Selker (2017, https://doi.org/10.1002/2017WR021014) recently presented an analytical estimation of evaporative fluxes from deep aquifers. Regardless of the type of soil, ambient temperature, and relative humidity, assumed the thickness of liquid region above the water table equals to zero. Here we illustrate the limitation of this assumption and its impact on the estimation of the evaporative fluxes from deep aquifers.

Many cell-types that reside within load bearing tissues appear to exhibit mechanical homeostasis, that is, a tendency to regulate particular mechanical quantities near a preferred value, often called a set-point. It is suggested here that assessing potential mechanical homeostasis requires careful attention to derivations and definitions, that is, appropriate solutions to the initial-boundary value problems that define the biophysical situation of interest and appropriate definitions of what is meant by homeostasis. Noting that this term was coined carefully, with homeo meaning “similar to” in contrast to homo meaning “the same as”, one must be careful not only to identify the key mechano-regulated quantity (e.g., a stress rather than a flow or a force) but also the tolerance that defines the range of regulation, noting too that the specific target value of that variable may differ from region to region within the body while yet being regulated locally. Herein, we present a few examples to highlight specific derivations and definitions of importance when studying mechanical homeostasis across scales.