Geodesic Motion on Extended Taub-NUT Spinning Space

In this paper we investigate the geodesic motion of the pseudo-classical spinning particle for the extended Taub-NUT metric. The generalized equations for spinning space are investigated and the constants of motion are derived in terms of the solutions of these equations. We find only two types of extended Taub-NUT metrics with Kepler type symmetry admitting Killing-Yano tensors. The solutions for the lowest components of generalized Killing equations are presented for a particular form of extended Taub-NUT metric.     

Effect of CO<Subscript>2</Subscript> dilution on propane–air isothermal catalytic combustion on platinum

The present work aims to investigate several kinetic aspects of catalytic combustion of the stoichiometric propane–air mixture on a platinum wire in the presence of progressive CO₂ dilution, using a micro-calorimetric method. The method allowed the determination of the induction periods and of the reaction rates during transient and steady-state regimes at different initial pressures P ₀ (10–101 kPa), wire temperatures T _w (470–575 K) and gas-phase composition. The kinetic parameters were evaluated from regression analysis using empirical and mechanistic models. The dilution with CO₂ of the stoichiometric propane–air mixture (4.02% propane) was 10, 20, 30, 40, 50%. For additions equal to or greater than 23%, the gaseous system is outside the flammability limits reported in the literature. The kinetic characteristics of the catalytic combustion remain similar for the whole range, even for 50% CO₂ addition when the propane concentration in mixture diminishes to 2%, a concentration smaller than the lower explosion limit in air in normal conditions.     

Partial integrals and the first focal value in the problem of centre

Polynomial differential systems of degreen3 on the plane are investigated. It is assumed that the originO(0, 0) is a critical point with imaginary eigenvalues. We show that if the first focal value vanishes and there existN=(n²+n–4)/2 partial algebraical integrals then the origin is a centre. For cubic systems (n=3), we have obtained fourteen series of conditions each ensuring that the origin is a centre.     

HPTLC and GC-MS for Separation and Identification of Eugenol in Plants

JPC – Journal of Planar Chromatography – Modern TLC - Samples of clove, nutmeg, and cinnamon have been extracted by maceration with ethanol for 24 h and with aqueous ethanol 48 h....     

Temperature and pH effects on the kinetics of 2-aminophenol auto-oxidation in aqueous solution

The kinetics of the auto-oxidation of 2-aminophenol (OAP) to 2-amino-phenoxazin-3-one (APX) was followed in air-saturated aqueous solutions and the influence of temperature and pH on the auto-oxidation rate was studied. The kinetic analysis was based on a spectrophotometric method following the increase of the absorbance of APX. The process follows first order kinetics according to the rate law—d[OAP]/dt=k′[OAP]. The experimental data, within the pH range 4–9.85, were analyzed using both differential and incremental methods. The temperature variation of the overall rate constant was studied at pH=9.85 within the range 25–50°C and the corresponding activation energy was evaluated.     

Ultraporous single phase iron oxide-silica nanostructured aerogels from ferrous precursors

Monoliths of iron oxide-silica aerogel nanocomposites have been synthesized using a novel synthesis route which consists of impregnating silica wet gels with anhydrous iron(II) precursors followed by ethanol supercritical drying of the gels. The process yields aerogels exhibiting high porosity, large surface areas (approximately 900 m2/g), rather low densities (approximately 0.6 g/cm3), and a homogeneous distribution of single-phase maghemite, gamma-Fe2O3, nanoparticles with average sizes in the 7-8 nm range. Remarkably, the gamma-Fe2O3 nanoparticles are obtained in the as-dried state without the need of postannealing. The nanoparticles are mostly superparamagnetic at room temperature but become blocked in a ferrimagnetic state at lower temperatures.     

Synthesis of highly branched perfluoroethers by direct fluorination,promising new materials based on the hexafluoroacetone–ethylene copolymer

Direct fluorination of the hexafluoroacetone-ethylene copolymer, [CH₂CH₂OC(CF₃)₂]_n, under conditions designed to promote fragmentation of the polymer chain has led to the synthesis of a number of structurally unusual branched perfluoropolyethers [? CF₂? CF₂? O-C(CF₃)₂? ]_n. These new perfluoropolyethers have been characterized by ¹⁹F-NMR, and their physical properties are reported. Direct fluorination under milder conditions yields a high-molecular-weight perfluoropolyether.     

The investigation of soliton solutions and conservation laws to the coupled generalized Schrödinger–Boussinesq system

This paper employed the principle of undetermined coefficients and Bernoulli sub-ODE methods to acquire the topological, non-topological, periodic wave and algebraic solutions of the coupled generalized Schrödinger–Boussinesq system (CGSBs). The concept of Lie point symmetry is applied to derive the point symmetries of the CSGE. The problem on nonlinear self-adjointness of the CSGE has not been solved in previous time. In the present paper, we solve this problem and find an explicit form of the differential substitution providing the nonlinear self-adjointness. Then we use this fact to construct a set of conserved vectors using the classical symmetries admitted by the equation and the general conservation laws (Cls) theorem presented by Ibragimov. Numerical simulation of the obtained results are analyzed with interesting figures showing the physical meaning of the solutions.