SummaryThe bovine prion protein gene (PRNP) potentially plays a key role in the development of bovine spongiforme encephalopathy (BSE). In species other than cattle, expression of BSE is clearly dependent on polymorphisms in this gene. PRNP has previously been assigned to the bovine chromosome 13 (BTA13). The present study is an attempt to embed PRNP into a grid of published marker maps. A genetic mapping panel consisting of 266 animals has been genotyped with 19 microsatellites and a polymerase chain reaction‐amplified polymorphism within the PRNP coding region. The linear locus order and the relative distances of these loci are presented. Our linkage map spans 111.6c m of BTA13. The results suggest PRNP to be located telomeric of the microsatellite BMS1580 and centromeric of BM9248 with a log‐likelihood of 2. Our findings further characterize the vicinity of PRNP on BTA13.

The two-dimensional incompressible Navier-Stokes equations including a low-Reynolds-number two-layer k-tau turbulence model are solved by an implicit time-stepping routine using the method of artificial compressibility. The two-layer model uses a transport equation for the turbulent kinetic energy k and a new algebraic relationship for the turbulent time scale tau near the wall but reverts to the two-equation k-tau turbulence model in the bulk of the flow away from the wall. The algebraic relationship for the turbulent time scale tau and the eddy-viscosity damping function f(mu) are validated by direct numerical simulation data and asymptotic analysis of near-wall turbulence. A fifth-order upwind-biased differencing scheme is used to discretize the convective and pressure terms and second-order central differences are employed for other spatial derivatives. The nonlinear equations are solved using the preconditioned generalized minimal residual technique in conjunction with numerical linearization. A LD(-1)U factorization of the approximate Jacobian matrix is used as preconditioning matrix. The iterative scheme has good vectorization properties and runs at about 160 Mflops on one processor of a Gray Y-MP. The results for turbulent channel hows at low Reynolds numbers are in good agreement with direct numerical simulation data even in the viscous sublayer. Compared with experimental data, the simulation of the turbulent flow over a backward-facing step in a parallel and a diverging channel shows a better agreement for the reattachment length than comparable two-equation models.

The flow structure associated with a line bubble plume in shallow water is investigated. G. I. Taylor has proposed the use of such plumes as wavebreakers. To be effective the surface current generated should be stable for a distance of the order of the wavelength, which in turn could be several times the depth. It appears that the formation of recirculating cells can affect the wavebreaking potential of line bubble plumes. The paper presents observations and measurements of the cell structure associated with line bubble plumes as obtained in a model towing basin of dimensions 1 x 1 x 40 m. A recirculating region was found on both sides of the plume, but the secondary (and higher-order) cell structures proposed by other investigators were not observed. The primary cells were found to be appreciably longer than those reported in the literature for vertical plane jets. The difference can in part be attributed to different definitions of cell length. The definitions used herein are based on observables, both on the water surface and in the interior of the flow, and they lead to consistent measures of length. Bubble-plume parameters (such as entrainment coefficient) are known to depend on gas flow rate, and it was found that the length of the primary cell is a weak function of this variable as well. Additional experiments with a vertical plane jet were conducted for comparison. Longer cells than those previously reported were again observed. The paper contains a complete theory for line bubble plumes, including the effects of compressibility, bubble slip and finite release volume, as well as a simplified similarity analysis useful in estimating plume properties and horizontal-current depth and velocity.