Science: Technoquest: The brain revealed/ Red leaves/ Quarks' strange names/ Pingos and Eskimos
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Q How do doctors look inside brains without surgery?
The oldest technique is X-ray imaging. X-rays are good for examining skull fractures, but reveal little about the fine structure of soft brain tissues. An improvement came with computerised tomography (CT), which uses a series of small X-ray beams at different angles to one another to give a more detailed picture. CT gives pictures of a slice of brain (tomos is the Greek word for "cut") which help diagnose many brain diseases.
In positron emission tomography (PET), the patient is injected with weakly radioactive compounds. A scanner picks up the radioactivity emitted, indicating where the blood is being used - ie, where the brain is working hardest. Such scans are useful not just for diagnosing brain problems, but also to understand how a healthy brain works.
More recently, magnetic resonance imaging (MRI) has become popular. It can detect the presence of a particular substance in the brain by scanning for its unique chemical "signature". The images produced are amazingly detailed, but it's an expensive means of getting them.
Q Where does the red colour in some plants come from?
The red colour results from the presence of pigments known as anthocyanins. Anthocyanin production results from gene mutation, and is widespread in plants. It has been selected for (for ornamental purposes) in trees such as copper beeches and maples. Their leaves have the red colour in addition to the green of chlorophyll. They therefore photosynthesise normally.
Q What are the names for quarks?
Of the six forms of quark, the first two discovered (in the late Sixties) were classified as "up" and "down". The third was found in a very odd particle (called a K meson) so it was called "strange". The fourth was named "charm" because someone thought it was a smart name. This was not as bad as the names originally given to the last two: "truth" and "beauty". Their names were changed to "bottom" and "top". The top quark was not confirmed found until 1994.
Q What is a pingo?
A pingo is an ice-cored hill, typically conical in shape, growing and persisting only in permafrost. The word is of Inuit (Eskimo) origin and was first used by the botanist AE Porsild in 1938 to describe the ice- cored hills typical of the Mackenzie Delta in north-west Canada. Pingos range in height from a few to several tens of metres. The greatest concentration - about 1,450 of them - occurs in the Tuktoyaktuk area, east of the present Mackenzie Delta. Pingos grow through the force of freezing of water, which is moving due to a pressure gradient to the site which becomes the pingo. Some types typically form in recently drained lake basins or channels.
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