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In the field of environmental nanotechnology, opinions on the novelty of engineered nanomaterials vary; some scientists believe that many engineered nanomaterials are indeed unique, while others are convinced that we are simply fabricating structures already designed in nature. In this article, we present balanced, objective evidence on both sides of the debate. While the idea of novel nanomaterials opens the mind to imagine truly unique structures with architectures unparalleled in nature, the idea that these structures have related analogs in nature has environmental relevance as scientists and engineers aim to design and manufacture more sustainable and environmentally benign nanomaterials.

Obstructive sleep apnea (OSA) is associated with intermittent hypoxia during sleep. Vascular endothelial growth factor (VEGF) has detectable levels in the circulation and its expression is highly regulated by oxygen tension. We therefore hypothesized that serum VEGF levels will be elevated in patients with OSA.

A hydraulic model was developed to determine all flows and pressures in a continuous‐flow hollow‐fiber ultrafiltration (UF) system. A pilot‐scale UF system was constructed to test the validity of the model. Deionized water was filtered through the system to simulate nonfouling conditions, and two colloidal suspensions of powdered activated carbon and clay simulated fouling conditions. All flows and pressures were continuously logged for later analysis. For fouling conditions, the flux was described by the resistance‐in‐series model, and a relationship was developed to describe the increase in effective membrane resistance as a function of time. This fitted function was then input into the hydraulic model to predict the flows and pressures in the system under nonsteady fouling conditions. For nonfouling and fouling conditions, the predicted flows and pressures correlated well with the system flows and pressures.