3,336 research outputs found
HALOGAS: HI Observations and Modeling of the Nearby Edge-on Spiral Galaxy NGC 4565
We present 21-cm observations and models of the neutral hydrogen in NGC 4565,
a nearby, edge-on spiral galaxy, as part of the Westerbork Hydrogen Accretion
in LOcal GAlaxieS (HALOGAS) survey. These models provide insight concerning
both the morphology and kinematics of HI above, as well as within, the disk.
NGC 4565 exhibits a distinctly warped and asymmetric disk with a flaring layer.
Our modeling provides no evidence for a massive, extended HI halo. We see
evidence for a bar and associated radial motions. Additionally, there are
indications of radial motions within the disk, possibly associated with a ring
of higher density. We see a substantial decrease in rotational velocity with
height above the plane of the disk (a lag) of -40 +5/-20 km/s/kpc and -30
+5/-30 km s/kpc in the approaching and receding halves, respectively. This lag
is only seen within the inner ~4.75' (14.9 kpc) on the approaching half and
~4.25' (13.4 kpc) on the receding, making this a radially shallowing lag, which
is now seen in the HI layers of several galaxies. When comparing results for
NGC 4565 and those for other galaxies, there are tentative indications of high
star formation rate per unit area being associated with the presence of a halo.
Finally, HI is found in two companion galaxies, one of which is clearly
interacting with NGC 4565.Comment: 17 pages, 16 figures, accepted for publication in the Astrophysical
Journal, modified affiliatio
HALOGAS: HI Observations and Modeling of the Nearby Edge-on Spiral Galaxy NGC 4244
We present 21-cm observations and models of the HI kinematics and
distribution of NGC 4244, a nearby edge-on Scd galaxy observed as part of the
Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey. Our models
give insight into the HI kinematics and distribution with an emphasis on the
potential existence of extra-planar gas as well as a negative gradient in
rotational velocity with height above the plane of the disk (a lag). Our models
yield strong evidence against a significantly extended halo and instead favor a
warp component along the line of sight as an explanation for some of the
observed thickening of the disk. Based on these models, we detect a lag of -9
+3/-2 km s-1 kpc-1 in the approaching half and -9 +/-2 km s-1 kpc-1 in the
receding half. This lag decreases in magnitude to -5+/-2 km s-1 kpc-1 and
-4+/-2 km s-1 kpc-1 near a radius of 10 kpc in the approaching and receding
halves respectively. Additionally, we detect several distinct morphological and
kinematic features including a shell that is probably driven by star formation
within the disk.Comment: 18 pages, 14 figures, Full resolution version may be found at:
http://www.astron.nl/halogas/papers/NGC4244.Zschaechner.arXiv.p
Pulsive feedback control for stabilizing unstable periodic orbits in a nonlinear oscillator with a non-symmetric potential
We examine a strange chaotic attractor and its unstable periodic orbits in
case of one degree of freedom nonlinear oscillator with non symmetric
potential. We propose an efficient method of chaos control stabilizing these
orbits by a pulsive feedback technique. Discrete set of pulses enable us to
transfer the system from one periodic state to another.Comment: 11 pages, 4 figure
Multiple Comparison Procedures, Trimmed Means And Transformed Statistics
A modification to testing pairwise comparisons that may provide better control of Type I errors in the presence of non-normality is to use a preliminary test for symmetry which determines whether data should be trimmed symmetrically or asymmetrically. Several pairwise MCPs were investigated, employing a test of symmetry with a number of heteroscedastic test statistics that used trimmed means and Winsorized variances. Results showed improved Type I error control than competing robust statistics
Probing the Magnetized Interstellar Medium Surrounding the Planetary Nebula Sh 2-216
We present 1420 MHz polarization images of a 2.5 X 2.5 degree region around
the planetary nebula (PN) Sh 2-216. The images are taken from the Canadian
Galactic Plane Survey (CGPS). An arc of low polarized intensity appears
prominently in the north-east portion of the visible disk of Sh 2-216,
coincident with the optically identified interaction region between the PN and
the interstellar medium (ISM). The arc contains structural variations down to
the ~1 arcminute resolution limit in both polarized intensity and polarization
angle. Several polarization-angle "knots" appear along the arc. By comparison
of the polarization angles at the centers of the knots and the mean
polarization angle outside Sh 2-216, we estimate the rotation measure (RM)
through the knots to be -43 +/- 10 rad/m^2. Using this estimate for the RM and
an estimate of the electron density in the shell of Sh 2-216, we derive a
line-of-sight magnetic field in the interaction region of 5.0 +/- 2.0 microG.
We believe it more likely the observed magnetic field is interstellar than
stellar, though we cannot completely dismiss the latter possibility. We
interpret our observations via a simple model which describes the ISM magnetic
field around Sh 2-216, and comment on the potential use of old PNe as probes of
the magnetized ISM.Comment: 25 pages, 4 figures. Accepted for publication in the Astrophysical
Journa
A Scoping Study of Psychosocial Factors in Women Diagnosed With and/or Treated for Pelvic Organ Prolapse
Objective
Pelvic organ prolapse (POP) is prevalent and can impact women's physical and psychosocial health. To develop interventions that support this population, an understanding of the state of research on psychosocial factors related to POP is essential. We conducted a scoping study focused on the psychosocial experience of women with POP. The purpose of this review was to (1) inventory and describe the current state of knowledge of the psychosocial experience of women with POP, (2) identify gaps in knowledge, and (3) identify targets for future research.
Method
Electronic databases PsycINFO, PubMed, EMBASE, and CINAHL were searched through November 1, 2017.
Results
Of 524 titles reviewed, 103 articles met all inclusion criteria. Articles were grouped by the disease period (ie, prediagnosis, diagnosis/preintervention, intervention, follow-up, and mixed) and psychosocial factors. Most articles (n = 73) focused on women undergoing intervention. Articles focusing on the preintervention period was the next largest category (n = 14). Follow-up after intervention (n = 8) and samples of mixed disease periods (n = 7) were less common. One article focused on women before diagnosis. Articles focused on quality of life (QOL; n = 79), sexual function (n = 51), satisfaction (n = 16), body image (n = 13), psychological distress (n = 4), and knowledge (n = 3).
Conclusions
Research on the psychosocial experience of POP has largely focused on changes in QOL and sexual function. Future research should target emotional experience of women with POP; relationships among QOL, psychological distress, body image, and sexual function; and psychosocial factors related to treatment outcomes
HALOGAS observations of NGC 5023 and UGC 2082: Modeling of non-cylindrically symmetric gas distributions in edge-on galaxies
In recent years it has become clear that the vertical structure of disk
galaxies is a key ingredient for understanding galaxy evolution. In particular,
the presence and structure of extra-planar gas has been a focus of research.
The Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey aims to provide a
census on the rate of cold neutral gas accretion in nearby galaxies as well as
a statistically significant set of galaxies that can be investigated for their
extra-planar gas properties.
In order to better understand the the vertical structure of the neutral
hydrogen in the two edge-on HALOGAS galaxies NGC 5023 and UGC 2082 we construct
detailed tilted ring models. The addition of distortions resembling arcs or
spiral arms significantly improves the fit of the models to these galaxies. In
the case of UGC 2082 no vertical gradient in rotational velocity is required in
either symmetric models nor non-symmetric models to match the observations. The
best fitting model features two arcs of large vertical extent that may be due
to accretion. In the case of NGC 5023 a vertical gradient is required in
symmetric models (dV/dz = km s kpc) and its
magnitude is significantly lowered when non-symmetric models are considered
(dV/dz = km s kpc). Additionally it is shown that the
underlying disk of NGC 5023 can be made symmetric, in all parameters except the
warp, in non-symmetric models. In comparison to the "classical" modeling these
models fit the data significantly better with a limited addition of free
parameters.Comment: 27 Pages, 22 Figures. Accepted for publication in MNRA
Breakdown of Conformal Invariance at Strongly Random Critical Points
We consider the breakdown of conformal and scale invariance in random systems
with strongly random critical points. Extending previous results on
one-dimensional systems, we provide an example of a three-dimensional system
which has a strongly random critical point. The average correlation functions
of this system demonstrate a breakdown of conformal invariance, while the
typical correlation functions demonstrate a breakdown of scale invariance. The
breakdown of conformal invariance is due to the vanishing of the correlation
functions at the infinite disorder fixed point, causing the critical
correlation functions to be controlled by a dangerously irrelevant operator
describing the approach to the fixed point. We relate the computation of
average correlation functions to a problem of persistence in the RG flow.Comment: 9 page
Sustainable institutionalized punishment requires elimination of second-order free-riders
Although empirical and theoretical studies affirm that punishment can elevate
collaborative efforts, its emergence and stability remain elusive. By
peer-punishment the sanctioning is something an individual elects to do
depending on the strategies in its neighborhood. The consequences of
unsustainable efforts are therefore local. By pool-punishment, on the other
hand, where resources for sanctioning are committed in advance and at large,
the notion of sustainability has greater significance. In a population with
free-riders, punishers must be strong in numbers to keep the "punishment pool"
from emptying. Failure to do so renders the concept of institutionalized
sanctioning futile. We show that pool-punishment in structured populations is
sustainable, but only if second-order free-riders are sanctioned as well, and
to a such degree that they cannot prevail. A discontinuous phase transition
leads to an outbreak of sustainability when punishers subvert second-order
free-riders in the competition against defectors.Comment: 7 two-column pages, 3 figures; accepted for publication in Scientific
Report
Near-field interactions between metal nanoparticle surface plasmons and molecular excitons in thin-films: part I: absorption
In this and the following paper (parts I and II, respectively), we systematically study the interactions between surface plasmons of metal nanoparticles (NPs) with excitons in thin-films of organic media. In an effort to exclusively probe near-field interactions, we utilize spherical Ag NPs in a size-regime where far-field light scattering is negligibly small compared to absorption. In part I, we discuss the effect of the presence of these Ag NPs on the absorption of the embedding medium by means of experiment, numerical simulations, and analytical calculations, all shown to be in good agreement. We observe absorption enhancement in the embedding medium due to the Ag NPs with a strong dependence on the medium permittivity, the spectral position relative to the surface plasmon resonance frequency, and the thickness of the organic layer. By introducing a low index spacer layer between the NPs and the organic medium, this absorption enhancement is experimentally confirmed to be a near field effect In part II, we probe the impact of the Ag NPs on the emission of organic molecules by time-resolved and steady-state photoluminescence measurements
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