Ranger ready for anything in desert scape High noon and the desert is hot as a wok, yet Tim Duncan is wearing body armor under his uniform. A handgun and a Taser hang from his belt. Next to him in the truck are a shotgun and an M-16 assault rifle with extra magazines. "Out here, you have to be prepared," he said. Duncan is a National Park Service ranger at the Mojave National Preserve, a Mordor-like sweep of serrated mountains, feral deserts, Joshua tree forests, dry lakes and lava beds - a park five times the size of Los Angeles that's patrolled by eight law officers. Here the wilds of nature meet the wilds of man, an incongruous environment that has hidden meth labs and illegal waste dumps, plant and wildlife poachers, archaeological thieves, the occasional dumped body and train robbers. Yes, train robbers. Union Pacific trains laden with goods from the coast rumble into the Mojave National Preserve at the aptly named Devil's Playground, 40 miles of hellish sand dunes and salt flats at the base of the Kelso Mountains. Mile-long caravans of double-stacked cars wheeze to a crawl as they labor up the steep Cima Grade through the heart of the preserve. Sometimes they stop on side tracks to let other trains pass. Thieves typically strike at night - busting into boxcars and tossing down the booty to waiting accomplices with trucks....