(完整版)雅思阅读冲刺模拟试题

雅思阅读冲刺模拟试题

Rogue theory of smell gets a boost

，which claims

1. A controversial theory of how we smell

that our fine sense of odour depends on quantum mechanics ，has been given the thumbs up by a team of

physicists.

2. Calculations by researchers at University College

London (UCL) show that

the idea that we smell odour molecules by sensing their molecular vibrations makes sense in terms of the physics involved.

3. That 's still some way from proving that the th eory ，proposed in the

mid-1990s by biophysicist Luca Turin ，is correct. But it

should make other scientists take the idea more seriously.

4. “ This is a big step forward ，” says Turin ，who has now set up his own perfume company Flexitral in Virginia. He says that since he published his

theory ，“ it has been ignored rather than criticized.

5. Most scientists have assumed that our sense of smell depends on

receptors in the nose detecting the shape of incoming molecules ，which triggers

a signal to th e brain. This molecular 'lock and key '

process is thought to lie

behind a wide range of the body 's detection systems ：it is

how some parts of the

immune system recognise invaders ，for example ，and how the tongue recognizes

some tastes.

6. But Turin a rgued that smell doesn 't seem to fit this picture very well.

Molecules that look almost identical can smell very different —such as

alcohols ，which smell like spirits ，and thiols ，which smell like rotten eggs.

And molecules with very different structures can smell similar. Most strikingly ，

some molecules can smell different —to animals ，if not necessarily to humans —

simply because they contain different isotopes (atoms that are chemically

identical but have a different mass) o

7. Turin 's explanat ion for these smelly facts invokes the idea that the

smell signal in olfactory receptor proteins is triggered not by an odour

molecule 's shape ，but by its vibrations ，which can enourage an electron to jump

between two parts of the receptor in a quantum-mechanical process called

tunnelling. This electron movement could initiate the smell signal being sent to

the brain.

8. This would explain why isotopes can smell different their vibration

frequencies a re changed if the atoms are heavier. Turin 's

mechanism，says

Marshall Stoneham of the UCL team ，is more like swipe-card identification than a

key fitting a lock.

9. Vibration-assisted electron tunnelling can undoubtedly occur —it is

used in an experimental technique for measuring molecular vibrations. “The

question is whether this is possible in the nose ，” says Stoneham's colleague ，