Simple slime seeks downer kicks

10 June 2011 Last updated at 11:16 GMT By Jason Palmer Science and technology reporter, BBC News The slime mould at centre sought out sleeping tablets (l) significantly more than honey (r) A simple life form known as a slime mould, used in unconventional computing, seems to have a taste for sedatives.

Physarum polycephalum is known to grow toward food sources, and this propensity has been exploited to solve mazes and even to mimic "logic gates", the building blocks of computers.

It is normally fed honey or oats in these experiments, but a paper in Nature Precedings suggests that plants and commercial tablets with sedative effects work far better.

Slime moulds are a type of primitive life form known as protists. P. polycephalum tends to live in damp locations feeding on bacteria and other micro-organisms.

It is essentially a single cell; in its growing stages, it extends a network of tubes of cellular material in search of food, which it surrounds and then digests.

This searching method has been used in solving simple mazes, and in 2010 was even shown in a paper in Science to recreate the fault-tolerant network structure of the Tokyo subway system.

Andrew Adamatzky of the University of the West of England has long been interested in using the slime mould to solve computational problems using similar approaches.

Most recently, he has coaxed P. polycephalum to solve a computational geometry problem (normally solved by complex computer approaches) of finding the many-sided shape that encompasses a number of points - called the "concave hull".

This procedure is useful, among other things, for computation-based processing and manipulation of images.

It also surrounds a number of the tablets, in what can be a complex geometry conundrum

Professor Adamatzky has now published the result on the Arxiv repository, but in the course of those experiments he found that the usual food sources were not doing the job.

"For some tasks, oats and honey are not enough," he told BBC News. "We cannot approximate the concave hull using only attractants. So, last November I was trying to find what would be an ideal substance which can play the role of a long-distance attractant and short-distance repellent."

In his search, Professor Adamatzky found that commercial, herbal sleeping tablets did exactly that.

"Then I became curious why Physarum becomes so mad about these tablets - it ignores vitamin pills completely," he said. "So I tested all active substances present in the tablets."

He compared the effects of a wide range of over-the-counter sedatives and plant extracts with sedative effects; P polycephalum's strongest preference was for valerian root (Valeriana officinalis).

Professor Adamatzky said that the experiments were nothing more than pursuing his curiosity about the slime mould's unusual tastes, though the outcome will help with future experiments exploiting its computational abilities.

"We can now compute planar shapes, and therefore do more advanced procedures of image analysis with slime moulds," he said. "Also, using these herbal tablets we can attract slime moulds and keep them 'concentrated' in a local domain of space."

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A simple ribbon

16 May 2011 Last updated at 16:23 GMT It's just a picture of a tartan ribbon and may seem unremarkable, yet it marks a crucial moment in the development of colour photography and forms the basis of the photographs we take today.

The photograph was first seen at King's College London during a Royal Institution lecture on colour theory by the Scottish physicist James Clerk Maxwell on the 17 May 1861 and the college is marking the 150th anniversary of that demonstration with an evening of talks celebrating his scientific discoveries.

The first permanent colour photograph was taken by Thomas Sutton who was working with Clerk Maxwell and is a composite of three black and white pictures, each one taken through a red, green or blue filter. The resulting slides were then projected through three similarly filtered lenses resulting in a colour photograph.

Looking at the ease with which we now capture colour pictures and transmit them around the world in seconds it's easy to forget that it was not that long ago news agencies were transmitting their wire photographs as colour separations, usually cyan, magenta and yellow - a process that relied on Clerk Maxwell's discovery. Indeed even the latest digital camera relies on the separation method to capture light.

As late as the 1980s wire photographs would be transmitted by news agencies such as the Associated Press and printed out by the client as three black and white pictures; these would then be photographed through the same filters and re-constituted as a colour print.

As electronic delivery took over this method moved to the computer, but even then the pictures would arrive in three parts ready for the client to reassemble. It was sometime before full colour transmission was widespread.

Having searched the basement archive here at Television Centre for a suitable example, the only one I have located so far where the separations and a colour hard copy exist is a picture taken during the assassination attempt on US President Ronald Reagan in 1981 that was issued by the White House at that time.

Reagan was injured as were three others, Secret Service agent Jerry Parr, White House press secretary James Brady and police officer Thomas Delahanty.

You can see the three flimsy black and white wire photos as small images above, though they are somewhat faded now. The small holes at the top of the prints were made for registration purposes when re-photographing them. Failure to align each picture correctly would result in an unusable end product.

The colour image above is a Polaroid that would at the time have been placed in front of a TV camera and shown on air.

Anyone who has ever taken a colour photograph should salute Clerk Maxwell. He maybe best remembered for his work on electromagnetism but for photographers his work on colour theory stands as a high point.

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