The Developing Laminar Flow and Pressure Drop in the Entrance Region of Annular Ducts

BRIEF NOTES the most frequently used assumption is that of uniform flow at inlet, which simulates the actual condition of well-rounded entrance. This assumption was adopted in the present analysis and thus, at x = 0, the axial velocity and pressure are uniform with values u 0 and p 0 , respectively. Following the procedure suggested in TT/32, 2.03 for ex = TT/16, 1.92 for a = ir/8, and 1.86 for a = 7r/4) seem to conform with the asymptotic value of 1.82 obtained in The most commonly used parameters for presenting the pressure results are the product of the friction factor and Reynolds number fRe, and the pressure defect K. In the present analysis, the friction factor was defined as: f=(D h /2)(-dp/dx)/(pu 2 b ), and hence The pressure defect is normally defined as: , which reduces to the following nondimensional form: Results based on equations Acknowledgments The authors gratefully acknowledge the support provided for this research by the Natural Sciences and Engineering Research Council of Canada. References 1 Shah, R. K., and London, A. L., Laminar Flow Forced Convection in Duels, Academic Press, 1978. 2 Wendt, R. L., and Wiginton, C. L., "Incompressible Laminar Entrance Flow in a Circular Sector Duct," JOURNAL OF APPLIED MECHANICS, Vol. 98, 1976, pp.357-359. 3 Munis, A A., "Analysis of Laminar Fluid Flow in the Entrance Region of Circular Sector Ducts," M.Sc. Thesis, University of-Manitoba, 1981. 4 Sparrow, E. M., Lin, S. H., and Lundgren, T. S., "Flow Development in the Hydrodynamic Entrance Region of Tubes and Ducts," Physics of Fluids, Vol. 7, 1964, pp. 338-347. 5 Sparrow, E. M., and Lin, S. H., "The Developing Laminar Flow and Pressure Drop in the Entrance Region of Annular Ducts," Journal of Bask Engineering, Vol. 86,1964, pp. 827-834. 6 Fleming, D. P., and Sparrow, E. M., "Flow in the Hydrodynamic Entrance Region of Ducts of Arbitrary Cross-Section," ASME Journal of Heat Transfer, Vol. 91,1969, pp. 345-354. Numerical Results The resulting values of Le are listed i

Sp1 is essential for both enhancer-mediated and basal activation of the TATA-less human adenosine deaminase promoter.

Tissue-specific expression of the human adenosine deaminase (ADA) gene is mediated by transcriptional activation over a thousand-fold range. Cis-regulatory regions responsible for high and basal levels of activation include an enhancer and the proximal promoter region. While analyses of the T-cell specific enhancer have been carried out, detailed studies of the the promoter region or promoter-enhancer interactions have not. Examination of the promoter region by homology searches revealed six putative Sp1 binding sites. DNase I footprinting showed that Sp1 is able to bind these sites. Deletion analysis indicated that the proximal Sp1 site is required for activation of a reporter gene to detectable levels and that the more distal Sp1 sites further activate the level of expression. Inclusion of an ADA enhancer-containing fragment in these deletion constructions demonstrated that Sp1 sites are also essential for enhancer function. Apparently Sp1 controls not only low level expression but is also an integral part of the mechanism by which the enhancer achieves high level ADA expression. Mutagenesis of a potential TBP binding site at base pairs -21 to -26 decreased activity only two-fold indicating that it is not essential for transcriptional activation or enhancement