Superconductivity in Group III-V Semiconductor AlN Under High Pressure

The electronic properties of cubic zinc blende type group III-V semiconductor AlN under pressure is studied using full potential linear muffin-tin orbital (FP-LMTO) method. At normal pressure, AlN is an indirect bandgap semiconductor with band gap value 4.56 eV. When the pressure is increased, there is enhanced overlapping between the wave functions of the neighboring atoms. As a result the widths of the valence and empty conduction bands increase. These changes lead to the narrowing and indirect closing of the band gaps in AlN (metallization). On further increase of pressure, AlN becomes a superconductor and AlN comes under the class of electron-phonon-mediated high pressure superconductors. The superconducting transition temperatures (Tc) of AlN are obtained as a function of pressure for the CsCl structure. It is also confirmed that the metallization, structural phase transition and onset of superconductivity do not occur simultaneously in this compound. DOI: http://dx.doi.org/10.17807/orbital.v7i3.62

WATER REPELLENT RENDERINGS FOR THE DAMP-PROOFING OF MONUMENTS

The global transitional justice tool kit—involving the use of criminal prosecutions, amnesties, and other mechanisms to address past human rights abuse—has become a primary means for thwarting future human rights violations and consolidating democracy. Nevertheless, evidence on the consequences of transitional justice remains mixed and amenable to contradictory interpretations. Existing studies fail to adequately address issues of selection, the difference between short- and long-term effects of transitional justice mechanisms, and qualitative and quantitative differences in state practices. This article uses a new database of transitional justice mechanisms to address these concerns and test propositions from realist, constructivist, and holistic approaches to this set of policy issues. We find, among other things, that prosecutions increase physical integrity protections, while amnesties increase the protection of civil and political rights. Our analysis suggests that different transnational justice policies each play a potentially positive, but distinct, role in new democracies and in decreasing violations of human rights

Being More Realistic About Reasons: On Rationality and Reasons Perspectivism

This paper looks at whether it is possible to unify the requirements of rationality with the demands of normative reasons. It might seem impossible to do because one depends upon the agent’s perspective and the other upon features of the situation. Enter Reasons Perspectivism. Reasons perspectivists think they can show that rationality does consist in responding correctly to reasons by placing epistemic constraints on these reasons. They think that if normative reasons are subject to the right epistemic constraints, rational requirements will correspond to the demands generated by normative reasons. While this proposal is prima facie plausible, it cannot ultimately unify reasons and rationality. There is no epistemic constraint that can do what reasons perspectivists would need it to do. Some constraints are too strict. The rest are too slack. This points to a general problem with the reasons-first program. Once we recognize that the agent’s epistemic position helps determine what she should do, we have to reject the idea that the features of the agent’s situation can help determine what we should do. Either rationality crowds out reasons and their demands or the reasons will make unreasonable demands

Economics, Agency, and Causal Explanation

The paper considers three questions. First, what is the connection between economics and agency? It is argued that causation and explanation in economics fundamentally depend on agency. So a philosophical understanding of economic explanation must be sensitive to an understanding of agency. Second, what is the connection between agency and causation? A causal view of agency-involving explanation is defended against a number of arguments from the resurgent noncausalist tradition in the literature on agency and action-explanation. If agency is fundamental to economic explanation, it is argued, then so is causation. Third, what is the connection between causal explanation and the natural sciences? It is argued that, though the explanations given in economics and other social sciences are causal explanations, they are different in kind from the causal explanations of the natural sciences. On the one hand, then, the causal explanations of the social sciences are irreducible to those found in the natural sciences. On the other hand, the causal relations described by the social sciences are not completely autonomous; they do not float free of, or operate independently from, the causal relations charted by the natural sciences

Normative Reference Magnets

The concept of moral wrongness, many think, has a distinctive kind of referential stability, brought out by moral twin earth cases. This article offers a new account of the source of this stability, deriving it from a metaphysics of content: “substantive” radical interpretation, and first-order normative assumptions. This story is distinguished from extant “reference magnetic” explanations of the phenomenon, and objections and replies are considered

Superconductivity in Group III-V Semiconductor AlN Under High Pressure

The electronic properties of cubic zinc blende type group III-V semiconductor AlN under pressure is studied using full potential linear muffin-tin orbital (FP-LMTO) method. At normal pressure, AlN is an indirect bandgap semiconductor with band gap value 4.56 eV. When the pressure is increased, there is enhanced overlapping between the wave functions of the neighboring atoms. As a result the widths of the valence and empty conduction bands increase. These changes lead to the narrowing and indirect closing of the band gaps in AlN (metallization). On further increase of pressure, AlN becomes a superconductor and AlN comes under the class of electron-phonon-mediated high pressure superconductors. The superconducting transition temperatures (Tc) of AlN are obtained as a function of pressure for the CsCl structure. It is also confirmed that the metallization, structural phase transition and onset of superconductivity do not occur simultaneously in this compound. DOI: http://dx.doi.org/10.17807/orbital.v7i3.62

Rationality as the Rule of Reason

The demands of rationality are linked both to our subjective normative perspective (given that rationality is a person-level concept) and to objective reasons or favoring relations (given that rationality is non-contingently authoritative for us). In this paper, I propose a new way of reconciling the tension between these two aspects: roughly, what rationality requires of us is having the attitudes that correspond to our take on reasons in the light of our evidence, but only if it is competent. I show how this view can account for structural rationality on the assumption that intentions and beliefs as such involve competent perceptions of downstream reasons, and explore various implications of the account

Using a disciplinary discourse lens to explore how representations afford meaning making in a typical wave physics course

We carried out a case study in a wave physics course at a Swedish university in order to investigate the relations between the representations used in the lessons and the experience of meaning making in interview–discussions. The grounding of these interview–discussions also included obtaining a rich description of the lesson environment in terms of the communicative approaches used and the students’ preferences for modes of representations that best enable meaning making. The background for this grounding was the first two lessons of a 5-week course on wave physics (70 students). The data collection for both the grounding and the principal research questions consisted of video recordings from the first two lessons: a student questionnaire of student preferences for representations (given before and after the course) and video-recorded interview–discussions with students (seven pairs and one on their own). The results characterize the use of communicative approaches, what modes of representation were used in the lectures, and the trend in what representations students’ preferred for meaning making, all in order to illustrate how students engage with these representations with respect to their experienced meaning making. Interesting aspects that emerged from the study are discussed in terms of how representations do not, in themselves, necessarily enable a range of meaning making; that meaning making from representations is critically related to how the representations get situated in the learning environment; and how constellations of modes of disciplinary discourse may be necessary but not always sufficient. Finally, pedagogical comments and further research possibilities are presented.Web of Scienc