21.   The new exam can spot a structural defect that often precedes complete failure of the valve.

22.   In a report on the November incident released last month, the power company concluded that structural defects were the main cause of the ruptured pipe.

23.   But families of the crew, trade unions and shipping experts have long argued that the disaster was caused by structural defects in the vessel.

24.   Structural defects linked to the use of sub-standard materials are frequently blamed for building collapses in Nigeria.