Katherine Unger Baillie

PHILADELPHIA — Learning calculus is no easy feat.

PHILADELPHIA — Periodontitis, a form of chronic gum disease that affects nearly half of the U.S. adult population, results when the bacterial community in the mouth becomes unbalanced, leading to inflammation and eventually bone loss. In its most severe form, which affects 8.5 percent of U.S. adults, periodontitis can impact systemic health.

More than six decades after it was checked out, a rare treasure has been returned to its rightful home in Penn’s Van Pelt Library.

PHILADELPHIA — Passing one’s genes on to the next generation is a mark of evolutionary success. So it makes sense that the body would work to ensure that the genes the next generation inherits are exact replicas of the originals.

PHILADELPHIA — El Yunque rock is a majestic, anvil-shaped promontory that has been an icon of the island of Puerto Rico since pre-Columbian times. The barren rock, standing 3,412 feet high, protrudes above primary old growth forest and is enshrouded in clouds, swept constantly by the trade winds and frequently stricken by hurricanes.

Cat owners, take note: If your pet appears to be in pain while eating, chewing or grooming and has a red, inflamed mouth, it may be suffering from a common condition called feline stomatitis.

PHILADELPHIA — Toilets may not make for a glamorous subject, but they’re critical to global health. On Monday, Nov.

PHILADELPHIA — The University of Pennsylvania School of Dental Medicine has received a $1.5 million grant for student scholarships from the Health Resources and Services Administration of the U.S. Department of Health and Human Services.

PHILADELPHIA — When a virus such as influenza invades our bodies, interferon proteins are among the first immune molecules produced to fight off the attack. Interferon can also play a role in suppressing tumor growth and the effects of autoimmune diseases, and doctors may use an artificial form of interferon to treat patients with certain cancers or multiple sclerosis.

Cindy Nicoletti, a 2011 graduate of the University of Pennsylvania, is one of those lucky people who has known since childhood what she wanted to do with her life. “I always wanted to be a teacher,” she says. “That was my main focus, ever since second grade.”