Shear

Literally the sliding of one layer across another, with deformation and fracturing in the direction parallel to the movement. In the present context, used to describe 1. the forces that cells are subjected to in a bioreactor or a mechanical device used for cell breakage. 2. the intentional or unintentional fragmentation of large DNA molecules, achieved commonly by passing a concentrated DNA solution through a hypodermic needle. This treatment generates random breaks in the DNA, and the average size of fragments can be manipulated by varying the bore of the needle.

A structural break where differential movement has occurred along a surface or zone of failure.

Variation in wind speed (speed shear) and/or direction (directional shear) over a short distance within the atmosphere. Shear usually refers to vertical wind shear, i.e., the change in wind with height, but the term also is used in Doppler radar to describe changes in radial velocity over short horizontal distances.