A lamp includes an LED module, a drive unit supplying power to the LED module, and a base via which power is fed from an external power supply to the drive unit. The seat is provided with cuts through which the fuel flows when the sphere is in contact with the seat. The target device can send a response to the sending device to indicate that it is temporarily unavailable. The dam includes a face which is preferably tapered to enable optimization of speed of separation of a sample placed within the vessel. A polymer obtained from the acid-labile ester monomer has so high reactivity in acid-catalyzed elimination reaction that the polymer may be used to formulate a resist composition having high resolution. A computer cluster including such computer systems and a method of managing such a computer cluster are also disclosed.