:Shares of Nvidia closed at their highest ever on Monday, putting the heavyweight AI chipmaker on the brink of dethroning Apple as the world's most valuable company. With investors betting on strong demand for its current and next-generation AI processors, the Santa Clara, California company's stock climbed 2.4 per cent to end the day at $138.07. In June, Nvidia briefly became the world's most valuable company. It was overtaken by Microsoft, and the tech trio's market capitalizations have been