Embedded diagonally implicit Runge–Kutta–Nystrom 4(3) pair for solving special second-order IVPs

In this paper, third-order 3-stage diagonally implicit Runge–Kutta–Nystrom method embedded in fourth-order 4-stage for solving special second-order initial value problems is constructed. The method has the property of minimized local truncation error as well as the last row of the coefficient matrix is equal to the vector output. The stability of the method is investigated and a standard set of test problems are tested upon and comparisons on the numerical results are made when the same set of test problems are reduced to first-order system and solved using existing Runge–Kutta method. The results clearly shown the advantage and the efficiency of the new method.     

A coated piezoelectric crystal detector for phosgene

A piezoelectric quartz crystal coated with methyltrioctylphosphonium dimethylphosphate was found to be a good detector for phosgene in air. The coating is sensitive to phosgene in the μg 1^?1 range and has a reasonably long lifetime. The response curve is linear over the concentration range 5–140 μg 1^?1. The coated crystal can be used for more than six weeks without significant loss in sensitivity, provided that high ammonia concentrations are not encountered.     

A piezoelectric immunosensor for the detection of cortisol

A piezoelectric crystal immunosensor has been developed for the detection and determination of cortisol. Cortisol antibody was layered onto the gold electrodes of a 10 MHz piezoelectric crystal which was pre-coated with either protein A or gluteraldehyde. Crystals pre-coated with protein A showed the best results with respect to stability and sensitivity. The sensor was successfully used for the determination of cortisol in standard solutions from 36-3628 micrograms/L (part per billion). The advantages of the proposed sensor include simplicity, short analysis time, cost effectiveness and selectivity. The results demonstrate the feasibility of cortisol assay in clinical testing and in drug monitoring.     

Stability-indicating high-performance liquid chromatographic assay for the determination of metoclopramide hydrochloride in pharmaceutical dosage forms

A simple, reliable and selective high-performance liquid chromatographic method for the determination of metoclopramide hydrochloride in pharmaceutical dosage forms has been developed and evaluated. The drug and the internal standard (phenobarbitone) were eluted from a 5-micron C8 reversed-phase column at ambient temperature with a mobile phase consisting of phosphate buffer (10 mM)-methanol-acetonitrile (50 + 28 + 22) adjusted to pH 4.8 with orthophosphoric acid. The mobile phase was pumped at a flow-rate of 1.5 ml min-1 and the effluent was monitored spectrophotometrically at 214 nm. The retention times of the internal standard and metoclopramide hydrochloride were 3.0 and 7.5 min, respectively. Quantification was achieved by measuring the peak-height ratio of the drug to the internal standard. A linear relationship was found over the range 1-10 micrograms ml-1. Within-day coefficients of variation (CVs) ranged from 0.50 to 1.70% and between-day CVs from 0.68 to 4.07% at three different concentrations. The developed procedure was compared with the current BP method for the assay of metoclopramide hydrochloride in tablets. The proposed method was also used to study the stability of metoclopramide hydrochloride.     

Nanometer-sized zirconium dioxide microcolumn separation/preconcentration of trace metals and their determination by ICP-OES in environmental and biological samples

A new method is proposed using a microcolumn (20 mm × 2.0 mm) packed with nanometer-sized zirconia as solid-phase extractor for the separation/preconcentration of Mn, Cu, Cr, Zn, Ni and Co prior to their determination by inductively coupled plasma optical emission spectrometer (ICP-OES) in environmental samples. The factors affecting the separation and preconcentration of analytes such as pH, sample flow rate and volume, eluent concentration and volume were determined, interfering ions were studied, and the optimal experimental conditions were established. The adsorption capacity of nanometer-sized ZrO₂ for Mn, Cu, Cr, Zn, Ni and Co was found to be 1.3, 1.3, 1.7, 2.0, 3.9 and 1.5 mg g⁻¹, respectively. The detection limits of the method were 12, 58, 24, 2, 7 and 36 ng L⁻¹, respectively, with a preconcentration factor of 25. The precision of this method was 1.7% (Mn), 2.9% (Cu), 5.9% (Mn), 3.8% (Mn), 6.2% (Mn) and 4.3% (Mn) with 9 determinations of 10 ng mL⁻¹ of target analytes, respectively. The method was successfully applied to the determination of trace metals in lake water, dried fish samples, certified reference materials of human hair and milk, and provided satisfactory results.     

A practical access to new pyrrolizine carboxylates via KHMDS-catalyzed carbocyclizations

Easy and effective preparation of new 1H-pyrrolizine carboxylates was achieved with high efficiency via KHMDS-induced carbocyclization of N-alkynyl proline carboxylates under substantially mild conditions. Meanwhile, some trans-diiodoallylic N-proline carboxylates were obtained from N-propargyl proline carboxylates using molecular I₂ with or without KHMDS. This method is quite feasible in terms of practical and quick access to the pyrrolizines and their derivatives over the formation of carbanions.     

Potentiometric Determination of L-Asparagine with an Enzymatic Electrode

A new enzyme electrode for the determination of L-asparagine is constructed by chemical immobilization of L-aspartase [E.C. 4.3.1.1] on an ammonia-gas-sensing probe. L-Asparagine was determined over a concentration range of 1.6 × 10^?5 to 1.5 × 10^?3 M with a subnerstian response of -51 mV/decade. The electrode was stable for more than 30 days. The effect of pH, substrate and metal activator concentrations, amount of immobilized enzyme, and interferents on the electrode response are reported.     

Theory of radiation from a uniformly moving linear oscillator

The classical theory of radiation is extended to a relativistic linear oscillator, and the radiation properties are determined. Some basic particular cases are analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 7–11, November, 1975.In conclusion the authors thank Prof. A. A. Sokolov for his interest in the work.