497 research outputs found
The Wisconsin H-Alpha Mapper Northern Sky Survey
The Wisconsin H-Alpha Mapper (WHAM) has surveyed the distribution and
kinematics of ionized gas in the Galaxy above declination -30 degrees. The WHAM
Northern Sky Survey (WHAM-NSS) has an angular resolution of one degree and
provides the first absolutely-calibrated, kinematically-resolved map of the
H-Alpha emission from the Warm Ionized Medium (WIM) within ~ +/-100 km/s of the
Local Standard of Rest. Leveraging WHAM's 12 km/s spectral resolution, we have
modeled and removed atmospheric emission and zodiacal absorption features from
each of the 37,565 spectra. The resulting H-Alpha profiles reveal ionized gas
detected in nearly every direction on the sky with a sensitivity of 0.15 R (3
sigma). Complex distributions of ionized gas are revealed in the nearby spiral
arms up to 1-2 kpc away from the Galactic plane. Toward the inner Galaxy, the
WHAM-NSS provides information about the WIM out to the tangent point down to a
few degrees from the plane. Ionized gas is also detected toward many
intermediate velocity clouds at high latitudes. Several new H II regions are
revealed around early B-stars and evolved stellar cores (sdB/O). This work
presents the details of the instrument, the survey, and the data reduction
techniques. The WHAM-NSS is also presented and analyzed for its gross
properties. Finally, some general conclusions are presented about the nature of
the WIM as revealed by the WHAM-NSS.Comment: 42 pages, 14 figures (Fig 6-9 & 14 are full color); accepted for
publication in 2003, ApJ, 149; Original quality figures (as well as data for
the survey) are available at http://www.astro.wisc.edu/wham
Real time display of the vertical beam sizes in LEP using the BEXE X-ray detector and fast VME based computers
Fast X-ray detectors based on CdTe photoconductors have been installed in LEP since the beginning of its operation in 1989. The angular divergence of the high energy photons from the synchrotron radiation (x-rays) and the narrow spacing of the 64 photoconductors of the detector allow a good measurement of vertical beam profiles down to an rms beam size of 300 mm. This paper presents some specific parameters and experimental results of an upgrade program in which the local processing power of the front-end electronics has been increased by a factor 50. Such a powerful tool has allowed a real time display of the time evolution of the vertical beam sizes. An online correlation plot between the electron and positron beam sizes (turn by turn) is also displayed. These online video images are available in the LEP control room and are used in daily operation for luminosity optimisation
Interactions between carnivore species: limited spatiotemporal partitioning between apex predator and smaller carnivores in a Mediterranean protected area
Background: There is need of information on ecological interactions that keystone species such as apex predators establish in ecosystems recently recolonised. Interactions among carnivore species have the potential to influence community-level processes, with consequences for ecosystem dynamics. Although avoidance of apex predators by smaller carnivores has been reported, there is increasing evidence that the potential for competitive-to-facilitative interactions is context-dependent. In a protected area recently recolonised by the wolf Canis lupus and hosting abundant wild prey (3 ungulate species, 20–30 individuals/km2, together), we used 5-year food habit analyses and 3-year camera trapping to (i) investigate the role of mesocarnivores (4 species) in the wolf diet; (ii) test for temporal, spatial, and fine-scale spatiotemporal association between mesocarnivores and the wolf. Results: Wolf diet was dominated by large herbivores (86% occurrences, N = 2201 scats), with mesocarnivores occurring in 2% scats. We collected 12,808 carnivore detections over > 19,000 camera trapping days. We found substantial (i.e., generally ≥ 0.75, 0–1 scale) temporal overlap between mesocarnivores—in particular red fox—and the wolf, with no support for negative temporal or spatial associations between mesocarnivore and wolf detection rates. All the species were nocturnal/crepuscular and results suggested a minor role of human activity in modifying interspecific spatiotemporal partitioning. Conclusions: Results suggest that the local great availability of large prey to wolves limited negative interactions towards smaller carnivores, thus reducing the potential for spatiotemporal avoidance. Our study emphasises that avoidance patterns leading to substantial spatiotemporal partitioning are not ubiquitous in carnivore guilds
Local seismic cultures: the use of timber frame structures in the south of Portugal
Given the fact that using timber frame structures has proven to improve the seismic behavior of
vernacular architecture, as has been reported in past earthquakes in many countries, its
preservation as a traditional earthquake resistant practice is important. This paper firstly intends
to evaluate whether the use of timber frames as a traditional seismic resistant technique for
vernacular architecture in the South of Portugal, traditionally a seismic region, is still active.
Secondly, the city of Vila Real de Santo AntĂłnio was selected as a case study because it also
followed a Pombaline development contemporary to the reconstruction of Lisbon. The plan
included the provision of timber frame partition walls for some of the buildings and, thus, an
overview of the type of constructions originally conceived is provided. Finally, the alterations
done in the original constructions and the current state of the city center are described and the
effect of these changes on the seismic vulnerability of the city is discussed.The authors wish to express their gratitude to the Portuguese Science and Technology Foundation (FCT) for the scholarship granted in the scope of the research project 'SEISMIC-V-Vernacular Seismic Culture in Portugal' (PTDC/ATP-AQI/3934/2012)
Churg-Strauss syndrome: outcome and long-term follow-up of 38 patients from a single Italian centre
Objective: This study was aimed at verifying any potential correlation between anti-myeloperoxidase antineutrophil cytoplasmic antibodies (ANCA-MPO) and clinical features and outcome indices in Churg-Strauss Syndrome (CSS). Methods: Thirhty-eight Churg-Strauss syndrome patients were selected from the medical records of all vasculitis patients attending the Rheumatology and Immunology Unit at the Department of Internal Medicine of the University of Pisa in the decades between 1989 and 2008. Data were analysed retrospectively. Statistical analyses of the results were carried out using the Mann-Whitney test to determine the correlations between the clinical and serological parameters. Qualitative variables were compared using contingency table analysis and Fisher's exact test. Results: ANCA-MPO were detected in15/38 (39%) patients. Positive ANCA status was associated with peripheral neuropathy (p=0.0006), whereas negative ANCA status was associated with lung involvement (p=0.002). Relapses were strongly associated with positive ANCA status (p=0.01) and with an increase in- or a reappearence of ANCA-MPO levels (p=0.006). Finally, ANCA-MPO were significantly associated with neurological damage (p=0.003). Conclusions: The presence or absence of ANCA-MPO identify different clinical subsets in CSS. Overall, ANCA-MPO appears as a useful tool in the monitoring of CSS and in particular a good predictor of CSS relapse
A Hubble Space Telescope WFPC2 Investigation of the Disk-Halo Interface in NGC891
We present deep narrowband observations with high spatial resolution of
extraplanar diffuse ionized gas in the halo of NGC891, obtained with the WFPC2
on-board the HST. Our H-alpha observations, centered on the northern part of
NGC891, reveal an extended gaseous halo, which fills almost the entire field of
view of our WFPC2 observation. The majority of the H-alpha emission is diffuse.
Several discrete features (e.g., filaments) are visible as well. Some of the
filaments reach distances of up to 2.2 kpc above the galactic plane, and are
extremely collimated, even at high galactic latitudes. We compare the
morphology of these filaments with theoretical models, which describe possible
transport mechanisms in a general way. We also investigate extraplanar dust
features, which are best visible in unsharp-masked images of our broadband
F675W image, and we compare them to the spatial distribution of DIG filaments.
Individual dust features, however, are not spatially correlated with diffuse
ionized gas counterparts, such as individual filaments. Quite interestingly,
the orientation of the dust features changes from being mostly aligned
perpendicular to the disk at low galactic latitudes, to a parallel alignment at
high |z|. We compare the diffuse ionized gas distribution to the hot ionized
medium, traced by X-ray observations performed by Chandra. There exists a good
correlation of the presence of the warm and hot ionized gas, in particular, an
X-ray bright region at |z| ~ 1-1.5 kpc fills the entire northern halo region,
whereas the intensity in the midplane is considerably depressed. We also
compare the sizes of individual H-alpha emission line features in the midplane
of NGC891 with similar structures that are known in our Milky Way and in the
LMC.Comment: LaTeX, 15 pages, 11 figures, accepted for publication in The
Astronomical Journal, paper with high resolution figures can be accessed at
http://www.astro.rub.de/jrossa/ngc891
HST/STIS Spectra of Nuclear Star Clusters in Spiral Galaxies: Dependence of Age and Mass On Hubble Type
(Abridged) We study the nuclear star clusters in spiral galaxies of various
Hubble types using spectra obtained with STIS on-board HST. We observed the
nuclear clusters in 40 galaxies, selected from two previous HST/WFPC2 imaging
surveys. The spectra provide a better separation of cluster light from
underlying galaxy light than is possible with ground-based spectra. To infer
the star formation history, metallicity and dust extinction, we fit weighted
superpositions of single-age stellar population templates to the spectra. The
luminosity-weighted age ranges from 10 Myrs to 10 Gyrs. The stellar populations
of NCs are generally best fit as a mixture of populations of different ages.
This indicates that NCs did not form in a single event, but instead they had
additional star formation long after the oldest stars formed. On average, the
sample clusters in late-type spirals have a younger luminosity-weighted mean
age than those in early-type spirals (log(age/yr) = 8.37+/-0.25 vs.
9.23+/-0.21). The average cluster masses are smaller in late-type spirals than
in early-type spirals (log(M/Msun) = 6.25+/-0.21 vs. 7.63+/-0.24), and exceed
the masses typical of globular clusters. The cluster mass correlates strongly
with both the Hubble type of the host galaxy and the luminosity of its bulge.
The latter correlation has the same slope as the well-known correlation between
supermassive black hole mass and bulge luminosity. The properties of both
nuclear clusters and black holes are therefore intimately connected to the
properties of the host galaxy.Comment: AJ submitted (original submission Nov 30, 2005, present version
includes changes based on referee recommendations). 69 pages, 16 figures, 7
table
Communities as Well Separated Subgraphs With Cohesive Cores: Identification of Core-Periphery Structures in Link Communities
Communities in networks are commonly considered as highly cohesive subgraphs
which are well separated from the rest of the network. However, cohesion and
separation often cannot be maximized at the same time, which is why a
compromise is sought by some methods. When a compromise is not suitable for the
problem to be solved it might be advantageous to separate the two criteria. In
this paper, we explore such an approach by defining communities as well
separated subgraphs which can have one or more cohesive cores surrounded by
peripheries. We apply this idea to link communities and present an algorithm
for constructing hierarchical core-periphery structures in link communities and
first test results.Comment: 12 pages, 2 figures, submitted version of a paper accepted for the
7th International Conference on Complex Networks and Their Applications,
December 11-13, 2018, Cambridge, UK; revised version at
http://141.20.126.227/~qm/papers
Hydrostatic models for the rotation of extra-planar gas in disk galaxies
We show that fluid stationary models are able to reproduce the observed,
negative vertical gradient of the rotation velocity of the extra-planar gas in
spiral galaxies. We have constructed models based on the simple condition that
the pressure of the medium does not depend on density alone (baroclinic instead
of barotropic solutions: isodensity and isothermal surfaces do not coincide).
As an illustration, we have successfully applied our method to reproduce the
observed velocity gradient of the lagging gaseous halo of NGC 891. The fluid
stationary models discussed here can describe a hot homogeneous medium as well
as a "gas" made of discrete, cold HI clouds with an isotropic velocity
dispersion distribution. Although the method presented here generates a density
and velocity field consistent with observational constraints, the stability of
these configurations remains an open question.Comment: 12 pages, 9 figures. Accepted for publication in Astronomy and
Astrophysic
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