The compelling power of humor makes it a recurrent topic for research in many fields, including communication. Three theories of humor creation emerge in humor research: the relief theory, which focuses on physiological release of tension; the incongruity theory, singling out violations of a rationally learned pattern; and the superiority theory, involving a sense of victory or triumph. Each theory helps to explain the creation of different aspects of humor, but each runs into problems explaining rhetorical applications of humor. Because each theory of humor origin tries to explain all instances of humor, the diverging communication effects of humor remain unexplained. Humor's enactment leads to 4 basic functions of humor in communication. Two tend to unite communicators: the identification and the clarification functions. The other 2 tend to divide 1 set of communicators from others: the enforcement and differentiation functions. Exploration o f these effects-based functions of humor will clarify understanding of its use in messages. Humor use unites communicators through mutual identification and clarification of positions and values, while dividing them through enforcement of norms and differentiation of acceptable versus unacceptable behaviors or people. This paradox in the functions of humor in communication as, alternately, a unifier and divider, allows humor use to delineate social boundaries.

It has been shown that the only way to predict the size of the PTC effect displayed by a crystalline polymer when filled with conductive particles is through the knowledge of the glass transition point of the polymer. The size of the PTC anomaly is found to decrease sharply with rise in glass transition temperature and for a polymer to be a useful PTC material its glass transition must lie below 0°C. It has not been possible to explain this relationship by any of the current theories of the PTC mechanism in filled polymers.

This is a study of materials which are positive-temperaturecoefficient resistors. Such materials, composed of conductive particles dispersed in a crystalline polymeric matrix, have been found to be of limited stability. An example is carbon black in high-density polyethylene. On repeated cycling through the anomaly temperature or on extensive heating at or above the anomaly temperature, the room temperature resistivity rises and the anomaly height falls to zero. This phenomenon has been shown to be caused by the absorption of oxygen by the polymer matrix which alters the structure, reduces the crystallinity, and induces an unusual form of crosslinking of a reversible nature.

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