680 research outputs found
Star-forming galaxies in low-redshift clusters: Effects of environment on the concentration of star formation
We attempt to determine the dominant processes acting on star-forming disk
galaxies as a result of the cluster environment by studying the normalised
rates and radial distributions of star formation in galaxies within
low-redshift clusters. We develop indicators of different processes based on
the radial concentrations of R-band and H alpha light within each of the
galaxies studied. The tests are applied to galaxies in each of 3 environments -
cluster, supercluster (outside the cluster virial radius) and field. We develop
new diagnostic diagrams combining star-formation rate and spatial distribution
information to differentiate between stripping of outer disk gas, general gas
depletion, nuclear starbursts and galaxy-wide enhancement of star formation.
Hubble type classifications of cluster galaxies are found to correlate only
weakly with their concentration indices, whereas this correlation is strong for
non-cluster populations of disk galaxies. We identify a population of
early-type disk galaxies in the cluster population with both enhanced and
centrally-concentrated star formation compared to their field counterparts. The
enhanced cluster galaxies frequently show evidence of disturbance. A small but
non-negligible population of cluster galaxies with truncation of star formation
in their outer disks is also found.Comment: 14 pages, 16 figures; accepted for publication in Astronomy and
Astrophysic
The EU and Asia within an evolving global order: what is Europe? Where is Asia?
The papers in this special edition are a very small selection from those presented at the EU-NESCA (Network of European Studies Centres in Asia) conference on "the EU and East Asia within an Evolving Global Order: Ideas, Actors and Processes" in November 2008 in Brussels. The conference was the culmination of three years of research activity involving workshops and conferences bringing together scholars from both regions primarily to discuss relations between Europe and Asia, perceptions of Europe in Asia, and the relationship between the European regional project and emerging regional forms in Asia. But although this was the last of the three major conferences organised by the consortium, it in many ways represented a starting point rather than the end; an opportunity to reflect on the conclusions of the first phase of collaboration and point towards new and continuing research agendas for the future
Ozone depletion, greenhouse gases, and climate change
This symposium was organized to study the unusual convergence of a number of observations, both short and long term that defy an integrated explanation. Of particular importance are surface temperature observations and observations of upper atmospheric temperatures, which have declined significantly in parts of the stratosphere. There has also been a dramatic decline in ozone concentration over Antarctica that was not predicted. Significant changes in precipitation that seem to be latitude dependent have occurred. There has been a threefold increase in methane in the last 100 years; this is a problem because a source does not appear to exist for methane of the right isotopic composition to explain the increase. These and other meteorological global climate changes are examined in detail
Angular momentum transport by internal gravity waves III - Wave excitation by core convection and the Coriolis effect
This is the third in a series of papers that deal with angular momentum
transport by internal gravity waves. We concentrate on the waves excited by
core convection in a 3Msun, Pop I main sequence star. Here, we want to examine
the role of the Coriolis acceleration in the equations of motion that describe
the behavior of waves and to evaluate its impact on angular momentum transport.
We use the so-called traditional approximation of geophysics, which allows
variable separation in radial and horizontal components. In the presence of
rotation, the horizontal structure is described by Hough functions instead of
spherical harmonics. The Coriolis acceleration has two main effects on waves.
It transforms pure gravity waves into gravito-inertial waves that have a larger
amplitude closer to the equator, and it introduces new waves whose restoring
force is mainly the conservation of vorticity. Taking the Coriolis acceleration
into account changes the subtle balance between prograde and retrograde waves
in non-rotating stars. It also introduces new types of waves that are either
purely prograde or retrograde. We show in this paper where the local deposition
of angular momentum by such waves is important.Comment: 9 pages, 10 figures, accepted for publication by A&
The role of tank-treading motions in the transverse migration of a spheroidal vesicle in a shear flow
The behavior of a spheroidal vesicle, in a plane shear flow bounded from one
side by a wall, is analysed when the distance from the wall is much larger than
the spheroid radius. It is found that tank treading motions produce a
transverse drift away from the wall, proportional to the spheroid eccentricity
and the inverse square of the distance from the wall. This drift is independent
of inertia, and is completely determined by the characteristics of the vesicle
membrane. The relative strength of the contribution to drift from tank-treading
motions and from the presence of inertial corrections, is discussed.Comment: 16 pages, 1 figure, Latex. To appear on J. Phys. A (Math. Gen.
Expanding actorness to explain EU External engagement in originally internal policy areas
© 2018, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Despite its increasing importance for European integration, there remains a lack of scholarly attention to the growth of EU external action in originally internal policy areas. This article advances a comprehensive framework for understanding and explaining the emergence of EU external engagement in such areas. It combines insights from two sets of literatures: the EU external relations literature offers useful concepts–particularly ‘actorness’–as building blocks for explanatory purposes, while the public policy literature provides relevant insights regarding policy entrepreneurship and agenda-setting. The article contends that EU external engagement results from a favourable interplay between an external ‘opportunity’ and the EU’s ‘presence’ in a given domain, which is identified and capitalized upon by a set of policy entrepreneurs, who are driven by interest-based and/or ideational motives. To evaluate the salience of the framework, the article applies it across several policy areas.status: publishe
Phase Bubbles and Spatiotemporal Chaos in Granular Patterns
We use inelastic hard sphere molecular dynamics simulations and laboratory
experiments to study patterns in vertically oscillated granular layers. The
simulations and experiments reveal that {\em phase bubbles} spontaneously
nucleate in the patterns when the container acceleration amplitude exceeds a
critical value, about , where the pattern is approximately hexagonal,
oscillating at one-fourth the driving frequency (). A phase bubble is a
localized region that oscillates with a phase opposite (differing by ) to
that of the surrounding pattern; a localized phase shift is often called an
{\em arching} in studies of two-dimensional systems. The simulations show
that the formation of phase bubbles is triggered by undulation at the bottom of
the layer on a large length scale compared to the wavelength of the pattern.
Once formed, a phase bubble shrinks as if it had a surface tension, and
disappears in tens to hundreds of cycles. We find that there is an oscillatory
momentum transfer across a kink, and this shrinking is caused by a net
collisional momentum inward across the boundary enclosing the bubble. At
increasing acceleration amplitudes, the patterns evolve into randomly moving
labyrinthian kinks (spatiotemporal chaos). We observe in the simulations that
and subharmonic patterns emerge as primary instabilities, but that
they are unstable to the undulation of the layer. Our experiments confirm the
existence of transient and patterns.Comment: 6 pages, 12 figures, submitted to Phys. Rev. E on July 1st, 2001. for
better quality figures, visit http://chaos.ph.utexas.edu/research/moo
Action functionals for relativistic perfect fluids
Action functionals describing relativistic perfect fluids are presented. Two
of these actions apply to fluids whose equations of state are specified by
giving the fluid energy density as a function of particle number density and
entropy per particle. Other actions apply to fluids whose equations of state
are specified in terms of other choices of dependent and independent fluid
variables. Particular cases include actions for isentropic fluids and
pressureless dust. The canonical Hamiltonian forms of these actions are
derived, symmetries and conserved charges are identified, and the boundary
value and initial value problems are discussed. As in previous works on perfect
fluid actions, the action functionals considered here depend on certain
Lagrange multipliers and Lagrangian coordinate fields. Particular attention is
paid to the interpretations of these variables and to their relationships to
the physical properties of the fluid.Comment: 40 pages, plain Te
Clinicopathological correlations of mesenteric fibrosis and evaluation of a novel biomarker for fibrosis detection in small bowel neuroendocrine neoplasms
PURPOSE: Mesenteric fibrosis (MF) in small intestinal neuroendocrine neoplasms (SINENs) is often associated with significant morbidity and mortality. The detection of MF is usually based on radiological criteria, but no previous studies have attempted a prospective, multidimensional assessment of mesenteric desmoplasia to determine the accuracy of radiological measurements. There is also a lack of non-invasive biomarkers for the detection of image-negative MF. METHODS: A multidimensional assessment of MF incorporating radiological, surgical and histological parameters was performed in a prospective cohort of 34 patients with SINENs who underwent primary resection. Pre-operative blood samples were collected in 20 cases to evaluate a set of five profibrotic circulating transcripts-the "fibrosome"-that is included as an "omic" component of the NETest. RESULTS: There was a significant correlation between radiological and surgical assessments of MF (p < 0.05). However, there were several cases of image-negative MF. The NETest-fibrosome demonstrated an accuracy of 100% for the detection of microscopic MF. CONCLUSIONS: The detection of MF by radiological criteria has limitations. The NETest-fibrosome is a promising biomarker for fibrosis detection and further validation of these results would be needed in larger, multicentre studies
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