4,401 research outputs found
The morphology of the Milky Way - II. Reconstructing CO maps from disc galaxies with live stellar distributions
The arm structure of the Milky Way remains somewhat of an unknown, with
observational studies hindered by our location within the Galactic disc. In the
work presented here we use smoothed particle hydrodynamics (SPH) and radiative
transfer to create synthetic longitude-velocity observations. Our aim is to
reverse-engineer a top down map of the Galaxy by comparing synthetic
longitude-velocity maps to those observed. We set up a system of N-body
particles to represent the disc and bulge, allowing for dynamic creation of
spiral features. Interstellar gas, and the molecular content, is evolved
alongside the stellar system. A 3D-radiative transfer code is then used to
compare the models to observational data. The resulting models display arm
features that are a good reproduction of many of the observed emission
structures of the Milky Way. These arms however are dynamic and transient,
allowing for a wide range of morphologies not possible with standard density
wave theory. The best fitting models are a much better match than previous work
using fixed potentials. They favour a 4-armed model with a pitch angle of
approximately 20 degrees, though with a pattern speed that decreases with
increasing Galactic radius. Inner bars are lacking however, which appear
required to fully reproduce the central molecular zone.Comment: 16 pages, 15 figures, accepted by MNRA
Application of a Justice as Fairness Perspective to Laws Banning Same-Sex Marriage
This paper utilizes John Rawlsā theory of Justice as Fairness to assess laws banning same-sex marriage. It is argued that such laws are unjust from this perspective in that they do serve to disadvantage homosexuals in regards to the legal benefits of marriage. In addition, legal unions (i.e. domestic partnerships or civil unions) that stop short of marriage do not compensate for this unjustness in that they do not offer the same legal benefits of marriage
A comparison of risks from New Jersey chemical facilities and the benefits of risk communication
The purpose of this study is to determine if the amount of toxic chemicals a facility stores on-site is a valid indicator for determining a facility\u27s risk potential and need to communicate risk information to the public. This study analyzes New Jersey chemical facilities regulated under the CAA\u27s Risk Management Plan (section 112(r)) and their toxic chemical releases and other risk factors to determine if there is a relationship between the amount of toxic chemicals stored on-site and the potential risk from a toxic release. The analysis of data suggests that no relationship exists; therefore, one could assume that all local communities are at risk and could benefit from risk communications programs.
A limited number of interviews were conducted with owner/operators of facilities not required to communicate risk information. The interviews suggest that these owner/operators do not communicate risk voluntarily. One of the main reasons is because they do not identify their facilities\u27 as posing a risk to the surrounding communities
Diagrammatic perturbation theory and the pseudogap
We study a model of quasiparticles on a two-dimensional square lattice
coupled to Gaussian distributed dynamical fields. The model describes
quasiparticles coupled to spin or charge fluctuations and is solved by a Monte
Carlo sampling of the molecular field distributions. The non-perturbative
solution is compared to various approximations based on diagrammatic
perturbation theory. When the molecular field correlations are sufficiently
weak, the diagrammatic calculations capture the qualitative aspects of the
quasiparticle spectrum. For a range of model parameters near the magnetic
boundary, we find that the quasiparticle spectrum is qualitatively different
from that of a Fermi liquid in that it shows a double peak structure, and that
the diagrammatic approximations we consider fail to reproduce, even
qualitatively, the results of the Monte Carlo calculations. This suggests that
the pseudogap induced by a coupling to antiferromagnetic fluctuations and the
spin-splitting of the quasiparticle peak induced by a coupling to ferromagnetic
spin-fluctuations lie beyond diagrammatic perturbation theory
Pore geometry as a control on rock strength
This study was funded via RJW's University of Leicester start-up fund, as part of AAB's PhD project. We thank Don Swanson and Mike Poland at HVO, Hawai'i, for their help and advice during fieldwork planning and sample collection in the Koa'e fault system, and the National Park Service for granting a research permit to collect rock samples. Sergio Vinciguerra is thanked for access to the Rock Mechanics and Physics lab at the British Geological Survey and Audrey Ougier-Simonin is thanked for her help preparing samples and advice during testing. We thank Mike Heap (EOST Strasbourg) and an anonymous reviewer for their detailed and careful comments that greatly improved the manuscript.Peer reviewedPostprin
Critical velocity ionisation in substellar atmospheres
The observation of radio, X-ray and HĪ± emission from substellar objects indicates the presence of plasma regions and associated high-energy processes in their surrounding envelopes.Ā This paper numerically simulates and characterises Critical Velocity Ionisation, a potential ionisation process, that can efficiently generate plasma as a result of neutral gas flows interacting with seed magnetized plasmas. By coupling a Gas-MHD interactions code (to simulate the ionisation mechanism) with a substellar global circulation model (to provide the required gas flows) we quantify the spatial extent of the resulting plasma regions, their degree of ionisation and their lifetime for a typical substellar atmosphere. It is found that the typical average ionisation fraction reached at equilibrium (where the ionisation and recombination rates are equal and opposite) ranges from 10-5 to 10-8, at pressures between 10-1 and 10-3 bar, with a trend of increasing ionisation fraction with decreasing atmospheric pressure. The ionisation fractions reached as a result of Critical Velocity Ionisation are sufficient to allow magnetic fields to couple to gas flows in the atmosphere
A technique for automatic real time scoring of several simultaneous sleep electroencephalograms
Automatic real-time scoring of simultaneous sleep electroencephalogram
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