You
should spend about 20 minutes on Questions 1-12, which are based on Reading Passage 1 below.
Scientists Are Mapping
the World's Largest Volcano
(A) After 36 days of battling sharks that kept biting their equipment,
scientists have returned from the remote Pacific Ocean with a new way of
looking at the world’s largest - and possibly most mysterious - volcano, Tamu
Massif.
(B) The team has begun making 3-D maps that offer the clearest look
yet at the underwater mountain, which covers an area the size of New Mexico. In
the coming months, the maps will be refined and the data analyzed, with the
ultimate goal of figuring out how the mountain was formed.
(C) It's possible that the western edge of Tamu Massif is actually a
separate mountain that formed at a different time, says William Sager, a
geologist at the University of Houston who led the expedition. That would
explain some differences between the western part of the mountain and the main
body.
(D) The team also found that the massif (as such a massive
mountain is known) is highly pockmarked with craters and cliffs. Magnetic
analysis provides some insight into the mountain’s genesis, suggesting that
part of it formed through steady releases of lava along the intersection of
three mid-ocean ridges, while part of it is harder to explain. A working theory
is that a large plume of hot mantle rock may have contributed additional heat
and material, a fairly novel idea.
(E) Tamu Massif lies about 1,000 miles (1,600 kilometers) east
of Japan. It is a rounded dome, or shield volcano, measuring 280 by 400 miles
(450 by 650 kilometers). Its top lies more than a mile (about 2,000 meters)
below the ocean surface and is 50 times larger than the biggest active volcano
on Earth, Hawaii’s Mauna Loa. Sager published a paper in 2013 that said the
main rise of Tamu Massif is most likely a single volcano, instead of a complex
of multiple volcanoes that smashed together. But he couldn’t explain how
something so big formed.
(F) The team used sonar and magnetometers (which measure
magnetic fields) to map more than a million square kilometers of the ocean
floor in great detail. Sager and students teamed up with Masao Nakanishi of
Japan’s Chiba University, with Sager receiving funding support from the
National Geographic Society and the Schmidt Ocean Institute.
(G) Since sharks are attracted to magnetic fields, the toothy
fish “were all over our magnetometer, and it got pretty chomped up,” says
Sager. When the team replaced the device with a spare, that unit was nearly
ripped off by more sharks. The magnetic field research suggests the mountain formed
relatively quickly, sometime around 145 million years ago. Part of the volcano
sports magnetic "stripes," or bands with different magnetic
properties, suggesting that lava flowed out evenly from the mid-ocean ridges
over time and changed in polarity each time Earth's magnetic field reversed
direction. The central part of the peak is more jumbled, so it may have formed
more quickly or through a different process.
(H) Sager isn’t sure what caused the magnetic anomalies yet, but
suspects more complex forces were at work than simply eruptions from the
ridges. It’s possible a deep plume of hot rock from the mantle also contributed
to the volcano’s formation, he says. Sager hopes the analysis will also help
explain about a dozen other similar features on the ocean floor, as well as add
to the overall understanding of plate tectonics.
Questions 1-8
Reading Passage 1 has
eight paragraphs, A-H.
What paragraph has the
following information? Write the correct letter, A-H, in boxes 1-8 on your answer sheet.
1. Possible
explanation of the differences between parts of the mountain
2. Size data
3. A new way of
looking
4. Problem with
sharks
5. Uncertainty of the
anomalies
6. Equipment which
measures magnetic fields
7. The start of
making maps
8. A working theory
Questions 9-12
Complete the sentences
using NO MORE THAN TWO WORDS from the passage.
Write your answers in
boxes 9–12 on your answer sheet.
9. A large plume
of rock may have contributed additional heat and
material.
10.Tamu Massif is a ,
or shield volcano.
11. Replacing the
device with a didn't help, as that unit was
nearly ripped off by more sharks.
12. Sager believes
that the magnetic anomalies were caused by something more than from
the ridges.
You
should spend about 20 minutes on Questions 13-28, which are based on Reading Passage 2 below.
We know the city where HIV first emerged
It
is easy to see why AIDS seemed so mysterious and frightening when US medics
first encountered it 35 years ago. The condition robbed young, healthy people
of their strong immune system, leaving them weak and vulnerable. And it seemed
to come out of nowhere.
Today
we know much more how and why HIV – the virus that leads to AIDS – has become a
global pandemic. Unsurprisingly, sex workers unwittingly played a part. But no
less important were the roles of trade, the collapse of colonialism, and 20th
Century sociopolitical reform.
HIV
did not really appear out of nowhere, of course. It probably began as a virus
affecting monkeys and apes in west central Africa.
From
there it jumped species into humans on several occasions, perhaps because
people ate infected bushmeat. Some people carry a version of HIV closely
related to that seen in sooty mangabey monkeys, for instance. But HIV that came
from monkeys has not become a global problem.
We
are more closely related to apes, like gorillas and chimpanzees, than we are to
monkeys. But even when HIV has passed into human populations from these apes,
it has not necessarily turned into a widespread health issue.
HIV
originating from apes typically belongs to a type of virus called HIV-1. One is
called HIV-1 group O, and human cases are largely confined to west Africa.
In
fact, only one form of HIV has spread far and wide after jumping to humans.
This version, which probably originated from chimpanzees, is called HIV-1 group
M (for "major"). More than 90% of HIV infections belong in group M.
Which raises an obvious question: what's so special about HIV-1 group M?
A
study published in 2014 suggests a surprising answer: there might be nothing
particularly special about group M.
It
is not especially infectious, as you might expect. Instead, it seems that this
form of HIV simply took advantage of events. "Ecological rather than
evolutionary factors drove its rapid spread," says Nuno Faria at the
University of Oxford in the UK.
Faria
and his colleagues built a family tree of HIV, by looking at a diverse array of
HIV genomes collected from about 800 infected people from central Africa.
Genomes
pick up new mutations at a fairly steady rate, so by comparing two genome
sequences and counting the differences they could work out when the two last
shared a common ancestor. This technique is widely used, for example to
establish that our common ancestor with chimpanzees lived at least 7 million
years ago.
"RNA
viruses such as HIV evolve approximately 1 million times faster than human
DNA," says Faria. This means the HIV "molecular clock" ticks
very fast indeed.
It
ticks so fast, Faria and his colleagues found that the HIV genomes all shared a
common ancestor that existed no more than 100 years ago. The HIV-1 group M
pandemic probably first began in the 1920s.
Then
the team went further. Because they knew where each of the HIV samples had been
collected, they could place the origin of the pandemic in a specific city:
Kinshasa, now the capital of the Democratic Republic of Congo.
At
this point, the researchers changed tack. They turned to historical records to
work out why HIV infections in an African city in the 1920s could ultimately
spark a pandemic.
A
likely sequence of events quickly became obvious. In the 1920s, DR Congo was a
Belgian colony and Kinshasa – then known as Leopoldville – had just been made
the capital. The city became a very attractive destination for young working
men seeking their fortunes, and for sex workers only too willing to help them
spend their earnings. The virus spread quickly through the population.
It
did not remain confined to the city. The researchers discovered that the
capital of the Belgian Congo was, in the 1920s, one of the best connected
cities in Africa. Taking full advantage of an extensive rail network used by
hundreds of thousands of people each year, the virus spread to cities 900 miles
(1500km) away in just 20 years.
Everything
was in place for an explosion in infection rates in the 1960s.The beginning of
that decade brought another change.
Belgian
Congo gained its independence, and became an attractive source of employment to
French speakers elsewhere in the world, including Haiti. When these young
Haitians returned home a few years later they took a particular form of HIV-1
group M, called "subtype B", to the western side of the Atlantic.
It
arrived in the US in the 1970s, just as sexual liberation and homophobic
attitudes were leading to concentrations of gay men in cosmopolitan cities like
New York and San Francisco. Once more, HIV took advantage of the sociopolitical
situation to spread quickly through the US and Europe.
"There
is no reason to believe that other subtypes would not have spread as quickly as
subtype B, given similar ecological circumstances," says Faria.
The
story of the spread of HIV is not over yet.
For
instance, in 2015 there was an outbreak in the US state of Indiana, associated
with drug injecting.
The
US Centers for Disease Control and Prevention has been analyzing the HIV genome
sequences and data about location and time of infection, says Yonatan Grad at
the Harvard School of Public Health in Boston, Massachusetts. "These data
help to understand the extent of the outbreak, and will further help to
understand when public health interventions have worked."
This
approach can work for other pathogens. In 2014, Grad and his colleague Marc
Lipsitch published an investigation into the spread of drug-resistant
gonorrhoea across the US.
"Because
we had representative sequences from individuals in different cities at
different times and with different sexual orientations, we could show the
spread was from the west of the country to the east," says Lipsitch.
What's
more, they could confirm that the drug-resistant form of gonorrhoea appeared to
have circulated predominantly in men who have sex with men. That could prompt
increased screening in these at-risk populations, in an effort to reduce
further spread.
In
other words, there is real power to studying pathogens like HIV and gonorrhoea
through the prism of human society.
Questions 13-20
Do
the following statements agree with the information given in Reading Passage 1?
In
boxes 13-20 on your answer sheet, 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
13. AIDS were first encountered 35 years ago.
14. The most important role in developing AIDS as a pandemia was
played by sex workers.
15. It is believed that HIV appeared out of nowhere.
16. Humans are not closely related to monkey.
17. HIV-1 group O originated in 1920s.
18. HIV-1 group M has something special.
19. Human DNA evolves approximately 1 million times slower than
HIV.
20. Scientists believe that HIV already existed in 1920s.
Questions 21-28
Complete
the sentences below.
Write NO MORE THAN TWO WORDS from the passage for each answer.
Write
your answers in boxes 21-28 on your answer sheet.
21. Scientists can place the origin of in
a specific city.
22. Kinshasa was a very for young
working men and many others willing to spend their money.
23. In just 20 years virus managed to to
cities 900 miles away.
24. Belgian Congo became an attractive source of employment to French
speakers when it gained .
25. HIV has spread quickly through the US and Europe because of
the .
26. It is said that outbreak in Indiana was associated with .
27. The same approach as for HIV can work for .
28. The form of gonorrhoea that is drug-resistant appeared to
have in men who have sex with men.
You should spend about 20 minutes on Questions 29-40, which
are based on Reading Passage 3 below.
Penguins' anti-ice trick
revealed
Scientists studying penguins’ feathers have revealed how the birds
stay ice free when hopping in and out of below zero waters in the Antarctic. A
combination of nano-sized pores and an extra water repelling preening oil the
birds secrete is thought to give Antarctic penguins’ feathers superhydrophobic
properties. Researchers in the US made the discovery using Scanning Electron
Microscopy (SEM) to study penguin feathers in extreme detail. Antarctic
penguins live in one of Earth’s most extreme environments, facing temperatures
that drop to -40C, winds with speeds of 40 metres per second and water that
stays around -2.2C. But even in these sub-zero conditions, the birds manage to
prevent ice from coating their feathers.
“They are an amazing species, living in extreme conditions, and
great swimmers. Basically they are living engineering marvels,” says research
team member Dr Pirouz Kavehpour, professor of Mechanical and Aerospace
Engineering at the University of California, Los Angeles (UCLA). Birds’
feathers are known to have hydrophobic, or non-wetting, properties. But
scientists from UCLA, University of Massachusetts Amherst and SeaWorld, wanted
to know what makes Antarctic penguins’ feathers extra ice repelling.
“What we learn here is how penguins combine oil and
nano-structures on the feathers to produce this effect to perfection,” explains
Kavehpour. By analysing feathers from different penguin species, the
researchers discovered Antarctic species the gentoo penguin (Pygoscelis papua) was
more superhydrophobic compared with a species found in warmer climes – the
Magellanic penguin (Spheniscus
magellanicus) – whose breeding sites include Argentinian desert.
Gentoo penguins’ feathers contained tiny pores which trapped air,
making the surface hydrophobic. And they were smothered with a special preening
oil, produced by a gland near the base of the tail, with which the birds cover
themselves. Together, these properties mean that in the wild, droplets of water
on Antarctic penguins’ superhydrophobic feathers bead up on the surface like
spheres – formations that, according to the team, could provide geometry that
delays ice formation, since heat cannot easily flow out of the water if the
droplet only has minimal contact with the surface of the feather.
“The shape of the droplet on the surface dictates the delay in
freezing,” explains Kavehpour. The water droplets roll off the penguin's
feathers before they have time to freeze, the researchers propose. Penguins
living in the Antarctic are highly evolved to cope with harsh conditions: their
short outer feathers overlap to make a thick protective layer over fluffier
feathers which keep them warm. Under their skin, a thick layer of fat keeps
them insulated. The flightless birds spend a lot of time in the sea and are
extremely agile and graceful swimmers, appearing much more awkward on land.
Kavehpour was inspired to study Antarctic penguins’ feathers after
watching the birds in a nature documentary: “I saw these birds moving in and
out of water, splashing everywhere. Yet there is no single drop of frozen ice
sticking to them,” he tells BBC Earth. His team now hopes its work could aid
design of better man-made surfaces which minimise frost formation.
“I would love to see biomimicking of these surfaces for important
applications, for example, de-icing of aircrafts,” says Kavehpour. Currently,
airlines spend a lot of time and money using chemical de-icers on aeroplanes,
as ice can alter the vehicles’ aerodynamic properties and can even cause them
to crash.
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