Correlation of the photorefractive sensitivity in doped LiNbO3 with chemically induced changes in the optical absorption spectra

Single crystals of LiNbO₃ doped with Mn, Fe, or Cu have been reduced or oxidized at 800°C. Changes in the optical absorption spectra and in the photorefractive sensitivity have been determined, and a close correlation between the latter and a particular optical absorption band is demonstrated.     

Power and Taxes in a multi-commodity economy

Taxation and redistribution in a democratic majority-rule society are analyzed, using the Harsanyi-Shapley non-transferable utility value. The context is that of a multi-commodity pure exchange economy. Two approaches are treated: one in which taxes are in kind and exchange takes the form of barter; and one in which taxes are in money, exchange takes the form of sale and purchase, and prices are determined by a process of supply and demand. It is shown that in the presence of a non-atomic continuum of agents, the two approaches are equivalent, but that this is not so when there are only finitely many agents. It is also shown that the value exists under both approaches, and a characterization is found in the non-atomic case. This work was supported by U.S. National Science Foundation Grant SOC74-11446 at the Institute for Mathematical Studies in the Social Sciences, Stanford University, and by a grant from the Israel National Council for Research and Development at the Hebrew University of Jerusalem.     

Laser excitation of single ion and clustered ion sites in SrF2 : Er3+

Selective laser excitation has been used to study the optical properties of the charge compensated sites in 0.0001%, 0.01%, 0.05% and 0.2% concentrations of SrF₂ : Er³⁺. Using a pulsed, tunable, narrowband dye laser, nine crystallographically inequavalent sites were observed, and the fluorescence and excitation lines associated with each were identified. Concentration dependences, ion pair energy transfer, and crystal field splittings were used to classify these sites as arising from either a single charge compensated Er³⁺ ion or clustered pairs of Er³⁺ ions. At lower concentrations, the four single ion sites dominated the spectra while at higher concentrations the cluster sites weredominant. Several of these sites were found to be similar to sites previously observed in CaF₂ : Er³⁺, and several were correlated to spectra of SrF₂ : Er³⁺ published by other workers.     

Three-dimensional spin structure on a two-dimensional lattice: Mn/Cu(111)

Based on first-principles vector spin-density total-energy calculations of the magnetic and electronic structure of Cr and Mn transition-metal monolayers on the triangular lattice of a (111) oriented Cu surface, we propose for Mn a three-dimensional noncollinear spin structure on a two-dimensional triangular lattice as magnetic ground state. This new spin structure is a multiple spin-density wave of three row-wise antiferromagnetic spin states and comes about due to magnetic interactions beyond the nearest neighbors and due to higher order spin interactions (i.e., four spin). The magnetic ground state of Cr is a coplanar noncollinear periodic 120 degrees Néel structure.     

On {\alpha }-roughly weighted games

Gvozdeva et al. (Int J Game Theory, doi:10.1007/s00182-011-0308-4, 2013) have introduced three hierarchies for simple games in order to measure the distance of a given simple game to the class of (roughly) weighted voting games. Their third class \({\mathcal {C}}_\alpha \) consists of all simple games permitting a weighted representation such that each winning coalition has a weight of at least \(1\) and each losing coalition a weight of at most \(\alpha \) . For a given game the minimal possible value of \(\alpha \) is called its critical threshold value. We continue the work on the critical threshold value, initiated by Gvozdeva et al., and contribute some new results on the possible values for a given number of voters as well as some general bounds for restricted subclasses of games. A strong relation between this concept and the cost of stability, i.e. the minimum amount of external payment to ensure stability in a coalitional game, is uncovered.     

Financial valuation of investments in future power generation technologies: nuclear fusion and CCS in an emissions trading system

This paper outlines a model approach for the financial valuation of future power generation technologies, such as nuclear fusion or carbon capture and storage (CCS) under an emissions trading regime. Since on imperfect markets, interdependencies between decisions inhibit the isolated valuation of an investment, we use simultaneous calculation of optimal production, sales and investment programs; these are subject to the constraints and conditions characteristic for investments in low- and zero-carbon technologies such as fusion and CCS. Duality theory allows to derive, identify and economically interpret the determinants for the price ceiling as (corrected) net present values. Sensitivity analysis shows how changes in the technical specification or environmental policies affect the maximum payable price. Particularly, tradable permits have several effects on low-carbon investments and do not always encourage CO ₂ abatement. While a zero-emissions technology like fusion always profits from a tightened emissions trading scheme, for low-carbon technology like CCS—in particular cases—this may even be counterproductive from an economic as well as an environmental point of view.