Semi-adjustable articulator with mounted casts. An articulator is a mechanical device used in dentistry to which casts of the maxillary (upper) and mandibular (lower) teeth are fixed, reproducing recorded positions of the mandible in relation to the maxilla.
The Greek scholar Heron of Alexandria created the earliest known automatic door in the 1st century AD during the era of Roman Egypt. The first foot-sensor-activated automatic door was made in China during the reign of Emperor Yang of Sui (r. 604â618), who had one installed for his royal library.
Knocking at Your Back Door. Knocking at Your Back Door is a song by the British hard rock band Deep Purple, the first track of the album Perfect Strangers, which was released in September 1984. Song was written by Ritchie Blackmore, Ian Gillan and Roger Glover. The track was widely broadcast by the media of that time.