4d graphic rendering of iron-platinum nanoparticle

Atomic motion is captured in 4D for the first time

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4d graphic rendering of iron-platinum nanoparticle

The image shows 4D atomic motion captured in an iron-platinum nanoparticle at three different times.
Credit: Alexander Tokarev

Results of UCLA-led study contradict a long-held classical theory

Everyday transitions from one state of matter to another — such as freezing, melting or evaporation — start with a process called “nucleation,” in which tiny clusters of atoms or molecules (called “nuclei”) begin to coalesce. Nucleation plays a critical role in circumstances as diverse as the formation of clouds and the onset of neurodegenerative disease.

A UCLA-led team has gained a never-before-seen view of nucleation — capturing how the atoms rearrange at 4D atomic resolution (that is, in three dimensions of space and across time). The findings, published in the journal Nature, differ from predictions based on the classical theory of nucleation that has long appeared in textbooks.

“This is truly a groundbreaking experiment — we not only locate and identify individual atoms with high precision, but also monitor their motion in 4D for the first time,” said senior author Jianwei “John” Miao, a UCLA professor of physics and astronomy, who is the deputy director of the STROBE National Science Foundation Science and Technology Center and a member of the California NanoSystems Institute at UCLA.

Research by the team, which includes collaborators from Lawrence Berkeley National Laboratory, University of Colorado at Boulder, University of Buffalo and the University of Nevada, Reno, builds upon a powerful imaging techniquepreviously developed by Miao’s research group. That method, called “atomic electron tomography,” uses a state-of-the-art electron microscope located at Berkeley Lab’s Molecular Foundry, which images a sample using electrons. The sample is rotated, and in much the same way a CAT scan generates a three-dimensional X-ray of the human body, atomic electron tomography creates stunning 3D images of atoms within a material.

Miao and his colleagues examined an iron-platinum alloy formed into nanoparticles so small that it takes more than 10,000 laid side by side to span the width of a human hair. To investigate nucleation, the scientists heated the nanoparticles to 520 degrees Celsius, or 968 degrees Fahrenheit, and took images after 9 minutes, 16 minutes and 26 minutes. At that temperature, the alloy undergoes a transition between two different solid phases.

Although the alloy looks the same to the naked eye in both phases, closer inspection shows that the 3D atomic arrangements are different from one another. After heating, the structure changes from a jumbled chemical state to a more ordered one, with alternating layers of iron and platinum atoms. The change in the alloy can be compared to solving a Rubik’s Cube — the jumbled phase has all the colors randomly mixed, while the ordered phase has all the colors aligned.

In a painstaking process led by co-first authors and UCLA postdoctoral scholars Jihan Zhou and Yongsoo Yang, the team tracked the same 33 nuclei — some as small as 13 atoms — within one nanoparticle.

“People think it’s difficult to find a needle in a haystack,” Miao said. “How difficult would it be to find the same atom in more than a trillion atoms at three different times?”

The results were surprising, as they contradict the classical theory of nucleation. That theory holds that nuclei are perfectly round. In the study, by contrast, nuclei formed irregular shapes. The theory also suggests that nuclei have a sharp boundary. Instead, the researchers observed that each nucleus contained a core of atoms that had changed to the new, ordered phase, but that the arrangement became more and more jumbled closer to the surface of the nucleus.

Classical nucleation theory also states that once a nucleus reaches a specific size, it only grows larger from there. But the process seems to be far more complicated than that: In addition to growing, nuclei in the study shrunk, divided and merged; some dissolved completely.

“Nucleation is basically an unsolved problem in many fields,” said co-author Peter Ercius, a staff scientist at the Molecular Foundry, a nanoscience facility that offers users leading-edge instrumentation and expertise for collaborative research. “Once you can image something, you can start to think about how to control it.”

The findings offer direct evidence that classical nucleation theory does not accurately describe phenomena at the atomic level. The discoveries about nucleation may influence research in a wide range of areas, including physics, chemistry, materials science, environmental science and neuroscience.

“By capturing atomic motion over time, this study opens new avenues for studying a broad range of material, chemical and biological phenomena,” said National Science Foundation program officer Charles Ying, who oversees funding for the STROBE center. “This transformative result required groundbreaking advances in experimentation, data analysis and modeling, an outcome that demanded the broad expertise of the center’s researchers and their collaborators.”

Other authors were Yao Yang, Dennis Kim, Andrew Yuan and Xuezeng Tian, all of UCLA; Colin Ophus and Andreas Schmid of Berkeley Lab; Fan Sun and Hao Zeng of the University at Buffalo in New York; Michael Nathanson and Hendrik Heinz of the University of Colorado at Boulder; and Qi An of the University of Nevada, Reno.

The research was primarily supported by the STROBE National Science Foundation Science and Technology Center, and also supported by the U.S. Department of Energy.

This story originally appeared in the UCLA Newsroom.

Photo of baby laughing

Babies Know the Difference between the Laughter of Friends and Strangers

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Five-month-olds may use chuckles to identify information about social interactions

Photograph of baby laughing

Credit: Aarti Kalyani Getty Images

Most people can share a laugh with a total stranger. But there are subtle—and detectable—differences in our guffaws with friends.

Greg Bryant, a cognitive scientist at the University of California, Los Angeles, and his colleagues previously found that adults from 24 societies around the world can distinguish simultaneous “co-laughter” between friends from that between strangers. The findings suggested that this ability may be universally used to help read social interactions. So the researchers wondered: Can babies distinguish such laughter, too?

Bryant and his fellow researcher Athena Vouloumanos, a developmental psychologist at New York University, played recordings of co-laughter between pairs of either friends or strangers to 24 five-month-old infants in New York City. The babies listened longer to the laughs shared between buddies—suggesting they could tell the two types apart, according to a study published in March in Scientific Reports.

The researchers then showed the babies short videos of two people acting either like friends or strangers and paired those with the audio recordings. The babies stared for longer at clips paired with a mismatched recording—for example, if they saw friends interacting but heard strangers laughing.

“There’s something about co-laughter that is giving information to even a five-month-old about the social relationship between the individuals,” Bryant says. Exactly what components of laughter the infants are detecting remains to be seen, but prior work by Bryant’s team provides hints. Laughs between friends tend to include greater fluctuations in pitch and intensity, for example.

Such characteristics also distinguish spontaneous laughs from fake ones. Many scientists think unprompted laughter most likely evolved from play vocalizations, which are also produced by nonhuman primates, rodents and other mammals. Fake laughter probably emerged later in humans, along with the ability to produce a wide range of speech sounds. The researchers suggest that we may be sensitive to spontaneous laughter during development because of its long evolutionary history.

“It’s really cool to see how early infants are distinguishing between different forms of laughter,” says Adrienne Wood, a psychologist at the University of Virginia, who was not involved in the study. “Almost every waking moment is a social interaction for [babies], so it makes sense that they are becoming very attuned to their social worlds.”

This story originally appeared in the Scientific American.

Graduates in Pauley Pavilion

UCLA College Celebrates Centennial Graduates

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Graduates in Pauley Pavilion taking selfies

Graduates in Pauley Pavilion

 

Amid cheers and tears of happiness, the centennial class of UCLA celebrated both its graduation and the 100 years of UCLA’s existence at today’s commencement ceremonies, embracing the message that extraordinary changes don’t happen inevitably, but because people like this year’s graduates fight for it.

About 6,000 seniors were expected at the UCLA College commencement ceremonies in Pauley Pavilion at 2 p.m. and 7 p.m., joined by more than 20,000 friends, family members and guests. At dozens of ceremonies across campus this graduation season, UCLA awarded roughly 8,400 undergraduate degrees and 5,000 graduate degrees, including just over 600 Ph.D.s.

Anna Lee Fisher speaking

Anna Lee Fisher speaking

This year’s UCLA College graduates include students like Haya Kaliounji, a Syrian immigrant whose organization, Rise Again, has helped more than 40 Syrian amputees get prosthetic limbs, and Helen and Rachel Lee, first-generation college students and twins who are working with state legislators to repeal the sales tax on menstrual products.

In its first 100 years, UCLA has become the most applied-to university in the country and is often ranked as the nation’s No. 1 public university. Bruins have earned 13 Nobel Prizes and three Pulitzers. Roughly a third of UCLA undergraduates are first-generation college students, and a similar number come from low-income families.

For the first time, the commencement program included an acknowledgment of the Tongva people as the original inhabitants of the Los Angeles basin. In his address, UCLA Chancellor Gene Block reminded the audience that students led or aided many positive changes – like the creation of UCLA’s prestigious ethnic studies centers, or programs to support students who are veterans, undocumented, transfers, parents or foster youth.

While UCLA can still improve, it has made dramatic changes for the better since 1919, Block said.

“We better embody the aspirations of all our members, and we are a lot more diverse — we represent a much more diverse and interesting family than we did when we started,” Block said. “All that has changed on this campus hasn’t changed by accident. It’s changed because of students, faculty and staff, alumni and others like you, who said ‘UCLA can do better.’”

Astronaut and three-time UCLA alumna Anna Lee Fisher delivered the keynote address at both ceremonies, telling students that her path to success was neither smooth nor guaranteed, but the result of perseverance in the face of setbacks, learning from mistakes, and back-up plans.

When she couldn’t become an astronaut because women weren’t allowed to be test pilots, she decided to become a doctor so NASA would send her up to care for other astronauts. When she didn’t get into medical school on her first try, she got her master’s degree in chemistry – a degree that was instrumental in her selection as one of the first six female astronauts.

“Sometimes, when you read or hear about a person who appears to be successful, it sounds as though it was smooth sailing the entire time,” Fisher said. “I’ve had many missteps and disappointments along the way, and inevitably, you will, as well. Learn from those experiences and use that newfound knowledge to continue to pursue your dreams.”

Through it all, she said the hardest things she ever did were leaving her then-14-month-old daughter during her first space flight, and returning to NASA after the birth of her second daughter.

“I also, incidentally … became the first mother to fly in space,” Fisher said. “I did not consider it a big deal, as most of my male colleagues had children as well. But of course my daughter says I owe it all to her. … For you parents and families, as you can see, even though I have three degrees, have been a doctor and an astronaut and have flown in space, I am still ‘just Mom’ to them.”

Graduating senior Kaitlyn Kim delivered the student speech at the 2 p.m. ceremony, noting that she has seen first hand how UCLA’s embrace of first-generation college students, immigrants and low-income families can lift up the generations that follow – because her parents were South Korean immigrants who both graduated from UCLA.

Student speaker Kaitlyn Kim

Student speaker Kaitlyn Kim

“Just because my parents and I went to the same school does not mean we had the same experience,” Kim said. “My dad worked as an on-campus vending machine cart driver in order to pay for his tuition, and my mom was a commuter student, responsible for taking care of her two younger siblings.”

Kim’s parents made it possible for her to live on campus and focus on her studies instead of working long hours at a job, she said. Soon, the California native and communications major starts her new job as a fashion buyer for a Fortune 500 company.

“Because of the sacrifices they made, my parents paved the path for me,” Kim said. Just as her parents lit the way for her and UCLA lit the way for them, she added, “let us hope to bring light to the entire world, one Bruin at a time.”

Graduating senior Ashraf Beshay delivered the student speech at the 7 p.m. ceremony. Beshay came to the United States as an asylum seeker to escape threats after taking part in the Egyptian Revolution. His mother, whom he hadn’t seen for five years, was able to visit UCLA for the first time to see Beshay and his sister both graduate, and the siblings have kept his role as student speaker a secret to surprise her. Commitment to each other and the betterment of society should be the graduates’ promise, according to his prepared speech.

“It is that promise that manifests into our social justice movements and strengthens our conviction that ‘Black Lives Matter,’ that immigration is beautiful, that we are now standing on Native American land, that women’s rights are human rights, and equal labor deserves equal pay, and that ‘the world is over-armed and peace is so sorely underfunded,’” Beshay wrote in his remarks. “These very basic human principles must guide our engagement with a world so far from where it needs to be, to be just.”

As Friday’s first commencement ceremony drew to a close, Block formally conferred the bachelor’s degrees to raucous applause. Kim stepped forward once more to lead her fellow students in the turning of the tassels to the left, one of their last college rituals.

“Graduates, let me congratulate all of us on becoming the newest alumni of UCLA – as the Class of 2019!” Kim said. The new graduates flung their hats in the air before pouring out of Pauley Pavilion to greet family members, perhaps remembering some of Fisher’s final words – words with extra resonance, coming from an astronaut.

“You, too, can aim for the stars,” she told them. “The sky is the limit.”

This article originally appeared on the UCLA Newsroom.

Eyes on the horizon, mortarboard reads