Nonconservative current-induced forces: A physical interpretation

We give a physical interpretation of the recently demonstrated non-conservative nature of interatomic forces in current-carrying nanostructures. We start from the analytical expression for the curl of these forces, and evaluate it for a point defect in a current-carrying system. We obtain a general definition of the capacity of electrical current flow to exert a non-conservative force, and thus do net work around closed paths, by a formal non-invasive test procedure. Second, we show that the gain in atomic kinetic energy in time, generated by non-conservative current-induced forces, is equivalent to the uncompensated stimulated emission of directional phonons. This connection with electron-phonon interactions quantifies explicitly the intuitive notion that non-conservative forces work by angular momentum transfer.

Open Adoption: Adoptive Parents' Experiences of Birth Family Contact and Talking to Their Child about Adoption

The trend towards more open adoption presents adopters with unique parenting challenges associated with satisfying the child’s curiosity about their origins, and maintaining relationships with birth family through contact. This paper focuses on the experiences of 20 sets of adoptive parents who were interviewed as part of the Northern Ireland Care Pathways and Outcomes Study. Interviews were analysed following the principles of Interpretative Phenomenological Analysis (IPA). It explores adoptive parents’ experience of talking to their child about adoption, and of post-adoption contact with members of the birth family. Adopters discussed adoption sensitively with their child, but were concerned that difficult and complex family histories would present a risk to the child’s self-esteem and emotional well-being. All forms of contact proved emotionally and practically burdensome, however adopters were committed to making it work for the child’s benefit, and were open to increased contact should the child wish it in the future. There was little relationship with birth family outside of formal contact. The study reveals a need for a mechanism to facilitate communication with birth family if adopters are to be able to respond to the child’s changing need for contact and information.

A comparison of the strengths of gastropod shells with forces generated by potential crab predators

Carcinus manenas, Liocarcinus puber and Cancer pagurs are thought to be three likely crab predators of the gastropod Calliostoma Zizyphinum. In order to compare the strenghts of predators and their prey, the whole shell and aperture lip strengh of white and pink Calliostoma morphotypes and the maximum forces exerted by the chelipeds of three crab species were measured. Although white shells were thicker than pink shells, Calliostoma colour morphotyes did not differ significantly in either the force required to break the shell lip or the whole shell. Both Liocarcinus puber and Carcinus maenas have dimorphic chelipeds and their “crusher” chelipeds deliver almost double the forces generated by the‘cutter’chelipeds. In constrast, Cancer pagurus has monomorphic chelipeds both delivering similar forces. When compared with Calliostoma shell strenght, the forces generated by the‘crusher’chelipeds of most L. puber tested were, in general, sufficient to break the shell lip of Calliostoma shells, whereas forces generated by the‘cutter’chelipeds of only the larger individuals were sufficient to break the shell lip. In C. manenas, forces generated by both the‘cutter’and‘crusher’chelipeds often exceeded the minimum recorded force required to break the shell lip and the‘crusher’cheliped reached the minimum force required to break whole Calliostoma shells. Both chelipeds of all C. pagurus tested generated forces in excess of the minimum required to break the shell lip, and the proportion of individuals capable of generating the minimum force required to break the whole shell increased with the size of the size of the crab. Carcinus maenas and Cancer pagurus were capable of breaking both the shell lips and the whole shells of a wider range of shell sizes than L. puber.

Direct Contact as a Moderator of Extended Contact Effects: Cross-Sectional and Longitudinal Impact on Outgroup Attitudes, Behavioral Intentions, and Attitude Certainty

Cross-group friendships (the most effective form of direct contact) and extended contact (i.e., knowing ingroup members who have outgroup friends) constitute two of the most important means of improving outgroup attitudes. Using cross-sectional and longitudinal samples from different intergroup contexts, this research demonstrates that extended contact is most effective when individuals live in segregated neighborhoods having only few, or no, direct friendships with outgroup members. Moreover, by including measures of attitudes and behavioral intentions the authors showed the broader impact of these forms of contact, and, by assessing attitude certainty as one dimension of attitude strength, they tested whether extended contact can lead not only to more positive but also to stronger outgroup orientations. Cross-sectional data showed that direct contact was more strongly related to attitude certainty than was extended contact, but longitudinal data showed both forms of contact affected attitude certainty in the long run.

Extended contact effects as a function of closeness of relationship with ingroup contacts

Using survey data from Catholics and Protestants in Northern Ireland (N = 428), the authors examined the effects of extended contact via different types of ingroup contacts (neighbors, work colleagues, friends, and family members) and tested whether closeness to ingroup contacts moderated the effects of extended contact on outgroup trust. Results demonstrated that extended contact effects varied as a function of the relationship to ingroup contacts, and that extended contact interacted with closeness ratings in predicting outgroup trust. Consistent with hypotheses, extended contacts via more intimate ingroup relationships (i.e., friends and family) were overall more strongly related to outgroup trust than extended contacts via less intimate ingroup relations (i.e., neighbors and work colleagues). Moreover, within each level of intimacy extended contact was related to outgroup trust only at high, and not at low, levels of rated closeness to ingroup contacts. The theoretical contributions, limitations and practical implications of these findings are discussed.

Contact, trust and social capital in Northern Ireland: a qualitative study of three mixed communities

In a recent paper, Robert Putnam (2007) challenges the contact hypothesis by arguing that ethnic diversity causes people to ‘hunker down’ and essentially withdraw themselves from society. Drawing on
qualitative data collected from three mixed communities in Northern Ireland, this paper explores the extent and quality of contact experienced by Protestants and Catholics in their everyday lives. Themes emerging from our data are generally consistent with the contact hypothesis. There is also some support for Putnam’s theory that mixed environments can induce ‘hunkering down’ and that inter-group trust may be compromised. However, our data challenge Putnam’s argument that these responses are a consequence of ‘anomie’ or ‘social malaise’. Rather, we find that withdrawal from social activity in the neighbourhoods we observed was a calculated response at times of threat, often aimed at protecting existent positive inter-ethnic relations.