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LISTEN AND READ 07
Beach Forensics
NAME THAT DUNE
The sound of sand reveals its source
Lift a shell from the sand to your ear and everyone knows you can hear the sea. But listen carefully enough and you can hear shells in the sand too. Sand, it turns out, has a signature sound of its own, and now scientists have found a way to tune in.
To the untrained eye, one bucket of beach sand looks much like another but mixed into the multitude of microscopic minerals are carbonate chemicals left behind from the shells of long-dead sea creatures such as molluscs. The carbonate concentration varies according to local geology, and Saskia van Ruth, a researcher at Wageningen University in the Netherlands, and her colleagues say this leaves each batch of sand with its own distinctive noise. The results could extend forensic techniques, providing a quick way to determine the source of disputed sand.
After water, sand and gravel are the most used natural materials in the world. But a looming global shortage has led to a boom in clandestine sand mining and even outright theft. In the southern Indian state of Tamil Nadu, authorities are battling a so-called “sand mafia” who supply the construction industry through illegal dredging of riverbanks. Last year Malaysia became the latest country in the region to ban the sale and export of its sand, demand for which has soared as Singapore seeks to reclaim land from the sea. A decade ago an entire beach, 500 truckloads, was stolen from a resort in northern Jamaica and, it is believed, sold to rival operators.
Writing in Applied Acoustics, Dr van Ruth’s team show they can distinguish between sand samples retrieved (legally) from nine seaside spots along the Dutch coast.
Thẩm tâm Vy, Sept. 14
th
, 2019 LISTEN AND READ 07
LISTEN AND READ 07
Beach Forensics
NAME THAT DUNE
The sound of sand reveals its source
Lift a shell from the sand to your ear and everyone knows you can hear the sea.
But listen carefully enough and you can hear shells in the sand too. Sand, it turns
out, has a signature sound of its own, and now scientists have found a way to
tune in.
To the untrained eye, one bucket of beach sand looks much like another but
mixed into the multitude of microscopic minerals are carbonate chemicals left
behind from the shells of long-dead sea creatures such as molluscs. The
carbonate concentration varies according to local geology, and Saskia van Ruth,
a researcher at Wageningen University in the Netherlands, and her colleagues
say this leaves each batch of sand with its own distinctive noise. The results
could extend forensic techniques, providing a quick way to determine the
source of disputed sand.
After water, sand and gravel are the most used natural materials in the world.
But a looming global shortage has led to a boom in clandestine sand mining and
even outright theft. In the southern Indian state of Tamil Nadu, authorities are
battling a so-called “sand mafia” who supply the construction industry through
illegal dredging of riverbanks. Last year Malaysia became the latest country in
the region to ban the sale and export of its sand, demand for which has soared as
Singapore seeks to reclaim land from the sea. A decade ago an entire beach, 500
truckloads, was stolen from a resort in northern Jamaica and, it is believed, sold
to rival operators.
Writing in Applied Acoustics, Dr van Ruth’s team show they can distinguish
between sand samples retrieved (legally) from nine seaside spots along the
Dutch coast. And armed with that information as a reference tool, they could
work out which beach a given sand sample had come from.
The scientists used a technique called Broad Acoustic Dissolution Spectroscopy
analysis (BARDS). It is done with a sensitive listening device that picks up
changes in acoustic properties when a scoop of sand or other powder is dropped
into a beaker of mild acid and mixed. Chemical changes, including the
breakdown of carbonates to carbon dioxide, release bubbles that increase the
compressibility of the liquid and therefore slow down the passage of sound
through it. Tap the side of the beaker as the sand and acid are mixed together and
the sound that emerges drops in frequency over time. After a few minutes, all of
the carbonate is broken down so the production of gas slows and stops. In
response, the frequency of sound passing through the liquid goes back to normal.
This gives each sample of sand two distinct measurements: how quickly the
sound changes pitch, and how much it does so.
Dara Fitzpatrick, a chemist at University College Cork, who developed the
BARDS technique, says the change, from high notes to low and then back again,
can be heard when many powders dissolve and is known to physicists as the hot-
chocolate effect. “You can do it in your kitchen,” he says. His team is selling the
kit to drug companies as a quicker and cheaper way to analyse powders. It has
also been used to distinguish expensive Himalayan table salt from inferior fakes.
With sand, the more carbonate there is to produce carbon-dioxide gas, the
greater the acoustic shift. That is what allows the eavesdropping scientists to
pinpoint its source. They can also pick up more subtle influences, including the
effect of the remains of different-shaped shells, because variations in their
thickness and surface area speed or slow the release of gas.
Follow the sand
In places like the Netherlands, forensic tracing could help track the
effectiveness of coastal-management practices, such as the dumping of millions
of tonnes of sand to bolster natural defences against the sea. Where that sand
ends up is not always clear. Placing the sand directly onto beaches is believed to
be wasteful because much of it is washed back into the sea. Newer methods drop
the sand into the shallow water just off the beach, allowing the tides to deposit it
onto the land over time. Dr Fitzpatrick says existing methods to distinguish sand
samples are crude and slow as they rely on looking at the size and shape of
individual grains under a microscope. He sells sea shells as a way to see more.
[The Economist, 14.9.2019]
Notes:
- forensic techniques: kỹ thuật pháp y
- beaker : cốc vại
- pinpoint: định vị chính xác
- to bolster lót, đỡ, chèn bằng gối, đệm
~(**)~
^
Ageing
REJUVENATION JUICE
Uncovering how the body ages is leading to drugs to reverse it
In 2006, a startup in California called Ambrosia began offering its customers
startup in California called Amtransfusions of blood from the young. At $8,000
per litre, it was a service for the wealthy who believed that young blood could
slow down or reverse the ageing process, thereby reducing their chances of
developing cancers, Alzheimer’s disease and heart disease. Earlier this year Thẩm tâm Vy, Sept. 14
th
, 2019 LISTEN AND READ 07
America’s Food and Drug Administration (FDA) cautioned potential customers
that there was no proven scientific benefit to receiving such blood.
In response, Ambrosia shut down its clinics. But ill-fated startups aside, there
is a kernel of truth to the idea that young blood can be rejuvenating. Experiments
in the early 2000s in which mice of different ages had been stitched together to
share their circulatory systems, known as heterochronic parabiosis, had
demonstrated dramatic improvements in the cognition, muscle repair and liver
function of the elderly partners. The race this work sparked to translate the idea
into something useful to humans, however, raises issues, not least in the
squeamishness and hazards associated with sharing blood.
Perhaps no longer. One of the pioneers of parabiosis, Irina Conboy, a
bioengineer at the University of California, Berkeley, has now developed a way
to get some of the benefits of parabiosis without any of the gruesome methods.
She and other scientists in the field had previously found that not only did old
partners benefit from parabiosis, but young partners suffered: the old blood aged
them prematurely. Some of the decline was caused by a protein called
transforming growth factor beta (TGFbeta). This is normally responsible for
regulating everything from cell proliferation to differentiation and death. As
people age, TGF-beta accretes in the blood and this leads to problems such as
inflammation or fibrosis.
In a new study published in Ageing, Dr Conboy describes a way to slow down
this damage. Her team gave ageing mice a cocktail of oxytocin, a hormone, and
ALK5 inhibitor, an enzyme. Previous studies showed that these had positive
effects on some of the symptoms of ageing. By suppressing the amount of TGF-
beta in cells, the ALK5 inhibitor had been shown to stimulate the growth of new
brain cells and improve muscle and tissue health. And oxytocin, which activates
stem-cell formation in response to tissue damage or atrophy, declines naturally
with age.
However, to have any effects, ALK5 inhibitor usually had to be given at very
high doses. And when researchers tried to add extra oxytocin by itself, the
hormone’s benefits were overwhelmed by waste accreted in old blood. By
putting them together, however, it was possible to reduce the dose of ALK5
inhibitor by a factor of ten and reap the benefits of the oxytocin.
After seven days on this cocktail, the mice had less inflammation in their
brains, more neural stem cells in the brain area responsible for memory and
learning, and better cognitive capacity. Their livers had less scarring and fat, and
their muscles healed better and faster. In short, their bodies and brains looked a
lot like the old mice after parabiosis—but without the drawbacks of a blood
buddy.
Because both ingredients of this chemical cocktail are already approved by the
FDA, Dr Conboy’s team is now planning a clinical trial of 20 volunteers over
65, to see if the cocktail’s rejuvenating powers will work in people.
The latest findings have been welcomed, albeit cautiously. Scientists at the
American National Institute on Ageing say the latest work may show a way
forward in a field that currently seems stuck. But they think it is too early to
advance the research into human trials. The concern is that the drugs being used
have not previously been tested together in people. Dr Conboy points out,
however, that prescribing approved drugs in multiple combinations is a standard
procedure in medicine. Entrepreneurs in Silicon Valley might have jumped the
gun in selling the rejuvenating effects of parabiosis to their clients. Nevertheless,
this vampire-like concept is not gone yet—and could still rise up from the dead
someday soon. [The Economist, 14.9.2019]
Notes:
- heterochronic parabiosis: đời sống ghép nhờ sự chuyển hóa gen của mô
- squeamishness: sự đắn đo, câu nệ
- accretes: cùng phát triển thành một khối
- fibrosis: chứng xơ hóa
- oxytocin: hormone tuyến yên