Search

Biological structural materials, although composed of unremarkable substances synthesized at low temperatures, often exhibit superior mechanical properties. In particular, the quality in which nearly all biologically derived materials excel is toughness. The advantageous mechanical properties are attributable to the hierarchical, composite, structural arrangements common to biological systems. Materials scientists and engineers have increasingly recognized that biological designs or processing approaches applied to man-made materials (biomimesis) may offer improvements in performance over conventional designs and fabrication methods. In this survey, the structures and processing routes of marine shells, avian eggshells, wood, bone, and insect cuticle are briefly reviewed, and biomimesis research inspired by these materials is discussed. In addition, this paper describes and summarizes the applications of biomineralization, self-assembly, and templating with proteins to the fabrication of thin ceramic films and nanostructure devices.

In this paper, we summarise the physiology of lactation and discuss the pathophysiology brought about by fasting, stress and anaesthetic drugs. Drug secretion into breast milk and subsequent absorption by the infant is considered. Maternal hydration must be well maintained with intravenous fluids, allowing an added 500 to 1000 ml for daily fluid loss in lactation. Maternal premedication, general anaesthesia and routine postoperative analgesics are also discussed as to the effects on the breast-fed infant. Drug side-effects may be avoided by timing breast feeding just before the next due dose. Sedatives with long half-lives should not be used. Endocrine and metabolic responses to anaesthesia and surgery are less with regional anaesthesia than with general, hence regional anaesthesia is preferred where it is a reasonable alternative technique.

Shock consolidation experiments were conducted via flyer impact on synthetic diamond (6–12 μm) and cubic boron nitride (c-BN) (4–8 μm) admixed with SiC whisker (SCW), Si3N4 whisker (SNW), SiC powder, and Si powder contained in stainless steel capsules under the shock pressure range of 10–30 GPa. Scanning electron microscopy and transmission electron microscopy imaging of the samples revealed no plastic deformation or melting of diamond and virtually no deformation of c-BN, whereas the SCW and SNW were extensively melted and recrystallized into bundle-shaped crystallites. In contrast, SiC powder mixed with diamond was also melted but demonstrated equant grain growth. A new method to calculate the shock temperature and melt fraction is formulated on the basis of Milewski's sphere-rod packing data. The new method assigns excess bulk volume to the zone around whiskers and yields a better description of the energy deposition mechanism of the consolidation of powder-whisker systems. Some of the experiments employed Sawaoka's post-shock annealing technique, in which the sample is sandwiched between two layers of a mixture of titanium powder plus carbon. Very well consolidated samples were obtained with post-shock heating under shock pressures of only about 11 GPa. Micro-Vickers hardness values up to 27 GPa were obtained for c-BN plus SCW at a low impact velocity of 1.45 km/s with post-shock heating. This hardness is similar to that obtained at a higher impact velocity of 1.95 km/s without post-shock heating. To understand the post-shock heating process, one-dimensional time dependent temperature profile calculations were conducted for the sample and Ti + C layers. Post-shock heating appears to be very important in the consolidation of powder and whisker admixture. The calculated optimum Ti + C thickness is about 0.8–1.7 mm at a porosity of 40% for a typical sample thickness of 2 mm. The heating and cooling time is a few milliseconds. Good compacts with micro-Vickers hardness values up to 28 GPa were also obtained upon shock consolidation of diamond plus Si admixtures.

A report on the findings of the first phase of the Birmingham oral contraceptive (OC) trial (1960) is presented. 48 women were selected for the initial trial. The actual contents of the pills used was 2.3 mg norethynodrel and .036 mg ethinyl estradiol-3-methyl ether. 14 pregnancies occured 11 of which were definately due to tablet failure. There appeared to be no adverse effects of the regimen on pregnancy delivery lactation and the health of the infants. Spotting was reported by 37.5% of the women. The length of the menstrual cycle was noticeably increased by OC use although almost 33% of the cycles were interrupted by breakthrough bleeding. Generally side effects were relatively frequent but slight. Headache nausea and swollen tender breasts accounted for about 62% of all side effects. Backache and abdominal or pelvic pain were reported by about 19% of the patients. The method was highly acceptable to the women and no drop-outs resulted from side effects. It is suggested that with the 2.5 mg dose of norethynodrel the estrogen concentration becomes critical and may merely delay ovulation rather than inhibit it.