USING THE CONCEPT OF STRUCTURE-INDUCED EQUIILIBRIUM, THIS ESSAY DEVELOPS A SIMPLE BEHAVIORAL MODEL OF ROLL CALL VOTING. THE MAIN RESULTS ARE (1) IF SOME COMMITTEES ARE PREFERENCE OUTLIERS RELATIVE TO THE LEGISLATURE AS A WHOLE, THEN ROLL CALL DATA ARE LIKELY TO BE ARTIFICIALLY UNIDIMENSIONAL. (2) THE UNIDIMENSIONAL BIAS PERSISTS EVEN AS THE DIMENSIONALITY OF THE POLICY SPACE BECOMES LARGE. (3) EVEN IF COMMITTEES ARE PREFERENCE OUTLIERS, IT MAY BE IMPOSSIBLE TO DISCOVER THIS FACT BY LOOKING ONLY AT ROLL CALL VOTES.
LiLuF4 scheelite (I41/a, Z = 4) has been investigated at high pressures using synchrotron angle-dispersive x-ray powder diffraction in a diamond anvil cell at room temperature. At 10.7 GPa, it reversibly undergoes a tricritical phase transition to the fergusonite structure (C12/c1, Z = 4), a distorted modification of the scheelite type. No other phase transition occurs in this material up to 19.5 GPa, the highest pressure in this study. Such a high-pressure behaviour is compared with the pressure-induced transformations in LiYF4 and LiGdF4, adding on to our knowledge of the structural systematics in LiMF4 compounds. (Some figures in this article are in colour only in the electronic version) 1.