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

The Power of Penn Arts & Sciences

On April 12, 2018, the Power of Penn Arts & Sciences fundraising campaign was announced by the Board of Overseers. Launched in conjunction with the University’s Power of Penn campaign, it aims to raise $550 million for the School of Arts and Sciences.

View Article >
2018 Penn Arts and Sciences Dean’s Scholars

Penn Arts and Sciences has named 20 students from the College of Arts and Sciences, the College of Liberal and Professional Studies, and the Graduate Division as Dean’s Scholars. This honor is presented annually to students who exhibit exceptional academic performance and intellectual promise.

View Article >
Joseph Subotnik Named Edmund J. and Louise W. Kahn Term Professor

Joseph Subotnik, Professor of Chemistry, has been named Edmund J. and Louise W. Kahn Term Professor of Chemistry. A theoretical chemist who focuses on electronic processes in the condensed phase, Dr. Subotnik has made key contributions in electronic structure theory, chemical dynamics, and statistical mechanics.

View Article >
Two Penn Arts and Sciences Professors Named Guggenheim Fellows

Charles L. Bosk, Professor of Sociology, and Charles Yang, Professor of Linguistics and Computer Science, have been awarded 2018 John Simon Guggenheim Memorial Foundation fellowships.

View Article >
Ahmad Family Endowment Supports Penn Global Seminars

Hyder Ahmad, W’90, and his family have made a generous gift to establish the Ahmad Family Endowment for Penn Global Seminars in Arts and Sciences.

View Article >
Abraham Nitzan Named Donner Professor of Physical Sciences

Abraham Nitzan, Professor of Chemistry, has been named Donner Professor of Physical Sciences. Nitzan’s research focuses on the interaction of light with molecular systems, chemical reactions in condensed phases and interfaces and charge transfer processes in such environments.

View Article >
2018 Teaching Award Recipients Announced

Steven J. Fluharty, Dean of Penn Arts and Sciences, and Paul Sniegowski, Stephen A. Levin Family Dean of the College of Arts and Sciences, have announced the recipients of the 2018 awards for distinguished teaching in the School.

View Article >
College Graduation Speakers for 2018 Revealed

Angela Duckworth, G’03, GR’06, Christopher H. Browne Distinguished Professor of Psychology, will address the Class of 2018 at the graduation ceremony for the College of Arts and Sciences on Sunday, May 13, 2018. She will be joined by student speaker Helena von Nagy, C’18.

View Article >
Individualized Care Will Become the Standard for Depression Patients

In a new paper for the Annual Review of Clinical Psychology, researchers Robert DeRubeis, Samuel H. Preston Term Professor in the Social Sciences, and Zachary Cohen of Psychology, address precision medicine, also known as customized-care, in the context of treatment for depression.

View Article >
Restoring Vacant Lots Reduces Gun Violence and Crime

In cities across the U.S., about 15 percent of land is considered vacant or abandoned. These areas can foster criminal activity, and urban residents, especially those in low-income neighborhoods, often view vacant land as a threat to their health and safety.

View Article >
Robert DeRubeis: Samuel H. Preston Term Professor in the Social Sciences

Professor of Psychology Robert DeRubeis has been named the Samuel H.

View Article >