The structure of 110 tilt boundaries in large area solar silicon

The models of Hornstra and their connection to the repeating group description of grain boundaries (7-10) are discussed. A model for the Sigma = 27 boundary containing a zig-zag arrangement of dislocations is constructed and it is shown that zig-zag models can account for the contrast features observed in high resolution transmission electron micrographs of second and third order twin boundaries in silicon. The boundaries discussed are symmetric with a 110 tilt axis and a (110) boundary plane in the median lattice (the median plane). The median lattice is identical in structure and halfway in orientation between the crystal lattices either side of the boundary

Manipulating expectancy violations to strengthen the efficacy of human fear extinction

Recent theoretical and clinical articles have emphasized a role for expectancy violations in improving the effectiveness of exposure therapy. Expectancy violations are critical to extinction learning and strengthening these violations has been suggested to improve the formation and retention of extinction memories, which should result in lasting symptom reductions after treatment. However, more detailed mechanistic insights in this process are needed to better inform clinical interventions. In two separate fear-conditioning experiments, we investigated whether stronger expectancy violations (Exp1) or fostering awareness of expectancy violations (Exp2) during extinction could reduce the subsequent return of fear. We measured fear potentiated startle (FPS) and skin conductance responses (SCR) as physiological indices of fear, and US expectancy ratings to assess our manipulations. While we successfully created stronger expectancy violations in Exp1, we found no evidence that these stronger violations reduced the return of fear at test. Interestingly, fostering awareness of violations (Exp2) reduced differential SCRs, but not FPS responses. These findings provide novel insights into the effect of US expectancies on fear extinction in the lab, but they also illustrate the complexity of capturing clinically relevant processes of change with fear-conditioning studies.</p

Origin of Rashba-splitting in the quantized subbands at Bi2Se3 surface

We study the band structure of the $\text{Bi}_2\text{Se}_3$ topological insulator (111) surface using angle-resolved photoemission spectroscopy. We examine the situation where two sets of quantized subbands exhibiting different Rashba spin-splitting are created via bending of the conduction (CB) and the valence (VB) bands at the surface. While the CB subbands are strongly Rashba spin-split, the VB subbands do not exhibit clear spin-splitting. We find that CB and VB experience similar band bending magnitudes, which means, a spin-splitting discrepancy due to different surface potential gradients can be excluded. On the other hand, by comparing the experimental band structure to first principles LMTO band structure calculations, we find that the strongly spin-orbit coupled Bi 6$p$ orbitals dominate the orbital character of CB, whereas their admixture to VB is rather small. The spin-splitting discrepancy is, therefore, traced back to the difference in spin-orbit coupling between CB and VB in the respective subbands' regions

The 'Adat' institutionand the Management of Grand Forest 'Herman Yohannes' in Indonesian Timor: The Role of Design Principles for Sustainable Management of Common Pool Resources

__Abstract__ Local success stories of sustainable forest management can inspire scientists and decision-makers. This article analyses the traditional ‘Adat’ institution that plays a role in the management of Grand Forest Park ‘Herman Yohannes’, in the Western part of Timor where the Adat forest management regulation has been formally restored. The original set of design principles for sustainable management of common pool resources of Elinor Ostrom (1990) has been used in this study as an analytical framework for understanding the role of the Adat institution in respect to the forest. In the park, the local community applies Adat for protection and management of the forest that has been its home for centuries. It appears that Ostrom’s design principles can be identified in the current Adat institution and play a role in the sustainable management of the forest. Although many other variables can lead to success or failure of institutions, the original (internal) design principles are still valuable as a practical tool for building institutions that are – under certain conditions – able to sustain common pool resources. The findings confirm the importance of traditional institutions in successful forest management. The study recommends that decision-makers take into account existing traditional management systems that have shown long term functionality

Demarcating the boundary conditions of memory reconsolidation: An unsuccessful replication

Disrupting memory reconsolidation provides an opportunity to abruptly reduce the behavioural expression of fear memories with long-lasting effects. The success of a reconsolidation intervention is, however, not guaranteed as it strongly depends on the destabilization of the memory. Identifying the necessary conditions to trigger destabilization remains one of the critical challenges in the field. We aimed to replicate a study from our lab, showing that the occurrence of a prediction error (PE) during reactivation is necessary but not sufficient for destabilization. We tested the effectiveness of a reactivation procedure consisting of a single PE, compared to two control groups receiving no or multiple PEs. All participants received propranolol immediately after reactivation and were tested for fear retention 24 h later. In contrast to the original results, we found no evidence for a reconsolidation effect in the single PE group, but a straightforward interpretation of these results is complicated by the lack of differential fear retention in the control groups. Our results corroborate other failed reconsolidation studies and exemplify the complexity of experimentally investigating this process in humans. Thorough investigation of the interaction between learning and memory reactivation is essential to understand the inconsistencies in the literature and to improve reconsolidation interventions