A discovery six years ago took the condensed-matter physics world by storm: Ultra-thin carbon stacked in two slightly askew layers became a superconductor, and changing the twist angle between layers could toggle their electrical properties. The landmark 2018 paper describing “magic-angle graphene superlattices” launched a new field called “twistronics,” and the first author was then-MIT graduate student and recent Harvard Junior Fellow Yuan Cao.

Together with Harvard physicists Amir Yacoby, Eric Mazur, and others, Cao and colleagues have built on that foundational work, smoothing a path for more twistronics science by inventing an easier way to twist and study many types of materials.

A new paper in Nature describes the team’s fingernail-sized machine that can twist thin materials at will, replacing the need to fabricate twisted devices one by one. Thin, 2D materials with properties that can be studied and manipulated easily have immense implications for higher-performance transistors, optical devices such as solar cells, and quantum computers, among other things.

“This development makes twisting as easy as controlling the electron density of 2D materials,” said Yacoby, Harvard professor of physics and applied physics. “Controlling density has been the primary knob for discovering new phases of matter in low-dimensional matter, and now, we can control both density and twist angle, opening endless possibilities for discovery.”

Cao first made twisted bilayer graphene as a graduate student in the lab of MIT’s Pablo Jarillo-Herrero. Exciting as it was, the achievement was tempered by challenges with replicating the actual twisting.

At the time, each twisted device was hard to produce, and as a result, unique and time-consuming, Cao explained. To do science with these devices, they needed tens or even hundreds of them. They wondered if they could make “one device to twist them all,” Cao said—a micromachine that could twist two layers of material at will, eliminating the need for hundreds of unique samples. They call their new device a MEMS (micro-electromechanical system)-based generic actuation platform for 2D materials, or MEGA2D for short.

The Yacoby and Mazur labs collaborated on the design of this new tool kit, which is generalizable to graphene and other materials.

“By having this new ‘knob’ via our MEGA2D technology, we envision that many underlying puzzles in twisted graphene and other materials could be resolved in a breeze,” said Cao, now an assistant professor at University of California Berkeley. “It will certainly also bring other new discoveries along the way.”

In the paper, the researchers demonstrated the utility of their device with two pieces of hexagonal boron nitride, a close relative of graphene. They were able to study the bilayer device’s optical properties, finding evidence of quasiparticles with coveted topological properties.

The ease of their new system opens several scientific roadways, for example, employing hexagonal boron nitride twistronics to produce light sources that can be used for low-loss optical communication.

“We hope that our approach will be adopted by many other researchers in this prosperous field, and all can benefit from these new capabilities,” Cao said.

The paper’s first author is nanoscience and optics expert Haoning Tang, a postdoctoral researcher in Mazur’s lab and a Harvard Quantum Initiative fellow, who noted that developing the MEGA2D technology was a long process of trial and error.

“We didn’t know much about how to control the interfaces of 2D materials in real time, and the existing methods just weren’t cutting it,” she said. “After spending countless hours in the cleanroom and refining the MEMS design—despite many failed attempts—we finally found the working solution after about a year of experiments.” All nanofabrication took place at Harvard’s Center for Nanoscale Systems, where staff provided invaluable technical support, Tang added.

“The nanofabrication of a device combining MEMS technology with a bilayer structure is a veritable tour de force,” said Mazur, the Balkanski Professor of Physics and Applied Physics. “Being able to tune the nonlinear response of the resulting device opens the door to a whole new class of devices in optics and photonics.”

This story is published courtesy of the Harvard Gazette, Harvard University’s official newspaper. For additional university news, visit Harvard.edu.

Female and male primates often form close bonds, but not purely out of affection. Close relationships usually evolve when there is a clear benefit for both parties, with protection and reproductive control playing key roles.

A new study, led by primatologists Liesbeth Sterck from Utrecht University and Julia Ostner from the University of Göttingen, provides theoretical insights into how these bonds are formed. The study, published in Evolution and Human Behavior, underlines the decisive role that females play.

Why do some female and male primates hit it off and form strong bonds, while others don’t? Science has long offered various theories to explain these connections, ranging from sheer physical attraction to deep-rooted evolutionary processes.

While these ideas are compelling, most studies on primate bonding have traditionally focused on males as the key players, often overlooking the crucial role that females might play in these relationships.

Benefits for both

Mapping hundreds of primate observations from the past decades, an international team of primatologists suggests that these ‘friendships with benefits’ between male and female primates usually evolve when both can gain something. For females, it’s about choosing whom they mate with. For males, it’s about caring for and protecting their young.

These dynamics are especially important in groups where males cannot just dominate females and where offspring need looking after. These bonds are also most likely to form in groups where males aren’t the boss and where male care is crucial. The primatologists mapped hundreds of earlier observations of chimpanzees, lemurs, macaques, and other species.

“Our findings show that these bonds aren’t just about attraction and affection,” says Sterck.

“They are also strategic. Both male and female primates unconsciously seek out these friendships that provide benefits. The benefits can be protection, better access to resources, or securing the survival of their offspring. For evolution to shape these behaviors, it is not needed that they know when or how the bonds pay off.”

Changing bonds and breaking up

The study also shows that the nature of these bonds can change over time. Initially, males tend to groom females more often during the mating season, but this dynamic can shift. Females might look for male support to protect their infants during nursing. A male may bond with a female initially to secure mating rights, and after the female gives birth, she may rely on the male for protection.

Once the offspring become independent, these bonds often dissolve, and both the male and female may move on to other partners.

However, in cases where females give males the opportunity to father multiple subsequent offspring, long-term bonds are more likely to form. These stable relationships are common in species like macaques, baboons and chimpanzees, where females repeatedly prefer the same male and males provide ongoing care. Such long-lasting bonds are often supported by mutual benefits, making continued investment worthwhile for both sides.

Human relationships

When it comes to human relationships, the dynamics might be more complex. Moreover, humans typically form exclusive pairs, while both female and male primates maintain a practice with multiple mating partners. But some of the same underlying principles from primate bonds apply, according to Sterck’s team.

“Just like our primate relatives, human bonds often involve a mix of affection and strategic partnership,” says Sterck. “While love and emotional connection are vital, unconsciously there’s also an element of mutual benefit, whether it’s support, protection, or shared resources.”

Love and affection still play a crucial role in primate bonding, says Sterck, even if the evolutionary foundation of these relationships is built on long-term benefits. “While the drive to form strong bonds may stem from evolutionary advantages, emotions like love and affection kick-start these connections. These feelings act as the lubricant, smoothing the way for the actions and behaviors necessary to maintain and deepen these bonds over time.”

Future research

To further investigate how widespread their bonding theory can be in the animal kingdom, Sterck’s team calls for additional research. They specifically call for additional research in great apes (such as gorillas and bonobos) and so-called New World primates, including tamarins and capuchins—or even further to non-primate species living in permanent social groups, such as wolfs and lions.

They also envision that this approach can shed new light on the evolution and dynamics of human pair bonding.

In October 2021, thousands of dead and dying crabs and lobsters washed up along 45 miles (70km) of coastline in north-east England. This mass-mortality event coincided with the redevelopment of one of the UK’s largest ports at Teesside.

At the time, many local environment groups and fishers believed that dredging had released a toxic chemical known as pyridine, an industrial substance thought to have settled in the water’s sediment, resulting in this mass-scale death of crustaceans.

But our recent research outlines why this “pyridine hypothesis” is wrong. It was based on inaccurate and unpublished science, and the theory was propagated through mistrust in government, toxic local politics, and inaccurate media coverage.

An investigation by the government bodies the Environment Agency (EA) and the Centre of Environment, Fisheries and Aquaculture Science (Cefas) could not determine the cause of death, but speculated it could have been an algal bloom. Various interim reports from this investigation were published between December 2021 and May 2022. In spring 2022, consultants funded by the fishing industry analyzed the EA data from those interim reports, and proposed pyridine as a cause.

Pyridine had been widely used in industrial processes and was historically manufactured in the area. Results from EA tests showed that pyridine concentrations were high in some crabs near Teesside, but not significantly different from other locations in the UK.

The EA had used a technique to detect pyridine in crab tissue which was designed for water samples, and warned its results might not be accurate. It had also only looked at four crabs close to where deaths had occurred, and compared these with four crabs elsewhere in the UK.

This was a very low number to be statistically confident in the results. Yet, for those who believed the crab and lobster deaths were caused by dredging, this data was the “smoking gun”.

Other potential explanations from government agencies were not believed by local environmental campaigners and opposition parties, and some newspaper articles started to suggest a cover-up.

When unpublished data from Newcastle, Durham and York universities was presented in October 2022 to a cross-party government committee, the researchers behind this data claimed that pyridine was “exceptionally toxic” to crabs, and that dying crabs exposed to pyridine display twitching behavior similar to that observed on the beaches.

A non-peer-reviewed study by this team claimed that a simulation of dredged material drifting down the coast mirrored the mortality event. They believed that dredging had unearthed large reservoirs of pyridine from within the sediment, left there by past industrial processes, which then swept down the coastline killing crustaceans due to its exceptional toxicity.

Some MPs called for an independent investigation into crab deaths and a pausing of the Teesside redevelopment.

However, the subsequent report—published by the Department for Environment, Food and Rural Affairs (Defra) in January 2023, written by independent scientists including ourselves—deemed the pyridine hypothesis “very unlikely”. It also ruled out other potential causes of the crustacean die-off including algal blooms, deoxygenation, chemical spills and unusual weather events.

But the report was unable to rule out parasites or disease, as a comprehensive analysis of different potential pathogens had not taken place. While it noted that other global mortality events had reported unusual twitching and tremors in crabs dying with infections from viruses and bacteria, there wasn’t enough evidence to prove or disprove disease as a cause of these deaths.

Having taken part in this independent inquiry, we, along with other scientists, immediately encountered considerable skepticism from politicians and media. The Times reinforced the pyridine hypothesis and the inaccurate claim that “dead crabs contained 40 times more pyridine than control crabs”, stating that our independent panel “did not merit the name”.

Channel 4 News, a broadcaster that commissioned special reports about the pyridine hypothesis, also questioned whether the panel was independent. Some journalists and politicians serving on the cross-party committee suggested we had deliberately made an alternative disease hypothesis to cover up for the government.

Even a nature charity, the RSPB, tweeted: “The results are clear, pyridine is extremely toxic to crabs.”

And it was not only scientists on the independent panel who were criticized. Those scientists who had earlier presented the pyridine hypothesis also received some unsavory tweets when our panel’s report was released.

The idea that politically independent scientists from universities, research laboratories and consultancies had colluded on a fictitious report is, in our view, preposterous and unprofessional. Our recent peer-reviewed paper outlines why we reject the pyridine hypothesis for five key reasons.

1) Evidence that crabs contained high levels of pyridine is weak

Re-analysis of crab tissues by Cefas using an optimized methodology found low levels of pyridine and no significant difference between the affected areas in north-east England and other parts of the UK.

2) Pyridine is no more toxic to crustaceans than to other wildlife

Claims that pyridine is “exceptionally toxic” to crustaceans when exposed in milligram/liter concentrations are not accurate. There are many contaminants present in the environment which can kill crustaceans in nanogram/liter concentrations, which are 1 million-fold lower than the milligrams/liter concentrations of pyridine found to kill crustaceans.

We found that the non-peer-reviewed study based predictions of crab deaths on inaccurate toxicity calculations—probably because the number of crabs used in its experiments was too low.

3) Pyridine has never been recorded at concentrations likely to cause acute toxicity

The non-peer-reviewed study predicted no effect on crabs at pyridine concentrations below 20,000 micrograms/liter. The highest pyridine concentration ever recorded in the Tees estuary is 2.4 micrograms/liter in 2012, at a time when it was being actively manufactured and discharged under license by the EA. This value is still approximately 400,000 times lower than the average values predicted to kill 50% of crustacean populations based on published literature.

4) Pyridine does not stick to sediments

Pyridine is a compound which breaks down very quickly—it doesn’t particularly adsorb or stick to sediments, so is unlikely to settle and accumulate on the seabed. Large reservoirs of pyridine in the sea sediment are therefore highly unlikely.

5) Pyridine wouldn’t persist long enough to cause mass deaths along a 45-mile stretch of coastline

Pyridine was not detected in the seawater at the time of the mass death, and concentrations in sediments were too low to be deemed toxic according to our research. Even modeling of a hypothetical spill of 20,000 liters of pyridine did not result in concentrations that would realistically cause acute toxicity. The claim that this compound could kill crustaceans along a 45-mile stretch of coastline without detection is unfounded.

Next steps

Unfortunately, neither the EA, Cefas nor the independent inquiry could determine a causal factor in the deaths of the crustaceans. Mistrust in the government led to a lack of trust in these public bodies. Broadcast and print media promoted unpublished research which hadn’t undergone rigorous scientific scrutiny with, we believe, an unusual degree of confidence.

We argue that this presents a problem for those serving on the cross-party committee and for wider society, who need politicians to make informed decisions based on the best available science. The committee’s decisions need to be based on rigorously tested scientific evidence, not politics.

Since 2021, there have been further dramatic shifts in the ecosystem of the waters around Teesside, such as major increases in the numbers of mussel beds and starfish. Climate change is also bringing new pressures on marine habitats, and exacerbating existing pressures from water quality, disease, coastal development and fishing.

We will probably never know the cause of the Teesside crustacean mortality event, unless something similar happens again. But better monitoring of our coastal environments is imperative. Only then can scientists understand what happens when potentially millions of keystone species across miles of coastline are disturbed or removed.

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