Selectively protected galactose derivatives for the synthesis of branched oligosaccharides

Synthesis and characterization of several new anomerically pure galactose derivatives, based on simple and effective protective group manipulations of benzyl β-d-galactopyranoside, are reported. The monosaccharides described contain selectively protected/deprotected hydroxyl functionalities at their 1,2,3,4- and 6-positions rendering them useful as building blocks for construction of branched oligosaccharides.     

Physical processes underlying the development of shear turbulence

A physical model of the development of turbulence in free shear flows is proposed. The model is based on the results of numerical simulations of turbulent flow development. The main ideas of the proposed theory of turbulence are stated as follows: the onset of turbulence begins with the formation of large vortices; spectral energy transfer involves both direct and inverse cascades; and the inertial range of the energy spectrum develops as a result of concurrent direct and inverse cascades. The dominant physical factors that determine the spectrum include Joukowski forces.     

Computing the sound power in non-uniform flow

An expression for the sound power in an annular duct with swirling mean flow is derived in the high-frequency limit relevant to fan aeroacoustics. The sound power is expressed in terms of the duct normal modes which are computed for several mean flows. It is shown that the mean flow non-uniformity modifies both the pressure-dominated modes and the expression for the sound power. The pressure-dominated modes are not orthogonal and thus one must account for interference between the different radial modes. The interference effects are small for the case of a potential mean flow. For a vortical mean flow interference terms may become significant.