Calcium sulfate an unusual property: when mixed with water at normal (ambient) temperatures, it quickly reverts chemically to the preferred dihydrate form, while physically "setting" to form a rigid and relatively strong gypsum crystal lattice: This reaction is exothermic and is responsible for the ease with which gypsum can be cast into various shapes including sheets (for drywall), sticks (for blackboard chalk), and molds (to immobilize broken bones, or for metal casting). Mixed with polymers, it has been used as a bone repair cement. Small amounts of calcined gypsum are added to earth to create strong structures directly from cast earth, an
Blackboard Inc. On July 1, 2011, Blackboard agreed to a $1.64 billion buyout by an investor group led by Providence Equity Partners, completed on October 4, 2011. Following the sale, Providence Equity Partners merged Edline, its K-12 learning system, with Blackboard. Edline was later renamed Blackboard Engage. According to a TechCrunch article from 2012, despite its success, Blackboard had become "one of the most disliked — even detested — companies in education." In December 2011, "Fast Company" reported that 93% of respondents to the Amplicate customer opinion survey "hate" the company. In September 2017, Blackboard announced its expansion to the Indian Educational