Mechanism of generation of photoelastic birefringence in methacrylate polymers for optical devices

We clarified the birefringence properties of poly(methyl methacrylate), poly(ethyl methacrylate), poly(isobutyl methacrylate), poly(cyclohexyl methacrylate), poly(isopropyl methacrylate), and poly(tert‐butyl methacrylate). We demonstrated that the conformational change in polymer molecules that causes orientational birefringence differs from that causing photoelastic birefringence. Orientational birefringence depends mainly on the orientation of the main chains of the methacrylate polymers above T_g. On the other hand, photoelastic birefringence in elastic deformation below T_g depends mainly on the orientation of the side chains while the main chains are scarcely oriented. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2029–2037, 2010     

Modeling Maher's Attribution Theory of Delusions as a Cusp Catastrophe

Maher's (1974, 1988) attribution theory of delusions was reformulated as a cusp catastrophe model and tested using 193 percipients' paranormal beliefs, paranormal experiences, and fear of the paranormal as measured by Kumar et al.'s (1994) Anomalous Experiences Inventory, and their tolerance of ambiguity as measured by McDonald's (1970) AT-20. The magnitude of the difference between percipients' fear and belief was used as the dependent variables, whereas experience and tolerance of ambiguity were used as asymmetry and bifurcation variables, respectively. Using the GEMCAT II software it was shown that this cusp provided a superior fit to the data than competing linear, fold, and cusp models. Consistent with Maher's formulation, two basic states were found to exist: one in which fear dominates belief, and a second in which belief dominates fear. Further, fear of the paranormal increased with greater intolerance of ambiguity while belief decreased with increasing tolerance. The model explains why paranormal beliefs are resistant to change in the face of counterargument or contradictory evidence.