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- Danielsson, D., et al.
(författare)
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Osteoradionecrosis, an increasing indication for microvascular head and neck reconstruction
- 2020
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Ingår i: International Journal of Oral and Maxillofacial Surgery. - : Elsevier BV. - 0901-5027 .- 1399-0020. ; 49:1, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Better cancer treatment has led to a steadily growing population of cancer survivors suffering from late adverse effects after cancer treatment. The aim of this study was to investigate whether there has been an increase in free flap reconstruction due to osteoradionecrosis (ORN). A retrospective review was conducted to identify all consecutive head and neck free flap reconstructions performed over an 18-year period (1995-2012) at Karolinska University Hospital. A total of 235 free flaps were identified. Cases were divided into two groups: head and neck cancer reconstructions and ORN reconstructions. A comparison between the two groups showed longer survival (P < 0.001) and higher rates of late complications (P < 0.001) among ORN cases. ORN as an indication for reconstruction increased over time, from 7.0% of the total number of free flaps performed in 1995-2000, to 15.2% during the period 2001-2006, and to 27.3% in 2007-2012 (P < 0.001). This, in accordance with the results of other studies, highlights the importance of the appropriate allocation of resources within the healthcare system to treat this patient group within the steadily increasing population of cancer survivors.
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| 4. |
- de Val-Borro, M., et al.
(författare)
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Modelling circumbinary gas flows in close T Tauri binaries star
- 2011
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 413:4, s. 2679-2688
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Tidskriftsartikel (refereegranskat)abstract
- Young close binaries open central gaps in the surrounding circumbinary accretion disc, but the stellar components may still gain mass from gas crossing through the gap. It is not well understood how this process operates and how the stellar components are affected by such inflows. Our main goal is to investigate how gas accretion takes place and evolves in close T Tauri binary systems. In particular, we model the accretion flows around two close T Tauri binaries, V4046 Sgr and DQ Tau, both showing periodic changes in emission lines, although their orbital characteristics are very different. In order to derive the density and velocity maps of the circumbinary material, we employ two-dimensional hydrodynamic simulations with a locally isothermal equation of state. The flow patterns become quasi-stable after a few orbits in the frame corotating with the system. Gas flows across the circumbinary gap through the corotating Lagrangian points, and local circumstellar discs develop around both components. Spiral density patterns develop in the circumbinary disc that transport angular momentum efficiently. Mass is preferentially channelled towards the primary and its circumstellar disc is more massive than the disc around the secondary. We also compare the derived density distribution to observed line profile variability. The line profile variability tracing the gas flows in the central cavity shows clear similarities with the corresponding observed line profile variability in V4046 Sgr, but only when the local circumstellar disc emission was excluded. Closer to the stars normal magnetospheric accretion may dominate, while further out the dynamic accretion process outlined here dominates. Periodic changes in the accretion rates on to the stars can explain the outbursts of line emission observed in eccentric systems such as DQ Tau.
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| 5. |
- Eriksson, BO, et al.
(författare)
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Upregulation of Plasminogen Activator Inhibitor-1 in Irradiated Recipient Arteries and Veins from Free Tissue Transfer Reconstruction in Cancer Patients
- 2018
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Ingår i: Mediators of inflammation. - : Hindawi Limited. - 1466-1861 .- 0962-9351. ; 2018, s. 4058986-
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Tidskriftsartikel (refereegranskat)abstract
- Background. Clinical studies have shown that radiotherapy can induce vascular disease at the site of exposure but is usually not clinically evident until years after treatment. We have studied irradiated human arteries and veins to better understand the underlying biology in search of future treatments. The aim was to investigate whether radiotherapy contributed to a sustained expression of plasminogen activator inhibitor-1 (PAI-1) in human arteries and veins. Methods. Irradiated arteries and veins were harvested, together with unirradiated control vessels, from patients undergoing free tissue transfer reconstruction at a median time of 90 weeks [5–650] following radiation exposure. Differential gene expression of PAI-1 was analysed, together with immunohistochemistry (IHC) and immunofluorescence (IF). Results. PAI-1 gene expression was increased in both arteries (p=0.012) and veins (p<0.001) in irradiated compared to unirradiated control vessels. IHC and IF indicated that cells expressing PAI-1 were located in the adventitia of both arteries and veins and colocalized with cells positive for CD68, CD45, and α-SMA in arteries and with CD45 and α-SMA in veins. Conclusion. The current study shows a sustained upregulation of PAI-1 in both arteries and veins after exposure to ionizing radiation, indicating a chronic inflammation mainly in the adventitia. We believe that the results contribute to further understanding of radiation-induced vascular disease, where targeting PAI-1 may be a potential treatment.
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- Gahm, Gösta F., 1942-, et al.
(författare)
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Expanding shells around young clusters - S 171/Be 59
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 663
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Tidskriftsartikel (refereegranskat)abstract
- Context. Some HII regions that surround young stellar clusters are bordered by molecular shells that appear to expand at a rate inconsistent with our current model simulations. In this study we focus on the dynamics of Sharpless 171 (including NGC 7822), which surrounds the cluster Berkeley 59. Aims. We aim to compare the velocity pattern over the molecular shell with the mean radial velocity of the cluster for estimates of the expansion velocities of different shell structures, and to match the observed properties with model simulations. Methods. Optical spectra of 27 stars located in Berkeley 59 were collected at the Nordic Optical Telescope, and a number of molecular structures scattered over the entire region were mapped in 13CO(1- 0) at Onsala Space Observatory. Results. We obtained radial velocities and MK classes for the clustera's stars. At least four of the O stars are found to be spectroscopic binaries, in addition to one triplet system. From these data we obtain the mean radial velocity of the cluster. From the 13CO spectra we identify three shell structures, expanding relative to the cluster at moderate velocity (4 km s- 1), high velocity (12 km s- 1), and in between. The high-velocity cloudlets extend over a larger radius and are less massive than the low-velocity cloudlets. We performed a model simulation to understand the evolution of this complex. Conclusions. Our simulation of the Sharpless 171 complex and Berkeley 59 cluster demonstrates that the individual components can be explained as a shell driven by stellar winds from the massive cluster members. However, our relatively simple model produces a single component. Modelling of the propagation of shell fragments through a uniform interstellar medium demonstrates that dense cloudlets detached from the shell are decelerated less efficiently than the shell itself. They can reach greater distances and retain higher velocities than the shell.
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| 13. |
- Gahm, G. F., et al.
(författare)
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Face to phase with RU Lupi
- 2013
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 560, s. A57-
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Tidskriftsartikel (refereegranskat)abstract
- Context. Some classical T Tauri stars, with intense line and continuous excess emission, show extremely complex spectral variations. Aims. We aim to map and interpret the spectral variations in one such extreme T Tauri star, namely RU Lupi, and to explore how the changes are related to stellar brightness and rotational phase.Methods. We followed the star over three observing runs, each covering a few days, collecting high-resolution optical spectra. In connection to the third run, complementary NIR spectra, multicolour photometric data, and X-ray observations were obtained.Results. The stellar photospheric absorption line spectrum is weakened by superimposed emission, and this veiling becomes extremely high on occasion. Interpreted as a variable continuous excess emission, its contribution would amount to several times the stellar continuum brightness. However, the stellar brightness does not change much when the veiling changes, and we conclude that the veiling is dominated by narrow line emission that fills in the photospheric lines. Continuous emission, originating at the hot spot on the stellar surface, plays a dominant role only at lower degrees of veiling. The radial velocity of narrow emission components in lines of He I vary periodically in anti-phase with the stellar velocity, reflecting the location and motion of the accretion footprint. The blue-shifted wings in He I, related to a stellar wind, are remarkably stable in equivalent width. This implies that the line flux responds directly to changes in the veiling, which in turn is related to the accretion rate close to the star. In contrast, the equivalent widths of the red-shifted wings change with rotational phase. From the pattern of variability we infer that these wings originate in accreting gas close to the star, and that the accretion funnels are bent and trail the hot spot. The profiles of the forbidden lines of [O I] and [S II] are very stable in strength and shape over the entire observing period, and like a system of narrow, blue-shifted absorption features seen in lines of Ca II and Na I, they originate at larger distances from the star in the disk wind. Slightly blue-shifted emission components are present in the forbidden lines and might be related to a wide angle molecular disk wind proposed by others.
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| 14. |
- Gahm, Gösta F., et al.
(författare)
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S Coronae Australis : a T Tauri twin
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 614
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Tidskriftsartikel (refereegranskat)abstract
- Context. The star S CrA is a tight visual binary consisting of two classical T Tauri stars. Both components are outstanding regarding their spectral characteristics and brightness variations. Aims. Our aim is to explore the extraordinary spectral features seen in these stars, derive stellar parameters, define spectral signatures of accreting gas and winds, estimate the inclinations of the disks, and to match numerical models with observed properties. Methods. High-resolution spectra were collected of each component over several nights at the European Southern Observatory (ESO) combined with photometric observations covering several years in UBVRI with the SMARTS telescope. The models developed include magnetospheric accretion and a disk wind. Results. Both stars undergo large variation in brightness, >= 2 mag in V band. The variations are caused mainly by variable foreground extinction from small-size dust grains, which may be carried along with the accreting gas. The photospheric absorption lines are washed out by superimposed continuous and line emission, and this veiling becomes occasionally exceptionally high. Nevertheless, we extracted the stellar spectra and found that both stars are very similar with regard to stellar parameters (T-eff, log g, v sin i, mass, radius, luminosity). The rotational periods, inferred from velocity shifts in lines originating in surface areas off-set from the pole, are also similar. Combined with the v sin i:s related inclinations were obtained, which agree well with those derived from our model simulations of Balmer line profiles: similar to 65 degrees for both stars. At this orientation the trajectories of infalling gas just above the stellar surfaces are parallel to the line-of-sight, and accordingly we observe extended red-shifted absorption components extending to +380 km s(-1), the estimated free-fall velocity at the surface. Rates of accretion and mass loss were obtained from the models. Conclusions. The two stars are remarkably similar, and S CrA can be regarded as a T Tauri twin. The components differ, however, in terms of degree of veiling and emission line profiles. We have found a good match between observed signatures of accreting gas, wind features, and rotational velocities with those resulting from our modelling for inclinations of similar to 65 degrees. These inclinations differ from those derived from interferometric near-infrared (NIR) spectroscopy, and possible causes for this puzzling discrepancy are discussed.
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| 15. |
- Gahm, Gösta F., et al.
(författare)
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Unveiling extremely veiled T Tauri stars
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 482:3, s. L35-L38
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Tidskriftsartikel (refereegranskat)abstract
- Context. Photospheric absorption lines in classical T Tauri stars (CTTS) are weak compared to normal stars. This so-called veiling is normally identified with an excess continuous emission formed in shock-heated gas at the stellar surface below the accretion streams.Aims. We have selected four stars (RW Aur A, RU Lup, S CrA NW and S CrA SE) with unusually strong veiling to make a detailed investigation of veiling versus stellar brightness and emission line strengths for comparisons to standard accretion models.Methods. We have monitored the stars photometrically and spectroscopically at several epochs.Results. In standard accretion models a variable accretion rate will lead to a variable excess emission. Consequently, the stellar brightness should vary accordingly. We find that the veiling of absorption lines in these stars is strongly variable and usually so large that it would require the release of several stellar luminosities of potential energy. At states of very large line dilution, the correspondingly large veiling factors derived correlate only weakly with brightness. Moreover, the emission line strengths violate the expected trend of veiling versus line strength. The veiling can change dramatically in one night, and is not correlated with the phase of the rotation periods found for two stars.Conclusions. We show that in at least three of the stars, when the veiling becomes high, the photospheric lines become filled-in by line emission, which produces large veiling factors unrelated to changes in any continuous emission from shocked regions. We also consider to what extent extinction by dust and electron scattering in the accretion stream may affect veiling measures in CTTS. We conclude that the degree of veiling cannot be used as a measure of accretion rates in CTTS with rich emission line spectra.
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| 24. |
- Kass, G E, et al.
(författare)
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Two separate plasma membrane Ca2+ carriers participate in receptor-mediated Ca2+ influx in rat hepatocytes.
- 1994
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 1878-2434. ; 1223:2, s. 226-33
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Tidskriftsartikel (refereegranskat)abstract
- The plasma membrane Ca2+ carrier system involved in receptor-mediated Ca2+ entry was studied. Using the Ca2+ readdition protocol, the rate of cytosolic free Ca2+ concentration ([Ca2+]i) increase in vasopressin-pretreated hepatocytes was significantly higher than in thapsigargin- or 2,5-di(tert-butyl)hydroquinone-pretreated cells. The addition of Mn2+ to unstimulated hepatocytes resulted in a biphasic quench of fura-2 fluorescence. After an initial phase that was fast in rate but of short duration, the rate of fura-2 quench by Mn2+ became much slower and lasted until all the cellular fura-2 was quenched. Pretreatment of the cells with vasopressin only accelerated the rate of the latter phase but not of the initial one. In agonist-stimulated cells, acidification of the extracellular medium or the presence of ruthenium red, econazole or SK&F 96365 decreased the rates of both [Ca2+]i increase and Mn2+ entry upon addition of the respective cation. By contrast, neomycin and N-tosyl-L-phenylalanine chloromethyl ketone markedly decreased the rate of [Ca2+]i increase upon Ca2+ readdition but had no effect on vasopressin-stimulated Mn2+ entry. None of the treatments affected the ability of vasopressin and thapsigargin to mobilize the internal Ca2+ store. It is concluded that in hepatocytes the two pathways of receptor-mediated Ca2+ entry control two distinct yet pharmacologically related cation carriers.
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| 27. |
- Petrov, P. P., et al.
(författare)
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Accretion-powered chromospheres in classical T Tauri stars
- 2011
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 535, s. A6-
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Tidskriftsartikel (refereegranskat)abstract
- Optical spectra of classical T Tauri stars (cTTS) are rich in emission lines of low-excitation species that are composed of narrow and broad components, related to two regions with different kinematics, densities, and temperatures. The photospheric spectrum is often veiled by an excess continuous emission. This veiling is usually attributed to radiation from a heated region beneath the accretion shock. The aim of this research is to clarify the nature of the veiling, and whether the narrow chromospheric lines of Fe I and other metals represent a standard chromosphere of a late-type star, or are induced by mass accretion. From high-resolution spectroscopy of DR Tauri we found that the amount of veiling in this star varies from practically nothing to factors more than 10 times the stellar continuum intensity, and that the veiling is caused by both a non-photospheric continuum and chromospheric line emission filling in the photospheric absorption lines. This effect can be shown to exist in several other T Tauri stars. We conclude that enhanced chromospheric emission in cTTS is linked not only to solar-like magnetic activity, but is powered to a greater extent by the accreting gas. We suggest that the area of enhanced chromospheric emission is induced by mass accretion, which modifies the local structure of stellar atmosphere in an area that is more extended than the hot accretion spot. The narrow emission lines from this extended area are responsible for the extra component in the veiling through line-filling of photospheric absorption lines.
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| 28. |
- Petrov, P. P., et al.
(författare)
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Doppler probe of accretion onto a T Tauri star
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 568, s. L10-
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Tidskriftsartikel (refereegranskat)abstract
- Context. The YY Ori stars are T Tauri stars with prominent time-variable redshifted absorption components that flank certain emission lines. S CrA, one of the brightest of these stars, affords the rare opportunity of directly probing the accretion processes on the line of sight to one of the components of this wide visual pair. Aims. We followed the spectral changes in S CrA to derive the physical structure of the accreting gas. Methods. A series of high-resolution spectra of the two components of S CrA was obtained during four nights with the UVES spectrograph at the Very Large Telescope. Results. We found that both stars are very similar with regard to surface temperature, radius, and mass. Variable redshifted absorption components are particularly prominent in the SE component. During one night, this star developed a spectrum unique among the T Tauri stars: extremely strong and broad redshifted absorption components appeared in many lines of neutral and ionized metals, in addition to those of hydrogen and helium. The absorption depths of cooler, low-ionization lines peak at low velocities - while more highly ionized lines have peak absorption depths at high velocities. The different line profiles indicate that the temperature and density of the accretion stream increase as material approaches the star. We derive the physical conditions of the flow at several points along the accretion funnel directly from the spectrum of the infalling gas. We estimated mass accretion rates of about 10(-7) M-circle dot/yr, which is similar to that derived from the relation based on the strength of Ha emission line. Conclusions. This is the first time the density and temperature distributions in accretion flows around a T Tauri star have been inferred from observations. Compared with predictions from standard models of accretion in T Tauri stars, which assume a dipole stellar magnetic field, we obtained higher densities and a steeper temperature rise toward the star.
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| 31. |
- Stempels, H. C., et al.
(författare)
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Periodic radial velocity variations in RU Lupi
- 2007
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 461:1, s. 253-259
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Tidskriftsartikel (refereegranskat)abstract
- Context: . RU Lup is a Classical T Tauri star with unusually strong emission lines, which has been interpreted as manifestations of accretion. Recently, evidence has accumulated that this star might have a variable radial velocity.Aims: .We intended to investigate in more detail the possible variability in radial velocity using a set of 68 high-resolution spectra taken at the VLT (UVES), the AAT (UCLES) and the CTIO (echelle).Methods: .Using standard cross-correlation techniques, we determined the radial velocity of RU Lup. We analysed these results with Phase-dispersion minimization and the Lomb-Scargle periodogram and searched for possible periodicities in the obtained radial velocities. We also analysed changes in the absorption line shapes and the photometric variability of RU Lup.Results: .Our analysis indicated that RU Lup exhibits variations in radial velocity with a periodicity of 3.71 days and an amplitude of 2.17 km s-1. These variations can be explained by the presence of large spots, or groups of spots, on the surface of RU Lup. We also considered a low-mass companion and stellar pulsations as alternative sources for these variations but found these to be unlikely.
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