US stocks were mixed on Monday as the federal government shutdown entered another week, while a megadeal between AMD (AMD) and OpenAI (OPAI.PVT) lifted hopes for the AI trade. The Nasdaq Composite (^IXIC) led the way higher, rising 0.4% amid an over-25% surge from AMD, while the S&P 500 (^GSPC) ticked up 0.1%. But the Dow Jones Industrial Average lost hold of opening gains to fall 0.5%. In another jolt to the AI outlook, AMD (AMD) said Monday it has signed a multiyear deal with OpenAI (OPAI.PVT) to supp ...