PHILADELPHIA — Two University of Pennsylvania professors have been named winners of Presidential Early Career Awards for Scientists and Engineers.

They are Peter Reese, assistant professor of medicine and epidemiology at Penn’s Perelman School of Medicine, and Joseph Subotnik, assistant professor of physical and theoretical chemistry in the School of Arts and Sciences.

The award is the highest honor bestowed by the United States government on science and engineering professionals in the early stages of their independent research careers. 

Reese, who cares for kidney-transplant recipients and living kidney donors, was recognized for his efforts to increase access to kidney and liver transplantation. He uses tools from epidemiology, biostatistics, health-services research and medical ethics to describe disparities in transplantation and methods to overcome them. Through policy-development work with the United Network for Organ Sharing, his work helps to translate clinical research into effective national policy.

Reese’s research was among the first to examine the practice and ethical implications of accepting live kidney donors with risk factors for kidney disease. He has written specifically about barriers to live-donor transplantation, the use of kidneys from deceased donors at increased risk of HIV and other blood-borne viral infection, and the implications of proposed organ-allocation systems for the elderly.

“I feel very grateful to receive this award.  I owe a great deal to my mentors and collaborators at Penn for their support," Reese said.  "I hope that the award will direct attention to the pressing need to increase organ donation and reduce waiting times for transplants.”

Reese’s research efforts have been supported by the National Institutes of Health, the American Society of Transplantation, a T. Franklin Williams Award in geriatric research (co-sponsored by the Association of Specialty Professors and the American Society of Nephrology) and Penn’s Leonard Davis Institute.

Subotnik received the PECASE award for his work on the fundamental dynamics of electron and energy transfer, particularly in the case of solar energy.

“When light shines on materials, what you really want to know is what happens to the energy of that light,” Subotnik said. “Take a tree leaf, for example. Does the light’s energy get captured by the leaf’s chloroplasts and go on to break down carbon dioxide, turning sunlight into chemical energy?  Or does it get lost as heat?

“It’s the same with solar cells; they’re usually operating at a hot temperature. The goal is to minimize the heat released and maximize the electrical current that can power a battery.”

In order to reach this goal, researchers need to model fundamental aspects of chemistry and physics in their simulations of how materials will behave after being struck by light. Improving the fine details of these simulations is critical to their overall accuracy, but researchers’ knowledge of such details are up against both computational and theoretical boundaries.  

“These theories are very hard,” Subotnik said.  “To model these things is incredibly computationally expensive. You really need to have practical algorithms and serious approximations, as well as some intuition about how things actually behave on the subatomic level.”

According to Subotnik, the difficulty of the problem can be traced to the different time scales and masses of electrons and nuclei.  On the one hand, electrons have very light masses, so their locations within an atom or molecule change quickly and can only be described in terms of probability.  On the other hand, nuclei are very heavy, so they behave classically, like slow-moving billiard balls. Subotnik’s work has helped correct several existing theories on how to balance these different perspectives.

Subotnik plans on using the five years of funding that comes with the PECASE award to further refine models of electron movement, especially at the moment when light strikes a surface.