Determination of Menbutone in Bovine Milk and Meat Using Micellar Liquid Chromatography: Application to Injectable Dosage Forms

A simple, sensitive, and rapid method was developed for the routine identification and quantification of menbutone in different matrices by micellar liquid chromatography. Separation was performed in less than 4 min using a C₁₈ column with UV detection at 234 nm. A micellar solution composed of 0.12 M sodium dodecyl sulfate, 8 % n-butanol, and 0.3 % triethylamine in 0.02 M phosphoric acid at pH 6.0 was used as the mobile phase. The method was fully validated in accordance with International Conference on Harmonization (ICH) guidelines. The limits of detection and quantitation were 0.95 and 2.86 ng mL^?1, respectively. The method showed good repeatability, linearity, and sensitivity according to the evaluation of the validation parameters. The micellar method was successfully applied for the analysis of menbutone in its commercial injections with a mean % recovery value of 99.73?±?1.634 % and in spiked bovine milk and meat samples with a mean % recovery values in the range of 98.00–100.60 %. High extraction efficiency was obtained without matrix interference in the extraction process and in the subsequent chromatographic determination. No organic solvent was used during the pretreatment step. Hence, this method can be considered as an interesting example for green chemistry.     

Control of methane flame properties by hydrogen fuel addition: Application to power plant combustion chamber

This study presents a numerical investigation of the effects of mixing methane/hydrogen on turbulent combustion processes taking place in a burner similar to that integrated in gas turbine power plants. Thereby, in comparison to the reference case where the burner is fuelled by 100% of methane, the variations of the axial velocity field, temperature field and mass fraction of carbon monoxide field are examined for different percentages of hydrogen fuel injection. The computed results, obtained by using the software Fluent-CFD, are compared and validated against experimental reference data. Results show that the hydrogen addition to the methane has an impact on all physical and chemical parameters of the reactive system.     

A facile route to the new triazene dyes based on substituted pyrazolidin-3,5-dione derivatives

Several substituted triazenes dyes were synthesized by coupling functionalized pyrazolidin-3,5-dione derivatives, to various heteroarene azides in excellent yields (98%). Electron delocalization between the two coupled components of these triazene dyes was studied using UV-vis spectra and NMR spectroscopy. Their thermolysis was investigated and by using an isotopically labeled triazene, the mechanism decomposition reaction was also identified. The protolysis of these triazenes was evaluated and showed that they are highly stable and even in strongly acidic medium.     

Design and Analysis of a Channel Assignment Scheme for CDMA/TDMA Mobile Networks

In this paper, a channel assignment scheme is proposed for use in CDMA/TDMA mobile networks carrying voice and data traffic. In each cell, three types of calls are assumed to compete for access to the limited number of available channels by the cell: new voice calls, handoff voice calls, and data calls. The scheme uses the movable boundary concept in both the code and time domains in order to guarantee the quality of service (QoS) requirements of each type. A traditional Markov analysis method is employed to evaluate the performance of the proposed scheme. Measures, namely, the new call blocking probability, the handoff call forced termination probability, the data call loss probability, the expected number of handoff and the handoff link maintenance probability are obtained from the analysis. The numerical results, which are validated by simulation, indicate that the scheme helps meet the QoS requirements of the different call types.     

Inhibitive properties, adsorption and a theoretical study of 3,5-bis(n-pyridyl)-4-amino-1,2,4-triazoles as corrosion inhibitors for mild steel in perchloric acid

Corrosion inhibition of mild steel in molar perchloric acid by 3,5-bis(n-pyridyl)-4-amino-1,2,4-triazoles (n-PAT, n = 2, 3 and 4) was studied at 30 °C using gravimetric and electrochemical impedance spectroscopy techniques. Protection efficiencies of 95% and 92% were obtained with 12 × 10⁻⁴ M of 3-PAT and 4-PAT, respectively; while 2-PAT reached only 65%. The inhibiting properties of n-PAT were found to depend on the concentration and the order of increasing inhibition efficiency was correlated with the modification of the position of the nitrogen atom in the pyridinium substituent. It was shown that adsorption of 4-aminotriazole derivatives on the steel surface is consistent with the Langmuir adsorption isotherm and the obtained standard free energy of adsorption () values indicate that the corrosion inhibition of the mild steel in 1 M HClO₄ is depends on both physic-and chemisorption. A significant correlation is obtained between inhibition efficiency and quantum chemical parameters using semi-empirical quantitative structure-activity relationships (QSAR) approach.     

Complex susceptibility analysis of magneto-fluids: Optical band gap and surface studies on the nanomagnetite-based particles

An aqueous stable magnetic fluid containing Fe₃O₄ nano-particles with a mean diameter of 4–7 nm, which is in the range of super-paramagnetism, is prepared. The particles are synthesized via co-precipitation method from ferrous and ferric solutions. X-ray diffraction, transmission electron microscopy, transformer method are used to study the physical properties of the magnetic fluids and powders. A method is given to analyze and resolve the real and imaginary parts of the measured complex susceptibility of magnetic fluids. The band gap parameters of the magneto-nanopowders such as the direct-, indirect-band gap energies, Fermi energy and Urbach energy are determined. A comparative study between the different techniques used to calculate the powder particle size is presented. Adsorption of nitrogen gas is used to identify and determine the particles mean diameter and to study their microstructure, the magnetic properties and surface porosity. The study showed that the total pore system of the magnetic nano-powders consists mainly of mesopores.     

Silane-functionalized Al2O3-modified polyurethane powder coatings: Nonisothermal degradation kinetics and mechanistic insights

This work reports on nonisothermal degradation kinetics of polyurethane (PU)-based powder coatings containing 1, 3, and 5%wt% vinyltrimethoxysilane functionalized Al₂O₃ (V-Al₂O₃) nanoparticles. Thermogravimetric analysis of PU/V-Al₂O₃ powder coatings with different V-Al₂O₃ contents has been performed at different heating rates. Variation of activation energy (E_a) of PU/V-Al₂O₃ powder coatings was modeled as a function of partial mass loss by using Kissinger–Akahira–Sunose, Ozawa–Wall–Flynn and modified Coats–Redfern isoconversional approaches. The results revealed hindered decomposition process of PU/V-Al₂O₃ nanocomposite powder coatings, featured by an increase in activation energy of degradation from ∼158 for blank PU to 225, 183, and 229 kJ/mol for nanocomposites filled with 1, 3, and 5 wt% of V-Al₂O₃, respectively. Likewise, pre-exponential factor values increased for samples containing V-Al₂O₃ nanoparticles compared to that of blank sample. Sestak–Berggren kinetic model appropriately captured thermal degradation behavior of PU/V-Al₂O₃ nanocomposites than that of nth order decomposition kinetic reaction models.     

Passivity and passivity breakdown of zinc anode in alkaline medium

The electrochemical behaviour of zinc in NaOH solutions has been investigated by using potentiodynamic technique and complemented by X-ray analysis. The E/i curves exhibit active, passive and transpassive regions prior to oxygen evolution. The active region displays two anodic peaks. The passivity is due to the Formation of a compact Zn(OH)₂ film on the anode surface. The transpassive region is assigned to the electroformation of ZnO₂. The reverse sweep shows an activation anodic peak and one catholic peak prior to hydrogen evolution. The influence of increasing additives of NaCl, NaBr and Nal on the anodic behaviour of zinc in NaOH solutions has been studied. The halides stimulate the active dissolution of zinc and tend to break down the passive film, leading to pitting corrosion. The aggressiveness of the halide anions towards the stability of the passive film decreases in the order: I^? > Br^? > Cl^?. The susceptibility of zinc anode to pitting corrosion enhances with increasing the halide ion concentration but decreases with increasing both the alkali concentration and the sweep rate.