The possibility of a Russian-backed deal on chemical weapons disarmament for Syria through the United Nations Security Council has, for the moment, stayed the hand of the United States and its allies.

More than 90% of online teens participate in social media, according to estimates from the Pew Internet & American Life Project. Facebook is the largest of the social networking sites — according to company records, the number of Facebook users rose from 845 million to more than 1 billion over the period November 2011 to October 2012, or approximately 14% of the world population.

Efforts to limit climate change generally focus on reducing carbon dioxide emissions caused by burning fossil fuels. However, another byproduct of fossil fuel combustion is black carbon, a major component of soot. Sources include diesel truck and car engines as well as wood fires, kilns, and stoves. Particles of black carbon in the atmosphere absorb sunlight and can have significant effects on the temperature, as do ozone, methane and other chemicals.

When cancer is caught early, it is easier and cheaper to treat. The Affordable Care Act (ACA), also known as Obamacare, sought to help Americans catch the disease early by requiring insurers to pay for some types of preventative care as well as an annual checkup.

Which American state has the most earthquakes? If you guessed Alaska or California, you might have been right — years ago. These days, the title goes to Oklahoma, where research links the oil and gas industry to the quakes.

U.S. emergency rooms are failing to identify elder abuse, a new study suggests.

Year zero in the history of U.S. big-box stores was 1962: In that one year, the first Walmart, Target and Kmart stores opened. While the firms’ origins varied, their common focus was on deep discounts and suburban locations. Shoppers would arrive by car, not foot, so what mattered was highway access, acres of parking and massive scale.