快速导航
学历类
职业资格
公务员
医卫类
建筑工程
外语类
外贸类
计算机类
财会类
技能鉴定
Rogue theory of smell gets a boost
1.A controversial theory of how we smell, which claims 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 theory, 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 the 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 argued 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).
7.Turin's explanation 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 are 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, Andrew
Horsfield.
10.Stoneham says that when he first heard about Turin's idea, while Turin was
himself based at UCL, "I didn't believe it".But, he adds, "because it was an
interesting idea, I thought I should prove it couldn't work.I did some simple
calculations, and only then began to feel Luca could be right." Now Stoneham and
his co-workers have done the job more thoroughly, in a paper soon to be
published in Physical Review Letters.
11.The UCL team calculated the rates of electron hopping in a nose receptor
that has an odorant molecule bound to it.This rate depends on various properties
of the biomolecular system that are not known, but the researchers could
estimate these parameters based on typical values for molecules of this
sort.
12.The key issue is whether the hopping rate with the odorant in place is
significantly greater than that without it.The calculations show that it is —
which means that odour identification in this way seems theoretically
possible.
13.But Horsfield stresses that that's different from a proof of Turin's
idea."So far things look plausible, but we need proper experimental
verification.We're beginning to think about what experiments could be
performed."
14.Meanwhile, Turin is pressing ahead with his hypothesis."At Flexitral we
have been designing odorants exclusively on the basis of their computed
vibrations," he says."Our success rate at odorant discovery is two orders of
magnitude better than the competition." At the very least, he is putting his
money where his nose is.
Questions 5-9
Complete the sentences below with words from the passage.Use NO MORE THAN
THREE WORDS for each answer.
5.The hypothesis that we smell by sensing the molecular vibration was made by
______.
6.Turin's company is based in ______.
7.Most scientists believed that our nose works in the same way as our
______.
8.Different isotopes can smell different when ______ weigh differently.
9.According to Audrew Horsfield, it is still to be proved that ______ could
really occur in human nose.
new weapon to fight cancer
1. British scientists are preparing to launch trials of a radical new way to
fight cancer, which kills tumours by infecting them with viruses like the common
cold.
2. If successful, virus therapy could eventually form a third pillar
alongside radiotherapy and chemotherapy in the standard arsenal against cancer,
while avoiding some of the debilitating side-effects.
3. Leonard Seymour, a professor of gene therapy at Oxford University, who has
been working on the virus therapy with colleagues in London and the US, will
lead the trials later this year. Cancer Research UK said yesterday that it was
excited by the potential of Prof Seymour’s pioneering techniques.
4. One of the country’s leading geneticists, Prof Seymour has been working
with viruses that kill cancer cells directly, while avoiding harm to healthy
tissue. "In principle, you’ve got something which could be many times more
effective than regular chemotherapy," he said.
5. Cancer-killing viruses exploit the fact that cancer cells suppress the
body’s local immune system. "If a cancer doesn’t do that, the immune system
wipes it out. If you can get a virus into a tumour, viruses find them a very
good place to be because there’s no immune system to stop them replicating. You
can regard it as the cancer’s Achilles’ heel."
6. Only a small amount of the virus needs to get to the cancer. "They
replicate, you get a million copies in each cell and the cell bursts and they
infect the tumour cells adjacent and repeat the process," said Prof Seymour.
7. Preliminary research on mice shows that the viruses work well on tumours
resistant to standard cancer drugs. "It’s an interesting possibility that they
may have an advantage in killing drug-resistant tumours, which could be quite
different to anything we’ve had before."
8. Researchers have known for some time that viruses can kill tumour cells
and some aspects of the work have already been published in scientific journals.
American scientists have previously injected viruses directly into tumours but
this technique will not work if the cancer is inaccessible or has spread
throughout the body.
9. Prof Seymour’s innovative solution is to mask the virus from the body’s
immune system, effectively allowing the viruses to do what chemotherapy drugs do
- spread through the blood and reach tumours wherever they are. The big hurdle
has always been to find a way to deliver viruses to tumours via the bloodstream
without the body’s immune system destroying them on the way.
10. "What we’ve done is make chemical modifications to the virus to put a
polymer coat around it - it’s a stealth virus when you inject it," he said.
11. After the stealth virus infects the tumour, it replicates, but the copies
do not have the chemical modifications. If they escape from the tumour, the
copies will be quickly recognised and mopped up by the body’s immune system.
12. The therapy would be especially useful for secondary cancers, called
metastases, which sometimes spread around the body after the first tumour
appears. "There’s an awful statistic of patients in the west ... with malignant
cancers; 75% of them go on to die from metastases," said Prof Seymour.
13. Two viruses are likely to be examined in the first clinical trials:
adenovirus, which normally causes a cold-like illness, and vaccinia, which
causes cowpox and is also used in the vaccine against smallpox. For safety
reasons, both will be disabled to make them less pathogenic in the trial, but
Prof Seymour said he eventually hopes to use natural viruses.
14. The first trials will use uncoated adenovirus and vaccinia and will be
delivered locally to liver tumours, in order to establish whether the treatment
is safe in humans and what dose of virus will be needed. Several more years of
trials will be needed, eventually also on the polymer-coated viruses, before the
therapy can be considered for use in the NHS. Though the approach will be
examined at first for cancers that do not respond to conventional treatments,
Prof Seymour hopes that one day it might be applied to all cancers.
Questions 1-6
Do the following statements agree with the information given in the reading
passage? For questions 1-6 write
TRUE if the statement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this in the passage
1.Virus therapy, if successful, has an advantage in eliminating
side-effects.
2.Cancer Research UK is quite hopeful about Professor Seymour’s work on the
virus therapy.
3.Virus can kill cancer cells and stop them from growing again.
4.Cancer’s Achilles’ heel refers to the fact that virus may stay safely in a
tumor and replicate.
5.To infect the cancer cells, a good deal of viruses should be injected into
the tumor.
6.Researches on animals indicate that virus could be used as a new way to
treat drug-resistant tumors.
Question 7-9
Based on the reading passage, choose the appropriate letter from A-D for each
answer.
7.Information about researches on viruses killing tumor cells can be
found
(A) on TV
(B) in magazines
(C) on internet
(D) in newspapers
8.To treat tumors spreading out in body, researchers try to
(A) change the body’ immune system
(B) inject chemotherapy drugs into bloodstream.
(C) increase the amount of injection
(D) disguise the viruses on the way to tumors.
9.When the chemical modified virus in tumor replicates, the copies
(A) will soon escape from the tumor and spread out.
(B) will be wiped out by the body’s immune system.
(C) will be immediately recognized by the researchers.
(D) will eventually stop the tumor from spreading out.
Questions 10-13
Complete the sentences below. Choose your answers from the list of words. You
can only use each word once.
NB There are more words in the list than spaces so you will not use them
all.
In the first clinical trials, scientists will try to ……10…… adenovirus and
vaccinia, so both the viruses will be less pathogenic than the ……11…….These
uncoated viruses will be applied directly to certain areas to confirm safety on
human beings and the right ……12…… needed. The experiments will firstly be
……13……to the treatment of certain cancers
（x>0，y>0）的极值
处一定没有切线.