A first-principles study of oxygen vacancy pinning of domain walls in PbTiO3

We have investigated the interaction of oxygen vacancies and 180-degree domain walls in tetragonal PbTiO3 using density-functional theory. Our calculations indicate that the vacancies do have a lower formation energy in the domain wall than in the bulk, thereby confirming the tendency of these defects to migrate to, and pin, the domain walls. The pinning energies are reported for each of the three possible orientations of the original Ti-O-Ti bonds, and attempts to model the results with simple continuum models are discussed.Comment: 8 pages, with 3 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/lh_dw/index.htm

Verbal ability and delinquency: Testing the moderating role of psychopathic traits

Background:  Impaired verbal abilities are one of the most consistent risk factors for serious antisocial and delinquent behavior. However, individuals with psychopathic traits often show serious antisocial behavior, despite showing no impairment in their verbal abilities. Thus, the aim of the current study was to examine whether psychopathy moderates the relationship between verbal abilities and delinquent behavior in a sample of detained youth. Methods:  The sample included 100 detained adolescent boys who were assessed on self-reported delinquent acts and psychopathic traits, as well as their age at first offense based on official records. Participants also completed a competitive computer task involving two levels of provocation, during which skin conductance was measured. A standard measure of receptive vocabulary was individually administered. Results:  As predicted, there was a significant interaction between callous-unemotional (CU) traits (a critical dimension of psychopathy) and verbal ability when predicting violent delinquency. Individuals who were high on CU traits with higher scores on the measure of verbal abilities reported the greatest violent delinquency. These individuals also showed the lowest level of skin conductance reactivity during the provocation task. Conclusions:  The results suggest CU traits are an important moderator of the relation between verbal abilities and violent delinquency