated through powder metallurgy (PM) route by reinforcing silica-rich E-waste CRT panel glass powder crushed for different particle sizes (10, 30, and 50?µm) at various weight percentages (5%, 10%, and 15%) and with 2% boron nitride (BN). Taguchi-based orthogonal array procedure was utilized to formulate the experimental plan for WEDM considering reinforcement level and size, pulse on time (P_on), pulse off time (P_off), and wire feed (W_f) as the input process parameters. ANOVA results reveal that P_on and wt% of reinforcement has more effect on R_a and MRR than any other considered parameters. The developed mathematical model for R_a and MRR predicted values similar to that of experimental results. Multi-criteria optimization was done through GRA technique and the so recommended optimum parameter set furnishes higher MRR (22.34?mm³/min) and reduced R_a (2.87?µm).     

<Emphasis Type="Italic">p</Emphasis>-AgCoO<Subscript>2</Subscript>/<Emphasis Type="Italic">n</Emphasis>-ZnO heterojunction diode grown by rf magnetron sputtering

P-type transparent semiconducting AgCoO₂ thin films were deposited by rf magnetron sputtering of sintered AgCoO₂ target. The AgCoO₂ films grown by rf sputtering were highly c-axis oriented showing only (001) reflections in the X-ray diffraction pattern unlike in the case of amorphous films grown by pulsed laser deposition (PLD). The bulk powder of AgCoO₂ was synthesized by hydrothermal process. The optical bandgap was estimated as 4·15 eV and has a transmission of about 50% in the visible region. The temperature dependence of conductivity shows a semiconducting behaviour. The positive sign of Seebeck coefficient (+220 μVK⁻¹) indicates p-type conductivity. Transparent p-n heterojunction on glass substrate was fabricated by rf magnetron sputtering of p-AgCoO₂ and n-type ZnO: Al thin films. The structure of the diode was glass/ITO/n-ZnO/p-AgCoO₂. The junction between p-AgCoO₂ and n-ZnO was found to be rectifying.