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A recently proposed nonlinear kinetic theory for a dense 6uid of square-well molecules reveals the existence of two temperature scales, one associated with kinetic energy and the other with potential energy. The scales are coupled through conservation of energy and, for nonequilibrium states, the temperature scales are not identical. The distinction between the temperature scales a8'ects the value of the bulk viscosity.Defining temperature for nonequilibrium states is a problem that has a long history. ' Though there is no general theory for nonequilibrium ensembles analogous to equilibrium statistical mechamcs, a great deal of effort has been devoted to this problem at a variety of conceptual levels. In macroscopic approaches, 2 temperature is defined formally within a framework of macroscopic conservation laws. In particular, linear irreversible thermodynamics directly extends the thermodynamic concepts and their interrelationships to the regime of linear devia-

The subtraction technique is a powerful tool for studying nonequilibrium phenomena in manybody systems at short times. Its major limitation lies in the long-time noise due to the Lyapunov divergence of initially close trajectories in phase space. We present a method to compute transport coefficients even when long-time tails are present, with a subtraction technique modified by adding a kind of frictional force field to monitor the phase-space divergence. The price to be paid is to perform an extrapolation of the results to zero field.