Does the transmutation of Quarks involve String components?

[newtonian]

This involves research concerning the big bang origins, which involves sub-atomic research.<br /><br />For example, when a down quark (mass 7MeV; charge -1/3) transmutes to an up quark (mass 5MeV; charge +2/3) what exactly has happened inside the down quark to cause this?<br /><br />Note also spin and angular momentum.<br /><br />It is often assumed that a quark is a fundemental particle. <br /><br />However, String theory indicates much smaller strings.<br /><br />Can the transmutation of Quarks be explained by the properties of component strings?<br />A related tiny question - can virtual particles be explained by strings - e.g. changing dimensional planes (or branes) of existence?<br /><br />Or is the latter simply changing from vacuum energy to matter?