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Beyond unicellular and multicellular organisms, there is a third type of structural complexity in living animals: that of the mechanical self-assembly of groups of distinct multicellular organisms into dynamical, functional structures. One of the most striking examples of such structures is the army ant bivouac, a nest which self-assembles solely from the interconnected bodies of hundreds of thousands of individuals. These bivouacs are difficult to study because they rapidly disassemble when disturbed, and hence little is known about the structure and rules that individuals follow during their formation. Here we use a custom-built Computed Tomography scanner to investigate the details of the internal structure and growth process of army ant bivouacs. We show that bivouacs are heterogeneous structures, which throughout their growth maintain a thick shell surrounding a less dense interior that contains empty spaces akin to nest chambers. We find that ants within the bivouac do not carry more than approximately eight times their weight regardless of the size of the structure or their position within it. This observation suggests that bivouac size is not limited by physical constraints of the ants' morphology. This study brings us closer to understanding the rules used by individuals to govern the formation of these exceptional superorganismal structures, and provides insight into how to create engineered self-assembling systems with, for instance, swarms of robots or active matter.

Gowanus is an industrial neighborhood changing into a gentrified area, but it faces such severe pollution that the EPA designated the Gowanus Canal, which bisects the area, a Superfund site in 2010. The industry still in Gowanus includes a mix of traditional industrial businesses, craft industries, and artists, but they might disappear if developers build luxury condos in the neighborhood. This study looks at the clash between activists over how the community has and will change, focusing on the pro-development Gowanus Canal Community Development Corporation and the preservationist and pro-Superfund Friends and Residents of Greater Gowanus. Many local activists embrace the vision of Gowanus as a place for making things and hope to maintain industry. Even though industry left the neighborhood polluted, most do not connect the two. The Superfund seeks to clean up the neighborhood but it may pave the way for environmental gentrification, which is the pollution cleanup causing gentrification. However, fears of the Superfund harming home prices do not appear to be true; GIS analysis shows that land closest to environmental hazards increased the most in value. Residents also hope to avoid the experiences of other New York neighborhoods, which saw gentrification cause displacement. More than residential displacement, though, activists worry about the culture of Gowanus disappearing and hope to save it. Their remedies such as historic preservation and zoning Gowanus for mixed use may not be effective or viable, though. Both major groups seem to accept the idea that attracting the creative class is crucial to economic success, and that they should make efforts to attract creatives to the area. However supporters of industry extend the definition of creative class from white-collar professionals to include blue-collar workers manufacturing custom-made designed products. Because of a lack of government involvement or a unified community forum, there is no clear path for resolving those differences and planning for the future, but a system of participatory planning could help resolve conflicts and develop plans to permit changes in ways that don't destroy the Gowanus community.

In current robotics research there is a vast body of work on algorithms and control methods for groups of decentralized cooperating robots, called a swarm or collective. These algorithms are generally meant to control collectives of hundreds or even thousands of robots; however, for reasons of cost, time, or complexity, they are generally validated in simulation only, or on a group of a few tens of robots. To address this issue, this paper presents Kilobot, an open-source, low cost robot designed to make testing collective algorithms on hundreds or thousands of robots accessible to robotics researchers. To enable the possibility of large Kilobot collectives where the number of robots is an order of magnitude larger than the largest that exist today, each robot is made with only $14 worth of parts and takes 5 min to assemble. Furthermore, the robot design allows a single user to easily operate a large Kilobot collective, such as programming, powering on, and charging all robots, which would be difficult or impossible to do with many existing robotic systems. We demonstrate the capabilities of the Kilobot as a collective robot, by using a small robot test collective to implement four popular swarm behaviors: foraging, formation control, phototaxis, and synchronization. (C) 2013 Elsevier B.V. All rights reserved.