In future work we will address the problem of characterizing and validating across subjects  the ROIs networks identified in the analysis, with the interesting perspective of relaxing  ROIs spatial superposability
assumptions across subjects.
Subsequently, when the time-strain superposability
is applicable (thermorheologically simple materials), the transient first normal stress difference in terms of shear damping function, i.
Non-superposability is observed for the different aging times in the 90 [degrees] C experiments as well as those carried out at 95 and 100 [degrees] C, a result that is somewhat different from what was observed for the 300F material where superposability was possible up to 95 [degrees] C.
In this data set, as well as that at 110 [degrees] C, the superposability of the creep responses at different aging times is primarily performed by vertical shifting, indicating no significant change in the retardation times due to aging at these temperatures.
As an additional point, the apparent superposability
of the time-strain data leads to questions about the use of reduced time concepts in nonlinear constitutive equations when data are obtained only isothermally.