The Pharmaceutical Journal
Vol 272 No 7288 p258
28 February 2004

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Stone-skimming science more
Antidepressants may prevent child suicides more
“Sleeping on it” can help decision-making more
And I quote ... more

Stone-skimming science

Skimming stones almost horizontally across water so that they skip as far as possible without sinking is a favourite pursuit of youngsters, though it appears to be a trivial way of passing the time. However, if the mechanics of the process are analysed, as they are by a group of three French scientists in a paper published in Nature for 1 January, there is more to the pursuit than meets the eye.

The writers point out that skimming stones across water has been popular for thousands of years, the rules remaining unchanged since ancient Greek times. The world record, set in 1992, is claimed to be 38 rebounds. By studying the collision of a spinning disc with water the investigators have discovered that for satisfactory results an angle of about 20 degrees between the stone and the water surface yields the greatest number of bounces.

Four parameters are involved in the skimming process. They are the translational and spin velocities, the attack angle of the stone at the surface, and the collision time. Rotation stabilises a thrown stone by a gyroscopic effect. The lowest translational velocity for a rebound is delivered at 20 degrees, and impacts at more than 40 degrees do not provoke rebound. With a 20 degree impact angle the number of bounces that follow reaches a maximum, since the amount of energy dissipated at the point of collision is directly proportional to the collision time.

The experiments that resulted in these conclusions were performed using an aluminium disc of radius 2.5cm and thickness 2.75mm. Of course, in real life the stones picked for skimming vary greatly in size and shape. Sometimes they are flat, sometimes triangular in section. Moreover, if you try skimming them in the sea there are the wavelets to take into account.

There is far more, indeed, in stone skimming than a mathematical model. If you are at the side of the pond, or on the margin of the beach, first select your stone. Its dimensions and shape will make all the difference in the world to how many bounces you can achieve, whatever science you bring to back up your effort. And sometimes nature offers little choice in this respect.

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Antidepressants may prevent child suicides

The Food and Drug Administration in the US has recently expressed concern that some antidepressants used to treat children are capable of inducing suicidal tendencies. In Science for 6 February there is a report of a public hearing called to discuss this hazard. Drug advisers have urged that, in the absence of more information, stronger warnings should be printed on labels for selective serotonin reuptake inhibitors, which include fluoxetine, paroxetine and sertraline.

These antidepressants have been widely prescribed for patients aged less than 18 years. They have been held to be generally acceptable and have proved highly popular. Nevertheless, there have been an increasing number of reports of serious adverse effects, including extreme agitation, hostile feelings, and even suicidal and homicidal activities.

In contrast, since the prescribing of the drugs has become widespread, there has been a reported dramatic reduction, averaging 33 per cent, in the rate of youth suicide in 15 countries. But there are contrary reports that have suggested a high suicide rate. The problem is that it is also reported that most of the 4,000 youngsters who kill themselves every year in the US have not been taking antidepressants, and it may be that serotonin reuptake inhibitors would have improved their health rather than threatened it.

In the UK the prescribing of such antidepressants, with the exception of fluoxetine, for patients under 18 has been banned. More information will need to be examined before the precise status of these drugs can be assessed.

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“Sleeping on it” can help decision-making

When we give up thinking about a tricky situation and decide to postpone any decision, we are likely to remark that we will “sleep on it”. Curiously enough, this may not be a relegation of responsibility but a wise and creative move that will bring results.

In a communication to Nature, published in the 22 January issue, a group of neurologists and psychologists from the universities of Lübeck and Cologne describe an examination of the effect of sleep upon the quality of insight. They started from the notion that sleep consolidates recent memories and, by changing their representational structure, may facilitate insight into their significance.

Participants in the study were asked to transform a string of eight digits into a new string through applying two simple rules, but not told that later responses were mirrored in earlier ones; insight into this would speed their response. The task was again performed after an interval of eight hours, spent either awake or sleeping. Those who slept were more than twice as likely to develop insight into the concealed rule than those who remained awake.

It was concluded that a favourable effect of sleep on insight occurred if a memory had been formed before the onset of sleep. Why and how this should occur is not evident, and what component of sleep, that associated with rapid eye movement (REM sleep) or non-REM sleep, remains unknown. However, most of the famous cases of artistic creativity and scientific insight reported to have been the outcome of a dream have been considered to be related to the sleep pattern known as REM sleep. Nevertheless, a sequence of the two modes of sleep may be necessary to produce the results observed.

We spend one third of our lives asleep, and have been in the habit of regarding this period as essential but mentally unproductive. In this assumption we may well have been wrong.

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And I quote ...

Lonely living

“We live together, we act on, and react to, one another; but always and in all circumstances we are by ourselves. The martyrs go hand in hand into the arena; they are crucified alone. Embraced, the lovers desperately try to fuse their insulated ecstasies into a single self-transcendence; in vain. By its very nature every embodied spirit is doomed to suffer and enjoy in solitude. Sensations, feelings, insights, fancies — all these are private and, except through symbols and at second hand, incommunicable. We can pool information about experiences, but never the experiences themselves. From family to nation, every human group is a society of island universes.”
— Aldous Huxley: ‘The doors of perception’ (1954).

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