Primitive function 374 Subject

The mapping of T from the subdomain of temperatures onto the interval [0, 1] is the membership or compatibility function fx T). The form of this function is subject to some relatively nonarbitrary constraints to be consistent with one s primitive notions of hotness, fx T) should increase monotonically and smoothly with T, and it should be roughly sigmoidal in shape. However, since a whole family of curves will fit this description, the choice of numerical values for the parameters of fi(T) will to a considerable extent be an arbitrary one. Therefore, the threshold criteria, which are given by fi(T), are themselves fuzzy. 

The lymphatic vessel is a unique transport system that is present even in primitive physiological systems. These vessels carry out a multitude of functions, many of which have yet to be discovered. Lymphatics have a two-valve system, a primary valve system at the level of the lymphatic endothelium and a secondary valve system in the lumen of the lymphatics, facflitating unidirectional transport toward the lymphatic nodes and thoracic duct. Details of lymphatic growth kinetics are subject to initial molecular analysis designed to identify key growth factors and their molecular control [Lohela et al., 2003 Saharinen et al., 2004]. A more detailed bioengineering analysis, especially at the molecular level [Jeltsch et al., 1997] is a fruitful area for future exploration. 

Cardiac-assist devices are mechanical pumps that provide cardiac output at an appropriate pressure, to allow normal circulation of blood through the patient s body, subject to the changing demands for cardiac output as a function of the patient s state (e.g., level of exercise, emotion, posture, etc.). The ideal device would mimic the body s own mechanisms for maintaining cardiac output at target levels however, currently available devices are rather primitive in terms of automation, requiring the patient to adjust the set point (Boston et al., 2000). The first such implantable device received approval by the FDA over a decade ago. 

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