Least-squares approach to problems with inexact values of the function and its argument
Least-squares approach to problems with inexact values of the function and its argument
A.B. Knurenko, Yu.P. Pyt'ev
A new approach is suggested to least-squares treatment of the problem of reproducing functional dependences from measurement data with errors in the values of the function and its argument.
Show AbstractChain of Bogolyubov equations for quantum systems on connected clusters
Chain of Bogolyubov equations for quantum systems on connected clusters
I.P. Bazarov, P.N. Nikolaev
A system of equations is derived for Bogolyubov statistical particle operators on connected clusters that makes it possible to construct a unified perturbation theory for the homogeneous and the ordered phases irrespective of the type of symmetry of a many-particle system.
Show AbstractHomogeneous isotropic cosmological models in the six-dimensional Kaluza-Klein theory
Homogeneous isotropic cosmological models in the six-dimensional Kaluza-Klein theory
Yu.S. Vladimirov, Americo Peraza Alvarez
Exact homogeneous isotropic open cosmological solutions to the Einstein equations of the six-dimensional Kaluza-Klein theory are found. Their analysis is presented and a comparison with analogous cosmological solutions in the five-imensional Kaluza-Klein model and the four-dimensional Fridman model is carried out.
Show AbstractFocusing effect of the ionosphere on the stochastic properties of signal envelope
Focusing effect of the ionosphere on the stochastic properties of signal envelope
A.G. Vologdin, V.D. Gusev, L.I. Prikhod'ko
The focusing effect of ionospheric plasma waves on the probabilistic properties of the short-wave signal envelope is studied. It is shown that if only one envelope time realization is available, effective statistical characteristics should be used. Effective differential and integral probability distributions for the Rayleigh-Rice laws are obtained and analyzed. The role of effective statistical distribution moments is studied in a specific problem. The main conclusion made in the study is that the focusing effect is very important in processing fast fluctuations of the short-wave signal envelope, with standard probability distributions undergoing considerable distortions.
Show AbstractPhotoenergetics of molecular forms of acridine dyes in polymer matrices
Photoenergetics of molecular forms of acridine dyes in polymer matrices
A.V. Grachev, A.N. Ponomarev, V.I. Yuzhakov
The spectral and luminescence properties of acridine yellow and acridine orange in polyvinyl alcohol matrices were studied. The concentration dependences of the relative quantum yield of fluorescence show that in the systems studied the dye molecules form dimers and more complex associates. The quantwn yield of fluorescence from acridine yellow dimers is higher than that from monomers. The quantum yields and fluorescence decay times of various acridine molecular forms were determined, and the patterns of excitation energy transfer between these forms were studied. The critical radii of nonradiative energy transfer were calculated. The kinetic data show that excited monomeric acridines undergo rotational relaxation while excited associates do not.
Show AbstractOn the difference in concentration dependences of lasing efficiency of Rhodamine 6G aqueous and ethanol solutions
On the difference in concentration dependences of lasing efficiency of Rhodamine 6G aqueous and ethanol solutions
A.I. Akimov, L.V. Levshin, A.M. Saletskii
Concentration dependences of the spectral and energy parameters of the lasing action by aqueous and ethanol solutions of Rhodamine 6G were studied. It was found that aqueous solutions of this dye generate two-band radiation.
Show AbstractPhotoluminescence of $Ce^{3+}$ ions in $Ca_{1-x}Sr_xS$ solid solutions
Photoluminescence of $Ce^{3+}$ ions in $Ca_{1-x}Sr_xS$ solid solutions
A.N. Bel'skii, 0. Krachni, V.V. Mikhailin, and M.-L.Yu. Allsalu
Luminescence spectra of $Ce^{3+}$ in $Ca_{1-x}Sr_xS$ ($0 < x <1$) have been measured following excitations in the activator's band and at the fundamental absorption edge. It is shown that the model of a crystal field of cubic symmetry can be used to explain, in general, the spectrum evolution with changing concentration upon activator's excitation (with the exception of $x$ = 0.05 and 0.9), but this model cannot account for the peculiarities of the spectra arising upon excitation at the fundamental absorption edge. It is suggested that with band-to-band excitation a radiation-induced distortion of part of cerium luminescence centers occurs. A step-like variation of the luminescence parameters was detected as $x$ changed from 0 to 1, which seems to indicate that solid solutions are locally inhomogeneous.
Show AbstractMechanisms of light control of the quantum yield of in situ phytoplankton fluorescence as studied by pulsed laser fluorometry
Mechanisms of light control of the quantum yield of in situ phytoplankton fluorescence as studied by pulsed laser fluorometry
M.Yu. Gorbunov, A.M. Chekalyuk
The mechanisms of the effect of natural illuminance on the initial $(\Phi^0)$ and maximum $(\Phi^{max})$ quantum yields of phytoplankton fluorescence and the efficiency of the initial stages of photosynthesis were studied. Remote measurements of $\Phi^0$ and $\Phi^{max}$ in phytoplankton samples were performed using the double-beam laser method. It was found that the principal mechanisms of control of the fluorescence yield by the light are the "energy-dependent" fluorescence quenching that occurs at illuminances about 5-20 klx and the photoinhibition of the initial stages of photosynthesis at illuminances of 30-100 klx.
Show AbstractInfluence of small losses in layers of thin-layer interference filters on their optical parameters
Influence of small losses in layers of thin-layer interference filters on their optical parameters
A.V. Kosar', E.V. Putrina
The influence of small losses in layers of thin-layer interference filters (containing two layers of the same thickness in the period) on their optical parameters was analyzed. Analytical expressions were obtained that help determine possible refractive indices of the medium to be matched and the wavelengths of matching as dependent on the losses. With a large number of periods of the filters, these parameters were shown to be independent of the number of periods and be determined only by the magnitude of specific losses.
Show AbstractOn the possibility of effective transformation of broad-band pumping into narrow-band Stokes radiation during stimulated Raman scattering in a selective resonator
On the possibility of effective transformation of broad-band pumping into narrow-band Stokes radiation during stimulated Raman scattering in a selective resonator
Yu.E. D'yakov
The theory of Raman laser is extended to the case of strong nonmonochromatic fields when the width of the pumping frequency spectrum is arbitrary and a transition saturation becomes possible. The resonator is assumed to include a selective element that narrows the spectrum of the generated Stokes wave. The conditions are determined at which the lasing efficiency may be made close to 100%.
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