After yuppies and dinkies, a new creature from ad land stalks the block. The NYLON, an acronym linking New York and London, is a refinement of those more familiar categories such as jet-setters and cosmocrats (cosmopolitan aristocrats---do keep up). Marketing professionals have noted that  1  the demise of Concorde, a new class of high-earner increasingly  2 his or her time shuttling  3 the twin capitals of globalization. And NYLONS prefer their home comforts  4  tap in both cities. Despite the impressive 5 of air miles, they are not adventurous people.