Dynamics of fluorescence of solid solutions of quantum dots and the organic dye DODCI: Experiment and numerical simulation

The fluorescence of solid solutions of CdSe/ZnS quantum dots and the organic dye DODCI is investigated. It is shown that nonradiative transfer of electronic excitation energy to dye molecules, which with some probability lose their acceptor properties as a result of photoisomerization or photodegradation, is responsible for a significant increase in the fluorescence intensity of a donor. The degree of polarization of the donor fluorescence attains values exceeding 0.5, which is due to the difference in the fluorescence quantum yields of donors with different orientations of the oscillator with respect to the electric vector of an excitation light wave. A numerical simulation of the experimentally observed dependences is performed.     

Failure of an infinitely compressible composite containing a finite cylindrical crack in axial compression

S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of the Ukraine. Translated from Prikladnaya Mekhanika, Vol. 31, No. 9, pp. 15–23, September, 1995.     

Average and local magnetic moments on Fe atoms in microcrystalline and amorphous Fe100−xPx alloys

We have measured the concentration dependence of the average magnetic moment per Fe atom _Fe(x) in microcrystalline and amorphous Fe-P alloys obtained over a wide concentration range using electrochemical deposition. The model of local magnetic moments has been used to described _Fe(x). On the basis of this model the effects of phosphorus on the value _Fe are explained in terms of the parameters of the local environment of the Fe atom.     

Mössbauer investigation of amorphous-to-crystalline transformation of Fe62Ni16B14Si8 by isothermal annealing

Room temperature transmission Mössbauer spectra of Fe₆₂Ni₁₆B₁₄Si₈ ribbons, annealed in vacuum for time periods ranging from 5 to 60 minutes at the crystallization temperatureT _x=720 K, have been used to investigate the crystallization mechanism by isothermal annealing. Reorientation of the magnetic anisotropy almost normal to the ribbon plane was observed and correlated to the annealing time dependence of the mean hyperfine field (HF) of the amorphous component. Crystallization started at the surface before the bulk and was found to occur in two steps: a metastable equilibrium of the amorphous phase with (FeNi), (FeNi)Si and t-(FeNi)₃B, followed by the decomposition of t-(FeNi)₃B into t-(FeNi)₂B and (FeNi). The increase of the mean magnetic moment at the Fe sites as compared to related iron-based alloys was attributed to compositional small Ni additions.     

Lattice gas state functions

State equations for simple lattice systems are constructed by extending the Gibbs method to a non-equilibrium system.In memory of D. N. Zubarev, teacher and scientist, whose advice and attention are gratefully remembered.The idea of constructing such a model (on the basis of the vacancy model of condensed matter proposed by the author) belongs to D. N. Zubarev.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 105, No. 3, pp. 478–490, December, 1995.     

Estimating the observation parameters of a switching Poisson stream at random moments

We investigate the properties of maximum likelihood estimators in observation schemes of random variables that arrive at random time moments on a Poisson trajectory defined on some ergodic process.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 59, pp. 98–105, 1986.