4,275 research outputs found
Effective competition in telecommunications, rail and energy markets
The markets for network-based products and services pose particular problems with regard to competition. The transition from monopolistic to competitive structures and the issues of infrastructure sharing, dominant players and network externalities have all been subject to intensive debates. Despite liberalisation, deregulation and privatisation - and the quasiautomatic solutions they seemed to present - a number of problems persist. Furthermore, the regulation which was introduced as a remedy for distortions of competition during the period of transition from monopoly to competition has not ended with market liberalisation. Each new generation of network technologies creates new challenges to be addressed by regulators and competition authorities, and each industry presents specific problems. The following article discuss a number of the persisting and new questions concerning competition in selected network-based industries
Physico-chemical spectroscopic mapping of the planetary nebula NGC 40 and the 2D_NEB, a new 2D algorithm to study ionised nebulae
In this paper we present an analysis of the physical and chemical conditions
of the planetary nebula NGC 40 through spatially-resolved spectroscopic maps.
We also introduce a new algorithm --2D_NEB-- based on the well-established IRAF
nebular package, which was developed to enable the use of the spectroscopic
maps to easily estimate the astrophysical quantities of ionised nebulae. The
2D_NEB was benchmarked, and we clearly show that it works properly, since it
compares nicely with the IRAF nebular software.
Using this software, we derive the maps of several physical parameters of NGC
40. From these maps, we conclude that Te[NII] shows only a slight temperature
variation from region to region, with its values constrained between ~8,000 K
and ~9,500 K. Electron densities, on the other hand, have a much more prominent
spatial variation, as Ne[SII] values vary from ~1,000 cm^(-3) to ~3,000
cm^(-3). Maps of the chemical abundances also show significant variations. From
the big picture of our work, we strongly suggest that analysis with spatial
resolution be mandatory for more complete study of the physical and chemical
properties of planetary nebulae.Comment: 15 pages, 10 figures, 8 tables; Accepted for publication in MNRA
The Disk and Dark Halo Mass of the Barred Galaxy NGC 4123. I. Observations
The non-circular streaming motions in barred galaxies are sensitive to the
mass of the bar and can be used to lift the degeneracy between disk and dark
matter halo encountered when fitting axisymmetric rotation curves of disk
galaxies. In this paper, we present photometric and kinematic observations of
NGC 4123, a barred galaxy of modest size (V_rot = 130 km/sec, L = 0.7 L_*),
which reveal strong non-circular motions. The bar has straight dust lanes and
an inner Lindblad resonance. The disk of NGC 4123 has no sign of truncation out
to 10 scale lengths, and star-forming regions are found well outside R_25. A
Fabry-Perot H-alpha velocity field shows velocity jumps of >100 km/sec at the
location of the dust lanes within the bar, indicating shocks in the gas flow.
VLA observations yield the velocity field of the H I disk. Axisymmetric mass
models yield good fits to the rotation curve outside the bar regionfor disk
I-band M/L of 2.25 or less, and dark halos with either isothermal or power-law
profiles can fit the data well. In a companion paper, we model the full 2-D
velocity field, including non-circular motions, to determine the stellar M/L
and the mass of the dark halo.Comment: accepted by ApJ, 16 pages, 9 figures (1 color), uses emulateapj.sty,
onecolfloat.st
Kinematics of the outer pseudorings and the spiral structure of the Galaxy
The kinematics of the outer rings and pseudorings is determined by two
processes: the resonance tuning and the gas outflow. The resonance kinematics
is clearly observed in the pure rings, while the kinematics of the gas outflow
is manifested itself in the pseudorings. The direction of systematical motions
in the pure rings depends on the position angle of a point with respect to the
bar major axis and on the class of the outer ring. The direction of the radial
and azimuthal components of the residual velocities of young stars in the
Perseus, Carina, and Sagittarius regions can be explained by the presence of
the outer pseudoring of class R1R2' in the Galaxy. We present models, which
reproduce the directions and values of the residual velocities of
OB-associations in the Perseus and Sagittarius regions, and also model
reproducing the directions of the residual velocities in the Perseus,
Sagittarius, and Carina regions. The kinematics of the Sagittarius region
accurately defines the solar position angle with respect to the bar elongation,
theta_b=45 (+/-5) deg.Comment: 16 pages, 10 figures, accepted for publication in Astronomy Letter
Financial phantasmagoria: corporate image-work in times of crisis
Our purpose in this article is to relate the real movements in the economy during 2008 to the ?image-work? of financial institutions. Over the period January?December 2008 we collected 241 separate advertisements from 61 financial institutions published in the Financial Times. Reading across the ensemble of advertisements for themes and evocative images provides an impression of the financial imaginaries created by these organizations as the global financial crisis unfolded. In using the term ?phantasmagoria? we move beyond its colloquial sense of a set of strange images designed to dazzle towards the more technical connotation used by Ranci�re (2004) who suggested that words and images can offer a trace of an overall determining set-up if they are torn from their obviousness so they become phantasmagoric figures. The key phantasmagoric figure we identify here is that of the financial institution as timeless, immortal and unchanging; a coherent and autonomous entity amongst other actors. This notion of uniqueness belies the commonality of thinking which precipitated the global financial crisis as well as the limited capacity for control of financial institutions in relation to market events. It also functions as a powerful naturalizing force, making it hard to question certain aspects of the recent period of ?capitalism in crisis?
Three-dimensional chemically homogeneous and bi-abundance photoionization models of the "super-metal-rich" planetary nebula NGC 6153
Deep spectroscopy of the planetary nebula (PN) NGC\,6153 shows that its heavy
element abundances derived from optical recombination lines (ORLs) are ten
times higher than those derived from collisionally excited lines (CELs), and
points to the existence of H-deficient inclusions embedded in the diffuse
nebula. In this study, we have constructed chemically homogeneous and
bi-abundance three-dimensional photoionization models, using the Monte Carlo
photoionization code {\sc mocassin}. We attempt to reproduce the multi-waveband
spectroscopic and imaging observations of NGC\,6153, and investigate the nature
and origin of the postulated H-deficient inclusions, as well as their impacts
on the empirical nebular analyses assuming a uniform chemical composition. Our
results show that chemically homogeneous models yield small electron
temperature fluctuations and fail to reproduce the strengths of ORLs from C, N,
O and Ne ions. In contrast, bi-abundance models incorporating a small amount of
metal-rich inclusions ( per cent of the total nebular mass) are able
to match all the observations within the measurement uncertainties. The
metal-rich clumps, cooled down to a very low temperature (~K) by
ionic infrared fine-structure lines, dominate the emission of heavy element
ORLs, but contribute almost nil to the emission of most CELs. We find that the
abundances of C, N, O and Ne derived empirically from CELs, assuming a uniform
chemical composition, are about 30 per cent lower than the corresponding
average values of the whole nebula, including the contribution from the
H-deficient inclusions. Ironically, in the presence of H-deficient inclusions,
the traditional standard analysis of the optical helium recombination lines,
assuming a chemically homogeneous nebula, overestimates the helium abundance by
40 per cent.Comment: 19 pages, 18 figures, accepted for publication in MNRA
Climate-informed stochastic hydrological modeling: Incorporating decadal-scale variability using paleo data
A hierarchical framework for incorporating modes of climate variability into stochastic simulations of hydrological data is developed, termed the climate-informed multi-time scale stochastic (CIMSS) framework. A case study on two catchments in eastern Australia illustrates this framework. To develop an identifiable model characterizing long-term variability for the first level of the hierarchy, paleoclimate proxies, and instrumental indices describing the Interdecadal Pacific Oscillation (IPO) and the Pacific Decadal Oscillation (PDO) are analyzed. A new paleo IPO-PDO time series dating back 440 yr is produced, combining seven IPO-PDO paleo sources using an objective smoothing procedure to fit low-pass filters to individual records. The paleo data analysis indicates that wet/dry IPO-PDO states have a broad range of run lengths, with 90% between 3 and 33 yr and a mean of 15 yr. The Markov chain model, previously used to simulate oscillating wet/dry climate states, is found to underestimate the probability of wet/dry periods >5 yr, and is rejected in favor of a gamma distribution for simulating the run lengths of the wet/dry IPO-PDO states. For the second level of the hierarchy, a seasonal rainfall model is conditioned on the simulated IPO-PDO state. The model is able to replicate observed statistics such as seasonal and multiyear accumulated rainfall distributions and interannual autocorrelations. Mean seasonal rainfall in the IPO-PDO dry states is found to be 15%-28% lower than the wet state at the case study sites. In comparison, an annual lag-one autoregressive model is unable to adequately capture the observed rainfall distribution within separate IPO-PDO states. Copyright © 2011 by the American Geophysical Union.Benjamin J. Henley, Mark A. Thyer, George Kuczera and Stewart W. Frank
Climate-informed stochastic hydrological modeling: Incorporating decadal-scale variability using paleo data
A hierarchical framework for incorporating modes of climate variability into stochastic simulations of hydrological data is developed, termed the climate-informed multi-time scale stochastic (CIMSS) framework. A case study on two catchments in eastern Australia illustrates this framework. To develop an identifiable model characterizing long-term variability for the first level of the hierarchy, paleoclimate proxies, and instrumental indices describing the Interdecadal Pacific Oscillation (IPO) and the Pacific Decadal Oscillation (PDO) are analyzed. A new paleo IPO-PDO time series dating back 440 yr is produced, combining seven IPO-PDO paleo sources using an objective smoothing procedure to fit low-pass filters to individual records. The paleo data analysis indicates that wet/dry IPO-PDO states have a broad range of run lengths, with 90% between 3 and 33 yr and a mean of 15 yr. The Markov chain model, previously used to simulate oscillating wet/dry climate states, is found to underestimate the probability of wet/dry periods >5 yr, and is rejected in favor of a gamma distribution for simulating the run lengths of the wet/dry IPO-PDO states. For the second level of the hierarchy, a seasonal rainfall model is conditioned on the simulated IPO-PDO state. The model is able to replicate observed statistics such as seasonal and multiyear accumulated rainfall distributions and interannual autocorrelations. Mean seasonal rainfall in the IPO-PDO dry states is found to be 15%-28% lower than the wet state at the case study sites. In comparison, an annual lag-one autoregressive model is unable to adequately capture the observed rainfall distribution within separate IPO-PDO states. Copyright © 2011 by the American Geophysical Union.Benjamin J. Henley, Mark A. Thyer, George Kuczera and Stewart W. Frank
Evolutionary distances in the twilight zone -- a rational kernel approach
Phylogenetic tree reconstruction is traditionally based on multiple sequence
alignments (MSAs) and heavily depends on the validity of this information
bottleneck. With increasing sequence divergence, the quality of MSAs decays
quickly. Alignment-free methods, on the other hand, are based on abstract
string comparisons and avoid potential alignment problems. However, in general
they are not biologically motivated and ignore our knowledge about the
evolution of sequences. Thus, it is still a major open question how to define
an evolutionary distance metric between divergent sequences that makes use of
indel information and known substitution models without the need for a multiple
alignment. Here we propose a new evolutionary distance metric to close this
gap. It uses finite-state transducers to create a biologically motivated
similarity score which models substitutions and indels, and does not depend on
a multiple sequence alignment. The sequence similarity score is defined in
analogy to pairwise alignments and additionally has the positive semi-definite
property. We describe its derivation and show in simulation studies and
real-world examples that it is more accurate in reconstructing phylogenies than
competing methods. The result is a new and accurate way of determining
evolutionary distances in and beyond the twilight zone of sequence alignments
that is suitable for large datasets.Comment: to appear in PLoS ON
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