Section 1
Australia's cane toad problem
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In the north of Australia there are many sugar cane plantations, which early in the 20th century were being damaged by a particular pest. This was a species of beetle whose larvae, the infant form of the beetle, live underground in the soil in the sugar cane fields. The sugar cane plants were weakened or died because their roots were eaten by the larvae. This had serious economic consequences for sugar cane farmers. Modern pesticides were not developed until the 1940s, so farmers had to use what was available at the time. Chemicals like arsenic and copper were used, but these were not only expensive but also stayed in the environment and were poisonous to people, plants and animals. It was generally acknowledged by government, farmers and scientists that cheaper and safer methods of pest control had to be found.
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A promising replacement for copper and arsenic was the use of biological control. Farmers already used some forms of biological pest control in the form of predatory and parasitic wasps and flies, insect-eating birds, and plants from different regions or countries to control pests. Common practice was to release these introduced agents into new environments, the expectation being that they would destroy resident pests. Some species of toad already had successful records as agents of biological control in gardens. For example, in 19th-century France toads were sold to gardeners at markets in Paris to eat insect pests in their gardens. In the early 20th century French sugar cane farmers first took giant toads from South America to control pests in their Caribbean sugar cane plantations. Although there is no evidence that these toads did help to control pests, sugar cane scientists then carried some of these toads from Jamaica and Barbados to Puerto Rico and from there to Hawaii.
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The idea of biological control of pests was not new to Australia. For example, in 1926 there had been a highly successful prevention of the increase of the exotic prickly-pear cactus by the introduction of a moth from Argentina. This success added strength to the argument that biological control was the answer to the sugar cane industry's pest problems. Accordingly, in the early 1930s a decision was taken to introduce the giant South American toads, which in Australia are now commonly called cane toads, into Australian sugar cane plantations.
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In 1935, an Australian entomologist brought 101 cane toads from Hawaii and released them in sugar cane plantations in the north of Australia. However, over the following years it became clear that the cane toads were a failure. There was a fatal flaw in the plan to use them as a form of biological control. This was that earthbound cane toads were expected to eat the mostly flying adult beetles in order to eliminate the soil-dwelling beetle larvae that ate the roots of the cane sugar plants. This, of course, cane toads could not do.
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Prior to their introduction in Australia, there had been very few opponents and only one made his views public. He was a retired former Chief Entomologist from the state government of New South Wales named Walter Froggatt. He forecast that cane toads might become as great a pest in Australia as rabbits. However, Froggatt's peers rebuked him and eminent scientists branded his views 'decidedly pessimistic'. It is estimated that today as many as a hundred million cane toads form a toxic infestation which is slowly spreading throughout the land.
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Cane toads are large, heavily built amphibians. Average-sized adults are 10-15 cm long and weigh more than a kilo. They have large swellings on each shoulder from which they squirt poison when they are threatened. This venom contains 14 different chemicals, but they do not appear to be harmful to humans as no-one has died in Australia from cane toad poison. Until recently there was no understanding of the toxicity of cane toad poison, but it is now clear that freshwater crocodiles, goannas (large lizards) and dingoes (wild dogs) have died after eating cane toads. Cane toads compete with native Australian fauna for food, and eat the eggs and young of ground-nesting birds. As their numbers increase, they are taking over more and more of the land where native Australian fauna live.
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The lesson that can be learned from the introduction of cane toads is important. It is wrong to think that such an awful biological event could not be repeated. In this instance, the catalyst was the overwhelming consensus of support for introducing cane toads to Australia. The error was that there was little or no testing of these biological agents before they were introduced to see what unplanned effects they might have on the environment.
Section 2
Roller coaster: the great fairground attraction
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Like a passenger train, a roller coaster consists of a series of connected cars that move on a track. But unlike a passenger train, it has no engine or power source of its own. For most of the ride, it is moved only by the forces of inertia and gravity. The only exertion of energy occurs at the very beginning of the ride when the coaster train is pulled up the lift hill.
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The traditional lifting mechanism is a long length of chain running up the hill under the track. The chain is fastened in a loop, which is wound around a gear at the top of the hill and another one at the bottom of the hill. The gear at the bottom of the hill is turned by a motor. This turns the chain so that it continually moves up the hill like a long conveyor belt. The coaster cars grip onto the chain, which simply pulls them to the top of the hill. At the summit, the train is released and starts its descent.
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The purpose of this initial ascent is to build up a sort of reservoir of potential energy, which simply means that as the coaster gets higher in the air, there is a greater distance gravity can pull it down.
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As the train starts coasting down the hill, this potential energy is converted into kinetic energy (energy of motion), and the train speeds up. At the bottom of the hill, this has reached its maximum, and this propels the train up the second hill, again building up the potential energy level.
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In this way, the course of the track is constantly converting energy from kinetic to potential and back again. This fluctuation in acceleration is what makes roller coasters so much fun. At its most basic level, this is all a roller coaster is – a machine that uses gravity and inertia to send a train along a winding track.
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Roller coasters have a long, fascinating history. Their direct ancestors were ice slides, popular in Russia in the 16th and 17th centuries. They consisted of a long, steep, wooden slide covered in ice. Riders walked up a ladder or set of stairs to the top of the slide, as high as 21 meters up. At the top, they climbed into sleds made out of wood or blocks of ice and shot down the slope. At the base of the slide, the sleds would crash-land in a sand pile.
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It seems that the idea was then imported into France. For most of the year, the warmer climate would melt the ice, so the French started building waxed slides instead. To help the sleds move down these slides, they added wheels, and in 1817, for the first time, a train was attached to the track. The French continued to expand on this idea, coming up with more complex track layouts, with multiple cars and all sorts of twists and turns.
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The first American roller coaster was built in the mountains of Pennsylvania in the mid-1800s originally to provide an easy way to send coal to the railway 29 km down to mountain. When the track was first built, a crew at the bottom of the mountain would attach the cart to a team of mules after emptying the load, and the mules would drag it back up to the top. They were eventually replaced with steam engines, to make the system more efficient.
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Soon after these improvements were made, the railway company built a new tunnel that brought the freight trains much closer to the coal mine. Now no longer required for its original purpose, the roller coaster was configured as a 'scenic tour'. For one dollar, tourists got a leisurely ride up to the top of the mountain, followed by a wild, bumpy ride straight down. This was soon a resounding success, attracting thousands of tourists every year.
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Scenic rides like this continued to thrive and were joined by wooden roller coasters similar to the ones we know today. These coasters were the main attraction at popular amusement parks throughout the United States, such as the many parks of Coney Island in New York. By the 1920s, roller coasters were in full swing, with some 2,000 rides in operation around the country. Following the Great Depression, a decline in roller coaster production began in the early 1930s but a second roller-coaster boom in the 1970s and the beginning of the 1980s revitalized the amusement park industry, and introduced a slew of innovative tubular steel coasters.
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This was followed by a decline in interest for the rest of the decade, but since the early 1990s the amusement-park industry has experienced another coaster boom of sorts. New launching techniques and other technological developments have opened up a world of options for designers so in some rides you feel as if you are flying. In the next few years we can expect to see many faster, taller and more twisted rides popping up in amusement parks around the world.
Section 3
Seeing the colour of sounds, hearing the colour of numbers
When the senses mix together
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What is the colour of five? What is the sound of blue? To most of us such questions are either meaningless or suitable only for poetry. But for some people these are questions to which very precise answers can be given. Five, for example, for some people is green, while others say the sound of a guitar is like someone blowing on their ankles. People who 'see' colour in numbers or letters of the alphabet and 'feel' sensation in sound have synesthesia – meaning literally 'joined sensation' – an extraordinary condition that causes certain senses to 'leak' into one another.
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People whose senses behave in this way are called 'synesthetes'. Some synesthetes take pleasure in it. 'To me it's like other people see the world in black and white,' says one, who sees every letter, number, sound and pain in colour. Others learn to keep it a secret for fear of people laughing at them. But to neurologists investigating the brain it is of great interest. 'When scientists study normal perception,' says Daniel Smilek of the University of Waterloo in Ontario, Canada, 'there are lots of things we don't question because most of us perceive in the same way. Synesthesia, because it's abnormal, can give us new insights into normal perception.'
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Seventeenth-century English philosopher John Locke was the first westerner to describe synesthesia. He wrote about a man who experienced bright red as the sound of the trumpet. Later, the condition excited the imagination of nineteenth-century European painters, such as the non-synesthete Wassily Kandinsky, who believed synesthetes were like good, much-played violins, which vibrate in all their parts and fibres. But it proved impossible to research and people lost interest. Recently, however, advances in brain imaging have sparked renewed interest.
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Early claims that the multi-sensory experiences of synesthesia were linked with the hallucinations of mental illness have long been disproved. Until 1993, many researchers dismissed it as another name for a vivid imagination, but then an experiment by Simon Baron-Cohen of Cambridge University in the UK showed that synesthetes who, when tested, had linked particular colours or shapes to letters, gave the same answers in 92 per cent of instances when tested again a week later. Non-synesthetes, given similar examples to imagine, returned the same answers in only 37 per cent of instances.
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Although there is some overlap between synesthetes as to what colour is linked to what – 56 per cent see the letter 'o' as white – most of the responses are individual. There are 30 possible sensory combinations, but links between sounds and colours are the most common. Women are between two and eight times more likely than men to have the condition.
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As yet there is no explanation for any of this, but small pieces of the jigsaw are emerging. A brain scanning experiment by Baron-Cohen in 1995 found that when synesthetes were listening to words, areas of the brain lit up that are normally only active in response to vision and colour. From this comes the notion that we may all have synesthesia at birth, when many parts of the brain are linked, but, as we develop, connections are pruned, so our senses become separated and the synesthetic mechanism is no longer intact. Somehow, synesthetes have kept their synaptic connections intact. It's an idea that has been challenged, however, on the grounds that if you give people certain drugs they will have synesthetic experiences, which suggests the mechanism is intact in adults but repressed.
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There are many more unanswered questions about synesthesia. For example, is the synesthete's colour response to a number five triggered by actually seeing the number five written on a page, or does the synesthete 'see' the colour just by thinking of the number five? The neurologist Vilyanur Ramachandran came up with a test for synesthesia which seemed to suggest it was the sight of the number that was important. He asked people to look at a page made up of specially drawn twos and fives that were a mirror image of each other. The fives were placed at random on the page but the twos were placed to form shapes such as circles or triangles. To most people the numbers just looked like a jumble without order, but to synesthetes the patterns made by the twos were very obvious as a different colour from the fives. 'This shows they were really sensing colour in the numbers they saw,' says Ramachandran. 'Ideas don't form these kinds of patterns.'
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However, Smilek subsequently came up with evidence that what really matters is the idea of a number rather than the sight of it on a page. He asked a synesthete to do some simple mental arithmetic while looking at different coloured papers. The subject did not write her answers, but only thought of them and said them aloud. Smilek found that when the colour of the paper clashed with the colour of the answer, the subject's response was slower than when the colours were the same. An actual colour (the colour of the paper) could interfere with the colour of a number that existed only in her head (the answer to the mental arithmetic question). 'My research suggests that colour experiences coincide with the processing of meaning,' says Smilek. 'It's the concept of a number that's coloured.'
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So which is it? At present, we don't know, but in the future neurologists may be able to explain what's going on in the brains of people like the novelist Nabokov, who perceived the English 'a' as dark brown and the French 'e' as black.