If world agricultural authorities don't get their act together soon enough, your morning orange juice may disappear from the supermarket shelves – for good.

This is how critical the situation has become in the citrus growing world. In the past decades, a disease called Huanglongbing (HLB), also known as "citrus greening" disease, has been devastating orchards in Asia, the Americas and several African countries.

Although world production has increased in recent years thanks to strong market demand and new plantings, the disease's relentless expansion is leading growers to fear the worst.

The economic impacts are dramatic in some countries. In Brazil, production has fallen by more than 20%, 60% in Guadeloupe and and plummeted by more than 90% in Florida.

Florida, a well-known producer of oranges, saw thousands of jobs in the citrus sector disappear. Drastic quarantine and management measures have been put in place everywhere. The price of orange juice has doubled in the space of a year, with manufacturers now struggling to get their hands on fruits.

The disease is caused by a bacterium of the genus Candidatus Liberibacter, which parasitises the sap-conducting vessels, the phloem. Faced with the bacterium, the trees react by producing a sugar known as callose, which piles up in the vessels and chokes them off, just like in a thrombosis. The photosynthesis products synthesised in the leaves are then no longer distributed throughout the tree.

Following a long asymptomatic phase, internal damage is revealed in the form of yellow mottling on the leaves. The fruit becomes deformed, abnormally coloured and more bitter, making it impossible to sell. Twigs and then branches die back. These symptoms start on one branch before spreading to the whole tree. After a few years, clogged up vessels inevitably cause the trees to die.

A bacterium transmitted by insects

The bacterium is transmitted by two insects of the psyllid family. Measuring between 2 and 5 millimetres, these small winged insects, like aphids, feed themselves by inserting long their skinny tubes called rostrum into plants to suck the sap.

When they feed on very young citrus shoots carrying the HLB disease, they can pick up the bacterium, which then grows in them and is passed on to other trees, in the same way as mosquitoes transmit the dengue or chikungunya viruses. These two psyllid species are quite specific to citrus and related species such as the jasmine orange (Murraya paniculata), often used as an ornamental plant.

Psyllids are extremely effective at transmitting the bacterium. A single bite can be enough to transmit the disease. The Asian psyllid (Diaphorina citri) of tropical and subtropical origin has so far been observed in Asia, South America, the Caribbean, Florida and California. The African psyllid (Trioza erytreae) is better adapted to the cool conditions of certain African plateaus.

At present, of the world's major citrus-growing areas, only the Mediterranean basin and Australia are free of the disease. However, the African psyllid, even though it does not carry the disease, has already been well established in Spain and Portugal since 2014 and 2015 respectively. The Asian psyllid, which is considered to be the most efficient vector for transmitting the bacterium, was identified in Israel in 2021.

More recently still, in the summer of 2023, this same insect was identified for the first time in Europe in Cyprus. It is suspected that these long-distance movements could be linked to trade in citrus plants or the transport of ornamental plants by travellers. Warmer temperatures associated with climate change could also be favourable to the adaptation of D. citri throughout the Mediterranean basin.

Billions of dollars lost

In Florida, citrus trees have been devastated in the space of twenty years and orange production has fallen by more than 60%. The Florida orange juice industry has lost more than 3 billion dollars and almost 50% of associated jobs. Add to this the hurricanes of the past years, which have exacerbated the problem by causing fruits to fall from trees already weakened by the disease.

As research has no immediate solution to offer, some believe that the Florida citrus industry is over, while the other southern states of the United States are also under threat. Despite enormous preventive efforts, the disease is progressing in California.

In all, billions of dollars have been invested over the last two decades to combat the disease worldwide, but no lasting solution has been found.

In Brazil, in the state of São Paulo, where the disease has been present since 2004, the uprooting of infected trees and the massive use of pesticides ̶ up to more than 46 treatments per year ̶ against psyllid populations, has made it possible to restrict the infection rate of trees to around 20% over the last two decades.

However, in recent months, the infection rate has risen to almost 38% in medium-sized farms, suggesting the emergence of pesticide resistance in psyllids and a deterioration in the control of the disease's vection. This situation is leading investors to plant in areas where psyllids aren't present, or present only to a limited extent, such as the state of Minas Gerais.

Very active research

In the Mediterranean basin, the biggest priority is to limit psyllid populations, in particular through biological control. Portugal and Spain are currently carrying out successful mass releases of psyllid parasitoids, small insects that lay their eggs in psyllids and whose larvae then develop at their expense, devouring them from the inside. The plan is to also follow that policy in Cyprus.

Scientists will also be looking to stave off the bacterium by biomonitoring the area through regularly sampling throughout the Mediterranean region. In the event of positive results, this should lead to the immediate uprooting of infected trees in order to eradicate sources of contamination.

Finally, it is crucial to inform not only the citrus-growing sector, but also the general public, of the risks involved in moving plants, since the importation and use of grafts from infected territories to non-infected areas is the main source of new outbreaks of the disease.

The EU has already taken the measure of the problem by categorising HLB bacteria and their psyllid vectors as priority quarantine organisms, requiring Member States to draw up appropriate surveillance and contingency plans. In France, the departments in charge of surveillance and the research community have deployed dedicated unit within the National Platform of Epidemiological Surveillance in Plant Health as well as several action-based research projects.

All cultivated citrus fruits are vulnerable to HLB, and research into resistant varieties and rootstocks is now a key area of research with a view to developing sustainable production systems. Recent research suggests that certain genotypes related to cultivated citrus within the Aurantioideae, such as the caviar lemon, may be hardier.

It is therefore this type of variety that the French Agricultural Research Centre for International Development (CIRAD) and its partners are studying to understand the biological traits governing interactions between the bacterium and citrus plants.

This involves developing populations of hybrids between resistant and vulnerable individuals and gauge their resistance to the disease. The genetic and genomic studies carried out on this plant material should enable us to identify the genes associated with resistance mechanisms.

Ultimately, it will then be possible, through new crosses between pre-selected genotypes or biotechnological approaches, to propose rootstocks and varieties that are resistant to the disease, paving the way for citrus growing that no longer requires the massive use of pesticides in orchards.

Raphael Morillon, Research director at Cirad- molecular physiologist, Cirad; Barbara Hufnagel, Researcher in plant genomics and genetics, Cirad; Patrick Ollitrault, Researcher in genetics and genomics, Cirad; and Virginie Ravigné, Researcher in ecology of microbial and viral communities, Cirad

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Scientists have synthesized a form of glass that can knit itself back together after being damaged by gamma radiation.

Researchers observed films of chalcogenide glass with gamma-ray-induced defects gradually become whole again over time at room temperature, returning to a state of structural integrity without any other intervention.

The discovery, led by engineer Myungkoo Kang of Alfred University in the US, reveals a material that could be really useful in places like space environments, where gamma radiation is streaming constantly, or radioactive facilities where sensors durable to radiation would make a huge difference.

"People are increasingly looking at glasses that have similar optical transparency to crystals such as germanium that can be engineered for their composition and properties for use in applications where germanium may be used," says physicist Kathleen Richardson of the University of Central Florida.

"These glasses are seeing more and more use in systems where the community is looking for alternatives to some of the crystalline solutions that have historically been used before."

Glass is a pretty strange material at the best of times, but extremely useful in various ways. Chalcogenide glasses – those that include sulfur, selenium, tellurium, or polonium – interact with light in ways that make them useful for optical devices, especially in the realm of infrared sensing.

Kang and his colleagues were making just such a glass for use in satellite circuitry, using very precisely mixed amounts of sulfur, germanium, and antimony.

"These glasses exclude oxygen, and that's what makes them special for the infrared," Richardson says. "These are made of elements on the far-right side of the periodic table. When they bond together, they make very infrared-transparent materials but with very large atoms and weak bonds."

These glasses need to be tested under the stresses to which they may be exposed in operating conditions, and one of these for space environments is gamma radiation.

We're not exposed to space gamma rays here on Earth's surface, since our atmosphere works as a highly effective shield, but the radioactive decay of certain elemental isotopes can produce gamma radiation.

To expose their samples to the highly energetic form of light, the researchers placed their samples in irradiators powered by cobalt-60, a synthetic form of radioactive cobalt. This exposure created microscopic defects in the glass by distorting the weak bonds between the atoms.

Then, the glass was placed in room-temperature conditions. By 30 days later, the glass had recovered.

"Because they're big atoms and weak bonds, over time, these bonds can relax back and reform from this distorted arrangement, and therefore heal," Richardson says.

"So, the concept of self-healing glass is that when our experiments get exposed to high-energy radiation, these bonds are distorted or broken. Over time, room temperature is enough to heal these bonds so that the structures can reform themselves."

The potential here is pretty interesting. The glass, or a future form of it, could one day be used as a durable, reversible radiation sensor for extreme environments, for example.

The team hopes to develop the glass further, and use it as a springboard for hopefully creating other glasses that have the same self-healing ability.

"Moving forward, my new research group aims to develop irradiation-induced novel ceramics along with in-situ microstructural and optical metrology methods as a route toward the realization of ultra-fast lightweight optical platforms," Kang says.

"My research under the unifying theme of irradiation effects in chalcogenide ceramics has yielded such an impactful takeaway."

The research has been published in the Materials Research Society Bulletin.

While scratching surfaces is a normal cat behavior, a new study explains why some of our beloved clawed floofs are more destructive than others. And no, they're not just trolling you with their rapscallion ways.

"We show that certain factors – such as the presence of children at home, personality traits of cats, and their activity levels – significantly impact the extent of scratching behavior," says veterinary researcher Yasemin Salgirli Demi̇rbas from Ankara University in Türkiye.

It is important to provide cats with surfaces for them to scratch on, as this activity keeps their claws sharp and prevents them from overgrowing and causing health problems. Scratched surfaces also act as a territorial marker, allowing cats to communicate with their fellow felines.

This, however, is where problems can arise. The more frustrated an owner gets at the cat tearing up the expensive leather couch, the more the cat is likely to scratch in response to heightened social tension, according to Salgirli Demi̇rbas and her colleagues from Portugal, Canada, and France.

The researchers surveyed over 1,200 cat owners – all of whom owned just one cat – to discover stress is the leading cause of excessive scratching in domestic cats. While self-reported data is prone to biases, they found a strong association.

"We see a clear link between certain environmental and behavioral factors and increased scratching behavior in cats," says Salgirli Demirbas.

"Specifically, the presence of children in the home as well as high levels of play and nocturnal activity significantly contribute to increased scratching. Cats described as aggressive or disruptive also exhibited higher levels of scratching."

This tells us how we can work with our cats to alter their behavior.

"Providing safe hiding places, elevated observation spots, and ample play opportunities can help alleviate stress and engage the cat in more constructive activities," advises Salgirli Demirba.

So if your cat is scratching where it should not, it is important to use positive reinforcement strategies, and avoid tactics that could exacerbate the cat's stress. Positive tactics include providing an alternative surface for scratching, close to the cat's chosen scratching area.

Cats usually scratch in socially significant areas, likely as a way to express their emotional state. So the location of their scratching post does matter to them.

It is also crucial to play with your feline companion in a way that works for them. Cats who played for extended periods were more likely to scratch more often, possibly from the stress of being overstimulated, the researchers suspect.

"Promoting regular and brief interactive play sessions, coupled with offering suitable toys, can alleviate stress and consequently reduce undesirable scratching behavior," the team recommends in their paper.

Cats really are particular creatures. They have strong preferences about many things, including how we pat them. Trying to pinpoint a specific stressor behind your cat's scratching response could help you work out how to mitigate the problematic behavior.

"Understanding the underlying emotional motivations of scratching behavior, such as frustration, which seem to be linked to personality traits and environmental factors, allows caregivers to address these issues directly," says Salgirli Demirbas.

Calming cat pheromones can help diffuse the situation in the meantime, while other tactics are investigated.

"Our findings can help caregivers manage and redirect scratching to appropriate materials, which could help foster a more harmonious living environment for both cats and their caregivers," Salgirli Demi̇rbas concludes.

Cats have been our companions for over 10,000 years now, protecting our crops, entertaining us, and providing affection. Trying to understand them better is the least we can do in return.

This research was published in Frontiers in Veterinary Science.

Understanding how life began and evolved on Earth is a question that has fascinated humans for a long time, and modern scientists have made great advances when it comes to finding some answers.

Now, our recent study hopes to offer new insights into the origin of life on Earth.

Around 375 million years ago, our fish-like ancestors breathed through gills. Over 600 million years ago, the common ancestor of all animals emerged – the microscopic urmetazoan.

Billions of years before all of that happened, however, the common ancestor of all living organisms, the last universal common ancestor (Luca), must have existed.

Scientists have worked on identifying Luca over the decades with different ideas about what Luca was like. Another point of contention is Luca's age. The earliest fossil evidence we have for life is around 3.4 billion years old.

Some studies push back Luca's age close to the birth of Earth, 4.5 billion years ago. Others think this is impossible because of the time it would take to establish the genetic code and DNA replication machinery.

Luca was not the first form of life; it was the organism from which all living organisms have descended. Nevertheless, scientists think living organisms may have existed way before Luca.

Understanding what Luca was like, and when it lived, is important for helping us figure out how life has evolved on Earth.

In our recent study, published in Nature Ecology & Evolution, we used a combination of scientific methods to reconstruct Luca's genome and show how the genes we found might have allowed Luca to live. This project was the result of several years of work and an international team of collaborators.

The nature of Luca

To reconstruct Luca's genome, we needed a sample of genomes (all the genetic information in an organism) from across different groups of bacteria and archaea (single cell organisms distinct from bacteria) so that we could be sure we were sampling modern life.

We excluded eukaryotes (plants, animals, and fungi) because scientists think they evolved from a union of archaea and bacteria, much later on. We had a set of 700 genomes (350 archaea and 350 bacteria), already curated from a 2022 study some of us were involved in.

We sorted these genes into different families to understand their purpose in modern organisms. We used a database for this, called KEGG, that helps scientists figure out organisms' metabolic pathways (how they sustain life).

Next, we used these families to infer phylogenetic trees (or phylogenies, somewhat like a family tree) to understand the relationship between different species and see how they evolved over time.

We also built a separate set of 57 genes that are common to all the 700 organisms in our study and that are probably in almost all life. These types of genes have not changed much over the last few billion years.

We used these 57 genes to build a species tree, which shows the Darwinian relationship of the different organisms. We could then combine our KEGG gene trees with the species tree, by modelling rates of gene duplication, gene transfer and loss. This also allowed us to calculate the likelihood of different gene families being present in Luca.

Reconstructing Luca's genome allowed us to estimate its metabolism, as if it were alive today. We picture Luca as a quite complex organism such as modern bacteria and archaea, with a small genome. However, we did not find evidence for photosynthesis (which some bacteria use) or nitrogen fixation, a chemical process some modern bacteria and archaea use to stay alive.

How old was Luca?

We also tried a new method to estimate Luca's age by using genes which we think duplicated before Luca together with information from fossils.

Normally, to infer evolutionary timelines, we would obtain a phylogeny of our species of interest with homologous genes, which trace back to a common ancestor.

Then, we would find a group of species that are distantly related (an outgroup) to our species of interest to establish the root of the phylogeny.

The "branches" that connect the species in a phylogeny hold information about the rate at which genetic changes (mutations) happened and the time at which species diverged. We can use fossil or geological evidence to inform the molecular clock about potential minimum ages at which speciation events took place.

With Luca, however, we have two problems. There is no outgroup to the origin of life and there are not many fossils or much geological evidence from the early Earth that we can use to calibrate the molecular clock.

To overcome these restrictions, we used paralogous genes that scientists had already traced to Luca. Paralogous genes are related to each other through gene duplication. This can happen when a species splits into two, each with its own copy of the duplicated gene.

We estimate that Luca roamed the Earth around 4.2 billion years ago. If our time estimate is close to the truth, things such as the genetic code, protein translation, and life itself must have evolved rapidly, almost right after the Earth was formed.

Our reconstruction of Luca is not the first, and it certainly will not be the last. More and more organisms are being discovered and sequenced each year, computers are getting more powerful, and evolutionary models are continuously improving.

Therefore, our understanding of Luca may change when more data and powerful techniques are available.

For instance, we should consider that there were probably many other organisms living at the time of Luca which are no longer represented by any organisms today.

If any of Luca's early descendants did not make it to the modern day, and their genes did not survive, then we will never be able to map these gene families back to Luca, which means our reconstruction of Luca may be incomplete.

Despite all technical limitations, our study sets a new way to understand Luca. But there is still much more work to be done to better understand how life has evolved since the formation of our planet Earth.

Edmund R. R. Moody, Senior Research Associate in Computational Evolutionary Biology, University of Bristol and Sandra Álvarez-Carretero, Research Fellow, UCL

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A crucial feature of superconductivity has just been observed at much higher temperatures than scientists had thought possible.

Physicists have found electrons pairing up in the way they do in superconducting materials in an unexpected material, above the incredibly cold temperatures similar materials permit superconductivity to occur.

Superconductivity decribes the way electrons move through a material without any resistance and subsequent energy loss. We've observed this phenomenon in many different materials, but there's a catch. We only seem to be able to make it happen at extremely low temperatures, close to absolute zero (-273.15 degrees Celsius, or -460 degrees Fahrenheit), or slightly less cold temperatures with a lot of pressure.

Although the electrons in the newly tested materials didn't achieve resistance-free flow, their pairing is a critical step required for it to occur, potentially leading to superconductivity that won't need big equipment.

"The electron pairs are telling us that they are ready to be superconducting, but something is stopping them," says physicist Ke-Jun Xu of Stanford University. "If we can find a new method to synchronize the pairs, we could apply that to possibly building higher temperature superconductors."

The material is a layered, copper-based crystal, or cuprate, called neodymium cerium copper oxide (Nd_2−xCe_xCuO₄). At low temperatures, the crystal exhibits superconductivity, yet it becomes significantly more resistant at higher temperatures.

Now, in order for superconductivity to kick in, electrons need their quantum identity to be entangled, turning them into as what's known as a Cooper pair. Only then can they weave smoothly through the atomic forest with zero effort.

Conventional superconductors, which exhibit superconductivity below around 25 Kelvin (-248 degrees Celsius, or -415 degrees Fahrenheit), entangle their electrons through vibrations in the underlying material.

Cuprates are unconventional superconductors, exhibiting superconductivity at temperatures up to 130 Kelvin. Scientists think that there is another mechanism responsible for electron pairing in these materials, yet the exact process is still somewhat murky.

The neodymium cerium copper oxide Xu and his team studied is like a conventional superconductor in that it doesn't exhibit the phenomenon above 25 Kelvin, which allows them to study the stages of superconductivity. As the electrons entangle, they are less resistant to being ejected from the material as the temperature rises; that is, the material loses energy at a lower rate. This is known as the pairing gap.

The team observed their material retaining more energy at temperatures up to 140 Kelvin (-133 degrees Celsius, or -207 degrees Fahrenheit) – far higher than the 25 Kelvin superconductivity transition temperature. This suggests that the electrons form Cooper pairs at pretty high temperatures, relatively speaking.

It's still not clear what is inducing the pairing. And the specific material might not be the one to bring us to room temperature superconductivity. But it could be a means of finding both answers, and the material, in the future.

Superconductivity at ambient temperatures is kind of a big deal. Imagine 100 percent energy efficiency – we could reduce the size of the circuitry required to transport electrons, packing more power into a smaller space for faster, cheaper technology.

But cracking the code has been very hard. We've had a few claimed breakthroughs, such as the much-hyped LK-99, but all of them have amounted to nothing.

Progress is likely to be more incremental – such as observing some of the features of superconductivity in higher-temperature materials, working out why it happens, advancing step by painstaking step.

"Our findings open a potentially rich new path forward," says physicist Zhi-Xun Shen of Stanford University.

"We plan to study this pairing gap in the future to help engineer superconductors using new methods. On the one hand, we plan to use similar experimental approaches at SSRL to gain further insight into this incoherent pairing state. On the other hand, we want to find ways to manipulate these materials to perhaps coerce these incoherent pairs into synchronization."

The research has been published in Science.

A space rock that smacked into Earth 66 million years ago and devastated the ancient life living thereon took a remarkably circuitous route to get here, a new study has found.

The Chicxulub event – the giant impact that ended the reign of non-avian dinosaurs, clearing the way for mammalian life to rise – was triggered by an asteroid from a region of the Solar System out past the orbit of Jupiter, the cold, dark outer limits, far from the Sun's light and warmth.

And an asteroid it was indeed, with the new findings by an international team of researchers ruling out that the object could have been a comet.

This discovery gives us a new understanding of Earth's history, and its interactions with the rest of the Solar System.

Since its infancy, Earth has been repeatedly slammed by large space rocks. It's thought that cometary impacts played a significant role in delivering water to Earth, and we can trace – albeit with varying degrees of difficulty – a number of huge craters scarring the planet after a collision with something large.

Earth has also experienced several mass extinctions, but the only one definitively linked to an impact was the Cretaceous-Paleogene extinction 66 million years ago, responsible for wiping out an estimated 76 percent of all animal species on Earth, including the dinosaurs that didn't go on to have bird descendants.

At the time, an asteroid some 10 kilometers (6 miles) across slammed into what is now the Yucatán Peninsula, leaving behind a colossal crater, and triggering a tsunami of extinctions that changed the world.

Whence originated this deadly rock? We can't exactly rewind time, observe its trajectory through the sky, and trace the arc back to a point in the Solar System. What we can do, however, is look at the layer of sediment preserved in the rock that would have been laid down at the time of the impact, looking for signatures in the minerals that can be matched to known types of space rocks.

In Cretaceous-Paleogene layers, a larger proportion of minerals such as iridium, ruthenium, osmium, rhodium, platinum, and palladium can be found. These platinum-group elements are pretty rare on Earth, especially on the surface. But they're common in meteorites – chunks of rock that fall through Earth's skies from space and slam into the surface.

On the other hand, the Chicxulub impact wasn't the only thing the Earth had going on back then. For nearly a million years around the Cretaceous-Paleogene boundary, a huge volcanic region known as the Deccan Traps was acting out, spewing volcanic material from Earth's underbelly out into the open. This is another possible source of those platinum-group elements observed in the boundary layers.

Led by geochemist Mario Fischer-Gödde of the University of Cologne in Germany, the team wanted to find out, once and for all, whether these minerals were indeed extraterrestrial in origin; and, if so, if they could be traced to a specific type of space rock.

Their studies focused on a mineral called ruthenium, several isotopes of which can be found in the boundary layer. Isotopes are forms of the same element with varying numbers of neutrons, and their ratios to each other in a given sample act as a fingerprint. In terrestrial ruthenium, the isotopes will be found in different proportions from the isotopes in meteorites.

They analyzed the ruthenium from the boundary layer from five different locations: one in Spain, one in Italy, and three from the chalk Cliffs of Stevns in Denmark. They also analyzed ruthenium from five other impacts from the last 541 million years, as well as spherule layers (tiny blobs of meteor sprayed out as the rock melts under the heat of atmospheric entry) dating back to 3.5 to 3.2 billion years ago.

In addition, the researchers analyzed ruthenium from actual meteorites, and checked these results against terrestrial reference samples of ruthenium that formed right here on Earth. This comparison revealed that the ruthenium in the Cretaceous-Paleogene boundary layer was not home-made – it came from space.

And not any old where in space. It was most consistent with a rare type of asteroid called a carbonaceous chondrite, rich in carbon, hailing from the outer Solar System, past the orbit of Jupiter.

The five other impacts were siliceous asteroids, which are found closer to the Sun, and are more common here on Earth. And the ancient spherule layers were, again, carbonaceous, hurled at Earth during the final stages of its mass accumulation.

These results finally reveal the identity of the rock that caused so much havoc. Jupiter is thought to act as something of a barrier to outer Solar System objects, catching asteroids in its orbital path and preventing them from traveling farther in towards the Sun. Some do manage to slip through from time to time, but they normally fall to Earth in smaller chunks than the Chicxulub impactor.

Which raises the question: why was that ancient rock on such a dedicated vendetta against the dinosaurs? Science may never know.

The research has been published in Science.

According to the infamous myth, groups of lemmings sometimes run off cliffs to their collective doom.

Imagine you are one of these rodents: on a sunny day you join your companions in a joyous climb up a mountain beneath clear skies, traipsing across grass and dirt and rock, glad to be among friends, until suddenly you plunge through the brisk air and all goes black.

The edge of the cliff is what scientists call a "critical point": the spot where the behaviour of a system (such as a group of lemmings) suddenly goes from one type of state (happily running) to a very different type of state (plummeting), often with catastrophic results.

Lemmings don't actually charge off cliffs, but many real-world systems do experience critical points and abrupt disasters, such as stock market crashes, power grid failures, and tipping points in climate systems and ecosystems.

Critical points aren't always literal points in space or time. They can be values of some system parameter – such as investor confidence, environmental temperature, or power demand – that marks the transition to instability.

Can we tell when a system is close to a cliff, and perhaps act to stop it going off the edge? What can we measure about a share market or ecosystem that could help us predict how far it is from such a critical point?

We have developed a new method for doing exactly this in real-world systems. Our work is published this week in Physical Review X.

How do you know when you're close to a cliff?

Previous work has shown that systems tend to "slow down" and become more variable near critical points. For a share market, for example, this would mean stock prices changing less rapidly and exhibiting a larger difference between weekly highs and lows.

But these indicators don't work when systems are "noisy", meaning we can't measure what they are doing very accurately. Many real systems are very noisy.

Are there indicators that do work for real-world systems? To find out, we searched through more than 7,000 different methods in hope of finding one powerful enough to work well, even when there is lots of noise in our system.

We found a few needles in our haystack: a handful of methods that performed surprisingly well at this very difficult problem. Based on these methods, we formulated a simple new recipe for predicting critical points.

We gave it an appropriately awesome name: RAD. (This gnarly acronym has a very nerdy origin: an abbreviation of "Rescaled AutoDensity".)

Do brains use critical points for good?

We verified our new method on incredibly intricate recordings of brain activity from mice. To be more specific, we looked at activity in areas of the mouse brain responsible for interpreting what the mouse sees.

When a neuron fires, neighbouring neurons might pick up its signal and pass it on, or they might let it die away. When a signal is amplified by neighbours it has more impact, but too much amplification and it can cross the critical point into runaway feedback – which may cause a seizure.

Our RAD method revealed that brain activity in some regions has stronger signs of being close to a critical point than others. Specifically, areas with the simplest functions (such as size and orientation of objects in an image) work further from a critical point than areas with more complex functions.

This suggests the brain may have evolved to use critical points to support its remarkable computational abilities.

It makes sense that being very far from a critical point (think of safe lemmings, far from the cliff face) would make neural activity very stable. Stability would support efficient, reliable processing of basic visual features.

But our results also suggest there's an advantage to sitting right up close to the cliff face – on the precipice of a critical point. Brain regions in this state may have a longer "memory" to support more complex computations, like those required to understand the overall meaning of an image.

A better guide to cliffs

This idea of systems sitting near to, or far from, a critical point, turns up in many important applications, from finance to medicine. Our work introduces a better way of understanding such systems, and detecting when they might exhibit sudden (and often catastrophic) changes.

This could be used to unlock all sorts of future breakthroughs – from warning individuals with epilepsy of upcoming seizures, to helping predict an impending financial crash.

Ben Fulcher, Senior Lecturer, School of Physics, University of Sydney and Brendan Harris, PhD student, Neurophysics, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Extreme weather events and rising seas are putting precious heritage sites around the world in harm's way.

A precious stone pyramid in Mexico is the latest to succumb to an increasingly chaotic global climate. On the night of July 29, the 15-meter-high (roughly 50-foot-high) square monument located in the state of Michoacán suddenly slumped under the pressure of incessant rain, its south wall crumbling into a pile of rubble.

The pyramid was once one of the best-preserved monuments of the Michoacán Kingdom civilization. It is located at Ihuatzio, a remarkably preserved archaeological site that contains one other pyramid, a tower or fortress, and some tombs.

It was first occupied 1,100 years ago by indigenous Nahuatl-speaking groups. Later, it became the headquarters of the P'urhépechas people, the only empire the Aztecs couldn't conquer. The culture still thrives to this day.

Only one of the pyramids at the site has been damaged, but personnel from Mexico's National Institute of Anthropology and History (INAH) say that at least six of its 'stepped bodies' are in disrepair, including the outer wall, and the core and retaining wall.

They blame the extreme weather events of recent weeks.

In July, the peak of the Northern Hemisphere summer, heavy rainfall and thunderstorms battered much of Mexico. This came after the worst drought in the nation in 30 years, when rain became so scarce, several lakes dried up completely.

"The high temperatures, previously recorded in the area, and the consequent drought caused cracks that favored the filtration of water into the interior of the pre-Hispanic building," said an INAH statement.

From there, collapse became all but inevitable. Officials are now focused on repairing the structure of the building "in favor of the cultural heritage of Mexicans."

It's the job of archaeologists to study human behavior in times gone by, but inevitably, their work is also impacted by current human activities.

Extreme weather and rising seas, driven by human-caused climate change, are proving to be a serious nuisance for important sites of bygone cultures.

Recently, archaeologists found that ancient cave paintings in oceania are deteriorating with accelerating climate changes.

And just this year, a study on cultural heritage building materials in Europe and Mexico found when precipitation increases substantially, it puts these buildings at risk of damage.

According to Tariakuiri Alvarez, who identifies as a living member of the P'urhépecha tribe, his ancestors would have interpreted the crumbling of the pyramid at Ihuatzio as a "bad omen."

In a recent Facebook post Alvarez said that before the arrival of foreign conquerors in Mexico, something similar happened, and it was because the gods were "displeased".

Just days before the pyramid in Mexico tumbled down, Utah's iconic 'Double Arch' also caved in, probably due to changing water levels and erosion.

Heritage sites like these are priceless places that humans wish to preserve for future generations. Watching them collapse from a climate that has been drastically altered by our own behavior is disgusting to watch, and not just for immortals.

We all had to make adjustments as the COVID-19 pandemic unfolded – even zoo animals who were suddenly not seeing crowds of visitors pass by every single day.

In a study published in 2022, researchers discovered how primates reacted to that shift, looking at the behavior of bonobos, chimpanzees, western lowland gorillas, and olive baboons, and finding that the animals changed their habits in a variety of ways, including the amount of time they spent resting and eating.

Visitor interactions are thought to be crucial to the welfare of zoo animals. Yet these interactions have the potential to be either positive or negative. So the researchers were keen to see the difference when the crowds weren't there.

"Primates are some of the most cognitively advanced species in zoos and their interactions with visitors are complex," zoo animal welfare scientist Samantha Ward from Nottingham Trent University in the UK explained at the time.

"A limitation to understanding how visitors can affect behavior of animals in zoos and parks is that they rarely close to the public for prolonged periods, so this provided us with a unique opportunity."

Observations were recorded at Twycross Zoo and Knowsley Safari in the UK, both before and after visitors returned.

Over several months and multiple open and closure periods, there were noticeable changes in primate behavior, which varied depending on the animal.

As visitors began to return to the zoo, the bonobos and gorillas spent less time alone, while the gorillas also spent less time resting. Chimpanzees, meanwhile, were eating more and engaging with their enclosures more when zoos reopened.

The olive baboons in the safari park were seen to engage in less sexual and dominance behavior when the visitors came back. They also tended to approach visitor cars more often, compared with the ranger vehicles they saw when the park was closed.

Whether or not these changes were positive is more difficult to say.

The researchers suggest that the returning visitors seemed to stimulate the chimpanzees and baboons, while gorillas and bonobos spending less time alone could also be viewed as positive.

At the same time, it could be argued that gorillas – naturally more sedentary animals – were disrupted by the crowds in that they spent less time resting.

That the gorillas changed the parts of their enclosures they spent the most time in when visitors came back suggests that the animals can to some extent manage this disruption.

"Behavioral changes and changes in enclosure use in the presence of visitors highlights the adaptability of zoo species to their environments," said zoo animal welfare researcher Ellen Williams from Harper Adams University in the UK.

"Provision of environments which enable animals to actively adapt in this manner is really important for their welfare."

The team also observed that there was a visitor number threshold when it came to olive baboons, beyond which the animals stopped becoming increasingly active and stimulated by the passing cars in the safari park.

This is all valuable data for animal welfare researchers, who know that visitors can have all kinds of effects on wildlife – from adding feelings of companionship and safety, to being sources of annoyance or even threats. This needs to be factored into how zoos and parks are run and designed.

While there might not be any more lockdowns in the foreseeable future (hopefully), the research team wants to continue the work of studying how visitor numbers affect animal behavior, including collecting data involving more animals and across a longer time scale.

"Future work could involve looking at the impact on a wider range of species in both zoos and safari parks as well as differences among individual animals," said Williams.

The research was published in Animals.

An earlier version of this article was published in September 2022.

The World Health Organization (WHO) has declared mpox a public health emergency of international concern, after rising cases in the Democratic Republic of the Congo and the potential for further spread.

This now triggers a coordinated international response to an extraordinary event and the mobilization of resources, such as vaccines and diagnostic testing, to curb the spread of this infectious disease.

But WHO has not declared mpox a pandemic. Rather, the measures it has triggered are designed to prevent it from becoming one.

World Health Organization (WHO) declares #mpox outbreak a Public Health Emergency of International Concern (PHEIC). pic.twitter.com/pAlOx9Bq13

— WHO Ghana (@WHOGhana) August 14, 2024

What triggered this latest alert?

Mpox, once known as monkeypox, is a viral infection closely related to smallpox. Initial symptoms include a fever, headache, swelling of the lymph nodes and muscle ache. A typical rash follows, mainly on the face, hands and feet.

The spread of mpox through certain African countries led the Africa Centres for Disease Control and Prevention to declare earlier this week mpox a public health emergency of continental security. This is the first time the organization has issued such an alert since it was established in 2017.

The situation in the Democratic Republic of the Congo in central Africa has been particularly worrying for more than a year.

There are two types or clades of mpox. Clade II, which originates in west Africa, is less severe. It has a fatality rate of up to 1% (in other words, roughly one in 100 are expected to die from it). But clade I, from central Africa, has a fatality rate of up to 10% (up to one in ten die). This compares to a 0.7% fatality rate for the Omicron variant of SARS-CoV-2, the virus that causes COVID. The Democratic Republic of the Congo is seeing large epidemics of the more deadly clade I mpox.

Mpox is endemic in some parts of central and west Africa, where the virus exists in animals and can spread to humans. Outbreaks have been increasing, with more human-to-human spread, since 2017.

This is partly due to very low levels of immunity to the mpox virus, which is related to the virus that causes smallpox. Mass vaccination against smallpox ceased more than 40 years ago globally, resulting in minimal immunity in populations today against mpox.

The WHO designation announced this week relates to the clade I. Not only does this have a higher fatality rate, it has new mutations that enhance spread between people. These changes, and the global lack of immunity to mpox, makes the world's population vulnerable to the virus.

There are two different epidemics

In 2022, an epidemic of mpox swept through non-endemic countries, including beyond Africa. This was a variant of clade II originating from Nigeria, called clade IIb. This was sexually transmitted, predominantly affecting men who have sex with men, and had a low fatality rate.

That epidemic peaked in 2022, with vaccines made available to people at risk in high-income countries, but there has been an uptick in 2024.

At the same time, large clade I epidemics were occurring in the Democratic Republic of the Congo, but with far less attention.

Vaccines were not available there, even in 2023, when there were 14,626 cases and 654 deaths. Mortality was 4.5 percent, and higher in children.

In fact, most cases and deaths in the Democratic Republic of the Congo have been children. This means most transmission there is non-sexual and is likely to have occurred through close contact or respiratory aerosols.

However, in 2023 an outbreak in a non-endemic part of the country, South Kivu in the east, appeared to be by sexual transmission, indicating more than one epidemic and different transmission modes in the Democratic Republic of the Congo.

By mid-2024, there were already more cases in the country than all of 2023 – more than 15,600 cases and 537 deaths.

Testing capacity is low in the Democratic Republic of the Congo, most cases are not confirmed by lab testing, and the data we have are from a small sample of genomic sequences from the Kamituga region of South Kivu.

This show mutations to the clade I virus around September 2023, to a variant termed clade Ib, which is more readily transmissible between people. We do not have much data to compare these viruses with the viruses causing cases in the rest of the country.

Mpox cases are soaring in Africa – what must be done to prevent a global pandemic https://t.co/JKGBqSSYzp

Cheryl Walter, University of Hull @UniofHullOnline#HealthAndMedicine#Mpox

— The Conversation Africa (@TC_Africa) August 13, 2024

Mpox is spreading internationally

In the past month, the virus has spread to countries that share a border with the Democratic Republic of the Congo – Rwanda and Burundi. It has also spread to other east African countries, such as Kenya and Uganda. None of these countries have had mpox cases previously.

In an interconnected, mobile world, cases may spread to other continents, as mpox did in 2018 from Nigeria to the United Kingdom and other countries.

A few travel-related cases between 2018 and 2019 may have led to the large multi-country 2022 clade IIb epidemic.

We have vaccines, but not where they are needed

As the mpox virus and smallpox viruses are related (they are both orthopoxviruses), smallpox vaccines offer protection against mpox. These vaccines were used to control the 2022 clade IIb epidemic.

However, most of the world has never been vaccinated, and has no immunity to mpox.

The newer vaccine (called Jynneos in some countries and Imvamune or Imvanex in others) is effective. However, supplies are limited, and vaccine is scarce in the Democratic Republic of the Congo.

WHO's declaration of mpox as a public health emergency of international concern will help mobilize vaccines to where they are needed. The Africa Centres for Disease Control had already begun negotiations to secure 200,000 doses of vaccine, which is a fraction of what is required to control the epidemic in the Democratic Republic of the Congo.

What happens now?

Ultimately, a serious epidemic anywhere in the world is a concern for all of us, as it can spread globally through travel, as we saw with the COVID pandemic.

Controlling it at the source is the best measure, and WHO's latest declaration will help mobilize the required resources.

Surveillance for spread of this more serious version of mpox is also essential, bearing in mind that many countries do not have the capacity for widespread testing. So we'll have to rely on "suspected cases", based on a clinical definition, to keep track of the epidemic.

Open-source epidemic intelligence – such as using AI to monitor trends in rash and fever illness – can also be used as an early warning system in countries with weak health systems or delayed reporting of cases.

A further complication is that 20-30 percent of people with mpox may simultaneously have chickenpox, an unrelated infection that also causes a rash. So an initial diagnosis of chickenpox (which is easier to test for) does not rule out mpox.

Effective communication and tackling push-back against public health measures and disinformation is also key. We saw how important this was during the COVID pandemic.

Now, WHO will coordinate the global mpox response, focusing on equity in disease prevention and access to diagnostics and vaccines. It is up to individual countries to do their best to comply with the International Health Regulations, and the protocols for how such a global emergency are managed.

The World Health Organization has more information about mpox, including symptoms and treatment. For information about vaccine access and availability, contact your local health department or doctor, as this varies from country to country.

C Raina MacIntyre, Professor of Global Biosecurity, NHMRC L3 Research Fellow, Head, Biosecurity Program, Kirby Institute, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.