New Scientist - USA (2021-10-30)

30 October 2021 | New Scientist | 25

Materials

WOODEN knives that are much

sharper than steel ones could help

us to cut energy use and plastic

cutlery waste.

Teng Li at the University of

Maryland and his team developed

a material called hardened wood

that is 23 times harder than raw

wood and can be carved to make

blades three times sharper than

standard steel ones.

The key to these wooden knives

is the use of strong cellulose fibres

found in plant cell walls, which make

up almost half the mass of wood,

rather than the weaker polymers in

cell walls. The team removed the

weaker polymers from raw wood

chemically, before compressing

the remaining cellulose fibres at

a pressure of 20 megapascals for

6 hours and drying them at around

100°C to produce hardened wood.

Metal cutlery requires much more

energy to produce.

The researchers compared the

sharpness of knives made from

hardened wood with those made

from steel. They found that the

wooden knives required around

three times less force to slice

through a standard electrical wire

and felt comparable with steel

knives when cutting through a

medium well-done steak (Matter,

doi.org/g3g8). Carissa Wong

Extra sharp knife is made

entirely out of wood

BO

CH

EN

Quick saliva test can

reveal cannabis use

It is possible to tell whether

someone has consumed

cannabis within the past

12 hours with a saliva test

that detects THC, the main

psychoactive component of

the drug. Each test would

cost just £3.60 once

commercialised (Science

Translational Medicine,

doi.org/g3hn).

Elephants evolved

due to poaching

Female African elephants

in Mozambique evolved to

lose their tusks in response

to intense ivory poaching

that occurred during the

1977 to 1992 civil war.

Males retained their tusks

because the genetic

mutations that lead to tusk

loss kill male embryos

(Science, doi.org/g3hp).

Fossil fuel plans bad

news for climate

Collectively, countries

around the world plan to

extract twice the amount

of fossil fuels permitted by

the toughest targets of the

Paris Agreement, according

to an analysis for the UN.

In 2030, 110 per cent

more fossil fuels will be

produced than the Paris

deal’s target of keeping

warming to 1.5°C or below

allows, concludes the

Production Gap report.

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A

Really brief

Insects

IMPORTANT information about

how ant populations are evolving

in the face of global warming,

forest farming and urbanisation

has come from a citizen science

project involving hundreds of

Danish children.

The children and their families

trapped 19,000 ants across

Denmark. Comparing the new

catches with specimens dating

back to 1900, a research team has

detected major population shifts

in these “hugely important, but

vastly underappreciated” insects,

says team member Julie Sheard at

the University of Copenhagen.

Taking into consideration the

year in which historical specimens

were captured and their locality,

the researchers used modelling to

estimate how the geographical

range and population size of 29 ant

species has changed over the years

(Biology Letters, doi.org/g3dj).

They discovered that while half

of the species have had stable

populations since 1900, the

other half have either declined,

increased or fluctuated, says

Sheard. They found jet ants (Lasius

fuliginosus), European fire ants

(Myrmica rubra) and two other

Myrmica species have seen their

populations decline, mainly

since the 1950s. CLL

Ants caught by kids

show insect changes

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Global warming

TINY bits of plastic in the air may

have a minor cooling effect on our

climate by reflecting sunlight.

In recent years, microplastics in

the atmosphere have been found

around the world, with the highest

concentrations in the air above

London and Beijing. With a size of

between 15 and 250 micrometres,

about as thick as a strand of hair,

airborne microplastics are bigger

than most other aerosols in the

atmosphere. However, due to their

low density, they are easily carried

over large distances.

These very small bits of plastic

typically come from synthetic

textiles, such as polyester,

synthetic rubber tyres, paint

and larger plastic that breaks up.

Laura Revell at the University

of Canterbury in New Zealand

and her team investigated the

effect of these particles on

our climate. They found that the

microplastics both reflect sunlight

back to space and absorb heat

coming from Earth’s surface,

which means they can cool and

warm the climate. However, the

team found they have an overall

cooling effect, reflecting more

heat than they absorb.

But the team also found that

this cooling effect is negligible

compared with the cooling

and warming influences of

greenhouse gases and other

atmospheric aerosols (Nature,

doi.org/g3hk).

The concentration of

microplastic particles in the

atmosphere is several orders of

magnitude smaller than other

types of atmospheric aerosols,

which is why their climate effect

is so small, says Revell. CL

Airborne plastic

slightly cools Earth