Investigation of pre-separation boundary layer flows on the basis of various algebraic models of turbulence

The problem of the three-dimensional incompressible turbulent boundary layer developing ahead of a circular cylinder mounted at right angles on a flat plate is considered. The direction of the uniform approach stream is normal to the leading edge of the plate. The turbulence is simulated by means of five different isotropic algebraic models of eddy viscosity. The boundary layer equations are solved numerically by means of a second-order-accurate implicit finite-difference method. The principal characteristics of the flow obtained on the basis of the turbulence models selected are compared for a free-stream Reynolds number Re = 10⁷.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 36–43, November–December, 1991.     

Precise determination of Stokes shifts in stimulated-Brillouin-scattering-active substances with the use of Brillouin loop lasers pumped by Gaussian monochromatic beams

A method for determination of Stokes shifts in stimulated Brillouin scattering is suggested and implemented; the method is based on the jumplike behavior of the spatial structure of the emission of a Brillouin loopscheme laser upon change in the loop length in the vicinity of Δk _B L=π(2n+1), where Δk _B is the Brillouin shift,L is the loop length, andn is an integer.     

Vector meson production and [SU(3) ⊗SU(3)]coll symmetry

The collinear production of a vector meson is considered in the scattering of pseudoscalar mesons on baryons. Relations between the experimental quantities, following from the symmetry [SU(3) SU(3)]_coll, are obtained.On leave from the Nuclear Research Institute of the Czechoslovak Academy of Sciences, e.     

Integrable model of the interaction of counter-propagating weakly nonlinear waves on the fluid boundary in a horizontal electric field

Theoretical and Mathematical Physics - We consider the nonlinear dynamics of the free surface of a high-permittivity dielectric fluid in a strong horizontal electric field. In the framework of the...     

High-reflectivity multilayer mirrors for a vacuum-ultraviolet interval of 35-50nm

Sc-Si multilayers are suggested as high-reflectivity coatings for a VUV interval of 35-50 nm. Fabricated mirrors show normal-incidence reflectivity of 30-54%, which is high enough for effective manipulation of the beams of compact-discharge, laser-driven x-ray lasers. The values obtained are not, however, limits for Sc-Si coatings. Theoretical estimations as well as electron microscopy studies of Sc-Si interfaces indicate a large potential for a further increase in their reflectivity.     

Bifurcating fragmentation behavior of gas-phase tryptic peptide dications in collisional activation

Collision-activated dissociation (CAD) of tryptic peptides is a cornerstone of mass spectrometry-based proteomics research. Principal component analysis of a database containing 15,000 high-resolution CAD mass spectra of gas-phase tryptic peptide dications revealed that they fall into two classes with a good separation between the classes. The main factor determining the class identity is the relative abundance of the peptide bond cleavage after the first two N-terminal residues. A possible scenario explaining this bifurcation involves trans- to cis-isomerization of the N-terminal peptide bond, which facilitates solvation of the N-terminal charge on the second backbone amide and formation of stable b(2) ions in the form of protonated diketopiperazines. Evidence supporting this scenario is derived from statistical analysis of the high-resolution CAD MS/MS database. It includes the observation of the strong deficit of a(3) ions and anomalous amino acid preferences for b(2) ion formation.