Hagfish slime consists of mucins and protein threads that are released from slime glands and mix with seawater to produce an ephemeral material with intriguing physical properties. We recently characterized the mechanics of the slime's fibrous component, and here we report the first mechanical properties of the mucin component and the slime as a whole. Our results suggest that hagfishes can produce remarkable quantities of the slime because it is almost three orders of magnitude more dilute than typical mucus secretions. Mechanical experiments using whole slime produced in vitro demonstrate that the slime threads dominate the slime's material properties and impart elasticity. Mucins impart viscosity at the strain rates tested and are important for rapid deployment of the slime. We also found that slime threads are tapered at both ends, which suggested to us that hagfish slime might best be modeled as a discontinuous fibre-reinforced composite. Our measurements demonstrate that the mucins are not capable of providing shear linkage between threads, but this is not necessary because the threads are long enough to span an entire slime mass. Our findings suggest that hagfish slime consists mainly of bulk seawater entrained between mucin-coated threads, and in this way functions more like a fine sieve than coherent mucus. These results are consistent with the hypothesis that the slime has evolved as a defense against gill-breathing predators.

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This work introduces a new high-level synthesis method for self-testable RTL designs. A basic feature of this method is a structural testability model which treats testability as a structural design style integrated in the design process. The main objective is to develop a system-level synthesis tool set mapping a behavioral description onto an optimized and testable RTL design subject t o user-defined constraints. The approach involves several major components within the following system-level iteration: scheduling and allocation, constraint estimation, testability tradeoffs.

The recent progress of high level synthesis has illuminated an effective aid for system designers.To keep pace with the development of such an environment, there is a need to consider design for testability (DFT) during the synthesis process. ThM paper proposes a DFT scheme that can be coordinated with data path synthesis by an interactive trade-off process. The basis of this work is a system level testability model. To quantify the qualitative description of testability, a controllability measure and an observability measure is developed. Based on these two measures, a procedure of tradingoff between testing time and test hardware overhead is demonstrated.Featuring the ability to work on partial designs, th~testing cost evaluation scheme is well suited to the demands of high level synthesis. Currently, simulation tools for obtaining testability measures have been completed and experiments have been conducted to validate this model.