Screen of Computer Speaks for Paralyzed Man

'Neuroprosthesis' restores words to man with paralysis.  Technology could lead to more natural communication for people who have suffered speech loss

From:  University of California San Francisco

July 14, 2021 -- Researchers at UC San Francisco have successfully developed a 'speech neuroprosthesis' that has enabled a man with severe paralysis to communicate in sentences, translating signals from his brain to the vocal tract directly into words that appear as text on a screen.

The achievement, which was developed in collaboration with the first participant of a clinical research trial, builds on more than a decade of effort by UCSF neurosurgeon Edward Chang, MD, to develop a technology that allows people with paralysis to communicate even if they are unable to speak on their own. The study appears July 15 in the New England Journal of Medicine.

"To our knowledge, this is the first successful demonstration of direct decoding of full words from the brain activity of someone who is paralyzed and cannot speak," said Chang, the Joan and Sanford Weill Chair of Neurological Surgery at UCSF, Jeanne Robertson Distinguished Professor, and senior author on the study. "It shows strong promise to restore communication by tapping into the brain's natural speech machinery."

Each year, thousands of people lose the ability to speak due to stroke, accident, or disease. With further development, the approach described in this study could one day enable these people to fully communicate.

Translating Brain Signals into Speech

Previously, work in the field of communication neuroprosthetics has focused on restoring communication through spelling-based approaches to type out letters one-by-one in text. Chang's study differs from these efforts in a critical way: his team is translating signals intended to control muscles of the vocal system for speaking words, rather than signals to move the arm or hand to enable typing. Chang said this approach taps into the natural and fluid aspects of speech and promises more rapid and organic communication.

"With speech, we normally communicate information at a very high rate, up to 150 or 200 words per minute," he said, noting that spelling-based approaches using typing, writing, and controlling a cursor are considerably slower and more laborious. "Going straight to words, as we're doing here, has great advantages because it's closer to how we normally speak."

Over the past decade, Chang's progress toward this goal was facilitated by patients at the UCSF Epilepsy Center who were undergoing neurosurgery to pinpoint the origins of their seizures using electrode arrays placed on the surface of their brains. These patients, all of whom had normal speech, volunteered to have their brain recordings analyzed for speech-related activity. Early success with these patient volunteers paved the way for the current trial in people with paralysis.

Previously, Chang and colleagues in the UCSF Weill Institute for Neurosciences mapped the cortical activity patterns associated with vocal tract movements that produce each consonant and vowel. To translate those findings into speech recognition of full words, David Moses, PhD, a postdoctoral engineer in the Chang lab and one of the lead authors of the new study, developed new methods for real-time decoding of those patterns and statistical language models to improve accuracy.

But their success in decoding speech in participants who were able to speak didn't guarantee that the technology would work in a person whose vocal tract is paralyzed. "Our models needed to learn the mapping between complex brain activity patterns and intended speech," said Moses. "That poses a major challenge when the participant can't speak."

In addition, the team didn't know whether brain signals controlling the vocal tract would still be intact for people who haven't been able to move their vocal muscles for many years. "The best way to find out whether this could work was to try it," said Moses.

The First 50 Words

To investigate the potential of this technology in patients with paralysis, Chang partnered with colleague Karunesh Ganguly, MD, PhD, an associate professor of neurology, to launch a study known as "BRAVO" (Brain-Computer Interface Restoration of Arm and Voice). The first participant in the trial is a man in his late 30s who suffered a devastating brainstem stroke more than 15 years ago that severely damaged the connection between his brain and his vocal tract and limbs. Since his injury, he has had extremely limited head, neck, and limb movements, and communicates by using a pointer attached to a baseball cap to poke letters on a screen.

The participant, who asked to be referred to as BRAVO1, worked with the researchers to create a 50-word vocabulary that Chang's team could recognize from brain activity using advanced computer algorithms. The vocabulary -- which includes words such as "water," "family," and "good" -- was sufficient to create hundreds of sentences expressing concepts applicable to BRAVO1's daily life.

For the study, Chang surgically implanted a high-density electrode array over BRAVO1's speech motor cortex. After the participant's full recovery, his team recorded 22 hours of neural activity in this brain region over 48 sessions and several months. In each session, BRAVO1 attempted to say each of the 50 vocabulary words many times while the electrodes recorded brain signals from his speech cortex.

Translating Attempted Speech into Text

To translate the patterns of recorded neural activity into specific intended words, the other two lead authors of the study, Sean Metzger, MS and Jessie Liu, BS, both bioengineering doctoral students in the Chang Lab used custom neural network models, which are forms of artificial intelligence. When the participant attempted to speak, these networks distinguished subtle patterns in brain activity to detect speech attempts and identify which words he was trying to say.

To test their approach, the team first presented BRAVO1 with short sentences constructed from the 50 vocabulary words and asked him to try saying them several times. As he made his attempts, the words were decoded from his brain activity, one by one, on a screen.

Then the team switched to prompting him with questions such as "How are you today?" and "Would you like some water?" As before, BRAVO1's attempted speech appeared on the screen. "I am very good," and "No, I am not thirsty."

The team found that the system was able to decode words from brain activity at rate of up to 18 words per minute with up to 93 percent accuracy (75 percent median). Contributing to the success was a language model Moses applied that implemented an "auto-correct" function, similar to what is used by consumer texting and speech recognition software.

Moses characterized the early trial results as a proof of principle. "We were thrilled to see the accurate decoding of a variety of meaningful sentences," he said. "We've shown that it is actually possible to facilitate communication in this way and that it has potential for use in conversational settings."

Looking forward, Chang and Moses said they will expand the trial to include more participants affected by severe paralysis and communication deficits. The team is currently working to increase the number of words in the available vocabulary, as well as improve the rate of speech.

Both said that while the study focused on a single participant and a limited vocabulary, those limitations don't diminish the accomplishment. "This is an important technological milestone for a person who cannot communicate naturally," said Moses, "and it demonstrates the potential for this approach to give a voice to people with severe paralysis and speech loss."

Co-authors on the paper include Sean L. Metzger, MS; Jessie R. Liu; Gopala K. Anumanchipalli, PhD; Joseph G. Makin, PhD; Pengfei F. Sun, PhD; Josh Chartier, PhD; Maximilian E. Dougherty; Patricia M. Liu, MA; Gary M. Abrams, MD; and Adelyn Tu-Chan, DO, all of UCSF. Funding sources included National Institutes of Health (U01 NS098971-01), philanthropy, and a sponsored research agreement with Facebook Reality Labs (FRL), which completed in early 2021.

UCSF researchers conducted all clinical trial design, execution, data analysis and reporting. Research participant data were collected solely by UCSF, are held confidentially, and are not shared with third parties. FRL provided high-level feedback and machine learning advice.

https://www.sciencedaily.com/releases/2021/07/210714174148.htm

Wolf Cubs Don’t Snuggle Like Dog Puppies

After 14,000 years of domestication, dogs have some of the same cognitive abilities as human babies.  Scientists have debated for decades how dogs got so good at reading people. New research comparing dog puppies to human-reared wolf pups offers some clues. 

From:  Duke Today

By Robin A. Smith

July 12, 2021 -- DURHAM, N.C. -- You know your dog gets your gist when you point and say “go find the ball” and he scampers right to it.

This knack for understanding human gestures may seem unremarkable, but it’s a complex cognitive ability that is rare in the animal kingdom. Our closest relatives, the chimpanzees, can’t do it. And the dogs’ closest relative, the wolf, can’t either, according to a new Duke University-led study published July 12 in the journal Current Biology.

More than 14,000 years of hanging out with us has done a curious thing to the minds of dogs. They have what are known as “theory of mind” abilities, or mental skills allowing them to infer what humans are thinking and feeling in some situations.

The study, a comparison of 44 dog and 37 wolf puppies who were between 5 and 18 weeks old, supports the idea that domestication changed not just how dogs look, but their minds as well.

At the Wildlife Science Center in Minnesota, wolf puppies were first genetically tested to make sure they were not wolf – dog hybrids. The wolf puppies were then raised with plenty of human interaction. They were fed by hand, slept in their caretakers’ beds each night, and received nearly round-the-clock human care from just days after birth. In contrast, the dog puppies from Canine Companions for Independence lived with their mother and littermates and had less human contact.

Then the canines were tested. In one test, the researchers hid a treat in one of two bowls, then gave each dog or wolf puppy a clue to help them find the food. In some trials, the researchers pointed and gazed in the direction the food was hidden. In others, they placed a small wooden block beside the right spot -- a gesture the puppies had never seen before -- to show them where the treat was hidden.

The results were striking. Even with no specific training, dog puppies as young as eight weeks old understood where to go, and were twice as likely to get it right as wolf puppies the same age who had spent far more time around people.

Seventeen out of 31 dog puppies consistently went to the right bowl. In contrast, none out of 26 human-reared wolf pups did better than a random guess. Control trials showed the puppies weren’t simply sniffing out the food.

Even more impressive, many of the dog puppies got it right on their first trial. Absolutely no training necessary. They just get it.

It’s not about which species is “smarter,” said first author Hannah Salomons, a doctoral student in Brian Hare’s lab at Duke. Dog puppies and wolf puppies proved equally adept in tests of other cognitive abilities, such as memory, or motor impulse control, which involved making a detour around transparent obstacles to get food.

It was only when it came to the puppies’ people-reading skills that the differences became clear.

“There's lots of different ways to be smart,” Salomons said. “Animals evolve cognition in a way that will help them succeed in whatever environment they're living in.”

Other tests showed that dog puppies were also 30 times more likely than wolf pups to approach a stranger.

“With the dog puppies we worked with, if you walk into their enclosure they gather around and want to climb on you and lick your face, whereas most of the wolf puppies run to the corner and hide,” Salomons said.

And when presented with food inside a container that was sealed so they could no longer retrieve it, the wolf pups generally tried to solve the problem on their own, whereas the dog puppies spent more time turning to people for help, looking them in the eye as if to say: “I’m stuck can you fix this?”

Senior author Brian Hare says the research offers some of the strongest evidence yet of what’s become known as the “domestication hypothesis.”

Somewhere between 12,000 and 40,000 years ago, long before dogs learned to fetch, they shared an ancestor with wolves. How such feared and loathed predators transformed into man’s best friend is still a bit of a mystery. But one theory is that, when humans and wolves first met, only the friendliest wolves would have been tolerated and gotten close enough to scavenge on the human’s leftovers instead of running away. Whereas the shyer, surlier wolves might go hungry, the friendlier ones would survive and pass on the genes that made them less fearful or aggressive toward humans.

The theory is that this continued generation after generation, until the wolf’s descendants became masters at gauging the intentions of people they interact with by deciphering their gestures and social cues.

“This study really solidifies the evidence that the social genius of dogs is a product of domestication,” said Hare, professor of evolutionary anthropology at Duke.

It’s this ability that makes dogs such great service animals, Hare said. “It is something they are really born prepared to do.”

Much like human infants, dog puppies intuitively understand that when a person points, they’re trying to tell them something, whereas wolf puppies don’t.

“We think it indicates a really important element of social cognition, which is that others are trying to help you,” Hare said.

“Dogs are born with this innate ability to understand that we're communicating with them and we're trying to cooperate with them,” Salomons said.

This research was supported by the Office of Naval Research (N00014- 16-12682), the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health (NIH-1Ro1HD097732) and the AKC Canine Health Foundation (#2700).

https://today.duke.edu/2020/07/you-can-snuggle-wolf-pups-all-you-want-they-still-wont-get-you-quite-your-dog

Artificial Intelligence Picks American Stocks

How EquBot is beating the market with AIEQ, the AI-powered Exchange Traded Fund (ETF)

By Katelyn Rothney at IBM

June 21, 2021 – A new exchange traded fund based on IBM’s Watson and artificial intelligence started three years ago and did not match the market indexes.  The second year, this ETF was matching the market’s performance.  For the third year, the ETF is performing better than the market because it learns on its own continuously.

See:  https://www.ibm.com/blogs/watson/2021/06/equbot-aieq-ai-powered-etf/

Part of the Brain Links Similar Objects

Leads to new insights about how the brain processes information out of context.

From: Johns Hopkins University

July 8, 2021 -- When people see a toothbrush, a car, a tree -- any individual object -- their brain automatically associates it with other things it naturally occurs with, allowing humans to build context for their surroundings and set expectations for the world.

By using machine-learning and brain imaging, researchers measured the extent of the "co-occurrence" phenomenon and identified the brain region involved. The findings appear in Nature Communications.

"When we see a refrigerator, we think we're just looking at a refrigerator, but in our mind, we're also calling up all the other things in a kitchen that we associate with a refrigerator," said corresponding author Mick Bonner, a Johns Hopkins University cognitive scientist. "This is the first time anyone has quantified this and identified the brain region where it happens."

In a two-part study, Bonner and co-author, Russell Epstein, a psychology professor at the University of Pennsylvania, used a database with thousands of scenic photos with every object labeled. There were pictures of household scenes, city life, nature -- and the pictures had labels for every mug, car, tree, etc. To quantify object co-occurrences, or how often certain objects appeared with others, they created a statistical model and algorithm that demonstrated the likelihood of seeing a pen if you saw a keyboard, or seeing a boat if you saw a dishwasher.

With these contextual associations quantified, the researchers next attempted to map the brain region that handles the links.

While subjects were having their brain activity monitored with functional magnetic resonance imaging, or fMRI, the team showed them pictures of individual objects and looked for evidence of a region whose responses tracked this co-occurrence information. The spot they identified was a region in the visual cortex commonly associated with the processing of spatial scenes.

"When you look at a plane, this region signals sky and clouds and all the other things," Bonner said. "This region of the brain long thought to process the spatial environment is also coding information about what things go together in the world."

Researchers have long-known that people are slower to recognize objects out of context. The team believes this is the first large-scale experiment to quantify the associations between objects in the visual environment as well as the first insight into how this visual context is represented in the brain.

"We show in a fine-grained way that the brain actually seems to represent this rich statistical information," Bonner said.

---

         https://www.sciencedaily.com/releases/2021/07/210708134756.htm

Global Pollution from Plastics

Is it reaching a tipping point for the earth?

From:  Stockholm University

July 1, 2021 -- Current rates of plastic emissions globally may trigger effects that we will not be able to reverse, argues a new study. According to the authors, plastic pollution is a global threat, and actions to drastically reduce emissions of plastic to the environment are 'the rational policy response.'

Plastic is found everywhere on the planet: from deserts and mountaintops to deep oceans and Arctic snow. As of 2016, estimates of global emissions of plastic to the world's lakes, rivers and oceans ranged from 9 to 23 million metric tons per year, with a similar amount emitted onto land yearly. These estimates are expected to almost double by 2025 if business-as-usual scenarios apply.

"Plastic is deeply engrained in our society, and it leaks out into the environment everywhere, even in countries with good waste-handling infrastructure," says Matthew MacLeod, Professor at Stockholm University and lead author of the study. He says that emissions are trending upward even though awareness about plastic pollution among scientists and the public has increased significantly in recent years.

That discrepancy is not surprising to Mine Tekman, a PhD candidate at the Alfred Wegener Institute in Germany and co-author of the study, because plastic pollution is not just an environmental issue but also a "political and economic" one. She believes that the solutions currently on offer, such as recycling and cleanup technologies, are not sufficient, and that we must tackle the problem at its root.

"The world promotes technological solutions for recycling and to remove plastic from the environment. As consumers, we believe that when we properly separate our plastic trash, all of it will magically be recycled. Technologically, recycling of plastic has many limitations, and countries that have good infrastructures have been exporting their plastic waste to countries with worse facilities. Reducing emissions requires drastic actions, like capping the production of virgin plastic to increase the value of recycled plastic, and banning export of plastic waste unless it is to a country with better recycling" says Tekman.

A poorly reversible pollutant of remote areas of the environment

Plastic accumulates in the environment when amounts emitted exceed those that are removed by cleanup initiatives and natural environmental processes, which occurs by a multi-step process known as weathering.

"Weathering of plastic happens because of many different processes, and we have come a long way in understanding them. But weathering is constantly changing the properties of plastic pollution, which opens new doors to more questions," says Hans Peter Arp, researcher at the Norwegian Geotechnical Institute (NGI) and Professor at the Norwegian University of Science and Technology (NTNU) who has also co-authored the study. "Degradation is very slow and not effective in stopping accumulation, so exposure to weathered plastic will only increase," says Arp. Plastic is therefore a "poorly reversible pollutant," both because of its continuous emissions and environmental persistence.

Remote environments are particularly under threat as co-author Annika Jahnke, researcher at the Helmholtz Centre for Environmental Research (UFZ) and Professor at the RWTH Aachen University explains:

"In remote environments, plastic debris cannot be removed by cleanups, and weathering of large plastic items will inevitably result in the generation of large numbers of micro- and nanoplastic particles as well as leaching of chemicals that were intentionally added to the plastic and other chemicals that break off the plastic polymer backbone. So, plastic in the environment is a constantly moving target of increasing complexity and mobility. Where it accumulates and what effects it may cause are challenging or maybe even impossible to predict."

A potential tipping point of irreversible environmental damage

On top of the environmental damage that plastic pollution can cause on its own by entanglement of animals and toxic effects, it could also act in conjunction with other environmental stressors in remote areas to trigger wide-ranging or even global effects. The new study lays out a number of hypothetical examples of possible effects, including exacerbation of climate change because of disruption of the global carbon pump, and biodiversity loss in the ocean where plastic pollution acts as additional stressor to overfishing, ongoing habitat loss caused by changes in water temperatures, nutrient supply and chemical exposure.

Taken all together, the authors view the threat that plastic being emitted today may trigger global-scale, poorly reversible impacts in the future as "compelling motivation" for tailored actions to strongly reduce emissions.

"Right now, we are loading up the environment with increasing amounts of poorly reversible plastic pollution. So far, we don't see widespread evidence of bad consequences, but if weathering plastic triggers a really bad effect we are not likely to be able to reverse it," cautions MacLeod. "The cost of ignoring the accumulation of persistent plastic pollution in the environment could be enormous. The rational thing to do is to act as quickly as we can to reduce emissions of plastic to the environment."

             https://www.sciencedaily.com/releases/2021/07/210701140931.htm

Irish Scientists’ Recipe for Renewable Energy

Scientists are homing in on a recipe that would enable the future production of entirely renewable, clean energy from which water would be the only waste product.

From:  Trinity College Dublin

July 7, 2021 -- Using their expertise in chemistry, theoretical physics and artificial intelligence, the team is now fine-tuning the recipe with the genuine belief that the seemingly impossible will one day be reality.

Using their expertise in chemistry, theoretical physics and artificial intelligence, the team is now fine-tuning the recipe with the genuine belief that the seemingly impossible will one day be reality.

Initial work in this area, reported just under two years ago, yielded promise. That promise has now been amplified significantly in the exciting work just published in leading journal, Cell Reports Physical Science.

Energy for a song -- the theory, and the problem

Reducing humanity's carbon dioxide (CO₂) emissions is arguably the greatest challenge facing 21stcentury civilisation -- especially given the increasing global population and the heightened energy demands that come with it.

One beacon of hope is the idea that we could use renewable electricity to split water (H₂O) to produce green, energy-rich hydrogen (H₂), which could then be stored and used in fuel cells. This is an especially interesting prospect in a situation where wind and solar energy sources produce electricity to split water, as this would allow us to store energy for use when those renewable sources are not available.

The essential problem, however, is that water is very stable and requires a great deal of energy to break up; there is no point using much more energy than you get back from such an effort. A particularly major hurdle to clear is this "overpotential" associated with the production of oxygen, which is the bottleneck reaction in splitting water to produce H2.

Although certain elements are effective at splitting water, such as Ruthenium or Iridium, these are prohibitively expensive and scarce for global commercialisation. Other, cheaper options tend to suffer in terms of their efficiency and/or their robustness. In fact, at present, nobody has discovered catalysts that are cost-effective and robust for significant periods of time.

So, how do you solve such a riddle? Stop before you imagine lab coats, glasses, beakers and funny smells; this work was done entirely through a computer.

By bringing together chemists and theoretical physicists, the Trinity team behind the latest breakthrough combined chemistry smarts with very powerful computers to find one of the "holy grails" of catalysis.

What did the team find?

Then: Two years ago, the team discovered that science had been underestimating the activity of some of the more reactive catalysts and, as a result, the dreaded "overpotential" hurdle seemed easier to clear. Furthermore, in refining a long-accepted theoretical model used to predict the efficiency of water splitting catalysts, they made it far easier to search for the elusive "green bullet" catalyst.

Now: Their subsequent searches, made using an automated combinatorial approach and advanced quantum chemical modelling, have pinpointed nine earth-abundant combinations of metals and ligands (which glue them together to generate the catalysts) as highly promising leads for experimental investigation.

Three metals stand out (chromium, manganese, iron) for the team as being especially promising. Thousands of catalysts based around these key components can now be placed in a melting pot and assessed for their abilities as the hunt for the magic combination continues.

Max García-Melchor, Ussher Assistant Professor in Chemistry at Trinity, is the senior author on the landmark research. He said:

"Two years ago, our work had made the hunt for the holy grail of catalysts seem a little more manageable. Now, we have taken another major leap forward by narrowing the search area significantly and speeding up the way we search.

"Until recently we were looking for a tiny needle in a huge haystack. After reducing the size of the haystack, we have now hoovered up plenty of the remaining hay. To put a sense of scale on this, two years ago we had screened 17 catalysts. Now we have screened 444 and believe it won't be long before we have a database with 80,000 'screenable' catalysts in it.

"'How can we live sustainably?' That is arguably the biggest and most pressing question facing 21st century society. I believe researchers from all disciplines can help to answer that, and we feel a particular strength of our pursuit is the multi-disciplinary approach we are taking."

Michael Craig, PhD Candidate at Trinity, is the first author of the journal article. He added:

"It seems hopeful that science could provide the world with entirely renewable energy, and this latest work provides a theoretical basis to optimise sustainable ways to store this energy and goes beyond that by pinpointing specific metals that offer the greatest promise.

"A lot of research has focused on the effective yet prohibitively expensive metals as possible candidates, even though these are far too rare to do the heavy lifting required to store enough hydrogen for society. We are focused on finding a long-term, viable option. And we hope we will."

                  https://www.sciencedaily.com/releases/2021/07/210707112521.htm

Why Does the Universe Have So Little Antimatter? This Violates Symmetry

Radioactive molecules are sensitive to subtle nuclear phenomena and might help physicists probe the violation of the most fundamental symmetries of nature.

By Jennifer Chu, MIT News Office

July 7, 2021 -- Imagine a dust particle in a storm cloud, and you can get an idea of a neutron’s insignificance compared to the magnitude of the molecule it inhabits.

But just as a dust mote might affect a cloud’s track, a neutron can influence the energy of its molecule despite being less than one-millionth its size. And now physicists at MIT and elsewhere have successfully measured a neutron’s tiny effect in a radioactive molecule.

The team has developed a new technique to produce and study short-lived radioactive molecules with neutron numbers they can precisely control. They hand-picked several isotopes of the same molecule, each with one more neutron than the next. When they measured each molecule’s energy, they were able to detect small, nearly imperceptible changes of the nuclear size, due to the effect of a single neutron.

The fact that they were able to see such small nuclear effects suggests that scientists now have a chance to search such radioactive molecules for even subtler effects, caused by dark matter, for example, or by the effects of new sources of symmetry violations related to some of the current mysteries of the universe.

“If the laws of physics are symmetrical as we think they are, then the Big Bang should have created matter and antimatter in the same amount. The fact that most of what we see is matter, and there is only about one part per billon of antimatter, means there is a violation of the most fundamental symmetries of physics, in a way that we can’t explain with all that we know,” says Ronald Fernando Garcia Ruiz, assistant professor of physics at MIT.

“Now we have a chance to measure these symmetry violations, using these heavy radioactive molecules, which have extreme sensitivity to nuclear phenomena that we cannot see in other molecules in nature,” he says. “That could provide answers to one of the main mysteries of how the universe was created.”

Ruiz and his colleagues have published their results today in Physical Review Letters.

A special asymmetry

Most atoms in nature host a symmetrical, spherical nucleus, with neutrons and protons evenly distributed throughout. But in certain radioactive elements like radium, atomic nuclei are weirdly pear-shaped, with an uneven distribution of neutrons and protons within. Physicists hypothesize that this shape distortion can enhance the violation of symmetries that gave origin to the matter in the universe.

“Radioactive nuclei could allow us to easily see these symmetry-violating effects,” says study lead author Silviu-Marian Udrescu, a graduate student in MIT’s Department of Physics. “The disadvantage is, they’re very unstable and live for a very short amount of time, so we need sensitive methods to produce and detect them, fast.”

Rather than attempt to pin down radioactive nuclei on their own, the team placed them in a molecule that futher amplifies the sensitivity to symmetry violations. Radioactive molecules consist of at least one radioactive atom, bound to one or more other atoms. Each atom is surrounded by a cloud of electrons that together generate an extremely high electric field in the molecule that physicists believe could amplify subtle nuclear effects, such as effects of symmetry violation.

However, aside from certain astrophysical processes, such as merging neutron stars, and stellar explosions, the radioactive molecules of interest do not exist in nature and therefore must be created artificially. Garcia Ruiz and his colleagues have been refining techniques to create radioactive molecules in the lab and precisely study their properties. Last year, they reported on a method to produce molecules of radium monofluoride, or RaF, a radioactive molecule that contains one unstable radium atom and a fluoride atom.

In their new study, the team used similar techniques to produce RaF isotopes, or versions of the radioactive molecule with varying numbers of neutrons. As they did in their previous experiment, the researchers utilized the Isotope mass Separator On-Line, or ISOLDE, facility at CERN, in Geneva, Switzerland, to produce small quantities of RaF isotopes.

The facility houses a low-energy proton beam, which the team directed toward a target — a half-dollar-sized disc of uranium-carbide, onto which they also injected a carbon fluoride gas. The ensuing chemical reactions produced a zoo of molecules, including RaF, which the team separated using a precise system of lasers, electromagnetic fields, and ion traps.

The researchers measured each molecule’s mass to estimate of the number of neutrons in a molecule’s radium nucleus. They then sorted the molecules by isotopes, according to their neutron numbers.

In the end, they sorted out bunches of five different isotopes of RaF, each bearing more neutrons than the next. With a separate system of lasers, the team measured the quantum levels of each molecule.

“Imagine a molecule vibrating like two balls on a spring, with a certain amount of energy,” explains Udrescu, who is a graduate student of MIT’s Laboratory for Nuclear Science. “If you change the number of neutrons in one of these balls, the amount of energy could change. But one neutron is 10 million times smaller than a molecule, and with our current precision we didn’t expect that changing one would create an energy difference, but it did. And we were able to clearly see this effect.”

Udrescu compares the sensitivity of the measurements to being able to see how Mount Everest, placed on the surface of the sun, could, however minutely, change the sun’s radius. By comparison, seeing certain effects of symmetry violation would be like seeing how the width of a single human hair would alter the sun’s radius.

The results demonstrate that radioactive molecules such as RaF are ultrasensitive to nuclear effects and that their sensitivity may likely reveal more subtle, never-before-seen effects, such as tiny symmetry-violating nuclear properties, that could help to explain the universe’s matter-antimmater asymmetry.

“These very heavy radioactive molecules are special and have sensitivity to nuclear phenomena that we cannot see in other molecules in nature,” Udrescu says. “This shows that, when we start to search for symmetry-violating effects, we have a high chance of seeing them in these molecules.”

                          https://news.mit.edu/2021/antimatter-neutron-0707