Numerical solution of the one‐dimensional wave equation with an integral condition

The hyperbolic partial differential equation with an integral condition arises in many physical phenomena. In this research a numerical technique is developed for the one‐dimensional hyperbolic equation that combine classical and integral boundary conditions. The proposed method is based on shifted Legendre tau technique. Illustrative examples are included to demonstrate the validity and applicability of the presented technique. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 282–292, 2007     

Chemically modified carbon paste electrode for iodide determination on the basis of cetyltrimethylammonium iodide ion-pair.

A new carbon paste electrode (CPE) for the determination of iodide ion based on a cetyltrimethylammonium iodide (CTMAI) ion pair as an electroactive material is described. The electrode shows a linear response for iodide ion over the concentration range of 4 x 10(-5) M to 1 x 10(-1) M with a lower detection limit of 4 x 10(-5) M at 25 degrees C. The electrode has a Nemstian slope of -55.0 +/- 0.4 mV/decade and a fast potential response of 45 s, which is almost constant over a pH range of 5.0 - 9.0. Selectivity coefficient data of the CTMAI-CPE for some common ions show negligible interference, and the electrode has high selectivity towards the iodide ion. An average recovery of 101.83% with a relative standard deviation of 1.53% has been achieved for the determination of iodide in Flaxedil (gallamine triethiodide) ampoules, a muscle relaxant drug. The electrode has been examined for the determination of iodide in saline water; the results were found to compare favorably with those obtained using Metrohm iodide ISE. The electrode has been utilized as an end-point indicator electrode for the determination of Hg(II) and phenylmercury(I) in their aqueous solutions using potentiometric titration with a potassium iodide standard solution.     

Diffuse reflectance spectroscopic determination of phosphate with applications of chromaticity coordinates and color temperature.

A simple and sensitive method has been developed for the determination of phosphate in the ng ml(-1) concentration range. The method utilizes the quantitative extraction of the Molybdenum Blue species of phosphate by polyurethane foam (PUF) discs prior to a diffuse reflectance spectrometric (DRS) measurement of the colored foam. A preconcentration factor of 150 has been achieved for a 100 ml sample volume. The effect of the pH of the solution on the rate of color development of the phosphomolybdenum blue has been carefully examined. A calibration graph has been established based on the Kubelka-Munk function (F(R)695), which was found to favorably correlate with the phosphate concentration. The lower detection limit (3sigma) was found to be 5 ng ml(-1), with a working analytical range of 5-70 ng ml(-1). At the same time, the chromaticity coordinates y (CIE 1931) and v' of the CIELUV (1976) were found to show good correlation with the concentration of phosphate in water. On the other hand, the calculated color temperature has been found to excellently correlate with the phosphate concentration. The different experimental parameters were thoroughly investigated.     

Tensor correlations and spin-isospin excitations

We study the effects of ground state tensor correlations with a phenomenological two body correlation function on the spin-isospin modes of excitations in nuclei. The correlation function is of Jastrow type with a tensor term. The energy weighted strength is drastically enhanced because of these correlations. We predict considerable amount of strength in the region of 60–70 MeV excitations if the sum is evaluated in a two-state model. Our results are also sensitively dependent on the strength of the tensor term in the phenomenological Jastrow function.     

Development and validation of a reversed-phase column liquid chromatographic method for the determination of five cephalosporins in pharmaceutical preparations

A new, simple, rapid, and precise RP-HPLC method has been developed and validated for the determination of five cephalosporins, namely, cefalexin, cefoperazone, ceftriaxone, ceftazidime, and cefepime. The method has been applied successfully for simultaneous determination of cefalexin in a binary mixture with sodium benzoate in a suspension, and cefoperazone in a binary mixture with sulbactam in vials. Chromatographic separation was achieved on a Waters microBondapak C18 column (250 x 4.6 mm id, 10 pm particle size) using the mobile phase monobasic potassium phosphate (50 mM, pH 4.6)-acetonitrile (80 + 20, v/v) with UV detection. A flow rate of 1 mL/min was applied. Linearity, accuracy, and precision were found to be acceptable over the concentration range of 30-300, 3-30, and 15-120 microg/mL for the studied cephalosporins, sodium benzoate, and sulbactam, respectively. The optimized method proved to be specific, robust, and accurate for QC of the cited drugs in their pharmaceutical preparations.     

New N-heterocyclic carbene mercury(II) complexes: Close mercury-arene interaction

Mononuclear mercury complexes (1, 2, and 3) bearing bis-N-heterocyclic carbene (NHC) ligands of the form [(NHC)₂-μ-Hg]⁺² have been prepared and structurally characterised. The complexes were derived from three bis-imidazolium salts as precursors to NHC; either 1,3-bis(N-methylimidazolium-1-ylmethyl)benzene bis(hexafluorophosphate) (I·2PF₆), 1,3-bis(N-butylimidazolium-1-ylmethyl)benzene bis(hexafluorophosphate) (II·2PF₆) or 3,5-bis(N-butylimidazolium-1-ylmethyl)toluene bis(hexafluorophosphate) (III·2PF₆) treated with mercury(II) acetate. Interestingly X-ray crystal structure analysis revealed a close interaction between the Hg metal centre with one carbon atom of the aryl linker in addition to coordination with two NHCs.     

A stable and conservative method for locally adapting the design order of finite difference schemes

A procedure to locally change the order of accuracy of finite difference schemes is developed. The development is based on existing Summation-By-Parts operators and a weak interface treatment. The resulting scheme is proven to be accurate and stable.