221 research outputs found
The interaction of planetary nebulae and their AGB progenitors with the interstellar medium
Interaction with the Interstellar Medium (ISM) cannot be ignored in
understanding planetary nebula (PN) evolution and shaping. In an effort to
understand the range of shapes observed in the outer envelopes of PNe, we have
run a comprehensive set of three-dimensional hydrodynamic simulations, from the
beginning of the asymptotic giant branch (AGB) superwind phase until the end of
the post--AGB/PN phase. A 'triple-wind' model is used, including a slow AGB
wind, fast post--AGB wind and third wind reflecting the linear movement through
the ISM. A wide range of stellar velocities, mass-loss rates and ISM densities
have been considered. We find ISM interaction strongly affects outer PN
structures, with the dominant shaping occuring during the AGB phase. The
simulations predict four stages of PN--ISM interaction whereby the PN is
initially unaffected (1), then limb-brightened in the direction of motion (2),
then distorted with the star moving away from the geometric centre (3) and
finally so distorted that the object is no longer recognisable as a PN and may
not be classed as such (4). Parsec-size shells around PN are predicted to be
common. The structure and brightness of ancient PNe is largely determined by
the ISM interaction, caused by rebrightening during the second stage; this
effect may address the current discrepancies in Galactic PN abundance. The
majority of PNe will have tail structures. Evidence for strong interaction is
found for all known planetary nebulae in globular clusters.Comment: 22 pages, 16 figures, accepted by MNRAS (consists of 14 page journal
paper and 8 page online-only appendix). Email C Wareing for high quality PDF
versio
A study of rotating globular clusters - the case of the old, metal-poor globular cluster NGC 4372
Aims: We present the first in-depth study of the kinematic properties and
derive the structural parameters of NGC 4372 based on the fit of a Plummer
profile and a rotating, physical model. We explore the link between internal
rotation to different cluster properties and together with similar studies of
more GCs, we put these in the context of globular cluster formation and
evolution. Methods: We present radial velocities for 131 cluster member stars
measured from high-resolution FLAMES/GIRAFFE observations. Their membership to
the GC is additionally confirmed from precise metallicity estimates. Using this
kinematic data set we build a velocity dispersion profile and a systemic
rotation curve. Additionally, we obtain an elliptical number density profile of
NGC 4372 based on optical images using a MCMC fitting algorithm. From this we
derive the cluster's half-light radius and ellipticity as r_h=3.4'+/-0.04' and
e=0.08+/-0.01. Finally, we give a physical interpretation of the observed
morphological and kinematic properties of this GC by fitting an axisymmetric,
differentially rotating, dynamical model. Results: Our results show that NGC
4372 has an unusually high ratio of rotation amplitude to velocity dispersion
(1.2 vs. 4.5 km/s) for its metallicity. This, however, puts it in line with two
other exceptional, very metal-poor GCs - M 15 and NGC 4590. We also find a mild
flattening of NGC 4372 in the direction of its rotation. Given its old age,
this suggests that the flattening is indeed caused by the systemic rotation
rather than tidal interactions with the Galaxy. Additionally, we estimate the
dynamical mass of the GC M_dyn=2.0+/-0.5 x 10^5 M_Sun based on the dynamical
model, which constrains the mass-to-light ratio of NGC 4372 between 1.4 and 2.3
M_Sun/L_Sun, representative of an old, purely stellar population.Comment: Accepted for publication in A&A, 12 pages, 14 figures, 2 table
Shaping point- and mirror-symmetric proto-planetary nebulae by the orbital motion of the central binary system
We present 3D hydrodynamical simulations of a jet launched from the secondary
star of a binary system inside a proto-planetary nebula. The secondary star
moves around the primary in a close eccentric orbit. From the gasdynamic
simulations we compute synthetic [NII] 6583 emission maps. Different jet axis
inclinations with respect to the orbital plane, as well as different
orientations of the flow with respect to the observer are considered. For some
parameter combinations, we obtain structures that show point- or
mirror-symmetric morphologies depending on the orientation of the flow with
respect to the observer. Furthermore, our models can explain some of the
emission distribution asymmetries that are summarized in the classification
given by Soker & hadar (2002).Comment: 15 pages, 3 figures, 2 tables, Accepted in Apj Letter
The massive expanding molecular torus in the planetary nebula NGC 6302
We measure the mass and kinematics of the massive molecular torus in the
planetary nebula NGC 6302. The nebula is the proto-typical butterfly nebula.
The origin of the wing-like morphology is disputed: determining the mass-loss
history of the confining torus is an important step in understanding the
formation of this structure. We performed submillimeter observations with JCMT
and the SMA interferometer. The continuum emission as well as the J=2-1 and 3-2
transitions of 12CO and 13CO are analysed at arcsecond resolution. The CO
emission indicates a mass of the torus of ~ 2Msun +/- 1Msun. The 12CO and 13CO
emission matches the dark lane seen in absorption in the Halpha image of the
object. The CO torus is expanding with a velocity of ~ 8 km/s, centred at
Vlsr=-31.5 km/s. The size and expansion velocity of the torus indicates that
the torus was ejected from ~ 7500 yr to 2900 yr ago, with a mass-loss rate of
5x10^{-4}Msun/yr. We also see a ballistic component in the CO images with a
velocity gradient of 140 km/s/pc.
The derived mass-loss history of the torus favours binary interaction as the
cause of the ejection of the torus. We predict the existence of a companion
with an orbital period P < 1 month.Comment: 13 pages, 10 figures, accepted for publication in A&
Six Years Follow-up of the Levels of TNF-α and IL-6 in Patients with Complex Regional Pain Syndrome Type 1
In an earlier study, levels of the proinflammatory cytokines TNF-α and IL-6 are higher in blisters fluid from the complex regional pain syndrome type 1 (CRPS1) side obtained at 6 and 30 months (median) after the initial event. The aim of this follow-up study is to determine the involvement of these cytokines in long lasting CRPS1. Twelve CRPS1 patients, with median disease duration of 72 months, participated. The levels of TNF-α and IL-6 were measured in blister fluid; disease activity was reevaluated by measuring pain and differences in temperature, volume, and mobility between both extremities. Differences in levels of IL-6 and TNF-α and mobility between both sides were significantly decreased. Pain and differences in temperature and volume were not significantly altered. No correlation was found between the cytokines and the disease characteristics. These results indicate that IL-6 and TNF-α are only partially responsible for the signs and symptoms of CRPS1
Anti-inflammatory actions of acupuncture.
Acupuncture has a beneficial effect when treating many diseases and painful conditions, and therefore is thought to be useful as a complementary therapy or to replace generally accepted pharmacological intervention. The attributive effect of acupuncture has been investigated in inflammatory diseases, including asthma, rhinitis, inflammatory bowel disease, rheumatoid arthritis, epicondylitis, complex regional pain syndrome type 1 and vasculitis. Large randomised trials demonstrating the immediate and sustained effect of acupuncture are missing. Mechanisms underlying the ascribed immunosuppressive actions of acupuncture are reviewed in this communication. The acupuncture-controlled release of neuropeptides from nerve endings and subsequent vasodilative and anti-inflammatory effects through calcitonine gene-related peptide is hypothesised. The complex interactions with substance P, the analgesic contribution of beta-endorphin and the balance between cell-specific pro-inflammatory and anti-inflammatory cytokines tumour necrosis factor-alpha and interleukin-10 are discussed
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