In one non-limiting aspect thereof this invention provides a structure having a generally planar quadrilateral shape that includes a bottom portion defining a mounting section; a vertical wall portion that extends upwards from the bottom portion and a top-most portion having a generally triangular shape in cross-section and forming along widest portion thereof a lip having a lower surface. The basic device is a two-terminal unit, denoted as a Signal Canceling Unit, which sensesthe signal available at its terminals, and applies negative feedback in order to cancel and absorb the signal. Also provided are methods of detection of aromatic oxidation activity. Normally, the control unit changes the mode of operation of the reader from a first mode, wherein the reader does not operate to decode or recognize image data to a second mode, wherein the reader operates to decode andor recognize image data. or higher in a surface layer of the toner particle, and silica particles having a volume average particle diameter of 30 nm to 300 nm and a coverage with respect to the toner particle from 50% to 100%.