Determination of the Avogadro constant by counting the atoms in a 28Si crystal

The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant. We describe a new approach for its determination by counting the atoms in 1 kg single-crystal spheres, which are highly enriched with the 28Si isotope. It enabled isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, NA = 6.022,140,78(18) × 10(23) mol(-1), is the most accurate input datum for a new definition of the kilogram.

Clinical application of artificial ligament for ankle instability--long-term follow-up

We have applied a reconstructive operation to patients with injury of the lateral ligament in the ankle joint using an artificial ligament made of polyester (Leeds-Keio) since 1985. The operation was performed on 451 feet of 436 patients. Average follow-up period was 5 years and 8 months. Talar tilt and anterior drawer translation before and after the operation were improved from 16 degrees to 4 degrees and from 11 mm to 4 mm, respectively. In this study, which has followed the same patients over an extended period, there were no cases with a decrease in the range of motion of the joint, with further development of osteoarthritis, or with a poorer result than those observed in our earlier study, which reported a short-term follow-up of the same patients. It may therefore be concluded that this reconstructive procedure of the lateral ligament of the ankle joint, using the artificial ligament, is also excellent after long-term follow-up.