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. distance learning and for conferencing. The company launched Blackboard Mobile in 2009 after having acquired TerriblyClever. The platform provides students with access to teaching and learning content and campus information through mobile applications for iOS, Android, BlackBerry and WebOS devices. Blackboard Mobile allows students to both access course materials, check grades, and participate in discussions, and to access information about campus life and services. The company began providing its Blackboard Connect service in 2008, for use by school districts and higher education institutions to send out mass phone, text and e-mail notifications. The service can be used for routine alerts