A method and apparatus of communicating by a relay station a wireless communication system including a relay station is provided. The external counterpulsation apparatus also has a new gas distribution device and devices for monitoring the blood pressure and oxygen levels in the blood of a patient for improving safety. A variable signal level attenuator in each path attenuates the amplified signal and receives current from current sources. The second cooling chamber adjoins the first cooling chamber. The present invention relates also to a method to form carbon nanotubes on metal-silicide nanoparticles, the metal-silicide containing particles hereby acting as catalyst during the growth process, e.