No abstract

Magnetic material carrying natural remanent magnetization is present in the head of the common Pacific dolphin (Delphinus delphis). A sample of this material, isolated from the dura mater, has a moment of 2 × 10 -5 gauss-cubic centimeter. The presence of such strongly magnetized material suggests that it may play a navigational role.

Experiments using a precessing liquid‐filled oblate spheroid with ellipticity (a − b)/a =1/400 extend and clarify earlier research. They yield flow data useful for estimating flows in the Earth’s liquid core. Observed flows illustrate and confirm a nearly rigid liquid sphere with retrograde drift and lagging a cavity (mantle) axis in precession. The similarities of the observed lag angle with that computed for a rigid sphere, and earlier energy dissipation research both support the use of a rigid sphere analytical model to predict energy dissipation and first‐order flow within the core–mantle boundary (CMB). Second‐order boundary layer and interior cylindrical flow structures also are photographed and measured. Interior flows are never turbulent or unstable at near‐Earth parameters, although complex and transient flow patterns are observed within the boundary layer. Other mechanisms proposed to explain net heat loss from the Earth and maintenance of the geodynamo typically require acceptance of some critical but unproven premise. Precession and CMB configuration are known with certainty and precision. Analytical difficulties have been the obstacle. Experiments illustrate the consequences of precession and ellipticity, provide criteria for validating analytical and numerical models, and may yield direct knowledge of the Earth’s deep interior with careful scaling.

Summary. Sheep plasTiia renin substralf was purified 1,200-fold l>y usinjj nephrfctomised sheep plasma, followed by DEAE-Sephadex chromatojijraphy and gel filtration. Th? purified substrate contained 8 nji angiotensin Il/nig protein and had an estimated molecular vveijjht of 52,000. The kinetic characteristics of the purified substrate were identical both to those of tuipurified nephrectomised sheep plasma and to normal sheep plasma substrates. At pH 7-5, K,,, of the human renin-sheep substrate reaction was 0-29 [iM and for sheep reninsheep substrate. 2-0 fiM. Sheep substrate was .susceptible to peptic diHeslion with generation of pepsitenshi.Hunuin renin substrate was less readily purified. DEAE-Sephadex chromatography of plasma from pregnant women at 36-40 weeks' gestation produced a 70-fold increase in purity (0-9 ng angiotensin Il/mg protein). No further increase was achieved with gel filtration. Human renin substrate behaved as a larger (mol. wt. 82.000) more anionic protein than sheep substrate and was resistant to the proteolytit actions of both pepsin and shi-ep renin. K,,, for the human renin-human substrate reaction was high and conid not be accurately detennined (range 3-8 nM. mean 5-7 ^iM). The presence of human substrate in a human rcnin-sheep substrate system did not alter the measured initial velocity.In both shet'p and man, the nonnal concentration (»f ri^nin substrate is considerably less than K,,, and must therefore be considered a dtterminant of angiotensin production rate j>i vivo.

An analytic expression is presented for the piezoelectric d constant of a binary piezoelectric 0-3 connectivity composite. The expression is developed under the limiting assumption that the dielectric constant of the ceramic is much greater than the matrix. Predictions made using the theory compare very favorably with available experimental data. A 0-3/1-3 mixed connectivity model is also described for composites in which the average piezoceramic particle size is a significant fraction of the thickness of the composite.