Pneumatic artificial muscles Pneumatic artificial muscles Pneumatic artificial muscles (PAMs) are contractile or extensional devices operated by pressurized air filling a pneumatic bladder. In an approximation of human muscles, PAMs are usually grouped in pairs: one agonist and one antagonist. PAMs were first developed (under the name of "McKibben Artificial Muscles") in the 1950s for use in artificial limbs. The Bridgestone rubber company (Japan) commercialized the idea in the 1980s under the name of Rubbertuators. The retraction strength of the PAM is limited by the sum total strength of individual fibers in the woven shell. The exertion distance is limited by the tightness
Human artificial chromosome by these vectors not only leads to different expression levels, but the inserts also disrupt the original genome. HACs differ in this regard, as they are entirely separate chromosomes. This separation from existing genetic material assumes that no insertional mutants would arise. This stability and accuracy makes HACs preferable to other methods such as viral vectors, YACs and BACs. HACs allow for delivery of more DNA (including promoters and copy-number variation) than is possible with viral vectors. Yeast artificial chromosomes and bacterial artificial chromosomes were created before human artificial chromosomes, which first appeared in 1997. HACs are useful in expression