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.
False Doors. False doors, also known as Ka doors as they allowed the Ka (an element of the soul) to pass through them, were common in the mortuary temples and tombs of ancient Egypt from around the Third Dynasty and temples of the New Kingdom.he deity or the deceased could interact with the world of the living either by passing through the door or receiving offerings though it. As a result it was not uncommon to find false doors depicted on the sides of coffins as well as on the cabinets of shawabti (or ushabti - magical servants).