Other fungi shoot spores aimed at openings in their surroundings, sometimes reaching distances over a meter. Fungi such as Phycomyces blakesleeanus employ a variety of sensory mechanisms to avoid obstacles as their fruiting body grows, growing against gravity, toward light (even on the darkest night), into wind, and away from physical obstacles (probably using a mechanism of chemical sounding). Other fungi form constricting rings or adhesive knobs that trap nematodes, which the fungus then digests. One hormone that is used by many fungi is Cyclic adenosine monophosphate (cAMP). Ceramic heater  A ceramic heater as a consumer product is a space heater that generates heat using a heating element of PTC (Positive Temperature Coefficient) ceramic. Ceramic heaters are usually portable and typically used for heating a room or small office, and are of similar utility to metal-element fan heaters. PTC ceramic material is semi-conductive and when voltage is applied to it, the power decreases quickly as it reaches a certain temperature according to the particular composition of the ceramic. The ceramic elements are in contact with aluminium fins, thereby heating the fins up. A fan blowing across the fins heats the air. Electric heating elements made of resistance wire also have a positive temperature coefficient of resistivity, but do not increase their resistance enough to be self-regulating; they are typically used with the wires red-hot. The ceramic, on the other hand, increases its resistance sharply at the Curie temperatures of the crystalline components, typically 120 degrees Celsius, and remains below 200 degrees Celsius, providing a significant safety advantage. Ceramic heaters have rheostats that are capable of sending voltage signals when the temperature of the room alters. Pound sterling in the South Atlantic and the Antarctic  The United Kingdom possesses a number of islands in the South Atlantic Ocean and claims a section of the Antarctic continent. These territories are St. Helena with Ascension Island and Tristan da Cunha, the Falkland Islands, South Georgia and the South Sandwich Islands, and the UK's claimed Antarctic territory, called the British Antarctic Territory. The official currency in these territories is either Pound sterling or a local currency that evolved from sterling and is at a fixed one-to-one parity with sterling. Until 1929–1930, when the Australian pound and New Zealand pound ceased to be at parity with sterling, sterling was the currency of much of the Antarctic continent, including the Australian Antarctic Territory and the Ross Dependency.