An integrated circuit structure includes a first semiconductor strip, first isolation regions on opposite sides of the first semiconductor strip, and a first epitaxy strip overlapping the first semiconductor strip. A message can be assigned a metric based, for example, on a weighted combination of user engagement rates, decayed with time to reflect an intuition that recent interactions by one or more users with the message will have a greater impact than older interactions with the message. A vent tube is mounted within the spacer with one end open to the filler and one end open to the exterior. The DC bus is connected to receive a secondary power supply.