Disclosed is a check valve which has an excellent sealing force compared with a conventional one by applying a relatively small force which lifts the edge of a valve body part even with a vacuum indicating part being sunk, and which can maintain a vacuum state for a longer time by preventing a ring shape from being dented at a low or high vacuum level. The multi-polymer-coated magnetic nanoclusters comprise a super paramagnetic core, with a first polymer attached thereto, which does not render the first polymer-super paramagnetic particle complex colloidally stable, and a second polymer attached thereto, which stabilizes the complex of multi-polymer-coated magnetic nanoparticles. Once all SMU inputoutput impedances are controlled, as well as properly terminated to eliminate reflections, the high-speed devices will no longer oscillate during device testing, so long as the instruments maintain a high isolation from instrument-to-instrument. The messaging system comprises a storage system for storing data providing a predetermined definition of message content to be sent to the remote party. The semiconductor device has the antenna and an integrated circuit which is connected to the antenna in a power feeding portion. Preforms with woven fabric elements extending radially from a common node include at least one reinforcing fiber interwoven between at least two elements and passing through the node.