6,112 research outputs found
A Theory of Dynamic Tariff and Quota Retaliation
This paper characterizes, under the most general conditions to date, the steady-state equilibria of a symmetric, two-country trade model in which countries move in alternating-move, dynamic either tariffsetting or quota-setting games in Markov Perfect strategies, and compares the respective equilibrium level of tariffs and quotas with the corresponding pairs in the equilibria of static games. Our results imply that the alleged non-equivalence of the outcomes of tariff-retaliation (neither free trade nor autarky) and quota-retaliation (asymptotic autarky) games in the literature depends crucially on complete myopia, and can be dismissed altogether once dynamic considerations are introduced in an operationally significant manner.Foreign trade policy; Tariff; Quota; Retaliation; Dynamic Game; Markov perfect equilibrium; Supermodular games
Probing the Low Surface Brightness Dwarf Galaxy Population of the Virgo Cluster
We have used public data from the Next Generation Virgo Survey (NGVS) to
investigate the dwarf galaxy population of the Virgo cluster beyond what has
previously been discovered. We initially mask and smooth the data, and then use
the object detection algorithm Sextractor to make our initial dwarf galaxy
selection. All candidates are then visually inspected to remove artefacts and
duplicates. We derive Sextractor parameters to best select low surface
brightness galaxies using g band central surface brightness values of 22.5 to
26.0 mag sq arc sec and exponential scale lengths of 3.0 - 10.0 arc sec to
identify 443 cluster dwarf galaxies - 303 of which are new detections. These
new detections have a surface density that decreases with radius from the
cluster centre. We also apply our selection algorithm to 'background',
non-cluster, fields and find zero detections. In combination, this leads us to
believe that we have isolated a cluster dwarf galaxy population. The range of
objects we are able to detect is limited because smaller scale sized galaxies
are confused with the background, while larger galaxies are split into numerous
smaller objects by the detection algorithm. Using data from previous surveys
combined with our data, we find a faint end slope to the luminosity function of
-1.35+/-0.03, which does not significantly differ to what has previously been
found for the Virgo cluster, but is a little steeper than the slope for field
galaxies. There is no evidence for a faint end slope steep enough to correspond
with galaxy formation models, unless those models invoke either strong feedback
processes or use warm dark matter.Comment: Accepted for publication in MNRA
A Theory of Dynamic Tariff and Quota Retaliation
This paper characterizes, under the most general conditions to date, the steady-state equilibria of a symmetric, two-country trade model in which countries move in alternating-move, dynamic either tariffsetting or quota-setting games in Markov Perfect strategies, and compares the respective equilibrium level of tariffs and quotas with the corresponding pairs in the equilibria of static games. Our results imply that the alleged non-equivalence of the outcomes of tariff-retaliation (neither free trade nor autarky) and quota-retaliation (asymptotic autarky) games in the literature depends crucially on complete myopia, and can be dismissed altogether once dynamic considerations are introduced in an operationally significant manner
Building research capacity in a practitioner network: the National Action Research Network on researching and evaluating Personal Development Plannin
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The HERE project toolkit: a resource for programme teams interested in improving student engagement and retention
Radiative hydrodynamic modelling and observations of the X-class solar flare on 2011 March 9
We investigated the response of the solar atmosphere to non-thermal electron
beam heating using the radiative transfer and hydrodynamics modelling code
RADYN. The temporal evolution of the parameters that describe the non-thermal
electron energy distribution were derived from hard X-ray observations of a
particular flare, and we compared the modelled and observed parameters. The
evolution of the non-thermal electron beam parameters during the X1.5 solar
flare on 2011 March 9 were obtained from analysis of RHESSI X-ray spectra. The
RADYN flare model was allowed to evolve for 110 seconds, after which the
electron beam heating was ended, and was then allowed to continue evolving for
a further 300s. The modelled flare parameters were compared to the observed
parameters determined from extreme-ultraviolet spectroscopy. The model produced
a hotter and denser flare loop than that observed and also cooled more rapidly,
suggesting that additional energy input in the decay phase of the flare is
required. In the explosive evaporation phase a region of high-density cool
material propagated upward through the corona. This material underwent a rapid
increase in temperature as it was unable to radiate away all of the energy
deposited across it by the non-thermal electron beam and via thermal
conduction. A narrow and high-density ( cm) region at
the base of the flare transition region was the source of optical line emission
in the model atmosphere. The collision-stopping depth of electrons was
calculated throughout the evolution of the flare, and it was found that the
compression of the lower atmosphere may permit electrons to penetrate farther
into a flaring atmosphere compared to a quiet Sun atmosphere.Comment: 12 pages, 12 figure
The Interstellar N/O Abundance Ratio: Evidence for Local Infall?
Sensitive measurements of the interstellar gas-phase oxygen abundance have
revealed a slight oxygen deficiency ( 15%) toward stars within 500 pc of
the Sun as compared to more distant sightlines. Recent observations of
the interstellar gas-phase nitrogen abundance indicate larger variations, but
no trends with distance were reported due to the significant measurement
uncertainties for many sightlines. By considering only the highest quality
( 5 ) N/O abundance measurements, we find an intriguing trend in
the interstellar N/O ratio with distance. Toward the seven stars within
500 pc of the Sun, the weighted mean N/O ratio is 0.217 0.011, while for
the six stars further away the weighted mean value (N/O = 0.142 0.008) is
curiously consistent with the current Solar value (N/O =
0.138). It is difficult to imagine a scenario invoking
environmental (e.g., dust depletion, ionization, etc.) variations alone that
explains this abundance anomaly. Is the enhanced nitrogen abundance localized
to the Solar neighborhood or evidence of a more widespread phenomenon? If it is
localized, then recent infall of low metallicity gas in the Solar neighborhood
may be the best explanation. Otherwise, the N/O variations may be best
explained by large-scale differences in the interstellar mixing processes for
AGB stars and Type II supernovae.Comment: accepted for publication in the Astrophysical Journal Letter
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