Friday 04 June 1999
Synthetic diamond is made from graphite under high temperatures and pressures. It differs from natural diamond in size, shape and the number of impurities. It is made specifically for industry. Natural diamonds are made over millions of years from carbon sources in the earth. But they, too, were made using high temperatures and pressures.
Q What are cellophane and Sellotape made of, and do they decompose?
Sellotape and cellophane are made from natural cellulose which comes from soft woods. They will degrade, but not all that readily. Factors such as temperature, humidity, acidity and microbial activity control how fast they degrade outside. In a tropical rainforest Sellotape will degrade within months. In a British compost heap it could take years.
Q Does eating fish make you brainy?
Possibly. There is some evidence that nutrients which are found at high levels in oily fish are important in brain development. The brain is rich in decosahexaenoic acid (DHA), a fatty acid which the body can produce, but not very efficiently. The best source for DHA is diet. It is found in meat and eggs and in particularly high levels in fish. Oily fish (mackerel, sardines, herring, tuna) are very high in DHA, whereas white fish (cod, plaice, monkfish) have high levels of DHA only in their livers.
It has been reported that DHA improves eyesight, circulation and skin and that it can alleviate rheumatoid arthritis. There has also been evidence to suggest that it increases learning ability and visual awareness. Rats fed on DHA-rich diets learn to escape from mazes more quickly than those deprived of it; experiments on primates revealed similar results. There is also evidence that premature babies fed on their mothers' milk have a higher IQ, visual acuity and dexterity than those fed on formula milk substitute. This doesn't contain DHA, whereas human milk does.
It seems that the intelligence-enhancing activities of a DHA-rich diet occur only between the fourth month of pregnancy and the ninth month after birth, during the development of the brain. It seems to be your mother's diet that has the strongest effect on your intelligence, not what you eat yourself.
Q Why are some clouds flat on top?
Cumulus clouds form when heat from the Earth (warmed by the Sun) causes convection in the lower atmosphere. The development and height of cumulus clouds will partly depend on the amount of convection, which is linked to the amount of heating. Strong convection leads to higher cloud tops.
Very often the atmosphere above the Earth will be layered and this means that winds may be stronger at greater altitudes. If the tops of the cumulus cloud reach a zone where wind speeds are greater than lower down, the tops can be sheared in the direction of the prevailing wind. This is called a castellate texture.
The Technoquest website is at http://www.sciencenet.org.uk
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