Thousands of protesters clashed with police Monday in Cairo in a spasm of violence that has lasted for three straight days and left dozens of people dead – the worst since the popular uprising that toppled Egypt's government.

First in a three-part series

Under rules announced by the White House this summer, cars will have to get an average of 54.5 miles per gallon by 2025 — nearly twice what the current average is. Reaching that goal will take not only feats of engineering but also changing how Americans think about their cars and how they drive them.

The electric car is one of the ways carmakers expect to lower their average fuel consumption and get to the 55 mpg average. The problem is, people aren't buying, whether all-electric or plug-in hybrid.

Seventh in a series

Presidential candidate Rick Santorum consistently polls near the bottom of the Republican pack. But he appears undeterred in his bid for the White House. Santorum's work life in his 20s provides some insight into why he perseveres despite long odds.

The former senator from Pennsylvania is best known for his conservative social positions, especially his opposition to abortion rights and gay marriage. He's also known for expressing what he thinks very frankly.

Among the chilly aisles at Murray's Cheese Shop in Manhattan, the entire continent of Europe is represented. Something like 60 percent of the cheese in Murray's comes from the continent, according to Aaron Foster, a cheese buyer at the store.

For all the talk about how the European debt crisis is effecting the global economy, it can be hard to connect it with daily life here in the U.S. Here's one link: Aaron Foster's bonus depends on how cheaply he can buy cheese from Europe. And the price of that cheese is driven largely by the strength (or weakness) of the euro.

Monday is the last day the congressional supercommittee can reach a deficit reduction deal and still make its Wednesday deadline. The legislation has to be publicly available for 48 hours before a vote and the clock is ticking, but instead of announcing an agreement, it is widely expected the committee will admit it has failed.

Enrico Frare isn't a well known name in Italian business. The 36-year-old runs E-group, a small clothing company in the commercial region around Treviso that makes winter sportswear.

But last month, Frare did something that attracted a lot of attention. He bought a full-page ad in Milan's main newspaper appearing in what might politely be called his birthday suit. The caption read: "Every day in Italy an entrepreneur risks losing his shirt."

Chocolate milk has an interesting rap these days. Endurance athletes increasingly love it as a recovery drink.

And who's loathing it? Schools — advocates for school food reform, to be more specific. They argue it's got too much added sugar and too many calories.

A scientist in Boston has been driving around the city measuring leaks in the gas mains. He's found a lot, and he wants the public to know where they are.

Gas leaks aren't uncommon, and gas companies spend a lot of time tracking them down and repairing them. But the scientific team says they're surprised at how many they've found, and what those leaks are doing to the health of the city's trees.

When it's time to renew her son's prescriptions for medicine to treat his attention-deficit/hyperactivity disorder, Roxanne Ryan prepares for another wild goose chase.

The Philadelphia mother says she typically has to call around to 10 to 15 different pharmacies to find where the prescriptions can be filled. And when 10-year-old Sergey doesn't get his medication, he's a bundle of uncontained energy.

The Golden Temple at Amritsar, India, doesn't look like an environmental pressure point. The gold-sheathed building gleams serenely as a jewel box in the midst of a broad reflecting pond. Music serenades pilgrims as they cross a causeway to reach the shrine.