The coil is typically wound on a ferrite rod or doughnut-shaped toroid. The transformer core is usually a ferrite toroid, with 1&colon;1 or 4&colon;9 winding ratio. Between the disks is a ferrite toroid. The term "toroid" is also used to describe a toroidal polyhedron. A standard way to visualize a solid torus is as a toroid, embedded in 3-space. And, a toroid permits fairly independent control of topload capacitance versus spark breakout voltage. Writhes can adopt two structures; plectoneme and solenoid or toroid. Seward proposes that ball lightning is a spinning plasma toroid or ring. When it comes to transmitting antennas the choice of the toroid core is crucial. This design is based on a toroid (the same shape as a doughnut). This led to a re-awakening of compact toroid research. Both are considered part of the compact toroid class of fusion devices. The streamers transfer charge between the leaders and toroid to nearby space charge regions. Supercoiled DNA forms two structures; a plectoneme or a toroid, or a combination of both. Each toroid stored one bit (0 or 1).