The TTL output stage is a rather complicated pushâpull circuit known as a totem-pole output (the transistors, diode, and resistor in the right-most slice of this TTL logic gate circuit). It sinks currents better than it sources current.
The theory for spontaneous generation refers to the idea that life can produced from nonliving things. Lazzaro Spallanzani proposed in his experiement that air was necessary for spontaneous generation.
One of the most remarkable features of the outside of the building is the socalled  Porta della Mandorla (north) (della mandorla = almond) that was given this name because of the large aureole around the figure of the Virgin sculptured also by Nanni di Banco (1380/90-1421) among others.