ALBERT

Description: In most work on the theory of stability of laminar flow, infinitesimal disturbances only have been considered, so that only the initial growth of the disturbance has been determined. It is the object of the present paper to extend the theory to larger amplitudes and to study the mechanics of disturbance growth with the inherent non-linearity of the hydrodynamical system taken into account. The Reynolds stress (where averages are taken with respect to some suitable space coordinate) is the fundamental consequence of the non-linearity, and its effects can be anticipated as follows. Initially a disturbance grows exponentially with time according to the linear theory, but eventually it reaches such a size that the transport of momentum by the finite fluctuations is appreciable and the associated mean stress (the Reynolds stress) then has an appreciable effect on the mean flow. This distortion of the mean flow modifies the rate of transfer of energy from the mean flow to the disturbance and, since this energy transfer is the cause of the growth of the disturbance, there is a modification of the rate of growth of the latter. It is suggested that, in many cases, an equilibrium state may be possible in which the rate of transfer of energy from the (distorted) mean flow to the disturbance balances precisely the rate of viscous dissipation of the energy of disturbance. A theory based on certain assumptions about the energy flow is given to describe both the growth of the disturbance and the final equilibrium state, and application is made to the cases of Poiseuille flow between parallel planes and flow between rotating cylinders. The distorted mean flow in the equilibrium state can be calculated and from this, in the latter case, the torque required to maintain the cylinders in motion. Good agreement is obtained with G. I. Taylor's measurements of the torque for the case when the inner cylinder rotates and the outer cylinder is at rest. © 1958, Cambridge University Press. All rights reserved.

Description: An experiment is described in which 64 individually-fed pigs were used to investigate the effects of dietary protein status, administration of aureomycin and hexoestrol implantation on growth, efficiency of feed utilization and carcass conformation. The results of hexoestrol implantation and interactions with the other two variables only are reported here. The pigs were implanted at 120 lb. and again at 150 lb. and killed at 200 lb. live-weight.The main features of hexoestrol treatment were:1. Body length taken from the anterior edge of the aitch bone to the junction of first rib and sternum was significantly increased by 9·75 mm.2. The percentage lean in the carcass was increased by 0·82%, representing approximately 1¼ lb. more lean meat in a 155 lb. carcass. The water content of the lean was increased but not significantly.3. Body fat was reduced but this was not reflected in a significant change in back fat measurements.4. No changes could be detected in the thyroid or adrenals, but whereas male castrates showed little effect of treatment on other organs apart from a certain amount of urethritis, the intact female manifested major changes in the genital tract. The uterus in particular was greatly enlarged and ovarian activity obviously reduced. The implications of these effects are being examined.5. There was no response to treatment in terms of growth rate or efficiency of feed utilization.