Nonlinear analysis of a reaction-diffusion system: Amplitude equations

A reaction-diffusion system with a nonlinear diffusion term is considered. Based on nonlinear analysis, the amplitude equations are obtained in the cases of the Hopf and Turing instabilities in the system. Turing pattern-forming regions in the parameter space are determined for supercritical and subcritical instabilities in a two-component reaction-diffusion system.     

Stimulated Low-Frequency Raman Scattering in LaF<Subscript>3</Subscript> Suspensions

We observe stimulated low-frequency Raman scattering (SLFRS) caused by laser pulse interaction with acoustic vibrations of nanoparticles in water suspensions of LaF₃ nanoparticles. We show that frequency shifts of the scattering correspond to the eigenfrequencies of nanoparticles vibrations. LaF₃ nanoparticles were synthesized in the presence of glycine by a double jet precipitation technique at various initial concentrations of reagents. We investigate the morphologies and particle sizes as well as size distributions of the particles prepared using transmission electron microscopy (TEM) and dynamical light scattering (DLS). In view of the absorption spectroscopy, we show that the reaction system components and products have no absorption in the visible region, including λ = 694.3 nm. From the luminescence spectroscopy, we find also that they do not emit at λ = 694.3 nm excitation.     

Turing instability in reaction-diffusion systems with nonlinear diffusion

The Turing instability is studied in two-component reaction-diffusion systems with nonlinear diffusion terms, and the regions in parametric space where Turing patterns can form are determined. The boundaries between super- and subcritical bifurcations are found. Calculations are performed for one-dimensional brusselator and oregonator models.     

Oscillatory traveling waves in excitable media

A new type of waves in an excitable medium, characterized by oscillatory profile, is described. The excitable medium is modeled by a two-component activator-inhibitor system. Reaction-diffusion systems with diagonal and cross diffusion are examined. As an example, a front (kink) represented by a heteroclinic orbit in the phase space is considered. The wave shape and velocity are analyzed with the use of exact analytical solutions for wave profiles.     

Optical and luminescent properties of the lead and barium molybdates

Time-resolved luminescence as well as excitation and reflectivity spectra of the oriented lead and barium molybdate single crystals were studied using synchrotron radiation. Features in reflectivity spectra in the fundamental absorption region were analyzed. The contribution of electronic states of lead cation to the formation of the bandgap in PbMoO₄ is supposed. The role of lead states in the intrinsic luminescence of PbMoO₄ is discussed.     

Current awareness

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (5 Weeks journals - Search completed at 22nd. Mar 2000)     

Finite-temperature effective potential of a system with spontaneously broken symmetry

A quantum-mechanical system with spontaneously broken symmetry is considered, the effective potential is determined, and it is shown that with reduction of temperature the system undergoes a phase transition of the first kind.Yaroslavl State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 111–114, June, 1995.     

Mathematical model of a fluid flowmeter

A mathematical model of operation of a fluid (jet) device measuring the liquid or gas flow rate is suggested. The model takes into account the effect of deep negative feedback produced by connecting the control channels of the bistable jet element.