The present invention relates to methods and compositions containing novel leptin peptides, preferably for the modulation of body mass, more specifically for novel diagnostic and therapeutic applications in homeostasis of body weight and adipose tissue mass. The spin-valve thin-film magnetic element includes a free magnetic layer, a nonmagnetic conductive layer, a pinned magnetic layer, an antiferromagnetic layer, a pair of bias layers, and a pair of conductive layers. The resistors are electrically connected in series to provide a plurality of voltage levels. The method includes performing a second implantation process to form a second doped region in the substrate, the second doped region being formed farther away from the gate than the first doped region, the second doped region having a higher doping concentration level than the first doped region. The connecting part is provided so as to connect the first tape roll and the second tape roll. The light-emitting film includes Cu as an addition element in a zinc sulfide compound which is a base material, wherein the zinc sulfide compound includes columnar ZnS crystals, and sites formed of copper sulfide on a grain boundary where the ZnS crystals are in contact with each other.