BlackBerry Ltd named Carl Wiese as global head of sales on Monday, an appointment that comes at a critical juncture for the company, which needs to spur top-line growth in order for its turnaround efforts to succeed. Wiese, who has spent the last 12 years at Cisco Systems Inc initially heading advanced technology sales and later its collaboration product sales efforts, replaces John Sims as BlackBerry’s global head of sales. BlackBerry did not provide any reasons for the departure of Sims, who was with BlackBerry for about 18 months.