Effect of the left lateral recumbent position compared with the supine and upright positions on placental blood flow in normal late pregnancy.
The placental blood flow was assessed by the 99mTc accumulation method in 10 normal pregnancies in the left lateral recumbent position accomplished by a 15 degree wedge and in the supine position. The postural change caused a 17% decrease in the mean placental accumulation rate, which was not statistically significant. Ten patients were moved from the left lateral recumbent position to the upright position, which caused a statistically significant 23% decrease in the mean accumulation rate. Other haemodynamic variables studied were the maternal heart rate and the systolic and diastolic blood pressures. The clinical significance of the haemodynamic changes produced by alterations in posture are briefly discussed.
A method is described for control of plants with long transportation lags. This is achieved by making use of the design advantages offered by optimal-linear-regulator theory and the pole-positioning technique. The system states required by the state-vector feedback algorithm are obtained from a Luenberger observer, thus eliminating the need for specific plant instrumentation to implement the scheme. To demonstrate the proposed ideas, a sinter plant model is used in the case study presented.