The artificial intelligence gold rush has pushed San Francisco’s residential rents up by the most in the nation, as A.I. companies lease apartments and offer rent stipends to employees.

© Amy Osborne for The New York Times

Drawn by local talent, cheap labor and state cash incentives, start-ups building the weapons of the future are revitalizing manufacturing in once-vibrant industrial towns.

The number combination refers to a work schedule — 9 a.m. to 9 p.m., six days a week — that has its origins in China’s hard-charging tech scene.