Spectrophotometric Study of the Complexation of Some Lanthanide (III) Ions with a Series of 18-Crowns-6 in DMSO Solution Using Murexide as a Metallochromic Indicator

The complexation of La(III), Ce(III), Pr(III) and Er(III) with 18-crown-6(18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 (DCY18C6) anddibenzopyridino-18-crown-6 (DBPY18C6) has been studied in dimethylsulfoxide(DMSO) by means of a competitive spectrophotometric method using murexide asa metal ion indicator. The formation constants of the 1 : 1 complexeswere found tovary in the order La(III) > Ce(III) > Pr(III) > Er(III). It was foundthat the structure influences the formation and stability of the resultingcomplexes. The effects ofvarious parameters on complexation are discussed. The order of the stabilityconstants of each lanthanide ion with these macrocycles are18C6 > DC18C6 > DB18C6 > DBPY18C6.     

Application of a dispersive micro‐solid‐phase extraction method for pre‐concentration and ultra‐trace determination of cadmium ions in water and biological samples

A method for the trace determination of cadmium ions in water, human urine and human blood serum samples using ultrasonic‐assisted dispersive micro‐solid‐phase extraction (UA‐D‐μSPE) was developed. Silica‐coated magnetic nanoparticles were coated with polythiophene, and the resulting sorbent was characterized using thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X‐ray diffraction. Following UA‐D‐μSPE, cadmium ions were quantified using graphite furnace atomic absorption spectrometry. A Box–Behnken design was used for optimization of important sorption and desorption parameters in UA‐D‐μSPE: in the sorption step, pH of solution, sorption amount and sonication time for sorption; in the desorption step, concentration of eluent, volume of eluent and sonication time. The optimum conditions for the method were: pH of solution, 7.5; sonication time for sorption, 3 min; sorption amount, 35 mg; type and concentration of eluent, HCl and 1.1 mol l^?1; volume of eluent, 360 μl; sonication time for desorption, 110 s. Under the optimized conditions the limit of detection and relative standard deviation for the detection of cadmium ions by UA‐D‐μSPE were found to be 0.8 ng l^?1 and <6%, respectively.     

A three-dimensional model of vocal fold abduction/adduction

A three-dimensional biomechanical model of tissue deformation was developed to simulate dynamic vocal fold abduction and adduction. The model was made of 1721 nearly incompressible finite elements. The cricoarytenoid joint was modeled as a rocking-sliding motion, similar to two concentric cylinders. The vocal ligament and the thyroarytenoid muscle's fiber characteristics were implemented as a fiber-gel composite made of an isotropic ground substance imbedded with fibers. These fibers had contractile and/or passive nonlinear stress-strain characteristics. The verification of the model was made by comparing the range and speed of motion to published vocal fold kinematic data. The model simulated abduction to a maximum glottal angle of about 31 degrees. Using the posterior-cricoarytenoid muscle, the model produced an angular abduction speed of 405 degrees per second. The system mechanics seemed to favor abduction over adduction in both peak speed and response time, even when all intrinsic muscle properties were kept identical. The model also verified the notion that the vocalis and muscularis portions of the thyroarytenoid muscle play significantly different roles in posturing, with the muscularis portion having the larger effect on arytenoid movement. Other insights into the mechanisms of abduction/adduction were given.     

Simultaneous microemulsion liquid chromatographic analysis of fat-soluble vitamins in pharmaceutical formulations: Optimization using genetic algorithm

An environmentally benign and simple method has been proposed for separation and determination of fat-soluble vitamins using isocratic microemulsion liquid chromatography. Optimization of parameters affecting the separation selectivity and efficiency including surfactant concentration, percent of cosurfactant (1-butanol), and percent of organic oily solvent (diethyl ether), temperature and pH were performed simultaneously using genetic algorithm method. A new software package, MLR-GA, was developed for this purpose. The results indicated that 73.6 mM sodium dodecyl sulfate, 13.64% (v/v) 1-butanol, 0.48% (v/v) diethyl ether, column temperature of 32.5 °C and 0.02 M phosphate buffer of pH 6.99 are the best conditions for separation of fat-soluble vitamins. At the optimized conditions, the calibration plots for the vitamins were obtained and detection limits (1.06–3.69 μg mL⁻¹), accuracy (recoveries > 94.3), precision (RSD < 3.96) and linearity (0.01–10 mg mL⁻¹) were estimated. Finally, the amount of vitamins in multivitamin syrup and a sample of fish oil capsule were determined. The results showed a good agreement with those reported by manufactures.     

Estimates of B-decays into K-resonances and dileptons

Short and long distance contributions to the exclusive B-decays into various K-resonances and dileptons, i.e. $B \to K^i \ell \bar \ell (\ell = e,\mu ,\nu )$ , are examined. The heavy quark effective theory has been used to calculate the hadronic matrix elements. Substantial branching fractions are obtained for the dileptonic B-decays into some higher excited states of K-mesons. The long distance (resonance) contributions to these exclusive rare B-decay modes dominate the short distance contributions mostly by two orders of magnitude. It is pointed out that, excluding the resonance contributions, the P-wave channels are dominant, accounting for about 50% of the inclusiveB??X _s ? ⁺ ? ^? branching fraction.