Validation of averaged equations for thermal vibrational convection in near-critical fluidsValidation d'équations moyennées pour l'étude de la convection vibrationnelle dans les fluides supercritiques.

Within an averaging approach, the governing equations and effective boundary conditions describing both the average and pulsation motion of a near-critical fluid subjected to high-frequency vibrations are obtained. Vibrations induce the non-homogeneities in average temperature. Owing to these non-homogeneities, the average flows can be generated even in isothermal cavity under weightlessness. These flows are examined for 1D and 2D configurations. The direct numerical simulations fulfilled earlier confirm the averaged model, we obtain the same flow structures by essentially smaller requirements for computational time. To cite this article: A.Vorobev et al., C. R. Mecanique 332 (2004).     

Asymmetric vibration effect on the flow of a thin layer of a viscoplastic fluid

The gravity field and vibration effect on the flow of a viscoplastic fluid layer along an inclined solid surface is investigated. The rheological properties of the fluid are described using the Williamson equation. The vibrations are shown to have a considerable effect on the fluid layer flow intensity and direction; in particular, they generate a considerable mean fluid flow even in the cases in which the fluid is at rest in the absence of the vibrations.     

Mean flow generation in a two-layer system under circularly polarized vibrations

The behavior of a system of two immiscible isothermal fluids in a cylindrical reservoir under circularly polarized vibrations orthogonal to the cylinder axis is considered. The fluctuating flow is studied with account for dissipation in the near-interface vortex layer. Different mean flow generation mechanisms are discussed. It is shown that the main role in the generation is played by nonlinear processes in the near-interface boundary layer, which can be taken into accounted by applying effective boundary conditions. The mean flow structure and intensity are studied. The results obtained are compared with experimental data.     

The phase shift for reflection of elastic waves in hexagonal piezoelectric crystals

The reflection of a transverse wave from the surface of a piezoelectric crystal of class 6 is considered for the case when the reflection plane coincides with or is close to the plane of transverse isotropy. The dependence of the phase shift of the reflected wave on crystal piezomoduli and other parameters is investigated. Reflection angles corresponding to maximum sensitivity of the phase shift φ to a change in piezomoduli are found. The influence of the piezoeffect on the reflection phase shift turns out to be most pronounced at grazing incidence along the transverse isotropic direction. Then the switching on of the (arbitrarily small) piezoeffect changes the phase from 0 to π, which gives annihilation between incident and reflected bulk waves.     

The value of the entropy at the surface of paraboloids

The author studies the magnitude of the entropy at paraboloid surfaces in supersonic perfect gas flow using the numerical results of the solution to the problem of three-dimensional flow past a blunt nose [1]. We first discuss briefly the state of the problem and information on the method of [1] and then present the main conclusions of the study and some data confirming these conclusions.In conclusion, the author thanks V. V. Rusanov for valuable comments and discussion and E. I. Nazhestkin for performing the computer computations and participating in the analysis of the computational results.     

Evaluation of hydrogen ion concentrations in prostates from rats and dogs using fluorescent confocal microscopy

The knowledge of intracellular spatial distribution of pH in prostates in animal models reflective of human prostate may have implications for drug development upon pH dependent drug delivery and activity. Freshly dissected prostate tissues (in vitro) or the entire prostate gland (in vivo) were loaded with fluorescent dyes and viewed using confocal microscopy. Images were initially taken in tissues perfused with RPMI-1640 medium. Calibration in situ was performed with high potassium buffers of known pH containing nigericin. Acetoxymethyl ester carboxy-SNARF-1 was visible in epithelial cells (but not stroma) in rat and dog prostates. The pH of lysosomes in prostate epithelial cells was 5.2 as determined by fluorescence of Lyso Sensor Green DND-189. A method of in situ confirmation of tissue viability was developed by a secondary loading and visualization of the BCECF fluorescent dye. Besides the direct measurement of the pH in rat and dog tissues (pH ≈ 7.0), a method of pH measurement in prostate tissue (rather than in cell culture) was developed.