Equation of state of fully ionized electron-ion plasmas

Thermodynamic quantities of Coulomb plasmas consisting of point-like ions immersed in a compressible, polarizable electron background are calculated for ion charges Z=1 to 26 and for a wide domain of plasma parameters ranging from the Debye-Hueckel limit to the crystallization point and from the region of nondegenerate to fully degenerate nonrelativistic or relativistic electrons. The calculations are based on the linear-response theory for the electron-ion interaction, including the local-field corrections in the electronic dielectric function. The thermodynamic quantities are calculated in the framework of the N-body hypernetted-chain equations and fitted by analytic expressions. We present also accurate analytic approximations for the free energy of the ideal electron gas at arbitrary degeneracy and relativity and for the excess free energy of the one-component plasma of ions (OCP) derived from Monte Carlo simulations. The extension to multi-ionic mixtures is discussed within the framework of the linear mixing rule. These formulae provide a completely analytic, accurate description of the thermodynamic quantities of fully ionized electron-ion Coulomb plasmas, a useful tool for various applications from liquid state theory to dense stellar matter.Comment: 13 pages, 2 tables, 7 figures, REVTeX using epsf.sty. To be published in Phys. Rev. E, vol. 58 (1998

Variational quantum Monte Carlo study of two-dimensional Wigner crystals: exchange, correlation, and magnetic field effects

The two-dimensional Wigner crystals are studied with the variational quantum Monte Carlo method. The close relationship between the ground-state wavefunction and the collective excitations in the system is illustrated, and used to guide the construction of the ground-state wavefunction of the strongly correlated solid. Exchange, correlation, and magnetic field effects all give rise to distinct physical phenomena. In the absence of any external magnetic field, interesting spin-orderings are observed in the ground-state of the electron crystal in various two-dimensional lattices. In particular, two-dimensional bipartite lattices are shown not to lead necessarily to an antiferromagnetic ground-state. In the quantum Hall effect regime, a strong magnetic field introduces new energy and length scales. The magnetic field quenches the kinetic energy and poses constraints on how the electrons may correlate with each other. Care is taken to ensure the appropriate translational properties of the wavefunction when the system is in a uniform magnetic field. We have examined the exchange, intra-Landau-level correlation as well as Landau-level-mixing effects with various variational wavefunctions. We also determine their dependences on the experimental parameters such as the carrier effective mass at a modulation-doped semiconductor heterojunction. Our results, when combined with some recent calculations for the energy of the fractional quantum Hall liquid including Landau-level-mixing, show quantitatively that in going from $n$-doping to $p$-doping in $GaAS/AlGaAS$ heterojunction systems, the crossover filling factor from the fractional quantum Hall liquid to the Wigner crystal changes from filling factor $\nu \sim 1/5$ to $\nu \sim 1/3$. This lends strong support to the claim that theComment: LaTex file, 14 figures available from [email protected]

Understanding Global Change: From Documentation and Collaboration to Social Transformation

The conclusion to the book situates the chapters within four programs of anthropological research on climate change: (1) documentation of local impacts of and adaptations to climate change, (2) connections to socioeconomic and political contexts, (3) collaborations with nonanthropologists, and (4) activism and social transformation. The final section notes the persistent challenges to creating positive change and meaningful research outcomes. It highlights some examples of success and outlines future directions for politically engaged anthropological work around climate change

Differential livelihood adaptation to social-ecological change in coastal Bangladesh

Social-ecological changes, brought about by the rapid growth of the aquaculture industry and the increased occurrence of climatic stressors, have significantly affected the livelihoods of coastal communities in Asian mega-deltas. This paper explores the livelihood adaptation responses of households of different wealth classes, the heterogeneous adaptation opportunities, barriers and limits (OBLs) faced by these households and the dynamic ways in which these factors interact to enhance or impede adaptive capacities. A mixed methods approach was used to collect empirical evidence from two villages in coastal Bangladesh. Findings reveal that households’ adaptive capacities largely depend on their wealth status, which not only determine their availability of productive resources, but also empower them to navigate social-ecological change in desirable ways. Households operate within a shared response space, which is shaped by the broader socio-economic and political landscape, as well as their previous decisions that can lock them in to particular pathways. While an adaptive response may be effective for one social group, it may cause negative externalities that can undermine the adaptation options and outcomes of another group. Adaptation OBLs interact in complex ways; the extent to which these OBLs affect different households depend on the specific livelihood activities being considered and the differential values and interests they hold. To ensure more equitable and environmentally sustainable livelihoods in future, policies and programs should aim to expand households’ adaptation space by accounting for the heterogeneous needs and complex interdependencies between response processes of different groups

Work and labour in the Bangladesh brackish-water shrimp export sector

South Asia263359-38

Tight-binding studies of surface effects on electronic structure of CdSe nanocrystals: the role of organic ligands, surface reconstruction, and inorganic capping shells

We utilize a tight-binding model to study the effects of surface structure on electronic properties of CdSe clusters. The model takes into account experimental information about structure and shape of the nanocrystals, as well as the nature and distribution of capping ligands. The effects of both organic capping ligands and inorganic capping shells on the densities of states (DOS) and on the single-particle absorption spectra of the clusters are calculated for various cluster shapes and sizes, and are compared to results for clusters with truncated surfaces. For organic capping ligands, the effect of ligand hybridization is investigated and a simple model of surface reconstruction is developed. Both ligand hybridization and surface reconstruction are seen to have a major influence on the band edge electronic and optical properties. Inorganic capping shells give rise to differential localization of valence and conduction band edge states, with the hole primarily confined to the core region and the electron more evenly distributed over both core and shell. 71.55.Gs II-VI semiconductors 73.20.Dx Electron states in low-dimensional structures (superlattices, quantum well structures and multilayers

Australian universities, government research and the application of climate change knowledge in Australian coastal zone management

One of the key issues in Australia for sustainable management of the coastal zone is that the science of climate change has not been widely used by decision-makers to inform coastal governance. There exist opportunities to enhance the dialogue between knowledge-makers and decision-makers, and universities have a key role to play in researching and fostering better linkages. At the heart of these linkages lies the principle of more informed engagement between historically disparate groups. In Australia, the new ‘Flagship’ research programme, funded by the Commonwealth Scientific and Industrial Research Organization (CSIRO), emphasizes their partnering with universities in a more systematic and collaborative manner than previously achieved in such research projects. In order to address sustainability in general and coastal adaptation to climate change in particular, interdisciplinary learning needs to occur between the social and natural sciences; also, transdisciplinary understanding of that interaction needs to be fully developed. New methods of communicative engagement such as computer visualizations and animations, together with deliberative techniques, can help policy-makers and planners reach a better understanding of the significance of the science of climate change impacts on the coast. Deeper engagement across historically disparate groups can lead to the development of epistemological and methodological synergies between social and natural scientists, adaptive learning, reflexive governance, and greater analytical and deliberative understanding among scientists, policymakers and the wider public. This understanding can lead in turn to enhance coastal governance for climate adaptation on the coast.Laura Stocker, Bob Pokrant, David Wood, Nick Harvey, Marcus Haward, Kevin O’Toole and Tim Smit