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.

"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.

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.

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.

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.

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.

Now it seems they were right, with a new study finding a spike in related web searches following the film's release.

For those who haven't seen the movie, Eva Sénéchal, a psychology researcher at McGill University in Montreal, and her colleagues, who conducted the new analysis of internet search trends, explain how the final line in the Barbie film may have done more than just make audiences laugh.

"In the film's final scene, after deciding to leave Barbieland for the real world, Barbie enthusiastically tells a receptionist, "I'm here to see my gynecologist," a joke that could be based either on her supposed lack of genitals or her evident excitement for care many women find unpleasant." Sénéchal and colleagues write in their paper.

"We hypothesized that this final line may have spurred public interest in gynecologic care."

The researchers charted weekly internet searches in the US following Barbie's release, looking for 34 terms ranging from questions about what gynecologists do to more general searches of "gynecologist near me", "make a doctor's appointment", and "pap smear".

There was a positive spike in searches relating specifically to gynecologists, with questions such as "Why see a gynecologist?" and "Do I need a gynecologist?" more than doubling in the three months following the film's release in July 2023 compared to the year prior.

However, looking up information about gynecologists is only the first step in seeking that kind of specialist healthcare. The study didn't look at other data that may have captured whether movie-watchers were prompted to make or attend appointments, but trends in other search terms suggest not.

"There were no changes in searches for gynecologist appointments, suggesting that searches for information about gynecologists did not translate to searches for new gynecologic care," Sénéchal and colleagues write.

"Therefore, it remains unclear whether a 'Barbie effect' in awareness would translate to improved measurable health outcomes."

But it's not out of the question; it has happened before.

In 2013, when actress Angelina Jolie went public with her decision to undergo a double mastectomy after testing positive for an inherited breast cancer gene, referrals for genetic counseling and testing in the UK more than doubled – a trend dubbed the 'Angelina Jolie effect'.

The Barbie film could have also had a wider impact on body image, just like the dolls themselves. Research shows that Barbie dolls, which traditionally have represented extreme and unrealistic body shapes, can influence young girls' ideas about body image and eating habits, although the results are a mixed bag.

"We know that children learn by observing, absorbing, and imitating the things they see around them, and that their early ideas about weight and appearance are shaped by their family, their peers, and the media," Zali Yager, a body image researcher, wrote for Women's Health Agenda after seeing the film in July 2023.

But it's difficult to tease apart the influence of those three factors – one's family, friends and (social) media – on a person's perception of themselves, or their healthcare-seeking behaviors, in the case of this new analysis.

"There's so much of the context that we are missing in these studies," clinical health psychologist Jennifer Webb, of the University of North Carolina at Charlotte, told Nature in a July 2023 interview, referring to the mixed results of research studies on Barbie's influence on body image and self-esteem among young girls.

"We don't know about the other aspects of the children's social environment, whether in the immediate home environment, at school or other activities."

The same is true of Sénéchal and colleagues' new analysis: Trends in internet searches give us only a snapshot of people's lives, and tell us nothing about who those anonymous people are, their age or their health.

Although we don't have the data to show it, some people might have been inspired to seek out reproductive healthcare for themselves because watching Barbie attend her first gynecologist appointment "normalizes the experience," physician and health policy researcher Leana Wen told CNN last year.

"It solidifies the understanding that reproductive health is an integral part of overall health."

The research has been published in JAMA Network Open.

There, in the ancient, long-abandoned Maya city of Cobá, near the towering Nohoch Mul pyramid, a vast stone slab was found tucked away in what was once the floor of a sacred pool. What makes this slab so special is what it bears: an inscription consisting of 123 glyphs, painstakingly carved into its surface.

Initial inspection suggests that the glyphs describe the founding date of a town called Keh Witz Nal, or "Deer Mountain", on 12 May 569 CE. They also name a previously unknown Maya ruler – K'awiil Ch'ak Chéen, a name invoking K'awiil, the Maya god of lightning.

Other glyphs refer to the gods who were thought to have founded Cobá, including Bolón Tz'akab Ajaw – the lord of countless generations.

Located in what is now the state of Quintana Roo on the eastern side of the Yucatán Peninsula, the once-glorious, now ruined city of Cobá may have been built by the Maya as early as 50 BCE and continuously inhabited for over 1,500 years, with the most recent buildings constructed between 1200 and 1500 CE. At its peak, it was a thriving cultural hub boasting an estimated 50,000 inhabitants.

It's one of the few archaeological sites to still carry its Maya name, Ko'ba a, a name that means rough waters, and it's filled with engravings and sculptures that reveal much about the spiritual and aesthetic lives of the Maya who once lived there.

Excavations at the site are very careful and painstaking, and Mexico's National Institute of Anthropology and History (INAH) has been taking its time to uncover and restore the monuments of the city that have become temporarily lost to the jungle and time.

The stone slab was discovered at the bottom of what was once a pool, and it's stunning. It covers an area of 11 square meters (118 square feet), with glyphs painstakingly carved onto its surface in a sort of L-shaped arrangement that accommodated the shape of the stone.

Previously, 14 rulers of Cobá had been identified, including three women, one of whom reigned for 40 years. With the new information contained in the heavily stylized script, the researchers were able to corroborate that many of these rulers adopted the name of the god K'awiil.

A more in-depth study of the inscription will be made, but for now, the archaeological team is focused on restoring and preserving the stone against further damage from water and erosion.

A detailed, high-resolution 3D construction has been made, and will enable further study without disturbing the stone further.

But if you wake up one morning, look in the mirror, and wonder when you suddenly grew so much older, you may not be imagining things.

According to new research into the molecular changes associated with aging, humans experience two drastic lurches forward, one at the average age of 44 and the other at the average age of 60.

"We're not just changing gradually over time; there are some really dramatic changes," says geneticist Michael Snyder of Stanford University, senior author of the study.

"It turns out the mid-40s is a time of dramatic change, as is the early 60s. And that's true no matter what class of molecules you look at."

Aging is complex, and associated with growing risks of diseases of all kinds. Snyder and his colleagues have been investigating the biology of aging to better understand what changes occur and how, in order to better mitigate and treat these ailments. To this end, they have been tracking a group of 108 adults, who have been donating biological samples every few months over several years.

They noticed that in some conditions, such as Alzheimer's and cardiovascular disease, risk doesn't rise gradually with time, it escalates sharply after a certain age. So they wanted to take a closer look at the biomarkers of aging to see if they could identify related changes.

Using the samples from their cohort, the researchers have been tracking different kinds of biomolecules. The different molecules studied include RNA, proteins, lipids, and gut, skin, nasal, and oral microbiome taxa, for a total of 135,239 biological features.

Each participant submitted an average of 47 samples over 626 days, with the longest-serving participant submitting 367 samples. This wealth of data resulted in more than 246 billion data points, which the researchers then processed, looking for patterns in the changes.

Several previous studies have found non-linear changes in molecular abundances that can be linked to aging in rats and humans. Studies of fruit flies, mice, and zebrafish have also pointed to a stepwise aging process in those species.

Snyder and his colleagues noticed that there's a very clear change in the abundances of many different kinds of molecules in the human body at two distinct stages.

Around 81 percent of all the molecules they studied showed changes during one or both of these stages. Changes peaked in the mid-40s, and again in the early 60s, with slightly different profiles.

The mid-40s peak showed changes in molecules related to the metabolism of lipids, caffeine, and alcohol, as well as cardiovascular disease, and dysfunctions in skin and muscle. The early 60s peak was associated with carbohydrate and caffeine metabolism, cardiovascular disease, skin and muscle, immune regulation, and kidney function.

The first peak, the mid-40s, is typically when women start undergoing menopause or perimenopause, but the researchers ruled this out as a main factor: men, too, also underwent significant molecular changes at the same age.

"This suggests that while menopause or perimenopause may contribute to the changes observed in women in their mid-40s, there are likely other, more significant factors influencing these changes in both men and women," explains metabolomicist and first author Xiaotao Shen, formerly of Stanford, now at Nanyang Technological University Singapore.

"Identifying and studying these factors should be a priority for future research."

The researchers note that their sample size is pretty small, and they tested limited biological samples, from people between the ages of 25 and 70.

Future research could help delve further into this phenomenon, studying it in more granular detail, across a wider range of subjects, to better understand how the human body changes over time.

The research has been published in Nature Aging.

A new, preclinical study on rats spotlights the possible dangers of managing morning sickness or other symptoms of pregnancy with products containing either THC (Δ9-tetrahydrocannabinol) or CBD (cannabidiol).

Researchers at the University of Western Ontario and Queen's University in Canada found rats that are regularly exposed to THC and CBD while still in the womb show significant changes to their development, even when the chemicals are administered without any additional compounds commonly found in cannabis.

THC is the more psychoactive of cannabis's mix of plant molecules. Concerningly, the cannabinoid can cross the placenta into fetal circulation in similar concentrations to what is seen in the blood of the mother. As early as 14 weeks, the human fetus possesses neural receptors for cannabinoids.

CBD is another major compound in cannabis. It is widely accessible and considered harmless by many, yet few studies have investigated whether it is safe for use during pregnancy.

While CBD doesn't deliver an intoxicating 'high', the compound has its own effects on the body. And, like THC, it can also readily cross the placenta in rodent studies, where it seems to impair the shape and function of the organ.

In the current study, researchers investigated both compounds. For nearly an entire pregnancy, rat mothers were given daily doses of THC, CBD, or a combination of both compounds.

The pups that were exposed to a low dose of THC had a reduced birth weight compared with control mice, as did pups exposed to CBD while in the womb. Rat offspring exposed to THC and CBD together were born with even lower body and brain weights.

While growth rates had recovered by adolescence, some of the pups went on to show behavioral changes and disrupted neuronal activity in certain brain regions.

The findings support human health studies that have linked cannabis exposure in pregnancy to low birth weight, cognitive and behavioral changes, and a higher risk of neuropsychiatric disorders.

"Marjiuana has been legalized in Canada and in many states in the US, however, its use during pregnancy has not been well studied up until this point," says David Natale from Queens.

"This study is important to support clinicians in communicating the very real risks associated with cannabis use during pregnancy."

In the US, 24 states have legalized cannabis for recreational use, and some surveys suggest the drug has doubled in popularity among those who are pregnant, who often use it to treat mood, morning sickness, pain, or sleep issues.

The US Surgeon General, the American College of Obstetricians and Gynecologists, and the American Academy of Pediatrics all agree that in the absence of further evidence, cannabis use of any kind during pregnancy is inadvisable.

Nevertheless, many women remain unaware of the possible risks.

An experiment on rats isn't enough to prove once and for all that cannabis use during pregnancy is dangerous, but it does provide insight into some of the concerning associations researchers are finding in epidemiological studies.

In the current research, male rat offspring that were exposed to THC in the womb were the only ones to exhibit impaired cognitive behavior in adolescence.

Female offspring exposed to THC in the womb showed typical neurological outcomes and almost a "complete lack of molecular changes", researchers say.

When mice were exposed to CBD on its own, however, it had a surprising impact on later brain development. In adolescence, both male and female mice exposed to CBD showed signs of neuropsychiatric issues.

Female offspring exposed to prenatal CBD alone and CBD and THC together displayed anxiety-like behavior in tests. Whereas male offspring exposed to THC and CBD, showed impulsivity-like behaviors.

"In contrast to the popular belief that CBD is safe for use in pregnancy, CBD alone produced distinct long-term neuropsychiatric effects and did not mitigate the consequences of prenatal THC," write the authors of the study.

Given how popular CBD and THC products have recently become, these findings emphasize the need for more rigorous research on cannabis use during pregnancy, and its possible impacts on a developing fetus.

The study was published in Neurobiology of Disease.