Short-and long-range order effects on resonance energy transfer in crystals and glasses

Resonance energy transfer by the Förster-Dexter mechanism in a cubic crystal and in a rigid homogeneous medium is studied. The homogeneous medium is modeled using a hard-sphere fluid (HSF) radial distribution function. This distribution is more realistic than the commonly used uniform distribution with excluded volume (UDEV) function. For the dipole-dipole mechanism, both models yield essentially the same donor luminescence decay, except for small critical radii. For the exchange mechanism, however, the two models differ significantly. In particular, to fit a given experimental decay, the UDEV model requires both a larger effective Bohr radius and a larger rate constant at collisional distance than the HSF model.     

Evaluation of the Degree of Cross-Linking of Epoxy-Acrylate Polymers with a Luminescence Probe

Luminophores, 4,4'-diaminodiphenylmethane and Oxazine-17, were introduced into a photopolymerizable formulation based on an epoxy-acrylate oligomer, and their behavior in thin-film polymerization was studied.     

Spectrophotometric Study of Interaction of Comenic Acid with Cetylpyridinium Chloride

The interaction of comenic acid with cetylpyridinium chloride in aqueous solutions was studied by spectrophotometry. Compositions of ionic associates formed depending on cetylpyridinum chloride concentration were found, and logarithms of equilibrium constants of corresponding association reactions were determined.     

Comparing different hard-thermal-loop approaches to quark number susceptibilities

We compare our previously proposed hard-thermal-loop (HTL) resummed calculation of quark number susceptibilities using a self-consistent two-loop approximation to the quark density with a recent calculation of the same quantity at the one-loop level in a variant of HTL-screened perturbation theory. Besides pointing out conceptual problems with the latter approach, we show that it severely over-includes the leading-order interaction effects, while including none of the plasmon terms, which is the main reason for requiring improved resummation schemes. Received: 27 June 2002 / Revised version: 23 September 2002 / Published online: 31 January 2003     

Whispering-gallery modes in a barrel-shaped dielectric resonator

We experimentally study a new type of resonator, namely, a barrel-shaped dielectric resonator with whispering-gallery modes which is formed by the cutting dielectric hemisphere. Compared with a hemispherical dielectric resonator, the E type oscillation spectrum of such a resonator is rarefied with respect to the azimuthal index. Comparative analysis of the electromagnetic characteristics of the barrel-shaped dielectric resonator and half-disk dielectric resonators shows that the radiation losses of the mode energy from the spherical surface are smaller than those from the cylindrical surface. This fact stimulates the high values of the internal Q-factor of modes of the barrel-shaped dielectric resonator. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 12, pp. 1041–1048, December 2005.     

On the computation of sound in free and wall-bounded domains

A new Dispersion-Relation-Preserving (DRP) scheme has been developed using the Lax-Wendroff methodology. Two collocated grids are placed in a staggered formation and a staggered DRP scheme is used to calculate the spatial differentiation of the propagation and convection terms. A staggered filtering scheme of a six points stencil is developed to complete the transformation from one grid to another. Existing DRP Runge-Kutta schemes are used for the time marching. Stability limits and accuracy issues are investigated using a simple 1D advection equation. The new method is then tested for monopole and quadrupole radiation, diffraction effects of an aperture in a wall, and convection effects of shear flow. All demonstrate the good accuracy and numerical stability of the new method.     

On simultaneous linear extensions of partial (pseudo)metrics

We consider the question of simultaneous extension of (pseudo) metrics defined on nonempty closed subsets of a compact metrizable space. The main result is a counterpart of the result due to Künzi and Shapiro for the case of extension operators of partial continuous functions and includes, as a special case, Banakh's theorem on linear regular operators extending (pseudo)metrics.