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Superfluids give new insight into turbulence

Australian scientists have validated a 70-year-old theory that explains the existence of large, long-lived vortices like cyclones and Jupiter’s great Red Spot. Until now, experiments had tended to conflict with its predictions because most fluids are viscous, meaning they resist flow.

The researchers studied the behaviour of vortices in a superfluid – a type of exotic fluid that has no viscosity – known as a Bose-Einstein condensate, which is produced by cooling a gas of rubidium atoms to extremely cold temperatures.

“We created a thin disk of the superfluid and then used lasers to inject vortices at carefully specified locations,” says co-author Dr Tyler Neely from the University of Queensland. “The vortices mixed rapidly, merging into a single large cluster in only a few seconds, much like a large cyclone forming from the turbulent atmosphere.

“However, the most exciting thing was the remarkable agreement between theory and experiment – the theory predicted the shape of the final giant vortex structures in the superfluid exceptionally well. Our results suggest superfluids can be used to learn new things about turbulence, and will be crucial for the development of precision sensors based on superfluids.”

The study was published in Physical Review X.

Fat cells in the skin help fight acne

Researchers have discovered a specific antimicrobial skin cell and the role it plays in acne development, which could result in more targeted treatment options.

A new study published in Science Translational Medicine has found that skin cells called fibroblasts – which provide structural support in the deeper layers of the skin – play a significant role in controlling the acne-causing bacteria species Cutibacterium acnes.

They found that when there is an infection within a hair follicle, the surrounding skin undergoes a process in which these fibroblasts are activated. They transform into fat cells and produce large amounts of an antimicrobial peptide called cathelicidin.

The team also performed skin biopsies on acne patients treated for several months with retinoids, and to their surprise they found that the drug enhances cathelicidin expression after treatment. This is an additional, previously unknown mechanism for why retinoids help treat acne.

“This research could assist in identifying new treatment options that specifically target the fibroblast’s ability to produce cathelicidin,” says first author Dr Alan O’Neill, from the UC San Diego School of Medicine in the US. “Thus creating a therapeutic for acne that would be more selective with potentially less harmful side effects.”

A link between temperature and reproduction for insect control

Scientists have discovered a set of neurons in fruit flies (Drosophila melanogaster) that shut down in cold temperatures and slow reproduction. This system is maintained in many insects, including mosquitoes, and could provide a new target for pest control.

In the study, researchers identified a subset of circadian neurons in the fly brain that are important for sensing and responding to environmental cues such as light and cold. The paper was published in Current Biology.

When exposed to cold temperatures, the flies’ rates of egg production slowed down and electrodes in the brain showed that the neurons were active in warm temperatures and inactive in the cold.

The scientists found that an insect signalling protein called Allotostatin (AstC) was expressed in these neurons, and it stimulated egg production in experiments where it was injected or overproduced from the neurons.

The expression of this AstC gene was regulated by temperature, with levels of AstC decreased in cold and increased in warm temperatures. The researchers then found the receptor that AstC binds to stimulate egg production; they hope that it could become a target for chemical intervention that could suppress mosquito and agricultural pest populations.

Forgotten species go extinct twice

Species go extinct twice, first when the last individual dies and second when the collective memory about it disappears. New research on societal extinction – the loss of species from our collective memory and attention – has found that whether a species will become societally extinct depends on many factors, including its charisma, its symbolic or cultural values, whether and how long ago it went extinct, and how distant and isolated its range is from humans.

“Societal extinction occurs not only in extinct species, but also in those species still living among us, often due to social or cultural changes, for example, the urbanization or digitisation of society, which can radically change our relationship with nature, and lead to the collective loss of memory,” says co-author Dr Diogo Verissimo of the University of Oxford, UK.

The research was published in Trends in Ecology & Evolution.

Scientists reveal how Venus fly traps snap shut

Scientists have revealed the three-dimensional structure of the protein channel – aptly named Flycatcher1 – that may enable Venus fly traps to snap shut in response to prey.

The study, published in Nature Communications, used cryo-electron microscopy – a cutting-edge technique that reveals the locations of atoms within a frozen protein sample – to analyse the precise arrangement of molecules that form the Flycatcher1 protein channel.

“Despite how different Venus fly traps are from humans, studying the structure and function of these mechanosensitive channels gives us a broader framework for understanding the ways that cells and organisms respond to touch and pressure,” says co-senior author Dr Andrew Ward, a biology professor at Scripps Research in the US.