Studies show as many as 15 percent of children in wealthy nations are physically abused by guardians each year, but the alleged torture of a boy who stumbled into a Tracy fitness club battered, half-starved and in chains last week stands out for its cruelty, a leading child abuse expert says. Cases that severe are "not a very common thing." But they continuously pop up, said Carole Jenny, a pediatrics professor at Brown University's medical school. Underfunding and a lack of resources for child protective services is a huge problem, said Jenny, who called what authorities say happened to the...