RUL, the chief sergeant major of Ukraine’s 126th Territorial Defense Brigade, which is known for its detailed preparation and its dangerous cross-river operations.

Gerald Navratil, a professor of plasma physics at Columbia, on the pursuit by start-ups for clean, unlimited power. Page A6.

Start the weekend off on the right note with one of these short and funny Friday quotes that celebrate being done with work, time off and having a good time.