Charles Abernathy
= Charles Abernathy
{c}
\b[Charles Abernathy] coauthored the 1971 experimental study of a tumour-derived angiogenic fraction with <Judah Folkman>, <Ezio Merler> and <Gretchen Williams>.<Isolation of a Tumor Factor Responsible for Angiogenesis by Judah Folkman and others>[Byline and Abstract]{ref} An important aspect of the experimental argument was spatial separation: <blood vessels> could respond outside filter chambers containing <tumour> <cells>.<Isolation of a Tumor Factor Responsible for Angiogenesis by Judah Folkman and others>[Printed p.275, membrane-chamber observations]{ref}
A barrier experiment tests whether direct cellular contact is necessary. Its interpretation depends on <membrane permeability>: passage of a dissolved substance differs from passage of an intact <cell>. Exclusion of <cells> with persistence of a vascular response supports a diffusible signal, but does not uniquely identify the signal's molecular structure.
An original dimensional estimate shows why distance and time belong in the interpretation. A characteristic <diffusion> time over a distance $L$ is $t\sim L^2/D$, where $D$ is a <diffusion coefficient>. Taking stipulated values $L=0.5\,\mathrm{mm}$ and $D=10^{-10}\,\mathrm{m^2\,s^{-1}}$ gives about $2500\,\mathrm s$, or 42 minutes. Doubling the distance multiplies that estimate by four. Binding, degradation and geometry can alter the actual response; the calculation is not a reconstruction of the experiment.