IELTS READING TEST 11

Hunting Perfume in Madagascar!

A  Ever since the unguentari plied their trade in ancient Rome, perfumers have to keep abreast of changing fashions. These days they have several thousand ingredients to choose from when creating new scents, but there is always demand for new combinations. The bigger the 'palette' of smells, the better the perfumer's chance of creating something fresh and appealing. Even with everyday products such as shampoo and soap, kitchen cleaners and washing powders, consumers are becoming increasingly fussy. And many of today's fragrances have to survive tougher treatment than ever before, resisting the destructive power of bleach or a high temperature wash cycle. Chemists can create new smells from synthetic molecules, and a growing number of the odours on the perfumer's palette are artificial. But nature has been in the business far longer.

B  The island of Madagascar is an evolutionary hot spot; 85% of its plants are unique, making it an ideal source for novel fragrances. Last October, Quest International, a company that develops fragrances for everything from the most delicate perfumes to cleaning products, sent an expedition to Madagascar in pursuit of some of nature's most novel fragrances. With some simple technology, borrowed from the pollution monitoring industry, and a fair amount of ingenuity, the perfume hunters bagged 20 promising new aromas in the Madagascan rainforest. Each day the team set out from their "hotel"-a wooden hut lit by kerosene lamps, and trailed up and down paths and animal tracks, exploring the thick vegetation up to 10 meters on either side of the trail. Some smells came from obvious places, often big showy flowers within easy reach. Others were harder to pin down. "Often it was the very small flowers that were much more interesting," says Clery. After the luxuriance of the rainforest, the little-known island of Nosy Hara was a stark, dry place-geologically and biologically very different from the mainland. "Apart from two beaches, the rest of the island is impenetrable, except by hacking through the bush," says Clery. One of the biggest prizes here was a sweet-smelling sap weeping from the gnarled branches of some ancient shrubby trees in the parched interior. So far no one has been able to identify the plant.

C  With most flowers or fruits, the hunters used a technique originally designed to trap and identify air pollutants. The technique itself is relatively simple. A glass bell jar or flask is fitted over the flower. The fragrance molecules are trapped in this 'headspace' and can be extracted by pumping the air out over a series of filters which absorb different types of volatile molecules. Back home in the laboratory, the molecules are flushed out of the filters and injected into a gas chromatograph for analysis. If it is impossible to attach the headspace gear, hunters fix an absorbent probe close to the source of the smell. The probe looks something like a hypodermic syringe, except that the 'needle' is made of silicone rubber which soaks up molecules from the air. After a few hours, the hunters retract the rubber needle and seal the tube, keeping the odour molecules inside until they can be injected into the gas chromatograph in the laboratory.

D  Some of the most promising fragrances were those given off by resins that oozed from the bark of trees. Resins are the source of many traditional perfumes, including frankincense and myrrh. The most exciting resin came from a Calophyllum tree, which produces a strongly scented medicinal oil. The sap of this Calophyllum smelt rich and aromatic, a little like church incense. But it also smelt of something like fragrance industry has learnt to live without, castoreum, a substance extracted from the musk glands of beavers and once a key ingredient in many perfumes. The company does not use animal products any longer, but it was wonderful to find a tree with an animal smell.

E  The group also set out from the island to capture the smell of coral reefs. Odors that conjure up sun kissed seas are highly sought after by the perfume industry. " From the ocean, the only thing we have is seaweed, and that has a dark and heavy aroma. We hope to find something unique among the corals," says Dir. The challenge for the hunters was to extract a smell from water rather than air. This was an opportunity to try Clery's new "aquaspace" apparatus – a set of filters that work underwater. On Nosy Hara, jars were fixed over knobs of coral about 2 meters down and water pumped out over the absorbent filters. So what does coral smell like? "It's a bit like lobster and crab," says Clery. The team's task now is to recreate the best of their captured smells. First they must identify the molecules that make up each fragrance. Some ingredients may be quite common chemicals. But some may be completely novel, or they may be too complex or expensive to make in the lab. The challenge then is to conjure up the fragrances with more readily available materials. "We can avoid the need to import plants from the rainforest by creating the smell with a different set of chemicals from those in the original material," says Clery. "If we get it right, you can sniff the sample and it will transport you straight back to the moment you smelt it in the rainforest."

Using Mathematics to Secure Our Money

A  Up until very recently people's wealth, mostly coins and jewels, was kept safe under lock and key. Rich medieval families would keep a strongbox with a large key, both of which were carefully hidden in different places. later the box may have been kept in a bank. In either case, potential thieves would need to find both the box and the key. A similar principle was used for sending secret diplomatic and military messages. The messages were written in code with both the sender and the receiver having the key to the code. Thus, while the message could be discovered its meaning could only be found if the 'key' was also known. And so began a long-running battle between code-makers who tried to make better keys and code-breakers who sought ways of finding them.

B  Nowadays, cryptography is central to how our money is kept secure, even though we may not be aware of it. Our money is no longer in a tangible form, but in the form of information kept with our banks. To keep everyone involved happy, the messages initiated by our plastic cards have to be sent and received safely and the entire operation must be carried out with a high level of confidentiality and security.

C  On a practical level, it is clear that the work of code-makers has been introduced into our daily financial lives. Our credit cards have 16-digit numbers on the front and a 3-digit number on the back. They also contain a 'chip' that can do all sorts of mysterious operations with these numbers. Finally, we also have a Personal Identification Number which we all need to memorize. All these numbers form a type of cryptographic key. However, as we shall see, modern cryptosystems are very different in the way the keys are used.

D  The main feature of the traditional systems was that only one key was needed by both the sender and the receiver to understand the message. However, the main problem was that the key itself needed to be communicated to both parties before they could use it. Obviously a major security risk. A very different approach was developed in the 1970s, based on a different way of using the keys. Now the main idea is that the typical user, let us call him Amir, has two keys; a 'public key' and a 'private key'. The public key is used to encrypt messages that other people wish to send to Amir, and the private key is used by Amir to decrypt these messages. The security of the system is based on keeping Amir's private key secret.

E  This system of public-key cryptography, known as RSA- from the names of the developers (Ronald Rivest, Adi Shamir and Leonard Adleman) – was developed in the late 1970s and is based on a collection of several mathematical algorithms. The first is a process that allows the user, Amir, to calculate two numerical keys: private and public, based on two prime numbers. To complete the RSA system, two more algorithms are then needed: one for encrypting messages and one for decrypting them.

F  The effectiveness of RSA depends on two things. It is efficient, because the encryption and decryption algorithms used by participants are easy, in a technical sense they can be made precise. On the other hand, it is believed to be secure, because no one has found an easy way of decrypting the encrypted message without knowing Amir's private key.

G  When the RSA system was first written about in Scientific American, the strength of the system was shown by challenging the readers to find the prime factors – the two original numbers – of a certain number with 129 digits. It took 17 years to solve this problem, using the combined efforts of over 600 people. So clearly it is a very secure system. Using mathematics in this way, scientists and technologists have enabled us to keep our money as secure as the rich medieval barons with their strong boxes and hidden keys.