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 Learn October 2017, Blackboard partnered with OpenEd to integrate OER with Learning Management Systems. Blackboard Learn provides users with a platform for communication and sharing content. Blackboard Inc has had several legal issues, including faulty patent rights claims. In addition, a number of educational institutions, teachers, and students have expressed concerns about the reliability of Blackboard. McMaster University in Hamilton, Ontario, Canada, has replaced their Blackboard system after multiple problems during one year of use. Citing numerous glitches and high costs, many universities are turning to the cheaper, open source alternative Moodle, including Montana State University, Vassar College, California State University,