Preference Erosion and Multilateral Trade Liberalization

Because of concern that OECD tariff reductions will translate into worsening export performance for the least developed countries, trade preferences have proven a stumbling block to developing country support for multilateral liberalization. We examine the actual scope for preference erosion, including an econometric assessment of the actual utilization, and also the scope for erosion estimated by modeling full elimination of OECD tariffs and hence full MFN liberalization-based preference erosion. Preferences are underutilized due to administrative burden—estimated to be at least 4 percent on average—reducing the magnitude of erosion costs significantly. For those products where preferences are used (are of value), the primary negative impact follows from erosion of EU preferences. This suggests the erosion problem is primarily bilateral rather than a WTO-based concern.preference erosion, GSP, WTO, Doha Round, trade and development

Transport in the metallic regime of Mn doped III-V Semiconductors

The standard model of Mn doping in GaAs is subjected to a coherent potential approximation (CPA) treatment. Transport coefficients are evaluated within the linear response Kubo formalism. Both normal (NHE) and anomalous contributions (AHE) to the Hall effect are examined. We use a simple model density of states to describe the undoped valence band. The CPA bandstructure evolves into a spin split band caused by the $p-d$ exchange scattering with Mn dopants. This gives rise to a strong magnetoresistance, which decreases sharply with temperature. The temperature ($T$) dependence of the resistance is due to spin disorder scattering (increasing with $T$), CPA bandstructure renormalization and charged impurity scattering (decreasing with $T$). The calculated transport coefficients are discussed in relation to experiment, with a view of assessing the overall trends and deciding whether the model describes the right physics. This does indeed appear to be case, bearing in mind that the hopping limit needs to be treated separately, as it cannot be described within the band CPA.Comment: submitted to Phys. Rev.

Black hole-neutron star mergers: effects of the orientation of the black hole spin

The spin of black holes in black hole-neutron star (BHNS) binaries can have a strong influence on the merger dynamics and the postmerger state; a wide variety of spin magnitudes and orientations are expected to occur in nature. In this paper, we report the first simulations in full general relativity of BHNS mergers with misaligned black hole spin. We vary the spin magnitude from a/m=0 to a/m=0.9 for aligned cases, and we vary the misalignment angle from 0 to 80 degrees for a/m=0.5. We restrict our study to 3:1 mass ratio systems and use a simple Gamma-law equation of state. We find that the misalignment angle has a strong effect on the mass of the postmerger accretion disk, but only for angles greater than ~ 40 degrees. Although the disk mass varies significantly with spin magnitude and misalignment angle, we find that all disks have very similar lifetimes ~ 100ms. Their thermal and rotational profiles are also very similar. For a misaligned merger, the disk is tilted with respect to the final black hole's spin axis. This will cause the disk to precess, but on a timescale longer than the accretion time. In all cases, we find promising setups for gamma-ray burst production: the disks are hot, thick, and hyperaccreting, and a baryon-clear region exists above the black hole.Comment: 15 pages, 13 figure

Towards A System-Based Model For Overall Performance Evaluation In A Supply Chain Context

International audienceThe paper deals with the wide issue of overall performance expression of a system made of interacting entities. Formal aspects of overall performance expression are considered as a first step of this reflection in the context of supply chains (SC's). Indeed, a SC being a network of interconnected business entities, it is proposed to consider it as a system of systems. Because system behavior depends on process dynamics, the performance of any company of the SC highly depends on the performance of its processes. However, while process performance is clearly defined in the literature, performance of complex systems or systems of systems is more difficult to assess due to process interactions. The overall performance concept is usually unsatisfactory either for each company or for the whole SC. To express such performance in SC's, recent proposals have focused on the performance of the prime manufacturer. This performance being linked to the ones of the suppliers, the impact of supplier performances on the prime manufacturer performance has to be integrated. It is therefore proposed to respectively use the SCOR model for describing the involved sub-system processes and, from a computational point of view, to use the MAUT (Multi Attribute Utility Theory) MACBETH methodology to consistently compute the expected performances. More specifically, the Choquet integral is used as the aggregation operator to handle interactions between systems and processes. The case of a bearings manufacturer is used to illustrate the proposal for a supplier selection problem

Electron transport through antidot superlattices in Si/SiGeSi/SiGe heterostructures: new magnetoresistance resonances in lattices with large diameter antidots

In the present work we have investigated the transport properties in a number of Si/SiGe samples with square antidot lattices of different periods. In samples with lattice periods equal to 700 nm and 850 nm we have observed the conventional low-field commensurability magnetoresistance peaks consistent with the previous observations in GaAs/AlGaAs and Si/SiGe samples with antidot lattices. In samples with a 600 nm lattice period a new series of well-developed magnetoresistance oscillations has been found beyond the last commensurability peak which are supposed to originate from periodic skipping orbits encircling an antidot with a particular number of bounds.Comment: To appear in EuroPhys. Let

A transcriptomic investigation of handicap models in sexual selection

We are grateful to D. Calder and T. Helps for access to study sites, and G. Murray-Dickson and M. Oliver for help with fieldwork and comments on manuscript drafts. This work was funded by NERC grant NE/D000602/1 (SBP), a NERC advanced fellowship (FM) and a BBSRC studentship (MAW)Peer reviewedPostprin

The Earliest Phases of Galaxy Evolution

In this paper we study the very early phases of the evolution of our Galaxy by means of a chemical evolution model which reproduces most of the observational constraints in the solar vicinity and in the disk. We have restricted our analysis to the solar neighborhood and present the predicted abundances of several elements (C, N, O, Mg, Si, S, Ca, Fe) over an extended range of metallicities $[Fe/H] = -4.0$ to $[Fe/H] = 0.0$ compared to previous models. We adopted the most recent yield calculations for massive stars taken from different authors (Woosley & Weaver 1995 and Thielemann et al. 1996) and compared the results with a very large sample of data, one of the largest ever used to this purpose. These data have been analysed with a new and powerful statistical method which allows us to quantify the observational spread in measured elemental abundances and obtain a more meaningful comparison with the predictions from our chemical evolution model. Our analysis shows that the ``plateau'' observed for the [$\alpha$/Fe] ratios at low metallicities ($-3.0< [Fe/H] <-1.0$) is not perfectly constant but it shows a slope, especially for oxygen. This slope is very well reproduced by our model with both sets of yields. This is not surprising since realistic chemical evolution models, taking into account in detail stellar lifetimes, never predicted a completely flat plateau. This is due either to the fact that massive stars of different mass produce a slightly different O/Fe ratio or to the often forgotten fact that supernovae of type Ia, originating from white dwarfs, start appearing already at a galactic age of 30 million years and reach their maximum at 1 Gyr.Comment: 32 pages, 9 figures, to be published in Ap

Semi-Classical Wavefunction Perspective to High-Harmonic Generation

We introduce a semi-classical wavefunction (SCWF) model for strong-field physics and attosecond science. When applied to high harmonic generation (HHG), this formalism allows one to show that the natural time-domain separation of the contribution of ionization, propagation and recollisions to the HHG process leads to a frequency-domain factorization of the harmonic yield into these same contributions, for any choice of atomic or molecular potential. We first derive the factorization from the natural expression of the dipole signal in the temporal domain by using a reference system, as in the quantitative rescattering (QRS) formalism [J. Phys. B. 43, 122001 (2010)]. Alternatively, we show how the trajectory component of the SCWF can be used to express the factorization, which also allows one to attribute individual contributions to the spectrum to the underlying trajectories

Magnetic structures of Mn3-xFexSn2: an experimental and theoretical study

We investigate the magnetic structure of Mn3-xFexSn2 using neutron powder diffraction experiments and electronic structure calculations. These alloys crystallize in the orthorhombic Ni3Sn2 type of structure (Pnma) and comprise two inequivalent sites for the transition metal atoms (4c and 8d) and two Sn sites (4c and 4c). The neutron data show that the substituting Fe atoms predominantly occupy the 4c transition metal site and carry a lower magnetic moment than Mn atoms. Four kinds of magnetic structures are encountered as a function of temperature and composition: two simple ferromagnetic structures (with the magnetic moments pointing along the b or c axis) and two canted ferromagnetic arrangements (with the ferromagnetic component pointing along the b or c axis). Electronic structure calculations results agree well with the low-temperature experimental magnetic moments and canting angles throughout the series. Comparisons between collinear and non-collinear computations show that the canted state is stabilized by a band mechanism through the opening of a hybridization gap. Synchrotron powder diffraction experiments on Mn3Sn2 reveal a weak monoclinic distortion at low temperature (90.08 deg at 175 K). This lowering of symmetry could explain the stabilization of the c-axis canted ferromagnetic structure, which mixes two orthorhombic magnetic space groups, a circumstance that would otherwise require unusually large high-order terms in the spin Hamiltonian.Comment: 11 pages, 13 figure

Sulfur reduction in sediments of marine and evaporite environments

Transformations of sulfur in sediments of ponds ranging in salinities from that of normal seawater to those of brines saturated with sodium chloride were examined. The chemistry of the sediment and pore waters were focused on with emphasis on the fate of sulfate reduction. The effects of increasing salinity on both forms of sulfur and microbial activity were determined. A unique set of chemical profiles and sulfate-reducing activity was found for the sediments of each of the sites examined. The quantity of organic matter in the salt pond sediments was significantly greater than that occurring in the adjacent intertidal site. The total quantitative and qualitative distribution of volatile fatty acids was also greater in the salt ponds. Volatile fatty acids increased with salinity