A new a posteriori error estimate for convection–reaction–diffusion problems

A new a posteriori error estimate is derived for the stationary convection–reaction–diffusion equation. In order to estimate the approximation error in the usual energy norm, the underlying bilinear form is decomposed into a computable integral and two other terms which can be estimated from above using elementary tools of functional analysis. Two auxiliary parameter-functions are introduced to construct such a splitting and tune the resulting bound. If these functions are chosen in an optimal way, the exact energy norm of the error is recovered, which proves that the estimate is sharp. The presented methodology is completely independent of the numerical technique used to compute the approximate solution. In particular, it is applicable to approximations which fail to satisfy the Galerkin orthogonality, e.g. due to an inconsistent stabilization, flux limiting, low-order quadrature rules, round-off and iteration errors, etc. Moreover, the only constant that appears in the proposed error estimate is global and stems from the Friedrichs–Poincaré inequality. Numerical experiments illustrate the potential of the proposed error estimation technique.     

Cold-electron bolometer arrays

To improve electron cooling, expand the dynamic range, and match the input and output impedances, series/parallel arrays of cold-electron bolometers have been developed, manufactured, and measured at temperatures from 50 to 350 mK. The bolometers are integrated into cross-slot antennas to analyze the polarization of cosmic microwave background radiation at a frequency of 345 GHz. The maximum temperature response is 6.5 μV/mK. The noise-equivalent electric power at a temperature of 300 mK is 1.2 × 10^?17 W/Hz^1/2.     

Reflecting electromagnetic waves from a surface of TbMnO3 with sinusoidal antiferromagnetic structure

A spectrum of coupled waves in TbMnO₃ with sinusoidal antiferromagnetic structure is investigated. Expressions for the activation frequencies are obtained, and temporal and spatial permittivity dispersions are considered. Frequency dependences for the reflectance of electromagnetic waves from the TbMnO₃ surface are calculated.     

Direct numerical Euler method for finding extrema of nonlocal functionals

A direct numerical method is considered, which is a generalization of the Euler method for nonlocal functionals depending on functions with differently signed deviations, and also for nonlocal functionals depending on functions of two independent variables.     

Formation of mixed J-aggregates of cyanine dyes stimulated by Eu<Superscript>+3</Superscript> cations

The block mechanism of the formation of J-aggregates from the dimers of various dyes in an aqueous solution under the action of the multiply charged Eu⁺³ cation was considered for the first time. It was shown that the structure and the position of the absorption maximum of the mixed J-aggregates are determined by the length of the dye chromophore moiety. It was concluded that the mixed J-aggregates are of interest as nanosized optical elements with varying optical and electronic properties depending on the structure of cyanines used.     

Determination of temperature in a plasma jet emanating from a plasma torch with sectioned inter-electrode insert from the molecular emission spectrum of nitrogen

Results of application of a method for measuring the distribution of temperature in a nitrogen plasma jet emanating from a dc plasma torch with sectioned inter-electrode insert from the relative intensities of the molecular emission bands of nitrogen in the N₂ ⁺(B²Σ_u ⁺ − X²Σ_g ⁺) first negative and N₂(C³Π_u ⁺ − B³Π_g ⁺) second positive systems are reported. The emission spectra were registered using a small-size spectrometer with medium-range spectral resolution enabling a contour analysis of ro-vibrational bands in molecular emission spectra. The obtained distribution of temperature was compared with the distribution that was determined from the emission lines due to copper atoms and with the mean-mass plasma temperature of the air plasma jet.     

Thermal multifragmentation in p + Au interactions at 2.16, 3.6 and 8.1 GeV incident energies

Multiple emission of intermediate-mass fragments has been studied for the collisions p + Au at 2.16, 3.6 and 8.1 GeV with the FASA setup. The mean IMF multiplicities for events with at least one IMF are equal to 1.7, 1.9 and 2.1 (±0.2) respectively. The multiplicity, charge distributions and kinetic energy spectra of IMF are described in the framework of a intranuclear cascade model followed by the statistical multifragmentation model. However, between the two parts of the calculation the excitation energies and the residual masses and charges are modified to take into account the losses during expansion. The results support a scenario of true thermal multifragmentation of a hot and expanded target spectator. Received: 15 December 1997 / Revised version: 24 April 1998     

Associated production of ϕ mesons and neutral kaons in the EXCHARM experiment

The features of the associated production of ? mesons and neutral kaons are studied on the basis of data obtained at the EXCHARM spectrometer (Serpukhov accelerator) in neutron—carbon interactions at neutron-beam energies in the range 20–70 GeV. The cross section for the inclusive associated production of ? and K ⁰/-K ⁰ is obtained. The fraction of processes allowed by the Okubo-Zweig-Iizuka rule is estimated in the reactions of ?-meson inclusive production.     

Aza-substitution,benzo-annulation effects and catalytic activity of <Emphasis Type="Italic">β</Emphasis>-octaphenyl-substituted tetrapyrrolic macroheterocyclic cobalt complexes. I. heterogeneous catalysis

The influence of the size of conjugated π-system on catalytic activity of cobalt complex with β-octaphenylporphyrin and its tetraaza-, tetrabenzo and tetrabenzotetraaza derivatives was studied in present work. It is found that catalytic activity for oxidation of sulfur-containing compounds increases under extension of conjugated macrocycle system according to the following series CoP < CoBP ≤ CoPz < CoPPz ? CoPc.