Researchers Solve a Decades-old Question About Glass Transitions


If one were to take a liquid—any liquid—and cool it down rapidly enough so that it doesn’t have a chance to crystallize, the result would be glass. Glass is so viscous that it takes too long to flow for anyone to realize that it is liquid rather than solid.

“We would never notice glass flow in our lifetimes or in a billion of our lifetimes or even hundreds of billions,” says Andrea Liu, Hepburn Professor of Physics. “Even in many, many times the lifetime of the universe. There are just ridiculous timescales involved here.”

Liu added that this is true of every liquid, and they all do it in very similar ways.

But how this process works has puzzled scientists ever since they realized it was happening. One huge question that remains is whether structure is connected to dynamics when it comes to these glass transitions.

“If you look at the viscosity, you can see it changing by ten orders of magnitude when you cool by only tens of degrees,” Liu says. “That’s called looking at the dynamics. But, if you look at the actual structure, at how the molecules are arranged, you'll hardly see any change at all. That’s one of the reasons why people had largely given up on finding any connection between structure and dynamics.”

In a paper published in the Proceedings of the National Academy of Sciences, researchers at Penn and Harvard University solved this decades-old question using an unconventional method: machine learning.

Click here to read the full story.

Arts & Sciences News

Elizabeth Rhoades Receives Award from Biophysical Society

The BPS grants the Michael and Kate Bárány Award to early-career academics who have made an outstanding contribution to biophysics.

View Article >
Ralph Rosen to Serve as Interim Associate Dean for Graduate Studies

Rosen previously held the position of Associate Dean for Graduate Studies from 2008 to 2013.

View Article >
Navigating Urban Waters, With an Interdisciplinary Approach

In a research-based fellowship program this summer, a group of Penn graduate and undergraduate students are creating new narratives of their own, tied to water.

View Article >
Cancer Cells Send Out ‘Drones’ to Battle the Immune System From Afar

Researchers show that, to assist in the fight, cancer cells release biological “drones,” small vesicles called exosomes circulating in the blood and armed with the protein PD-L1, which causes T cells to tire before they have a chance to reach the tumor and do battle.

View Article >
Mary Frances Berry Discusses Her New Book “History Teaches Us to Resist: How Progressive Movements Have Succeeded in Challenging Times”

In it, she shares her memories of being a protestor, provides an analysis of protest strategies, and highlights lessons from a lengthy history of fighting against injustice.

View Article >
Greening Vacant Lots Reduces Depression in City Dwellers

Revitalizing dilapidated environments may be an important, inexpensive tool to address mental health in urban communities.

View Article >