Perturbation of solitons due to power law nonlinearity

The generalization of solitons to a non-Kerr law media has been studied in this paper along with its perturbation. In particular, the higher nonlinear Schrödinger's equation (NLSE) due to power law nonlinearity is considered. The method of multiple-scales is used to study this equation in presence of a perturbation term. We show that, by newly introducing a proper definition of the phase of the soliton, for the first time, one can obtain the corrections to the pulse where the usual soliton perturbation approach fails.     

Stability and long time evolution of the periodic solutions to the two coupled nonlinear Schrödinger equations

The system of two coupled nonlinear Schrödinger equations has wide applications in physics. In the past, the main attention has been their solitary waves. Here we turn our attention to their periodic wave solutions. In this paper, the stability of the periodic solutions is studied analytically and the criteria for the stability are obtained. The long time evolution of the solutions to the coupled system is studied numerically for the unstable case emphasizing wave–wave interactions in nonlinear optics. Different kinds of evolution are observed depending on the coefficients of the system and the parameters of the unperturbed waves and perturbation. For certain ranges of parameters, the evolution appears to be periodic, while for some other ranges of parameters, solitary wave or solitary wave pairs can be excited among the irregular background although often the evolution is completely chaotic.     

Physico-chemical and Thermal Characteristics of Lime-silica Fume Pastes

Five lime-silica fume pastes were investigated using initial CaO/SiO₂ molar ratios of 0.80, 1.0, 1.30, 1.70 and 2.0. The kinetics and mechanism of hydration interaction between lime and silica fume were studied on the basis of the phase composition and the physical state of the formed hydration products. The developed strength could be related to the lime content of the lime-silica mixture and the formed hydrates. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of the absolute configuration of chiral benzylic alcohols and their esters or ethers,by ruthenium-mediated oxidative degradation

A sensitive analytical method for the reliable determination of the absolute configuration of chiral benzylic alcohols and the corresponding methyl ethers is described. After protection of the hydroxy function by acylation, they are degraded by Ru(VIII)-mediated oxidation, yielding chiral α-oxygenated carboxylic acids, whose stereoanalysis is achieved by GC–MS on a chiral phase. The method easily works down to 1 mg of the analyte.     

Generalized thermoelastic functionally graded orthotropic hollow sphere under thermal shock with three-phase-lag effect

This problem deals with the determination of thermo-elastic interaction due to step input of temperature on the boundaries of a functionally graded orthotropic hollow sphere in the context of linear theories of generalized thermo-elasticity. Using the Laplace transformation the fundamental equations have been expressed in the form of vector–matrix differential equation which is then solved by eigenvalue approach. The inverse of the transformed solution is carried out by applying a method of Bellman et al. Stresses, displacement and temperature distributions have been computed numerically and presented graphically in a number of figures. A comparison of the results for different theories (TEWOED(GN-II), TEWED(GN-III) and three-phase-lag model) is presented. When the material is homogeneous, isotropic and outer radius of the hollow sphere tends to infinity, the corresponding results agree with that of existing literature for GN-III model.     

TEM characterization of a nitrogen implanted austenitic stainless steel

Pure austenitic stainless-steel samples (18% Cr, 10% Ni) were implanted at room temperature with nitrogen ions at an energy of 40 keV with fluences from 10¹⁷ to 6X10¹⁷ ions cm^-2. Microstructures obtained after implantation were studied by transmission electron microscopy and selected-area diffraction. The observations show the formation of ε martensite (hexagonal), of α' martensite (tetragonal) and the appearance of nitrides (Fe, Cr, Ni)₂N_1-x hexagonal or orthorhombic.     

A highly convergent preparation of phosphonyloxyacylamino acids:

A very simple, mild and efficient method for the preparation of phosphonyloxyacylamino acids from readily available starting materials is described.     

Bis (trimethylsilyl) amide as nitrile precursor

Bis (trimethylsilyl) amides are converted into nitriles with high yields when they are treated wich a catalyst (tetrabutylammonium fluoride, Lewis acids or iron phthalocyanine).