The holmium laser, which operates in a wavelength of 2.1 microns, is highly absorbed by water and has a shallow penetration depth of approximately 0.4 mm. As a pulsed mode laser, the Holmium reduces deeper thermal effects and charring which are more prevalent in Continues Wave lasers (e.g. Thulium, KTP).
In statistical theory, covariance is a measure of how much two random variables change together. In other words, covariance is a measure of the strength of the correlation between two random variables. Also, it can be considered as a generalization of the concept of variance of two random variables.
Cohesive \Co*hesive\, a. 1. Holding the particles of a homogeneous body together; as, cohesive attraction; producing cohesion; as, a cohesive force. [1913 Webster] 2. Cohering, or sticking together, as in a mass; capable of cohering; tending to cohere; as, cohesive clay. [1913 Webster] Cohesive attraction.