The opening Monday of the world's tallest skyscraper could mark a turning point in Dubai's fortunes and those of its ruler after a year that saw both come under intense scrutiny. Sheik Mohammed bin Rashid al Maktoum, the city-state's 60-year-old hereditary leader, hopes the building and its surrounding $20 billion development will help enhance his reputation among international investors and restore Dubai's allure as a business hub.