An apparatus for studying the behavioural, cognitive, neurobiological andor muscular processes of an animal, the apparatus comprising an elevated platform with at least one panel extending from the platform, said panel providing a surface which has a gradient relative to the platform. The tubes preferably extend in the sheath in a helical or an SZ assembly. A DHCP request requesting an IP address for the mobile client is received from the mobile client. The second protective layer comprises a second surface having a second disposing zone, a second anti-stress zone and a second exposing zone, the second anti-stress zone is located at a corner of the second disposing zone. The method finds particular implementation in the rebalancing of tree data structures. The sensors can be configured to activate the electromagnetic field locally to cause the lead runner to slide along the track.