50 research outputs found
Evidence for deuterium astration in the planetary nebula Sh2-216?
We present FUSE observations of the line of sight to WD0439+466 (LS V +46
21), the central star of the old planetary nebula Sh2-216. The FUSE data shows
absorption by many interstellar and stellar lines, in particular D I, H2 (J = 0
- 9), HD (J = 0 - 1), and CO. Many other stellar and ISM lines are detected in
the STIS E140M HST spectra of this sightline, which we use to determine N(HI).
We derive, for the neutral gas, D/H=(0.76 +0.12 -0.11)E-5, O/H = (0.89 +0.15
-0.11)E-4 and N/H = (3.24 +0.61-0.55)E-5. We argue that most of the gas along
this sightline is associated with the planetary nebula. The low D/H ratio is
likely the result of this gas being processed through the star (astrated) but
not mixed with the ISM. This would be the first time that the D/H ratio has
been measured in predominantly astrated gas. The O/H and N/H ratios derived
here are lower than typical values measured in other planetary nebulae likely
due to unaccounted for ionization corrections.Comment: Accepted for publication is ApJ
Systematic review of native and graft-related aortic infection outcome managed with orthotopic xenopericardial grafts
International audienceObjective: Limited data are available on the use of xenopericardium in the treatment of native and graft-related aortic infections. The aim of this review was to assess outcomes of neoaortic reconstruction using xenopericardium in this challenging group of patients.Methods: Studies involving xenopericardial graft reconstruction to treat native and aortic graft infections were systematically searched and reviewed (Embase, Medline, and Cochrane databases) for the period of January 2007 to December 2017.Results: A total of 4 studies describing 71 patients treated for aortic graft (n = 54) and native aortic (n = 17) infections were included; 25 patients (35%) were operated on in an acute setting. The technical success rate was 100%. The mean 30-day mortality was 25% (range, 7.7%-31%). Only one death (1.4%) was linked to the operator-made pericardial tube graft (acute postoperative bleeding from proximal anastomosis). Septic multiorgan failure was the most common cause of perioperative death (72% [13/18]). Among the 53 patients who survived, only 3 presented with recurrent infection (5.7%), so 70.4% of patients were alive after intervention without evidence of infection (50/71). During follow-up, 2 false aneurysms (3.7% [2/53]), 1 early rupture (1.4% [1/71]), and 2 cases (3.7% [2/53]) of late rupture were reported. Other causes of late deaths unrelated to the aortic xenopericardial repair were not reported in the different series. The early reintervention rate was 1.4% (1/71), treated by open repair for rupture. The late reintervention rate was 7.5% (4/53) with thoracic endovascular aortic repair in three patients (one false aneurysm and two ruptures) and open repair in one patient (one false aneurysm). There were no cases of early or late graft thrombosis. One-year mortality rate was 38% but only 4.2% were related to the aortic repair using orthotopic xenopericardium (one early and two late ruptures).Conclusions: These data confirm the high morbidity of native and graft-related aortic infections and provide insight into the results of orthotopic xenografts as a treatment alternative. Larger series and longer follow-up will be required to compare the role of operator-made pericardial tube graft with other treatment options in infected fields
Double homemade fenestrated stent graft for total endovascular aortic arch repair.
International audienceThe aim of this retrospective analysis was to evaluate the outcomes of physician-modified double fenestrated stent grafts for total endovascular aortic arch repair: one proximal large fenestration for the brachiocephalic trunk and the left common carotid artery and one distal fenestration for the left subclavian artery (LSA)
Variations in D/H and D/O from New FUSE Observations
We use data obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE)
to determine the interstellar abundances of DI, NI, OI, FeII, and H2 along the
sigh tlines to WD1034+001, BD+393226, and TD132709. Our main focus is on
determining the D/H, N/H, O/H, and D/O ratios along these sightlines, with log
N(H) > 20.0, that probe gas well outside of the Local Bubble. Hubble Space
Telescope (HST) and International Ultraviolet Explorer (IUE) archival data are
used to determine the HI column densities along the WD1034+001 and TD132709
sightlines, respectively. For BD+393226, a previously published N(HI) is used.
We find (D/H)x10^5 = 2.14 + 0.53 - 0.45, 1.17 + 0.31 - 0.25, and 1.86 + 0.53 -
0.43, and (D/O)x10^2 = 6.31 + 1.79 - 1.38, 5.62 + 1.61 - 1.31, and 7.59 + 2.17
- 1.76, for the WD1034+001, BD+393226, and TD132709 sightlines, respectively
(all 1 si gma). The scatter in these three D/H ratios exemplifies the scatter
that has been found by other authors for sightlines with column densities in
the range 19.2 < log N(H) < 20.7. The D/H ratio toward WD1034+001 and all the
D/O ratios derived here are inconsistent with the Local Bubble value and are
some of the highest in the literature. We discuss the implications of our
measurements for the determination of the present-epoch abundance of deuterium,
and for the different scenarios that try to explain the D/H variations. We
present a study of D/H as a function of the average sightline gas density,
using the ratios derived in this work as well as ratios from the literature,
which suggests that D/H decreases with increasing gas volume density. Similar
behaviors by other elements such Fe and Si have been interpreted as the result
of depletion into dust grains.Comment: Accepted for publication in the Ap
O/H in the Local Bubble
We present new measurements of the oxygen gas-phase abundance along four
sightlines probing gas inside the Local Bubble, using data obtained with the
Far Ultraviolet Spectroscopic Explorer (FUSE) and the Hubble Space Telecope
(HST). Combining these with seven previously published N(O I) and N(H I)
measurements we determine a mean O/H ratio for the Local Bubble, (O/H) = (3.45
+/- 0.19)x10^(-4) (1 sigma in the mean). Our result is virtually identical to
O/H = (3.43 +/- 0.15)x10^(-4) derived from data for sightlines probing gas well
outside the Local Bubble. In contrast to the D/O and D/H ratios, which seem to
have different values beyond the Local Bubble, our results show that the O/H
ratio is constant and single-valued both inside and outside the Local Bubble,
for low density sightlines, with column densities up to log N (H) ~ 21. In
addition, the similarity of the two values above suggests that the net effect
of the uncertain O I f-values in the FUSE bandpass is not significant. Taking
into account the latest determinations of the Solar abundance of oxygen, our
result implies that ~25% of the oxygen in the Local Bubble is depleted onto
dust grains. The similarity of the value for O/H along low average density
sightlines in the Local Bubble with that of denser sightlines beyond may permit
a limit on the diluting effects of infalling low metallicity gas.Comment: Accepted for publication in the Astrophysical Journa
Interstellar Deuterium, Nitrogen, and Oxygen Abundances Toward GD 246, WD 2331475, HZ 21, and Lan 23: Results from the FUSE Mission
The interstellar abundances of D I, N I, and O I in the local ISM are studied
us ing high-resolution spectra of four hot white dwarfs. The spectra of GD 246,
WD 2331475, HZ 21, and Lan 23 were obtained with the {\it Far Ultraviolet
Spectroscopic Explorer} FUSE in the wavelength range 905-1187 A. The line of
sight to GD 246 probes the Local Interstellar Cloud and at least one other H I
cloud inside the Local Bubble, which contains most of the gas seen al ong this
line of sight. The column densities of H I, C II*, S II, and Si II are measured
using archival STIS echelle-mode observations. The H I column density is
determined by fitting the strong damping wings of inte rstellar Lyman alpha
using a model atmosphere to account for the stellar continuum. We combine the
different abundance ratios computed here with previous published values to
produce revised FUSE abundance ratios for DI/HI, OI/HI, NI/HI, DI/NI, DI/OI,
and OI/NI.Comment: 12 figures, 48 page
Interstellar Deuterium, Nitrogen, and Oxygen Abundances Toward BD +28 4211: Results from the Far Ultraviolet Spectroscopic Explorer
High resolution far-ultraviolet spectra of the O-type subdwarf BD +28 4211
were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) to measure
the interstellar deuterium, nitrogen, and oxygen abundances in this direction.
The interstellar D I transitions are analyzed down to Lyman iota at 920.7 A.
The star was observed several times at different target offsets in the
direction of spectral dispersion. The aligned and coadded spectra have high
signal-to-noise ratios (S/N =50-100). D I, N I, and O I transitions were
analyzed with curve-of-growth and profile fitting techniques. A model of
interstellar molecular hydrogen on the line of sight was derived from H2 lines
in the FUSE spectra and used to help analyze some features where blending with
H2 was significant. The H I column density was determined from high resolution
HST/STIS spectra of Lyman alpha to be log(N HI) = 19.846+/-0.035 (2 sigma),
which is higher than is typical for sight lines in the local ISM studied for
D/H. We found that D/H =(1.39+/-0.21) E-5 (2 sigma) and O/H = (2.37+/-0.55) E-4
(2 sigma). O/H toward BD +28 4211 appears to be significantly below the mean
O/H ratio for the ISM and the Local Bubble.Comment: 33 pages, 12 figures, accepted for publication in The Astrophysical
Journal Supplemen