Relevant social groups

A second point can be made about the way in which uni" processes came into existence. The emergence of unit process is analogous to that of unit operations, particularly with regard to relevant social groupings involved in this evolution. Industries, professional organizations, particularly AIChE and the American Chemical Society, and universities are involved, as in the case of unit operations. This time, however, the process leading to the identification of unit processes is simpler because the disciplinary identity of the chemical engineering profession is well defined and especially because unit processes, as the name shows, are patterned after unit operations. 

Though there may be differences between people of different social strata that are biologically relevant, such as differences in nutrition, exposure to pollution, amount of exercise, etc., it is these factors, not the social status itself, that causes differences in life expectancy between different groups. 

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