There are provided novel compounds of formula, wherein R1, R2, R3, T, U, X, Y, V and W are as defined in the specification, and pharmaceutically acceptable salts thereof, and enantiomers and racemates thereof; together with processes for their preparation, compositions containing them and their use in therapy. The gate electrode may be disposed around the phase change storage node, and may be used for applying an electric field to the phase change storage node. Due to the fact that address conversion is performed on the semiconductor storage device side in the present invention, it is sufficient for a control device to output, for example, the address of a word line having a high access count to the semiconductor storage device during a target row refresh operation. The anchor blade further includes an anchor portion with teeth at one end for engaging the ground to effect the traction and coupling holes at the other end for selective connection to the anchor blade at differing angles. The invention also relates to new compounds of formula, their preparation, use and compositions comprising said compound.