Search Results - (Author, Cooperation:Regev, O.)

King, A.R.; Regev, O.

Unknown

317 S.

1572-946X

Springer Online Journal Archives 1860-2000

Physics

Abstract We apply the two time method to weakly anharmonic (nonlinear) stellar pulsations. The problem contains two small parameters: ε-the ratio of the dynamical and the thermal timescale and μ-the measure of the anharmonicity in the oscillator equation. The 0(ɛ0) system is solved up to 0(μ) by the use of an asymptotic perturbation method. This solution is then used within the framework of the two time method to obtain the slow evolution of the amplitudes and entropy. Both monomode and double-mode pulsations are treated in a non-resonance case.

Electronic Resource

1573-4846

chromatography ; foams ; macroreticular

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract A new method for the formation of reticular silicate and organically modified silicate is introduced. Monoliths were prepared by incorporating a few percent hydrogen peroxide in the sol-gel starting solution. For example, incorporation of 6–10% (v) hydrogen peroxide in base catalyzed sol-gel precursors of methyl-Ormosil yielded macroporous monoliths with a bi-modal pore size distribution. The average characteristic pore diameters were approximately 1.2 nm and 0.7 μm, depending on the sol-gel precursors used and the preparation protocol. The specific surface area was approximately 160 m2/g, contributed mainly by the microporous structure. A similar preparation procedure without hydrogen peroxide yielded only fractured or powdery materials. Presumably, the decomposition of the hydrogen peroxide yielded microbubbles, which formed templates for the polycondensation reaction. SEM, nitrogen adsorption isotherms and small angle X-ray spectroscopy were used to characterize the reticular materials.

Electronic Resource