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

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

Tracking primary thermalization events in graphene with photoemission at extreme timescales

Direct and inverse Auger scattering are amongst the primary processes that mediate the thermalization of hot carriers in semiconductors. These two processes involve the annihilation or generation of an electron-hole pair by exchanging energy with a third carrier, which is either accelerated or decelerated. Inverse Auger scattering is generally suppressed, as the decelerated carriers must have excess energies higher than the band gap itself. In graphene, which is gapless, inverse Auger scattering is instead predicted to be dominant at the earliest time delays. Here, $<8$ femtosecond extreme-ultraviolet pulses are used to detect this imbalance, tracking both the number of excited electrons and their kinetic energy with time- and angle-resolved photoemission spectroscopy. Over a time window of approximately 25 fs after absorption of the pump pulse, we observe an increase in conduction band carrier density and a simultaneous decrease of the average carrier kinetic energy, revealing that relaxation is in fact dominated by inverse Auger scattering. Measurements of carrier scattering at extreme timescales by photoemission will serve as a guide to ultrafast control of electronic properties in solids for PetaHertz electronics.Comment: 16 pages, 8 figure

Values Connecting Societies and Water Systems

__Introduction__ Water systems such as rivers and lakes have many important values for ecosystems and human societies. Both economical, social-ecological, cultural and political values are met by the water systems, connecting different activities in human society and ecosystems. Water systems with low water quality serve different values than healthy water systems and have huge impact on the society. For example, for drinking water, biodiversity or recreational open space, a healthy water system is crucial. The values of the water systems are interlinked. The interlinking and overlapping values of the water systems at the spatial and temporal scales have determined a connective capacity in the water governance, be it the coordination between the values or the competition between the values and its linked governance approach. The challenge is values of water systems change with the change in the societal development and consequently influence the water governance approach. A reverse process is also evident. Unfortunately, today water systems in many cities have slowly reduced in their total value for society. The revival of the water systems such as river and lakes is thus seem to be urgent in order to enhance the values generated by these systems for the society

Sustainability of water resource systems in India: role of value in urban lake governance in Ahmedabad

Abstract. One of the ongoing discussions in water resource governance in India is on the revival of the river and lake systems. The new water-system as infrastructures are proving to be the connectors in the current societal (urban) development as they did in the times of traditional water management and old settlement pattern. Rivers and lakes have different social, ecological and economical demands made on them at different periods of societal development and that made them vulnerable to change. One of the core challenges documented in the governance of rivers and lakes in India is addressing the rapid changes in these value systems. Effectively addressing the change (or priority) in the values of water systems and urban systems linked to the governance can be a major step towards sustainability of these systems. There is still limited understanding of how the values of water resource systems are progressively linked to changing urban systems and how upward and downward causation linkages occur within the systems as well as across diverse sectors and scales of governance. The PhD research on ‘Sustainability of urban lake systems in India’ is an attempt to look at the interactions and outcomes of the spatial and temporal dynamics of urban systems and lake systems especially the values that sustain the institutional and ecological memory. The paper highlights the relationship and the role of values between urban lakes systems (ecological systems) and governance (social systems) and identifies that sustainability of both the systems is the key towards sustainable cities. The multitier framework for analyzing the social-ecological systems is used as the foundation to elaborate the link of the values with urban lake systems and governance in the context of Ahmedabad city. Then Vastrapur lake development in Ahmedabad is studied to elaborate the role of value