The air we breathe is composed primarily of two gasses: oxygen (21 per cent) and nitrogen (78 per cent), the remaining one per cent consisting of several trace gasses (such as argon and carbon dioxide). Oxygen is metabolised by our bodies in the process of respiration. Nitrogen, on the other hand, is an inert gas, i.e. it does not react with other substances. What does this mean for diving?

When a diver breathes air under pressure, the nitrogen ends up dissolving in the tissues. Being inert, it simply stays there, i.e. it cannot be ‘used up’ in any way by the body (unlike oxygen). The longer the diver stays underwater, and the deeper the dive, the more nitrogen gas ends up dissolved in the diver’s body. But when the diver begins to ascend, the ambient pressure (i.e. the pressure on the diver from the surrounding water) drops, and the nitrogen starts to come out of solution. If the diver does not ascend gradually in an appropriate manner, the nitrogen bubbles that form may become hazardous, resulting in decompression sickness, more popularly known as ‘the bends’. The entire process may be likened to the situation in the case of a fizzy drink bottle. Upon unscrewing the tap, the gas that is dissolved in the liquid comes out of solution as bubbles.

One might think that the problem should therefore be easy to avoid: ascend slowly and you will be fine. In general, this is true ­­– and divers use decompression tables – or, far more commonly these days, dive computers – that prescribe how they should ascend depending on the dive they carried out. These tables are theoretical in nature and adopt a one-size-fits-all approach. However, no two human bodies are exactly the same. For example, one diver might have more fat tissue than their buddy. For this reason, even though two divers may have carried out the same dive and followed the exact same decompression schedule, one of them may unexpectedly get a ‘hit’, that is to say, they may suffer some form of decompression sickness. And it is not just variation in physiology that matters; environmental factors, such as temperature, also come into play.

The project PerDeMon (Personal Decompression Monitor) seeks to develop a system that prescribes a decompression schedule tailored to the individual diver. Spearheaded by Dr Joseph Caruana (project leader) and Prof. Charles Sammut, it involves a collaboration between members of the Department of Physics (University of Malta), the Institute of Space Science and Astronomy, hyperbaric specialists, and private industry. The project is funded through the MCST FUSION Technology Development Programme.

Dr Joseph Caruana is a lecturer with the Department of Physics and the Institute of Space Science and Astronomy at the University of Malta.

Sound bites

• Scientists at Cambridge and Leeds have successfully reversed age-related memory loss in mice and say that their discovery could lead to the development of treatments to prevent memory loss in people as they age. The team show that changes in the extracellular matrix of the brain — ‘scaffolding’ around nerve cells — lead to loss of memory with ageing, but that it is possible to reverse these using genetic treatments.

• Researchers have found a low-cost way to solve one-half of the water-splitting equation to produce hydrogen as clean energy — using sunlight to efficiently split off oxygen molecules from water. The finding represents a step forward toward greater adoption of hydrogen as a key part of our energy infrastructure. The key to this breakthrough came through a method of creating electrically conductive paths through a thick silicon dioxide layer that can be performed at low-cost and scaled to high manufacturing volumes.

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Did you know?

• The ancient Olympic Games began in 776 BC and according to some literary traditions, the stadion race was the only athletic event for the first 13 Olympic festivals.

• From 766 BC, the Games were held in Olympia every four years for almost 12 centuries, until 393 AD. They were banned by Emperor Theodosius and seen as a ‘pagan cult’.

• It took 1503 years for the Olympics to return, with the first modern Olympics held in Athens in 1896.

• The idea of the Olympic torch or flame was first inaugurated in 1928 in Amsterdam and the first torch relay was instituted in the modern Olympics in 1936 in Berlin.

• When the teams from Liechtenstein and Haiti met at the 1936 opening, they were shocked to discover that their flags were identical. Liechtenstein responded by adding an emblem to their flag and Haiti added their coat of arms.

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