Scans reveal what makes beetle ‘uncrushable’
They don’t call it the diabolical ironclad beetle for nothing. Phloeodes diabolicus, a rugged insect native to western North America, has an almost supernatural ability to resist compression and blunt hits. Now, 3D scans have revealed that layered structures in its interlocking wing cases make the beetle twice as hardy as some of its relatives — and could provide inspiration for tough new materials.
Phloeodes diabolicus’s durability is unique among beetles. The insect is notorious among collectors for being difficult to pin to a board: pins tend to bend when pushed into its exoskeleton.
To understand what makes the beetle so resilient, materials scientist David Kisailus at the University of California, Irvine, and his collaborators carried out micro computed tomography scans on beetles using a synchrotron, a particle accelerator that produces bright beams of X-ray energy. They developed a device that could rotate the insect’s body inside the scanner while subjecting it to various levels of compression.
The study, published on 22 October (J. Rivera et al. Nature 586, 543–548; 2020), shows how the beetle’s wing cases, which lock together and to the insect’s abdomen like a 3D jigsaw puzzle, are able to withstand pressure. The researchers were surprised to see that, rather than being ripped off as the pressure approaches breaking point, the interlocking parts of the jigsaw pieces are able to shed layers like an onion. This allows them to take some damage without compromising the overall structural integrity of the wing cases.
The team then 3D-printed similar layered structures, and found them to be twice as resistant to being pulled apart as was a type of joint commonly used by engineers. Designs inspired by the beetle’s wing cases could prove especially useful for joining materials that have different properties, Kisailus says — such as the metal- and carbon-based materials used in composite parts for aerospace engineering.
COVID-19 shrugs at seasons
The arrival of spring and summer do not slow transmission of SARS-CoV-2, say researchers who studied the early stages of the pandemic.
Influenza viruses survive for longer outside the body in cold, dry air than in warmer, more humid environments, giving them the chance to infect more people in winter than in spring and summer. Research has given a mixed picture of whether the new coronavirus shows similar behaviour.
To see how the changing seasons affected the virus’s spread in China, Canelle Poirier and Mauricio Santillana at Harvard Medical School in Boston, Massachusetts, and their colleagues created a model incorporating data from China collected between mid-January and mid-February (C. Poirier et al. Sci. Rep. 10, 17002; 2020). These data included COVID-19 case counts, weather conditions and information about domestic travel. The model also took into account lockdowns instigated by the government.
The team found that the weather alone could not explain variability in the virus’s spread, which continued in areas of China with tropical climates as well as in those that are cold and dry.
Sold! Economics Nobel goes to auction theory
The 2020 Nobel prize in economic sciences was awarded to Paul Milgrom and Robert Wilson, both of Stanford University in California, for their insights into auction theory. Their work, which dates from the 1960s and 1970s, has found applications ranging from the pricing of government bonds to the licensing of radio-spectrum bands in telecommunications.
Diane Coyle at the University of Cambridge, UK, says the winners “not only did foundational work themselves, but also inspired cohorts of younger researchers”.
There are many ways to stage auctions: for example, in an ‘English auction’, the item on offer simply goes to the highest bidder, whereas in a ‘Dutch auction’, the selling starts at a high price and bidders submit the price they are willing to pay.
Bidding is also affected by factors that might cause losses for the winning bidder, create inefficiencies of allocation, or harm the public good. The laureates’ work has helped to reduce these problems and to suggest more efficient ways for auctions to be conducted.
“Unlike many theoreticians, Wilson and Milgrom brought their work to the real world, and transformed government policies toward auctions around the world,” says Preston McAfee, an economist at Google in San Marino, California.