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. and notifications, academic or instructor notifications, or by school districts and communities to share time-sensitive information, such as in the case of natural disasters and campus emergencies. Blackboard Transact, formerly Blackboard Commerce Suite, is transaction processing system tied to university ID cards, which can be used for meal plans, vending machines and laundry services, and an e-commerce front end for the transaction system. The Transact system is NFC-compatible and its ID cards use contactless technology. Blackboard Transact also includes a program for off-campus vendors that allow students to pay for goods using their college's campus card. Blackboard Analytics was developed