Stability of steady-state non-Newtonian fluid layer flow

The stability of the steady-state plane-parallel flow of a non-Newtonian fluid layer in the gravity field along an inclined rigid surface is investigated. It is shown that the most dangerous are the long-wave perturbations propagating over the free surface. The stability maps are plotted for such perturbations in the Reynolds number — gravity parameter plane. With increase in the gravity number the layer flow becomes less stable. The layer deviation from the vertical lines stabilizes the flow.     

Resonance excitation of polaritons and plasmons at the interface between a uniaxial crystal and a metal

A resonance is theoretically predicted in which a plane electromagnetic wave in a transparent optically uniaxial crystal, reflected from its metallized surface, creates a wave field at the interface whose intensity is considerably higher than the intensity of the incident wave. In the crystal, a high-intensity (bulk or surface) polariton is excited, whereas, in the metal, a large-amplitude localized plasmon is excited. The structure of the fields created in the crystal is close to that of the fields of bulk polaritons at the boundary with a perfectly conducting surface. The nonideality of the metal is taken into account in the Leontovich impedance approximation. Conditions are found under which the resonance is accompanied by a full transformation of the incident wave into a polariton-plasmon localized near the interface. This coupled wave can be considered as a pumped eigenmode. The intensity of the wave field localized at the boundary can amount to 10–15 times the intensity of the incident wave in the visible range. The resonance half-width with respect to the angles of incidence amounts to a few degrees. In the infrared range, the excitation factor can be an order of magnitude higher, while the resonance half-width sharply decreases down to about 0.1° for a wavelength of 5 μm. Conditions are obtained for the resonance excitation of high-intensity bulk polaritons that arise as reflected modes propagating at a small angle to the boundary. The phenomena investigated are completely attributed to the anisotropy of the crystal.     

Asymmetric Ir-catalyzed hydrogenation of 4-R-1,3-dihydro-2H-1,5-benzodiazepin-2-ones using a novel phosphoramidite ligand

Russian Chemical Bulletin - A novel chiral phosphoramidite ligand, (Sa)-2-[N-ethyl-N-(1-naphthylmethyl)amino]-dinaphtho[2,1-d:1´,2´-f][1,3,2]dioxaphosphepane, was obtained and tested in...     

Spectral anomalies of waveguide electromagnetic modes in layered structures

A theoretical study of electromagnetic guided eigenwaves in two-and three-layered plates with metallized surfaces is accomplished. The appropriate dispersion equations are explicitly analyzed using the discretization first introduced by Mindlin in the theory of Lamb acoustic waves. It is shown that the dispersion branches of independent eigenmode families cross each other in the nodes of a grid formed by two infinite series of bond lines. The latter represent the dispersion curves for homogeneous plates with permittivities ɛ₂ or ɛ₂ coinciding with those for the layers of the waveguide. It is proved that, beyond nodes of the grid, the dispersion curves do not intersect bond lines, which thus provides definite “corridors” for these curves. The dispersion lines have a wavy (“zigzag”) form in the grid zone and remain smooth beyond the grid. The crossing branches have coinciding cutoff frequencies. In dimensionless coordinates “slowness (S) vs. frequency (f),” the branches S _l (f) have two asymptotic levels: S = √ɛ₁ and S = √ɛ₂. At the lower level, the spectrum forms a steplike terracing pattern with a progressive closing to the asymptote of a succession of dispersion curves, which change each other at this level with further going up to the next asymptote. An extension to anisotropic waveguides with layers made of uniaxial crystals is considered. The text was submitted by the authors in English.     

Experimental investigation of the distribution of the charged particle concentration in the interelectrode gap of a freely burning atmospheric arc

The results of an investigation of the distribution of the charged particle concentration in the interelectrode gap of an arc burning freely in an air atmosphere for currents I = 50–100 A by means of a moving dual electric probe are presented. The methods used enable the probe voltage-current characteristic to be measured in times ～ 100 µs. This makes it possible to estimate the distribution of the charged particle concentration in the interelectrode gap during a single experiment. The charged particle distributions obtained are compared with the distribution of the various glow-level zones [1, 2]. On the basis of this comparison it is shown that the characteristic transverse dimension of the zone in which the current flows in the arc far away from the electrodes is of the order of a centimeter.     

Mechanics of lung bullas

During the development of emphysema the alveolar walls are destroyed and cavities, called bullas are formed. If the respiratory pathways leading to a bulla are free, then the bulla will be in communication with the atmosphere and during breathing its volume may change. From x-ray observations it is known that bullas may exhibit different mechanical behavior (bullas of variable or constant volume). Moreover, the walls of the bullas may have different mechanical properties. This is indicated, for example, by the fact that in some bullas gas exchange takes place, while in others it does not. The mechanical properties of bullas and, moreover, their behavior during respiration have not received much attention. It was therefore considered desirable to construct a mathematical model of lungs containing bullas in order to establish the dependence of the mechanical behavior of the bullas on the parameters of the pulmonary parenchyma and respiratory pathways.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.4, pp. 3–12, May–June, 1993.     

Luminescence of stereoisomers of the open form of spiropyran in polymer films

Conclusions Photocoloration of spyropyran in polymethyl methacrylate and polystyrene matrices at 293 and 77 K results in the formation of a set of photoproducts with individual spectral characteristics, and the structure of a certain stereoisomer was assigned to each photoproduct based on these characteristics.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2255–2259, October, 1988.