A door safety shield that completely overlies a door having a frame and a doorknob, replaceabley and slidably attaches to the frame of the door and not the door so as to eliminate damage to the door, and prevents unauthorized opening of the door. The PTC electrically conductive heat-dissipation layer includes at least one polymer, an electrically conductive filler, and a heat conductive filler. Devices and methods involve sensing a plurality of composite cardiac signals using a plurality of electrodes, the electrodes configured for implantation in a patient. When the column is actively processing chromatographic fluid, this exerted force can be expressed as the sum of the compression on the media, and the force of the fluid being processed. After implantation of the prosthetic heart valve into a patient, any gaps existing between the cuff and the native heart valve are exposed to bodily fluid, such as blood. An amount of memory storage is calculated for storing the enhanced array instance, and the amount of memory storage is allocated.