Two solids made of the same elements but with different geometric arrangements of the atoms, or crystal phases, can produce materials with different properties. Coal and diamond offer a spectacular example of this effect.
The blood stem cells that live in bone marrow are at the top of a complex family tree. Such stem cells split and divide down various pathways that ultimately produce red cells, white cells and platelets.
(This is the first in a series about University of Pennsylvania students who took their arguments in support of federal student financial aid to Washington this summer in a project organized by the Office of Student Registration and Financial Services.)
France is renowned the world over as a leader in the crafts of viticulture and winemaking—but the beginnings of French viniculture have been largely unknown, until now.
Marwan Kraidy of the Annenberg School for Communication discusses the recent acquisition of Current TV by Al-Jazeera.
At the University of Pennsylvania’s Herbert D. Katz Center for Advanced Judaic Studies, you can touch some of the oldest tomes in the history of Judaism, and you don’t have to wear white gloves, de rigueur for patrons at some rare-book libraries.