On a warm afternoon on Chicago's West Side, a young African-American man leans against the wall of the One Stop Food and Liquor store at the corner of Chicago Avenue and Homan Street. His puffy black jacket is so oversize that the collar hangs halfway down his back. Thirty feet up, a camera mounted on a telephone pole swivels toward him. Three miles away, in a bunkerlike, red granite building near Greektown, Ron Huberman watches the young man on a PC screen. "You see that guy?" asks Huberman, the 33-year-old chief of Chicago's Office of Emergency Management and Communications. "He's pitching dope - you can tell..." ... "We're gonna go on the air" - call for a police car - "and bust him."

With a move of his mouse, Huberman pans to the right. We're looking down at a second man, in a beige coat. He has a brown paper bag in one hand and a wad of cash in the other. "He's involved," Huberman says, staring hard at the screen. No cop, even undercover, could ever get this close for this long. But the cameras - housed in checkerboard-patterned, 2-foot-tall boxes the police here call pods - can zoom in so tight I can see the wisps of a mustache. Huberman decides not to have his suspected dealers picked up; too much of an Enemy of the State move to pull with a reporter around, perhaps. But the footage will be stored for review by antinarcotics teams. "Now you see the power of what we're doing?" Huberman asks, still staring at the screen.

[A]t any one time, approximately 300,000 pieces of the stuff are stuck to the pavement in Oxford Street. Just cleaning it up would cost about £30,000, but now an artist has come up with a novel way of dealing with the problem by painting on it.

And Ben Wilson, 41, originally from Barnet, but now living in Muswell Hill, does not do things by halves. He intends to paint pictures faces, animals, suns, name it and he will do it on pieces of discarded gum all the way from Barnet to the West End of London.

One route to this odd state, called chimerism, is the vanishing twin. Dr. Helain Landy of Georgetown University, who has no involvement in the Hamilton case [a competitive cyclist was charged with blood doping after what appeared to be another person's DNA showed up in his test results], has found that 20 to 30 percent of pregnancies that start out as twins end up as single babies, with one twin being absorbed by the mother during the first trimester.

Others researchers have found that in some cases, before the twin is absorbed, some of its cells enter the body of the other fetus and remain there for life. The cells can include bone marrow stem cells, the progenitors of blood cells. Another route to chimerism is through the cells that routinely pass from a mother to fetus and remain there for life.

Dr. Ann Reed, chairwoman of rheumatology research at the Mayo Clinic, who uses sensitive DNA tests to look for chimerism, finds that about 50 to 70 percent of healthy people are chimeras. The more scientists look for chimerism, the more they find it. It seemed not to exist in the past, she said, because no one was explicitly looking for small amounts of foreign cells in people's bodies.

"Some believe that if you look hard enough you can find chimerism in anybody," said Dr. Reed, who also has not been involved in the Hamilton case. It is so common that she thinks there must be a biological reason for it. [read full New York Times article, via Slate]