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.     

Simultaneous determination of diloxanide furoate and metronidazole in presence of diloxanide furoate degradation products

Three methods are presented for the simultaneous determination of diloxanide furoate (DLX) and metronidazole (MTR), used for their antiprotozoal and antiamoebic effect, in the presence of DLX alkaline degradates and in pharmaceutical formulations, without previous separation. The first method is chemometric-assisted spectrophotometry, in which principal component regression and partial least squares were applied. These two approaches were successfully applied to quantify each drug in the mixture using the information included in, the absorption spectra in the range of 225-320 nm. The second method is TLC-densitometry, in which the binary mixture and degradates were separated on silica gel plates using a chloroform-acetone-glacial acetic acid (9.5 + 0.5 + 0.07, v/v/v) mobile phase and the bands were scanned at 254 nm. The last method is HPLC, in which DLX, MTR, and degradates were separated using the mobile phase acetonitrile-0.05 M dibasic potassium phosphate (25 + 75, v/v), adjusted to pH 4 with orthophosphoric acid, at a flow rate of 1 mL/min, on a C18 analytical column. Detection was at 254 nm. The proposed methods were successfully applied for the analysis of DLX and MTR in pharmaceutical formulations, and the results were statistically compared with a reported spectrophotometric method.     

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.     

Synthesis and anti-bacterial activities of a bis-chalcone derived from thiophene and its bis-cyclized products

A chalcone was prepared by the reaction of terephthalaldehyde with 3-acetyl-2,5-dimethylthiophene. Treatment of this chalcone with thiosemicarbazide/phenyl hydrazine/guanidine hydrochloride/thiourea afforded the corresponding pyrazoline, pyrazole, and pyrimidine in good yields. All the new compounds have been characterized by IR, 1H-NMR, 13C-NMR, GC-MS and elemental analyses. The anti-bacterial activity of these compounds were first tested in vitro by the disk diffusion assay against two gram-positive and two gram-negative bacteria, and then the minimum inhibitory concentration (MIC) was determined with the reference of standard drug chloramphenicol. The results showed that the pyrazoline derivative is better at inhibiting growth of both types of bacteria (gram-positive and gram-negative) compared to chloramphenicol.     

Dating and classification of Syrian excavated pottery from Tell Saka Site,by means of thermoluminescence analysis,and multivariate statistical methods,based on PIXE analysis

Thermoluminescence (TL) dating and Proton Induced X-ray Emission (PIXE) techniques have been utilized for the study of archaeological pottery fragment samples from Tell Saka Site, which is located at 25 km south east of Damascus city, Syria. Four samples were chosen randomly from the site, two from third level and two from fourth level for dating using TL technique and the results were in good agreement with the date assigned by archaeologists. Twenty-eight sherds were analyzed using PIXE technique in order to identify and characterize the elemental composition of pottery excavated from third and fourth levels, using 3 MV tandem accelerator in Damascus. The analysis provided almost 20 elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb). However, only 14 elements as follows: K, Ca, Ti, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb were chosen for statistical analysis and have been processed using two multivariate statistical methods, Cluster and Factor analysis. The studied pottery were classify into two well defined groups.     

Refractive Indices, Viscosities, and Densities for L-Cysteine Hydrochloride Monohydrate + D-Sorbitol + Water, and Glycerol + D-Sorbitol + Water in the Temperature Range between T=303.15 K and T=323.15 K

Viscosities, refractive indices, and densities for ternary systems of (L-cysteine hydrochloride monohydrate [LCHCMH] + D-sorbitol + water) and (glycerol + D-sorbitol + water) and binary systems of ([LCHCMH] + water) and (D-sorbitol + water) have been measured at several temperatures (between T=303.15 K and T=323.15 K) and mass fractions (0.1 to 0.8) at atmospheric pressure. For these mixtures, the experimental values of density were correlated with an experimental equation and the experimental values of viscosity were correlated with the Jones-Dole equation.     

Synthesis of novel 2‐(2‐methylsulfonyl‐1‐methyl‐1H‐imidazol‐5‐yl)‐5‐(alkylsulfonyl)‐1,3,4‐thiadiazoles

Starting from 5‐hydroxymethyl‐2‐mercapto‐1‐methyl‐1H‐imidazole (1), a series of 2‐(1‐methyl‐2‐methylsulfonyl‐1H‐imidazol‐5‐yl)‐5‐alkylthio and 5‐alkylsulfonyl‐1,3,4‐thiadiazole derivatives ( 9a , 9b , 9c , 9d and 10a , 10b , 10c , 10d ) were prepared as potential antimicrobial agents. The structure of the obtained compounds was confirmed by NMR, IR, Mass spectroscopy, and elemental analysis. J. Heterocyclic Chem., (2010)     

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.