Selective serotonin reuptake inhibitor. Selective serotonin reuptake inhibitors (SSRIs), also known as serotonin-specific reuptake inhibitors or serotonergic antidepressants,[1] are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder and anxiety disorders.
Then you're looking for the midpoint! The midpoint of a line segment is the point located midway between the endpoints of the line segment. This tutorial tells you about the midpoint of a line segment.
Re: Concentric circles, constant offset. If both Linear Parameters are using midpoint as a basepoint, you only need to stretch the child from one end at a factor of 2. But you can also stretch it from both ends at a factor of one each.