… by Michael Graham Richard, Ottawa, Canada on 03. 3.10


Lemon leaf with interconnected loops. Photo: RU

A team of biophysicists at Rockefeller University recently published a paper in Physical Review Letters about a new way to design distribution networks based on the veins that carry water and nutrients in most tree leaves. This is a great example of biomimicry! Evolution by natural selection maybe be blind, but it has had billions of years of trial-and-error to figure out efficient and robust ways to do things. The interconnecting vein loops in leaves are a good example of that, and we can learn from them.


Ginko leaf, without interconnected loops. Photo: RU

“Operations researchers have long believed that the best distribution networks for many scenarios look like trees, with a succession of branches stemming from a central stalk and then branches from those branches and so on, to the desired destinations. But this kind of network is vulnerable: If it is severed at any place, the network is cut in two and cargo will fail to reach any point “downstream” of the break.”

A good example of that can be seen on the two pictures in this post. The big dots are damage in the network. In the pic on top, you can see that the flow isn’t stopped, and can go everywhere in the network. In the second pic, the flow is stopped everywhere downstream of the damage point.

“Operations researchers have appreciated that these redundancies are an effective hedge against damage. What’s most surprising in the new research, according to Marcelo O. Magnasco, head of the Laboratory of Mathematical Physics at Rockefeller University, is that the complex network also does a better job of handling fluctuating loads according to shifts in demand from different parts of the system — a common real-world need within dynamic distribution networks.”

This kind of network full of loops can also be found in the blood vessels of the retina, the architecture of some corals, and the structural veins of insect wings.

It remains to be seen if the benefits of more robust and easy to balance networks will outweigh the negatives (it would probably be more expensive), but I think resilience and robustness are worth a lot since our society is so dependent on these networks.

For something a bit similar, check out how slime mold can help design public transit networks.

Via Physical Review Letters, Rockefeller University

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by Michael Graham Richard, Ottawa, Canada on 10. 7.09

operation board game photo

What? How?
// We all know that air pollution is a bad thing. Not good for your lungs, not good for your heart. Asthmatics, children and older folks are particularly at risk. But a new Canadian study claims that air pollution is also increasing the risk of appendicitis in adults. Even short-term exposure to air pollution could have an effect.

air pollution appendicitis photo
Photo: Flickr, CC

Dominant Theory on Appendicitis
So far “the dominant theory of the cause of appendicitis has been obstruction of the appendix opening, but this theory does not explain the trends of appendicitis in developed and developing countries. Appendicitis cases increased dramatically in industrialized countries in the 19th and early 20th centuries, then decreased in the middle and late 20th century, coinciding with legislation to improve air quality. The incidence of appendicitis has been growing in developing countries as they become more industrialized.”

Methodology
The researchers identified 5191 adults who had been admitted to hospital with appendicitis between Apr. 1, 1999, and Dec. 31, 2006. The air pollutants studied were ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, and suspended particulate matter of less than 10 µ and less than 2.5 µ in diameter.

They then used government data on air pollution to figure out the level of exposure to various pollutants of the people with appendicitis. “They found correlations between high levels of ozone and nitrogen dioxide and the incidence of appendicitis between age groups and genders.” More men than women were found to have the condition, possibly because more men work outside, giving them a higher exposure to air pollution on “bad air quality” days.

What Now?
Now that a correlation has been found, researchers will try to figure out how air pollution could trigger appendicitis. They suspect that the pollutants may trigger inflammatory responses, but further studies will be necessary to figure out the causality (if any).

Via CMAJ, Science Daily