There’s an interesting news piece over at news@nature.com that caught my eye – a team led by Helge Riemann at the Institute of Crystal Growth is trying to generate a ‘pure’ sample of crystalline silicon-28:

The new barbell-shaped crystal, which weighs 5 kilograms and was completed on 23 May by Riemann’s team … is nearly isotopically pure. It was made from Russian source material, whose silicon was 99.994% pure silicon-28.

A standard kilogram is currently calibrated using the “”https://www.bipm.org/en/scientific/mass/pictures_mass/prototype.html">international prototype," which “”https://www.bipm.org/en/scientific/mass/prototype.html">was manufactured in the 1880s [from] an alloy of 90% platinum-10% iridium" and is housed in the Bureau International des Poids et Mesures in France. Over time, the loss and/or gain of atoms from the international prototype may have altered its weight – the news story suggests that it might be off by 0.1 milligrams/0.01% (but I couldn’t find any additional information to verify that statement…)

Making this (two-million euro/2.7-million USD) piece of silicon was no easy task:

The researchers spent six months eliminating contaminating elements by repeatedly melting the silicon in an apparatus that does not touch the material. The resulting crystal is thought to contain one foreign atom to every 10 million atoms of silicon.

Talk about a pure sample…

Joshua

Joshua Finkelstein (Senior Editor, Nature)

Members of the Caudwell Xtreme Everest expedition, testing human adaptation to hypoxia on the roof of the world, write a diary blog for Nature from 30 March, 2007.

We have now been in Nepal for a month and are beginning to set up one of our laboratories high on Mount Everest. This laboratory is situated at Camp 2 (6,800m) in the Western Cwm and will be home to the investigators of the Caudwell Xtreme Everest project for the following week. But before I set off to great heights, here’s some more explanation of what we’re trying to find out.

As lowland residents travel to high altitude they are exposed to increasing levels of hypoxia. The physiological response to this insult is known as acclimatisation and our current understanding of it consists of a number of processes which together increase systemic oxygen delivery. Changes such as hyperventilation, tachycardia [fast heart rate], increased cardiac output and increased red blood cell mass all ensure that as much oxygen as possible is extracted from the rarefied air and passed on to the metabolising tissues which require it. We have known about this adaptive process for many years and its subtleties are detailed in many well respected texts. But what if this increase in oxygen delivery is not the whole story? Perhaps there is more to the process of acclimatisation than we had previously thought.

(more…)