Moderate gains in weak trade at midday belied a morning of fiery action fueled by fourth-quarter earnings reports. The Nasdaq led with a 0.4% gain. The Dow Jones industrial average and the S&P 500 were steady, up 0.3% apiece. Trade remained mildly lower across both the Nasdaq and the NYSE. Earnings reports drove a rash of volatile gains Friday morning. Truck maker OshKosh (OSK) jumped 14%. Chip designer Lattice Semiconductor (LSCC) popped 15%.