31 August 2019 | New Scientist | 17ChemistryDemographics TechnologyHoney can tell us all
about lead pollutionBees pick up pollution as
they fly around and some
of it ends up in their honey,
although it is still safe to
eat. Kate Smith at the
University of British
Columbia in Canada found
that analysing honey is as
good a way to check lead
levels as using soil or air
samples. It could be used
to monitor remote areas.Time to get up and
move around a bitSitting for nine and a half
hours or more a day is
associated with a higher
risk of early death in middle
aged and older people,
according to a review of
data from over 36,
individuals. The study
found that any level of
physical activity, regardless
of intensity, is linked to a
lower risk of premature
death (BMJ, doi.org/c9nw).Blood pressure
linked to brain sizePeople with high blood
pressure in their 40s seem
to have smaller brains at
age 70. The findings, from
a group of 500 people
aged between 69 and 71,
hints that looking after
your health may help
prevent some forms of
dementia (The Lancet
Neurology, doi.org/c9nm).This material will
self-destructAGENTS might soon be able to
drop behind enemy lines and
leave no trace, thanks to a material
that can be made into gliders or
parachutes but that disintegrates
when exposed to heat or light.
The self-destructing polymer,
initially designed for use in
battlefield sensors, is the work of
Paul Kohl at the Georgia Institute
of Technology and his colleagues.
They began with polymers that
have a low ceiling temperature,A CHINESE government policy
allowing all couples to have two
children led to an extra 5.4 million
births in its first 18 months.
China’s universal two-child policy,
announced in October 2015, was
designed to boost the country’s
stagnating population growth.
It targeted 90 million women of
reproductive age who already had
at least one child – 60 per cent of
these women were older than 35.
Susan Hellerstein at Harvard
University and her team looked at
data on 67.8 million births in most
of China from January 2014 to
December 2017. They measured
birth rates from July 2016 toDecember 2017, covering the first
18 months after the policy began.
The team compared these with
baseline birth rates up to the end of
June 2016, nine months after the
October 2015 announcement.
In the 18-month period, there
were 5.4 million additional births
to women who already had one or
more children (BMJ, doi.org/c9n2).
Despite the national increase in
births, the total probably fell short
of the government’s annual target
of 20 million. China’s one-child
policy, introduced in 1979, was
scrapped amid concerns about an
ageing population and shrinking
workforce. ❚ Donna Luthe point at which the key bonds
in a material begin to break.
Lots of polymers slowly
decompose when they reach this
temperature because many
bonds have to be severed. But
Kohl designed his material so
that as soon as one bond breaks,
the whole thing unzips.
It is made from a chemical
called an aldehyde with various
additives that can either make the
material rigid for use in a glider or
sensor, or flexible to make a fabric.
Sunlight can trigger the
disintegration. Or, in true spy
style, a small light-emitting diodeApp designed to spot
winter vomiting bugA SMARTPHONE app can detect
signs of norovirus, the most
common cause of gastroenteritis.
Jeong-Yeol Yoon and his team at
the University of Arizona used a
phone with an add-on microscope
and a light source to detect low
levels of norovirus in water.
Their technique can spot as little
as 10 attograms (10−18 grams) of
norovirus per millilitre, six orders
of magnitude better than other
portable detectors, says Yoon. That
is important, as even tiny amounts
of norovirus can trigger illness.
Also known as the winter
vomiting bug, norovirus is
notorious for causing vomiting
and diarrhoea in crowded
situations, such as on cruise ships.
At the heart of the team’s test
is a paper chip that contains tiny
beads of fluorescent polystyrene.
These beads contain antibodies
against norovirus. When virus is
present, it binds to clumps of
beads. Under the light, these
clumps fluoresce. Analysis via the
phone microscope reveals the
level of norovirus present.
The team is using it to test water
supplies. A diagnostic version for
checking stool samples is planned.
The research was presented at
an American Chemical Society
meeting in California. ❚ DLcan be put in a device to trigger it
to self-destruct on demand.
When the substance falls apart,
all that is left is a residue and a
faint smell. Kohl and his team
have made a glider with a 2-metre
wingspan, and he says they can
make 5 kilograms of the polymer
at a time. The work was presented
at a meeting of the American
Chemical Society in California.
Marek Urban at Clemson
University in South Carolina
worries that the residue could be
toxic. Kohl says he has tested it
on plants, which survived. ❚
Chelsea WhyteTwo-child policy in China sees
millions more babies born
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