It is cylindrical in shape with helical cutting teeth. These structures are composed of longitudinal fibers surrounded by radial and helical fibers. Herringbone gears are a special type of helical gears. Screw-propelled vehicles are propelled by auger-like cylinders fitted with helical flanges. A plectonemic structure arises from the interwinding of the helical axis. It consists of parallel helical sulfur chains. Helical and other symmetries of chiral nanomaterials were also obtained. They have linear polarization (except for the helical antenna). A TCP actuator looks like a helical spring. A TCP actuator look like a helical spring. Carrageenans are large, highly flexible molecules that form curling helical structures. Twin helical strands form the DNA backbone. These secondary interactions induce bending of the DNA and helical unwinding. Viruses vary in shape from the simple helical and icosahedral to more complex structures. The majority of viruses have capsids with either helical or icosahedral structure.