Logarithmic chemotactic sensitivity
= Logarithmic chemotactic sensitivity
{title2=$\chi(c)=\alpha/c$}
For positive chemical concentration $c$, taking $\chi(c)=\alpha/c$ makes the <chemotaxis> drift velocity $\chi(c)c_x=\alpha\partial_x\log c$. Cells then respond to a relative chemical gradient. This singular response can remain finite where the concentration tends to zero if its logarithmic derivative has a finite limit.