Specifically they showed that the relationship between a pipe’s width and height — or aspect ratio — governs the shape of the chemical spread as it flows with the fluid down the tube. A circle and square are just as wide as they are tall, while an ellipse and rectangle are wider in one dimension than the other. By squishing the tube away from being a perfect circle, the researchers showed that they can change the way that a solute reaches its target: Solute traveling down a skinny pipe barrages its target fast, but if the same solution travels down a fat pipe, the solute crawls slowly upward to its target until the big punch hits at the end.Nature has designed various pipes with circular or oval cross sections. Dynamically, different pipes close and open in aspectually different ways. The Eustachian tube, larynx and lips are near-circular when open, closing toward flat. Blood vessels and the colon remain circular as they contract. Presumably Nature had different purposes in mind for these valves, requiring different static or dynamic shapes. Even in human invention, the use of aspect ratio is not new. Streamlining is all about aspect ratio. Designers of fluidic computers like HydraMatic paid close attention to the shape and roughness of various passages.
Labels: Grand Blueprint
Polistra was named after the original townsite of Manhattan (the one in Kansas). When I was growing up in Manhattan, I spent a lot of time exploring by foot, bike, and car. I discovered the ruins of an old mill along Wildcat Creek, and decided (inaccurately) that it was the remains of the original site of Polistra. Accurate or not, I've always liked the name, with its echoes of Poland (an under-appreciated friend of freedom) and stars. ==== The title icon is explained here. ==== Switchover: This 2007 entry marks a sharp change in worldview from neocon to pure populist. ===== The long illustrated story of Polistra's Dream is a time-travel fable, attempting to answer the dangerous revision of New Deal history propagated by Amity Shlaes. The Dream has 8 episodes, linked in a chain from the first. This entry explains the Shlaes connection.