Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Three modes of deformation of a helical structure. A ring is shown for clarity, but the same is true for any helix. (a) Relaxed state. (b) The stem can be bent, (c) stretched, or (d) twisted to squeeze the support. Deformations are exaggerated for illustration.
