NASHVILLE, TN—Vanderbilt University sophomore Derek Sellars drastically overestimated the mental clarity, physical replenishment, and restorative power he would attain from a 7 p.m. nap Tuesday. "I thought I'd feel fresh and good to go for the rest of the night," said Sellars, who added that the brief sleep completely failed to give him the wherewithal to complete his calculus assignment or inspire a "great topic" for his 19th-century English Literature class paper due Wednesday morning. "I couldn't really tell what day it was and I was all sweaty. In fact, I felt more tired somehow." Despite the setback, Sellars plans to work straight through until his next 30-minute nap, scheduled for 3 a.m.