Английский язык: Аннотирование и реферирование текста

178 Часть 2. ТЕКСТЫ ДЛЯ СТУДЕНТОВ НАПРАВЛЕНИЯ ПОДГОТОВКИ « ПРИБОРОСТРОЕНИЕ » И « ИНФОРМАТИКАИ ВЫЧИСЛИТЕЛЬНАЯ ТЕХНИКА » C оставление реферата и аннотации Текст A History of Superconductivity Heike Kamerlingh Onnes discovered superconductivity in 1911 when he used liquid helium as a coolant to study the electrical proper- ties of metals at low temperatures. To everyone's surprise, when mer- cury was cooled to about 4.2 kelvins, it suddenly lost all electrical resis- tance. This threshold is known as the critical temperature, or Tc. Other materials having ever higher critical temperatures were discovered slowly but surely during the first five decades of supercon- ductivity research. All these superconductors were either pure metallic elements or intermetallic compounds (made of two or more metallic elements). But from the 1960s through the mid-1980s the maximum value of Tc seemed to be stuck in the low 20s. All this changed in 1986 with the discovery of high-temperature superconductivity in a slew of copper oxide-based compounds. During the first few years after this discovery, Tc values shot up, with mercury- barium-calcium-copper-oxide having a Tc of about 130 K. This was a fantastically exciting time, but it soon became clear that the leading theory of how superconductivity arises-known as BCS theory – does not explain the absence of resistance in these materials. Despite almost