Interaction networks can describe many interesting things – human social systems, like facebook, but also complex engineered systems like the internet, or animal societies. The past century has seen the development of an area of mathematics called graph theory, which can be used to describe the structure of these networks. There are statistics that describe…

Walk through the Rocky Mountains in the summer, and you will be immersed in a sea of green, and will hear the soft rustling sound of millions of leaves. These are quaking aspen (Populus tremuloides) trees, and they dominate the landscape. When I first came to Colorado in late-fall 2009, I was captivated by the…