Given a 3-manifold M , there are generically infinitely many manifold which covers M . However, if we are restricted to the category of knot complements, the situation is quite different. It can be shown (see Lemma 1 and bellow) that if the complement E(K) of a knot K is n-fold covered by some knot complement, then the covering is cyclic, and K admits a cyclic surgery, i.e. a Dehn surgery such ...

orthomixoviridae family viruses (influenza viruses) are major cause of death in human with respiratory diseases. although avian influenza in iranian chickens are associated with h9n2 subtype, there was not any study for h9n2 human infection as yet. this investigation conducted to serological study of h9n2 avian influenza infection in different human groups. the number of 334 blood sera includin...