9,723 research outputs found
Exchange-rate effects on China's trade: an interim report
The rising current account deficit in the USA has attracted considerable attention in recent years. We use the "business cycle accounting" methodology to identify the principal distortions that have affected the external accounts of the US. In particular, we measure distortions in the optimality conditions of a simple two-country general equilibrium model using data from the US and the other G7 countries. We then feed these measured distortions into the model individually and use the simulated counterfactual paths of the current account to determine the contribution of each of these "wedges" to the overall external imbalance of the USA. We find that no single wedge in isolation can account closely for the observed current account. However, a combination of productivity differences and deviations from risk-sharing between the US and the rest of the G7 does the best job in accounting for most of the measured movement of the US current account.Foreign exchange rates - China ; Trade ; Econometric models
The effect of ram pressure on the star formation, mass distribution and morphology of galaxies
We investigate the dependence of star formation and the distribution of the
components of galaxies on the strength of ram pressure. Several mock
observations in X-ray, H and HI wavelength for different ram-pressure
scenarios are presented. By applying a combined N-body/hydrodynamic description
(GADGET-2) with radiative cooling and a recipe for star formation and stellar
feedback 12 different ram-pressure stripping scenarios for disc galaxies were
calculated. Special emphasis was put on the gas within the disc and in the
surroundings. All gas particles within the computational domain having the same
mass resolution. The relative velocity was varied from 100 km/s to 1000 km/s in
different surrounding gas densities in the range from to
g/cm. The temperature of the surrounding gas was
initially K. The star formation of a galaxy is enhanced by more
than a magnitude in the simulation with a high ram-pressure (
dyn/cm) in comparison to the same system evolving in isolation. The
enhancement of the star formation depends more on the surrounding gas density
than on the relative velocity. Up to 95% of all newly formed stars can be found
in the wake of the galaxy out to distances of more than 350 kpc behind the
stellar disc. Continuously stars fall back to the old stellar disc, building up
a bulge-like structure. Young stars can be found throughout the stripped wake
with surface densities locally comparable to values in the inner stellar disc.
Ram-pressure stripping can shift the location of star formation from the disc
into the wake on very short timescales. (Abridged)Comment: 19 pages, 25 figures, A&A accepted, high resolution version can be
found at http://astro.uibk.ac.at/~wolfgang/kapferer_rps_galaxies.pd
ATCA observations of the galaxy cluster Abell 3921 - I. Radio emission from the central merging sub-clusters
We present the analysis of our 13 and 22 cm ATCA observations of the central
region of the merging galaxy cluster A3921 (z=0.094). We investigated the
effects of the major merger between two sub-clusters on the star formation (SF)
and radio emission properties of the confirmed cluster members. The origin of
SF and the nature of radio emission in cluster galaxies was investigated by
comparing their radio, optical and X-ray properties. We also compared the radio
source counts and the percentage of detected radio galaxies with literature
data. We detected 17 radio sources above the flux density limit of 0.25
mJy/beam in the central field of A3921, among which 7 are cluster members. 9
galaxies with star-forming optical spectra were observed in the collision
region of the merging sub-clusters. They were not detected at radio
wavelengths, giving upper limits for their star formation rate significantly
lower than those typically found in late-type, field galaxies. Most of these
star-forming objects are therefore really located in the high density part of
the cluster, and they are not infalling field objects seen in projection at the
cluster centre. Their SF episode is probably related to the cluster collision
that we observe in its very central phase. None of the galaxies with
post-starburst optical spectra was detected down our 2 flux density
limit, confirming that they are post-starburst and not dusty star-forming
objects. We finally detected a narrow-angle tail (NAT) source associated with
the second brightest cluster galaxy (BG2), whose diffuse component is a partly
detached pair of tails from an earlier period of activity of the BG2 galaxy.Comment: 17 pages, 9 figures, accepted for publication in A&A, date of
acceptance 29/06/2006. A version of the paper with higher resolution images
can be downloaded at:
http://astro.uibk.ac.at/~c.ferrari/ATCA_Paper/A3921_ATCA.pd
X-ray measured metallicities of the intra-cluster medium: a good measure for the metal mass?
Aims. We investigate whether X-ray observations map heavy elements in the
Intra-Cluster Medium (ICM) well and whether the X-ray observations yield good
estimates for the metal mass, with respect to predictions on transport mech-
anisms of heavy elements from galaxies into the ICM. We further test the
accuracy of simulated metallicity maps. Methods. We extract synthetic X-ray
spectra from N-body/hydrodynamic simulations including metal enrichment pro-
cesses, which we then analyse with the same methods as are applied to
observations. By changing the metal distribution in the simulated galaxy
clusters, we investigate the dependence of the overall metallicity as a
function of the metal distribution. In addition we investigate the difference
of X-ray weighted metal maps produced by simulations and metal maps extracted
from artifcial X-ray spectra, which we calculate with SPEX2.0 and analyse with
XSPEC12.0. Results. The overall metallicity depends strongly on the
distribution of metals within the galaxy cluster. The more inhomogeneously the
metals are distributed within the cluster, the less accurate is the metallicity
as a measure for the true metal mass. The true metal mass is generally
underestimated by X-ray observations. The difference between the X-ray weighted
metal maps and the metal maps from synthetic X-ray spectra is on average less
than 7% in the temperature regime above T > 3E7 K, i.e. X-ray weighted metal
maps can be well used for comparison with observed metal maps. Extracting the
metal mass in the central parts (r < 500 kpc) of galaxy clusters with X-ray
observations results in metal mass underestimates up to a factor of three.Comment: 7 pages, 9 figures, accepted for publication in A&
Submillimeter detection of the Sunyaev -- Zel'dovich effect toward the most luminous X-ray cluster at z=0.45
We report on the detection of the Sunyaev -- Zel'dovich (SZ) signals toward
the most luminous X-ray cluster RXJ1347-1145 at Nobeyama Radio Observatory (21
and 43 GHz) and at James Clerk Maxwell Telescope (350 GHz). In particular the
latter is the first successful detection of the SZ temperature increment in the
submillimeter band which resolved the profile of a cluster of galaxies. Both
the observed spectral dependence and the radial profile of the SZ signals are
fully consistent with those expected from the X-ray observation of the cluster.
The combined analysis of 21GHz and 350GHz data reproduces the temperature and
core-radius of the cluster determined with the ROSAT and ASCA satellites when
we adopt the slope of the density profile from the X-ray observations.
Therefore our present data provide the strongest and most convincing case for
the detection of the submillimeter SZ signal from the cluster, as well as in
the Rayleigh -- Jeans regime. We also discuss briefly the cosmological
implications of the present results.Comment: 11 pages, The Astrophysical Journal (Letters), in pres
Low-T_c Josephson junctions with tailored barrier
Nb/Al_2O_3/Ni_{0.6}Cu_{0.4}/Nb based
superconductor-insulator-ferromagnet-superconductor (SIFS) Josephson tunnel
junctions with a thickness step in the metallic ferromagnetic
\Ni_{0.6}\Cu_{0.4} interlayer were fabricated. The step was defined by optical
lithography and controlled etching. The step height is on the scale of a few
angstroms. Experimentally determined junction parameters by current-voltage
characteristics and Fraunhofer pattern indicate an uniform F-layer thickness
and the same interface transparencies for etched and non-etched F-layers. This
technique could be used to tailor low-T_c Josephson junctions having controlled
critical current densities at defined parts of the junction area, as needed for
tunable resonators, magnetic-field driven electronics or phase modulated
devices.Comment: 6 pages, 6 figures, small changes, to be published by JA
Towards a Manitoba Hydro boreal woodland caribou strategy: Outcomes from Manitoba Hydro boreal woodland caribou workshop
Manitoba Hydro is responsible for the continued supply of energy to meet the needs of the province and is committed to protecting the environment when planning the construction and operation of its facilities. Corporate policy dictates ongoing improvement of Environmental Management Systems (EMS) in order to meet or surpass regulatory requirements. Environmental objectives are reviewed annually and programs are modified when necessary to address improvements in environmental performance. Manitoba Hydro plans and constructs major transmission projects throughout northern Manitoba which includes areas occupied by boreal woodland caribou. In recognition of the potential issues associated with hydro transmission construction in boreal caribou range, Manitoba Hydro hosted an expert workshop on May 8, 2007 to provide objective advice in the development of a draft corporate strategy that effectively directs targeted monitoring and research for environmental assessment and mitigation. The workshop focused on assessing the potential threats to boreal woodland caribou from a transmission line construction and operation perspective, and identifying appropriate approaches in site selection and environmental assessment (SSEA) and long-term monitoring and research. A total of nine threat categories were reviewed to determine the degree and magnitude of potential effects that may result from transmission construction and operation; and of the original nine, five final threat categories were delineated. The main elements of the workshop provided strategic approaches for proactive pre-construction monitoring, research on recruitment and mortality for local populations impacted by ROWs and control areas, and various habitat monitoring, management, and mitigation techniques. Research and monitoring priorities have been identified and continued collaboration with Manitoba Conservation and other land users were also identified
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