School of Arts & Sciences

A suspension of particles of different sizes during shearing experiments conducted in the lab of Paulo Arratia, with arrows indicating particle “flow” and trajectories. In a new study published in Nature Physics, researchers detail the relationship between a disordered material’s individual particle arrangement and how it reacts to external stressors. The study also found that these materials have “memory” that can be used to predict how and when they will flow. (Image: Arratia lab)

In a controlled field experiment on Penn’s campus, biologists tracked fruit fly evolution over the course of four months, documenting some of the fastest rates of adaptation ever in animals. (Image: Seth Rudman)

(Homepage image) “What we needed to do for our physical health—quarantining, staying away from other people and social situations—even when that kind of avoidance is the right thing to do, it makes people more anxious,” says Elizabeth Turk-Karan of the Center for the Study and Treatment of Anxiety. What remains to be seen is how these emotions and many others will play out as the pandemic recedes.

Michael E. Mann is Penn’s inaugural Presidential Distinguished Professor in the Department of Earth and Environmental Science. (Image: Joshua Yospin)

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Sweden's former Prime Minister Carl Bildt discusses the war in Ukraine with Clay Risen of The New York Times.

Political science doctoral candidate Meghan Garrity. (Image: OMNIA)