Quantum dots Unusual behaviour of electrons near the quantum dot has been found by R Ashoori and his colleagues at MIT using a potential well formed by three semiconductor layers and a metal electrode. Applying a voltage to the latter enables electrons to be confined in the well and the number of arriving electrons to be determined to the accuracy of a single electron. For quantum dots 0.6 to 18 microns across it is found that as the electric potential is increased, surprisingly, a significant part of the electrons come to the well by pairs rather than one by one. The reason for this pairing phenomenon is not clear. The presence of two phases in supercooled water was discovered by an international team of American and Japanese researchers.
Water can remain liquid at negative temperatures if it is very pure or under high pressure.
For temperatures below 220 K it is found that ice IV, one of the 14 known ice varieties, has two widely distant melting pressure points, implying the existence of two phases in liquid water. It is believed that one of these has its molecules much more clustered than the other. The existence of two phases is likely to affect water properties at room temperatures and pressures. According to the theory of general relativity, the Earth drags all objects in its vicinity around itself as it rotates. This extremely small effect, predicted by J Lense and H Thirring in 1918, has been observed by an international team of scientists from NASA and a number of European and American universities.