903 research outputs found

    Synthesis report with pro-poor trade research findings and policy recommandations

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    The purpose of the project was to investigate international trade in fisheries products and its relationship to poverty alleviation and livelihoods of poor aquatic resource users in developing countries in Asia, and to identify options to improve the effectiveness of poverty reduction through international seafood trade. The project directly addressed the EC-PREP priority area of trade and development, and indirectly provided valuable insight to two other priority areas: food security and sustainable rural development; and institutional capacity building. [PDF contains 60 pages.

    Background paper on the international seafood trade and poverty

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    (121 p.

    Petropolitics

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    The importance of energy to the functioning of any economy has meant that energy industries are amongst the most regulated of industries. What might appear to be purely private decisions are made within a complex and evolving web of government regulations. Petropolitics: Petroleum Development, Markets and Regulations, Alberta as an Illustrative History provides an economic history of the petroleum industry in Alberta as well as a detailed analysis of the operation of the markets for Alberta oil and natural gas, and the main governmental regulations (apart from environmental regulations) faced by the industry. The tools used within this study are applicable to oil and gas industries throughout the world. Winner, 2014 Book of the Year, Petroleum History Societ

    Cosmic rays from trans-relativistic supernovae

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    We derive constraints that must be satisfied by the sources of ~10^{15} to ~10^{18} eV cosmic rays, under the assumption that the sources are Galactic. We show that while these constraints are not satisfied by ordinary supernovae (SNe), which are believed to be the sources of <10^{15} eV cosmic rays, they may be satisfied by the recently discovered class of trans-relativistic supernovae (TRSNe), which were observed in association with gamma-ray bursts. We define TRSNe as SNe that deposit a large fraction, f_R>10^{-2}, of their kinetic energy in mildly relativistic, \gamma\beta>1, ejecta. The high velocity ejecta enable particle acceleration to ~10^{18} eV, and the large value of f_R (compared to f_R~10^{-7} for ordinary SNe) ensures that if TRSNe produce the observed ~10^{18} eV cosmic ray flux, they do not overproduce the flux at lower energies. This, combined with the estimated rate and energy production of TRSNe, imply that Galactic TRSNe may be the sources of cosmic rays with energies up to ~10^{18}eV .Comment: Accepted to ApJ. Expanded abstract, introduction, discussio

    Petropolitics

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    The importance of energy to the functioning of any economy has meant that energy industries are amongst the most regulated of industries. What might appear to be purely private decisions are made within a complex and evolving web of government regulations. Petropolitics: Petroleum Development, Markets and Regulations, Alberta as an Illustrative History provides an economic history of the petroleum industry in Alberta as well as a detailed analysis of the operation of the markets for Alberta oil and natural gas, and the main governmental regulations (apart from environmental regulations) faced by the industry. The tools used within this study are applicable to oil and gas industries throughout the world. Winner, 2014 Book of the Year, Petroleum History Societ

    Relativistic Jets from Collapsars

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    We have studied the relativistic beamed outflow proposed to occur in the collapsar model of gamma-ray bursts. A jet forms as a consequence of an assumed energy deposition of ∌1050−1051\sim 10^{50}- 10^{51} erg/s within a 30∘30^{\circ} cone around the rotation axis of the progenitor star. The generated jet flow is strongly beamed (\la few degrees) and reaches the surface of the stellar progenitor (r ≈31010\approx 3 10^{10} cm) intact. At break-out the maximum Lorentz factor of the jet flow is about 33. Simulations have been performed with the GENESIS multi-dimensional relativistic hydrodynamic code.Comment: 6 pages, 2 figures, to appear in the proceedings of the conference "Godunov methods: theory and applications", Oxford, October 199

    Infrared afterglow of GRB041219 as a result of reradiation on dust in a circumstellar cloud

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    Observations of gamma ray bursts (GRB) afterglows in different spectral bands provide a most valuable information about their nature, as well as about properties of surrounding medium. Powerful infrared afterglow was observed from the strong GRB041219. Here we explain the observed IR afterglow in the model of a dust reradiation of the main GRB signal in the envelope surrounding the GRB source. In this model we do not expect appearance of the prompt optical emission which should be absorbed in the dust envelope. We estimate the collimation angle of the gamma ray emission, and obtain restrictions on the redshift (distance to GRB source), by fitting the model parameters to the observational data.Comment: 6 pages, 2 figures, Submited to Astrofizik

    Stellar evolution with rotation and magnetic fields II: General equations for the transport by Tayler--Spruit dynamo

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    We further develop the Tayler--Spruit dynamo theory, based on the most efficient instability for generating magnetic fields in radiative layers of differentially rotating stars. We avoid the simplifying assumptions that either the Ό\mu-- or the TT--gradient dominates, but we treat the general case and we also account for the nonadiabatic effects, which favour the growth of the magnetic field. Stars with a magnetic field rotate almost as a solid body. Several of their properties (size of the core, MS lifetimes, tracks, abundances) are closer to those of models without rotation than with rotation only. In particular, the observed N/C or N/H excesses in OB stars are better explained by our previous models with rotation only than by the present models with magnetic fields that predict no nitrogen excesses. We show that there is a complex feedback loop between the magnetic instability and the thermal instability driving meridional circulation. This opens the possibility for further magnetic models, but at this stage we do not know the relative importance of the magnetic fields due to the Tayler instability in stellar interiors.Comment: 14 pages, 11 figures, accepted for publication in Astronomy and Astrophysic

    Nucleosynthesis of Nickel-56 from Gamma-Ray Burst Accretion Disks

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    We examine the prospects for producing Nickel-56 from black hole accretion disks, by examining a range of steady state disk models. We focus on relatively slowly accreting disks in the range of 0.05 - 1 solar masses per second, as are thought to be appropriate for the central engines of long-duration gamma-ray bursts. We find that significant amounts of Nickel-56 are produced over a wide range of parameter space. We discuss the influence of entropy, outflow timescale and initial disk position on mass fraction of Nickel-56 which is produced. We keep careful track of the weak interactions to ensure reliable calculations of the electron fraction, and discuss the role of the neutrinos.Comment: 10 pages, 9 figure

    Hyperaccreting Disks around Magnetars for Gamma-Ray Bursts: Effects of Strong Magnetic Fields

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    (Abridged) The hyperaccreting neutron star or magnetar disks cooled via neutrino emission can be a candidate of gamma-ray burst (GRB) central engines. The strong field ≄1015−1016\geq10^{15}-10^{16} G of the magnetar can play a significant role in affecting the disk properties and even lead to the funnel accretion process. We investigate the effects of strong fields on the disks around magnetars, and discuss implications of such accreting magnetar systems for GRB and GRB-like events. We discuss quantum effects of the strong fields on the disk, and use the MHD conservation equations to describe the behavior of the disk flow coupled with a large scale field, which is generated by the star-disk interaction. In general, stronger fields give higher disk densities, pressures, temperatures and neutrino luminosity, and change the electron fraction and degeneracy state significantly. A magnetized disk is always viscously stable outside the Alfv\'{e}n radius, but will be thermally unstable near the Alfv\'{e}n radius where the magnetic field plays a more important role in transferring the angular momentum and heating the disk than the viscous stress. The funnel accretion process will be only important for an extremely strong field, which creates a magnetosphere inside the Alfv\'{e}n radius and truncates the plane disk. Because of higher temperature and more concentrated neutrino emission of the magnetar surface ring-like belt region covered by funnel accretion, the neutrino annihilation rate from the accreting magnetars can be much higher than that from accreting neutron stars without fields. Furthermore, the neutrino annihilation mechanism and the magnetically-driven pulsar wind from the magnetar surface can work together to generate and feed an ultra-relativistic jet along the stellar magnetic poles.Comment: 62 pages, 14 figures, 4 tables, improved version following the referee's comments, accepted for publication in Ap
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