A developing device includes a developing housing that supports a developer carrier, and a developer cartridge. A venous valve is formed in situ from autologous vein conduit not having a valve present locally. Each of the plurality of amplifier cells may comprise a first transistor that is electrically insulated from the semiconductor substrate and a first feedback resistor configured to dynamically bias the first transistor. User interaction data that includes scroll data is obtained. Such a pump, connected to a drive motor and an encoder delivering a signal proportional to the number of pump cycles, enables to provide an accurate metering pump for numerous uses. Functionalization of the single-walled metal oxide nanotubes is performed in a single-step during synthesis of the nanotubes.