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For bottom-up particle fabrication, separation of complex particle assemblies from their precursor colloidal building blocks is critical to producing useable quantities of materials. The separations are often done using a density gradient sedimentation due to its simplicity and scalability. When loading density gradients at volume fractions greater than 0.001, however, an inherent convective instability arises. By translating the Rayleigh-Benard instability from the heat-transfer literature into an analogous mass-transfer problem, the variables affecting the critical stability limit were effectively catalogued and examined. Experiments using submicrometer particles loaded onto sucrose and Ficoll density gradients matched theoretical trends and led to a series of useful heuristics for prolonging density gradient stability. Higher particle loading heights, lower volume fractions, and smaller gradient material diffusion coefficients were found to improve stability. Centrifugation was useful at short times, as particles were removed from top of the gradient where the stable density profile degrades to unstable, and the resulting density inversion arises as the sucrose diffuses upward.

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We discuss the mathematical acumen of John Couch Adams together with cognitive and behavioural characteristics that suggest Asperger syndrome. We also review the historical events involved in the investigation of the unknown planet thought to be affecting the orbital motion of Uranus. Adams produced a vital computation necessary for the discovery of Neptune that was insufficient unless integrated with specialized knowledge of other members of a British 'team' and then presented formally to the scientific community. Reasoning from the premise that complex scientific discoveries often involve cooperative social dynamics, we conclude that Adams was precluded from sharing his contribution in a collaborative manner, in part, because of empathic and social communication deficiencies related to his disorder. However, it was a 'team' failure, not Adams's alone.

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