903 research outputs found
Synthesis report with pro-poor trade research findings and policy recommandations
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.
Petropolitics
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
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
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
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 erg/s within a 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 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
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
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 -- or the --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
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
(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 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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