226,308 research outputs found
Extending the automated zoning procedure to reconcile incompatible zoning systems
This paper concerns the problem of matching incompatible zonal geographies, for example in the context of comparing census outputs over time. The automated zoning procedure (AZP) proposed by Openshaw (1977) is reviewed and extended to permit its application to the intersection of two zonal systems. A population stress statistic is proposed which may be used in the extended AZP algorithm in order to maximise the match between two zonal geographies. An implementation of this approach is described, and illustrated by reference to UK Census dat
The GALEX Extended Mission: Surveying UV Tracers of the Hidden Side of Galaxy Evolution
The Galaxy Evolution Explorer (GALEX) continues its surveys of the ultraviolet sky. GALEX surveys have supported the following galaxy evolution investigations: calibrating UV as a star formation rate tracer, using wide and deep surveys to measure star formation history, studying the evolution of dust extinction and metallicity, selecting and analyzing galaxies in transitory states, finding local analogs to Lyman Break Galaxies, probing and time-dating star formation in a wide variety of physical regimes. Our continuing mission is focussed on relating star formation history and galaxy evolution paths to the properties of dark matter halos and their assembly history, and on beginning to relate the evolution of galaxies to that of black holes and the intergalactic medium. GALEX has proven that the UV is an ideal band to find and map star formation in low mass, low density objects, and potentially in primordial gas. With future UV missions it may be possible to map emission from the intergalactic and circum-galactic medium, and make a definitive connection between galaxy evolution and the cooling, accretion, heating, and enrichment of gas in the cosmic web
Effect of the Magellanic Clouds on the Milky Way disk and VICE VERSA
The satellite-disk interaction provides limits on halo properties in two
ways: (1) physical arguments motivate the excitation of observable Galactic
disk structure in the presence of a massive halo, although precise limits on
halo parameters are scenario-dependent; (2) conversely, the Milky Way as a
whole has significant dynamical effect on LMC structure and this interaction
also leads to halo limits. Together, these scenarios give strong corroboration
of our current gravitational mass estimates and suggests a rapidly evolving
LMC.Comment: 12 pages, 8 Postscript figures, uses paspconf.sty. To appear in the
Third Stromlo Symposium: The Galactic Halo (ASP Conference Series), in press.
HTML version available at: http://www-astro.phast.umass.edu/~weinberg/stroml
Kinematic Signature of a Rotating Bar Near a Resonance
There have been several recent suggestions that the Milky Way has rotating
bar-like features based on HI and star count data. In this paper, I show that
such features cause distinctive stellar kinematic signatures near OLR and ILR.
The effects of these resonances may be observable far from the peak density of
the pattern and relatively nearby the solar position. The details of the
kinematic signatures depend on the evolutionary history of the `bar' and
therefore velocity data, both systemic and velocity dispersion, may be used to
probe the evolutionary history as well as the present state of the Galaxy.
Kinematic models for a variety of simple scenarios are presented. Models with
evolving pattern speeds show significantly stronger dispersion signatures than
those with static pattern speeds, suggesting that useful observational
constraints are possible. The models are applied to the proposed rotating
spheroid and bar models; we find: 1) none of these models chosen to represent
the proposed large-scale rotating spheroid are consistent with the stellar
kinematics; and 2) a Galactic bar with semimajor axis of 3\kpc will cause a
large increase in velocity dispersion in the vicinity of OLR (\sim5\kpc) with
little change in the net radial motion and such a signature is suggested by
K-giant velocity data. Potential future observations and analyses are
discussed.Comment: 24 pages, AAS LaTeX macros v3.0, 23 figures (available on request
Summary Talk: First Workshop on Forward Physics and Luminosity Determination at the LHC
An attempt is made to summarize the discussion at the Workshop, except for
the panel discussion on the ability of the LHC detectors to accommodate forward
reactions. The Workshop focused on two main topics. The first topic was forward
physics at the LHC. Predictions were made for forward reactions, including
elastic scattering and soft diffractive processes, intopic was forward physics
at the LHC. Predictions were made for forward reactions, including elastic
scattering and soft diffractive processes, in terms of (multi) Pomeron
exchange, using knowledge gained at lower energies. The survival probability of
rapidity gaps accompanying hard subprocesses was studied. The nature of the
Pomeron, before and after QCD, was exposed, and some aspects of small x physics
at the LHC were considered. The second topic of the Workshop concerned the
accuracy of the luminosity measuring processes at the LHC. Attention
concentrated on three methods. The classic approach based on the optical
theorem, secondly, the observation of the pure QED process of lepton-pair
(l^+l^-) production by photon-photon fusion and, finally, the measurement of
inclusive W and Z production.Comment: 21 pages,10 figures, LaTeX, Workshop at Helsinki, 31 October - 3
November, 200
Pretreatment prognostic value of dynamic contrast-enhanced magnetic resonance imaging vascular, texture, shape, and size parameters compared with traditional survival indicators obtained from locally advanced breast cancer patients
Objectives: The aim of this study was to determine if associations exist between pretreatment dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI)-based metrics (vascular kinetics, texture, shape, size) and survival intervals. Furthermore, the aim of this study was to compare the prognostic value of DCE-MRI parameters against traditional pretreatment survival indicators. Materials and Methods: A retrospective study was undertaken. Approval had previously been granted for the retrospective use of such data, and the need for informed consent was waived. Prognostic value of pretreatment DCE-MRI parameters and clinical data was assessed via Cox proportional hazards models. The variables retained by the final overall survival Cox proportional hazards model were utilized to stratify risk of death within 5 years. Results: One hundred twelve subjects were entered into the analysis. Regarding disease-free survival-negative estrogen receptor status, T3 or higher clinical tumor stage, large ( > 9.8 cm 3 ) MR tumor volume, higher 95th percentile ( > 79%) percentage enhancement, and reduced ( > 0.22) circularity represented the retained model variables. Similar results were noted for the overall survival with negative estrogen receptor status, T3 or higher clinical tumor stage, and large ( > 9.8 cm 3 ) MR tumor volume, again all been retained by the model in addition to higher ( > 0.71) 25th percentile area under the enhancement curve. Accuracy of risk stratification based on either traditional (59%) or DCEMRI (65%) survival indicators performed to a similar level. However, combined traditional and MR risk stratification resulted in the highest accuracy (86%). Conclusions: Multivariate survival analysis has revealed thatmodel-retained DCEMRI variables provide independent prognostic information complementing traditional survival indicators and as such could help to appropriately stratify treatment
Status of Structure Functions and Partons
We briefly review some of the developments in the study of parton
distributions which have occurred since DIS2000, including discussion of
uncertainties, shadowing, unintegrated and generalized distributions.Comment: 12 pages including 4 figures, summary of talk at DIS200
Direct Simulation Monte Carlo for astrophysical flows: II. Ram pressure dynamics
We use the Direct Simulation Monte Carlo (DSMC) method combined with an
n-body code to study the dynamics of the interaction between a gas-rich spiral
galaxy and intracluster or intragroup medium, often known as the ram pressure
scenario. The advantage of this gas kinetic approach over traditional
hydrodynamics is explicit treatment of the interface between the hot and cold,
dense and rarefied media typical of astrophysical flows and the explicit
conservation of energy and momentum and the interface. This approach yields
some new physical insight. Owing to the shock and backward wave that forms at
the point ICM--ISM contact, ICM gas is compressed, heated and slowed. The shock
morphology is Mach-disk-like. In the outer galaxy, the hot turbulent post-shock
gas flows around the galaxy disk, while heating and ablating the initially cool
disk gas. The outer gas and angular momentum are lost to the flow. In the inner
galaxy, the hot gas pressurizes the neutral ISM gas causing a strong two-phase
instability. As a result, the momentum of the wind is no longer impulsively
communicated to the cold gas as assumed in the Gunn-Gott (1972) formula, but
oozes through the porous disk, transferring its linear momentum to the disk en
masse. The escaping gas mixture has a net positive angular momentum and forms a
slowly rotating sheath. The shear flow caused by the post-shock ICM flowing
through the porous multiphase ISM creates a strong Kelvin-Helmholtz instability
in the disk that results in Cartwheel-like ring and spoke morphology.Comment: 19 pages, 19 figures, submitted to MNRAS, additional clarifying
figures and arguments,revised figures, corrected typos, and incorporated
comment
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