A Price-Based Royalty Tax?

transfer pricing; extractive industries; natural resource taxation; royalties; resource rent tax.This paper considers the merits of a price-based royalty, a royalty for which the rate varies with the product price, as a fiscal instrument for taxing extractive industries. In light of the literature on natural resources taxation, the case for a price-based royalty is appealing. A price-based royalty captures some of the desirable attributes of an income or resource rent tax, but in comparison to such taxes, it is easier to administer since revenue is much less sensitive to transfer price manipulation and tax avoidance efforts. In order to explore how a price-based royalty might provide some of the advantages of income- or rent-based taxation, the paper analyses the relationship between product prices and firm profits, using a dataset of the world’s largest extractive firms from the Forbes Global 2000 list during the period 2003-2014. This analysis indicates that, for both oil/gas and mining firms, there is a nearly one-to-one relationship between product prices and firm profitability; prices 1 per cent higher tend to be associated with profits about 0.76 per cent higher for oil/gas firms and about 1.38 per cent higher for mining firms. The paper concludes by recommending that tax policymakers give serious consideration to increasing the use of price-based royalties.DfID, NORAD

Weak-Field Thermal Hall Conductivity in the Mixed State of d-Wave Superconductors

Thermal transport in the mixed state of a d-wave superconductor is considered within the weak-field regime. We express the thermal conductivity, $\kappa_{xx}$, and the thermal Hall conductivity, $\kappa_{xy}$, in terms of the cross section for quasiparticle scattering from a single vortex. Solving for the cross section (neglecting the Berry phase contribution and the anisotropy of the gap nodes), we obtain $\kappa_{xx}(H,T)$ and $\kappa_{xy}(H,T)$ in surprisingly good agreement with the qualitative features of the experimental results for YBa$_{2}$Cu$_{3}$O$_{6.99}$. In particular, we show that the simple, yet previously unexpected, weak-field behavior, $\kappa_{xy}(H,T) \sim T\sqrt{H}$, is that of thermally-excited nodal quasiparticles, scattering primarily from impurities, with a small skew component provided by vortex scattering.Comment: 5 pages, 2 figures; final version as published in Phys Rev Let

Effect of external magnetic field on electron spin dephasing induced by hyperfine interaction in quantum dots

We investigate the influence of an external magnetic field on spin phase relaxation of single electrons in semiconductor quantum dots induced by the hyperfine interaction. The basic decay mechanism is attributed to the dispersion of local effective nuclear fields over the ensemble of quantum dots. The characteristics of electron spin dephasing is analyzed by taking an average over the nuclear spin distribution. We find that the dephasing rate can be estimated as a spin precession frequency caused primarily by the mean value of the local nuclear magnetic field. Furthermore, it is shown that the hyperfine interaction does not fully depolarize electron spin. The loss of initial spin polarization during the dephasing process depends strongly on the external magnetic field, leading to the possibility of effective suppression of this mechanism.Comment: 10 pages, 2 figure

Observation of Apparently Zero-Conductance States in Corbino Samples

Using Corbino samples we have observed oscillatory conductance in a high-mobility two-dimensional electron system subjected to crossed microwave and magnetic fields. On the strongest of the oscillation minima the conductance is found to be vanishingly small, possibly indicating an insulating state associated with these minima.Comment: 4 pages, 3 figures, RevTex

Spectral and Transport Properties of d-Wave Superconductors With Strong Impurities

One of the remarkable features of disordered d-wave superconductors is strong sensitivity of long range properties to the microscopic realization of the disorder potential. Particularly rich phenomenology is observed for the -- experimentally relevant -- case of dilute distributions of isolated impurity centers. Building on earlier diagrammatic analyses, the present paper derives and analyses a low energy effective field theory of this system. Specifically, the results of previous diagrammatic T-matrix approaches are extended into the perturbatively inaccessible low energy regimes, and the long range (thermal) transport behaviour of the system is discussed. It turns out that in the extreme case of a half-filled tight binding band and infinitely strong impurities (impurities at the unitary limit), the system is in a delocalized phase.Comment: 14 pages, two figures include

Microwave conductivity of a d-wave superconductor disordered by extended impurities: a real-space renormalization group approach

Using a real-space renormalization group (RSRG) technique, we compute the microwave conductivity of a d-wave superconductor disordered by extended impurities. To do this, we invoke a semiclassical approximation which naturally accesses the Andreev bound states localized near each impurity. Tunneling corrections (which are captured using the RSRG) lead to a delocalization of these quasiparticles and an associated contribution to the microwave conductivity.Comment: 8 pages, 4 figures. 2 figures added to previous versio

Microwave Conductivity due to Scattering from Extended Linear Defects in d-Wave Superconductors

Recent microwave conductivity measurements of detwinned, high-purity, slightly overdoped YBa$_{2}$Cu$_{3}$O$_{6.993}$ crystals reveal a linear temperature dependence and a near-Drude lineshape for temperatures between 1 and 20 K and frequencies ranging from 1 to 75 GHz. Prior theoretical work has shown that simple models of scattering by point defects (impurities) in d-wave superconductors are inconsistent with these results. It has therefore been suggested that scattering by extended defects such as twin boundary remnants, left over from the detwinning process, may also be important. We calculate the self-energy and microwave conductivity in the self-consistent Born approximation (including vertex corrections) for a d-wave superconductor in the presence of scattering from extended linear defects. We find that in the experimentally relevant limit ($\Omega, 1/\tau \ll T \ll \Delta_{0}$), the resulting microwave conductivity has a linear temperature dependence and a near-Drude frequency dependence that agrees well with experiment.Comment: 13 pages, 7 figure

Fish Eating Birds Can Spread Bacterial Diseases Between Catfish Ponds

Severe outbreaks of Motile Aeromonad Septicemia disease in commercial catfish aquaculture ponds have been associated with a virulent Aeromonas hydrophila strain (VAh) that is genetically distinct from less virulent strains. We demonstrated that Great Egrets (Arde alba), Double-crested Cormorants (Phalacrocorax auritus), American White Pelicans (Pelecanus erythrorhynchos), and Wood Storks (Mycteria americana) can carry and shed viable VAh after consuming fish infected with Vah. Edwardsiella ictaluri and E. tarda are considered the primary species of Edwardsiella to cause disease outbreaks in North American catfish aquaculture. Genetic analysis has determined that most isolates designated as E. tarda were actually a new species, E. piscicida. There has been an increase in E. piscicida diagnostic cases in recent years possibly due to an increase in hybrid (Channel x blue) catfish production. We conducted a study to determine if Great Egrets (Ardea alba) shed viable E. piscicida when fed catfish infected with the bacteria. Great Egrets fed infected fish shed viable E. piscicida bacteria for multiple days, (Table 1), after last consuming infected fish on day 2 of the study. Great Egrets in the control group did not shed the bacteria. Given that Great Egrets can shed viable E. piscicida after consuming diseased fish, we hypothesize that they could also serve as a reservoir for E. piscicida and could spread the pathogen while predating fish in catfish ponds. Additional research is needed to determine if this shedding could cause disease in these ponds