224 research outputs found

    Rotational velocities of the giants in symbiotic stars: III. Evidence of fast rotation in S-type symbiotics

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    We have measured the projected rotational velocities (vsini) in a number of symbiotic stars and M giants using high resolution spectroscopic observations. On the basis of our measurements and data from the literature, we compare the rotation of mass-donors in symbiotics with vsini of field giants and find that: (1) the K giants in S-type symbiotics rotate at vsini>4.5 km/s, which is 2-4 times faster than the field K giants; (2) the M giants in S-type symbiotics rotate on average 1.5 times faster than the field M giants. Statistical tests show that these differences are highly significant: p-value < 0.001 in the spectral type bins K2III-K5III, M0III-M6III, and M2III-M5III; (3) our new observations of D'-type symbiotics also confirm that they are fast rotators. As a result of the rapid rotation, the cool giants in symbiotics should have 3-30 times larger mass loss rates. Our results suggest also that bipolar ejections in symbiotics seem to happen in objects where the mass donors rotate faster than the orbital period. All spectra used in our series of papers can be obtained upon request from the authors.Comment: MNRAS (accepted), 7 pages, 5 figure

    Yellow Supergiants in the Small Magellanic Cloud (SMC): Putting Current Evolutionary Theory to the Test

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    The yellow supergiant content of nearby galaxies provides a critical test of massive star evolutionary theory. While these stars are the brightest in a galaxy, they are difficult to identify because a large number of foreground Milky Way stars have similar colors and magnitudes. We previously conducted a census of yellow supergiants within M31 and found that the evolutionary tracks predict a yellow supergiant duration an order of magnitude longer than we observed. Here we turn our attention to the SMC, where the metallicity is 10x lower than that of M31, which is important as metallicity strongly affects massive star evolution. The SMC's large radial velocity (~160 km/s) allows us to separate members from foreground stars. Observations of ~500 candidates yielded 176 near-certain SMC supergiants, 16 possible SMC supergiants, along with 306 foreground stars and provide good relative numbers of yellow supergiants down to 12Mo. Of the 176 near-certain SMC supergiants, the kinematics predicted by the Besancon model of the Milky Way suggest a foreground contamination of >4%. After placing the SMC supergiants on the H-R diagram and comparing our results to the Geneva evolutionary tracks, we find results similar to those of the M31 study: while the locations of the stars on the H-R diagram match the locations of evolutionary tracks well, the models over-predict the yellow supergiant lifetime by a factor of ten. Uncertainties about the mass-loss rates on the main-sequence thus cannot be the primary problem with the models.Comment: Accepted by the Ap

    The Missing Luminous Blue Variables and the Bistability Jump

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    We discuss an interesting feature of the distribution of luminous blue variables on the H-R diagram, and we propose a connection with the bistability jump in the winds of early-type supergiants. There appears to be a deficiency of quiescent LBVs on the S Dor instability strip at luminosities between log L/Lsun = 5.6 and 5.8. The upper boundary, is also where the temperature-dependent S Dor instability strip intersects the bistability jump at about 21,000 K. Due to increased opacity, winds of early-type supergiants are slower and denser on the cool side of the bistability jump, and we postulate that this may trigger optically-thick winds that inhibit quiescent LBVs from residing there. We conduct numerical simulations of radiation-driven winds for a range of temperatures, masses, and velocity laws at log L/Lsun=5.7 to see what effect the bistability jump should have. We find that for relatively low stellar masses the increase in wind density at the bistability jump leads to the formation of a modest to strong pseudo photosphere -- enough to make an early B-type star appear as a yellow hypergiant. Thus, the proposed mechanism will be most relevant for LBVs that are post-red supergiants. Yellow hypergiants like IRC+10420 and rho Cas occupy the same luminosity range as the ``missing'' LBVs, and show apparent temperature variations at constant luminosity. If these yellow hypergiants do eventually become Wolf-Rayet stars, we speculate that they may skip the normal LBV phase, at least as far as their apparent positions on the HR diagram are concerned.Comment: 20 pages, 4 figs, accepted by Ap

    Patterns of recurrence following definitive chemoradiation for patients with proximal esophageal cancer

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    Introduction: The aim of this retrospective study was to determine the patterns of recurrence and overall survival (OS) in patients achieving clinical complete response after treatment with definitive chemoradiation (CRT) for proximal esophageal cancer. Materials and methods: Patients with proximal esophageal cancer treated with CRT between 2004 and 2014 in 11 centers in the Netherlands were included. OS and progression-free survival (PFS) were calculated using the Kaplan-Meier method. Cumulative incidence of first recurrence (locoregional or distant) and locoregional recurrence (LRR) were assessed using competing risk analyses. Results: In 197 of the 200 identified patients, response was evaluated, 133 (68%) showed a complete response. In complete responders, median OS, three-year OS, and PFS were 45.0 months (95% CI 34.8-61.5 months), 58% (95% CI 48-66), and 49% (95% CI 40-57), respectively. Three- and five-year risk of recurrence were respectively 40% (95% CI 31-48), and 45% (95% CI 36-54). Three- and five-year risk of LRR were 26% (95% CI 19-33), and 30% (95% CI 22-38). Eight of 32 patients with an isolated LRR underwent salvage surgery, with a median OS of 32.0 months (95% CI 6.8-not reached). Conclusion: In patients with a complete response after definitive CRT for proximal esophageal cancer, most recurrences were locoregional and developed within the first three years after CRT. These findings suggest to shorten locoregional follow-up from five to three years. (C) 2021 The Authors. Published by Elsevier Ltd

    Description of the Scenario Machine

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    We present here an updated description of the "Scenario Machine" code. This tool is used to carry out a population synthesis of binary stars. Previous version of the description can be found at http://xray.sai.msu.ru/~mystery//articles/review/contents.htmlComment: 32 pages, 3 figures. Corrected typo

    Phase II Feasibility and Biomarker Study of Neoadjuvant Trastuzumab and Pertuzumab With Chemoradiotherapy for Resectable Human Epidermal Growth Factor Receptor 2-Positive Esophageal Adenocarcinoma:TRAP Study

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    PURPOSE: Approximately 15% to 43% of esophageal adenocarcinomas (EACs) are human epidermal growth factor receptor 2 (HER2) positive. Because dual-agent HER2 blockade demonstrated a survival benefit in breast cancer, we conducted a phase II feasibility study of trastuzumab and pertuzumab added to neoadjuvant chemoradiotherapy (nCRT) in patients with EAC. PATIENTS AND METHODS: Patients with resectable HER2-positive EAC received standard nCRT with carboplatin and paclitaxel and 41.4 Gy of radiotherapy, with 4 mg/kg of trastuzumab on day 1, 2 mg/kg per week during weeks 2 to 6, and 6 mg/kg per week during weeks 7, 10, and 13 and 840 mg of pertuzumab every 3 weeks. The primary end point was feasibility, defined as ≥ 80% completion of treatment with both trastuzumab and pertuzumab. An exploratory comparison of survival with a propensity score-matched cohort receiving standard nCRT was performed, as were exploratory pharmacokinetic and biomarker analyses. RESULTS: Of the 40 enrolled patients (78% men; median age, 63 years), 33 (83%) completed treatment with trastuzumab and pertuzumab. No unexpected safety events were observed. R0 resection was achieved in all patients undergoing surgery, with pathologic complete response in 13 patients (34%). Three-year progression-free and overall survival (OS) were 57% and 71%, respectively (median follow-up, 32.1 months). Compared with the propensity score-matched cohort, a significantly longer OS was observed with HER2 blockade (hazard ratio, 0.58; 95% CI, 0.34 to 0.97). Results of pharmacokinetic analysis and activity on [18F]fluorodeoxyglucose positron emission tomography scans did not correlate with survival or pathologic response. Patients with HER2 3+ overexpression or growth factor receptor-bound protein 7 (Grb7) -positive tumors at baseline demonstrated significantly better survival (P = .007) or treatment response (P = .016), respectively. CONCLUSION: Addition of trastuzumab and pertuzumab to nCRT in patients with HER2-positive EAC is feasible and demonstrates potentially promising activity compared with historical controls. HER2 3+ overexpression and Grb7 positivity are potentially predictive for survival and treatment response, respectively

    Reasons for not reaching or using web-based self-management applications, and the use and evaluation of Oncokompas among cancer survivors, in the context of a randomised controlled trial

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    Introduction: The web-based self-management application Oncokompas was developed to support cancer survivors to monitor health-related quality of life and symptoms (Measure) and to provide tailored information (Learn) and supportive care options (Act). In a previously reported randomised controlled trial (RCT), 68% of 655 recruited survivors were eligible, and of those 45% participated in the RCT. Among participants of the RCT that were randomised to the intervention group, 52% used Oncokompas as intended. The aim of this study was to explore reasons for not participating in the RCT, and reasons for not using Oncokompas among non-users, and the use and evaluation of Oncokompas among users. Methods: Reasons for not participating were assessed with a study-specific questionnaire among 243 survivors who declined participation. Usage was investigated among 320 participants randomised to the intervention group of the RCT via system data and a study-specific questionnaire that was assessed during the 1 week follow-up (T1) assessment. Results: Main reasons for not participating were not interested in participation in scientific research (40%) and not interested in scientific research and Oncokompas (28%). Main reasons for not being interested in Oncokompas were wanting to leave the period of being ill behind (29%), no symptom burden (23%), or lacking internet skills (18%). Out of the 320 participants in the intervention group 167 (52%) used Oncokompas as intended. Among 72 non-users, main reasons for not using Oncokompas were no symptom burden (32%) or lack of time (26%). Among 248 survivors that activated their account, satisfaction and user-friendliness were rated with a 7 (scale 0–10). Within 3 (IQR 1–4) sessions, users selected 32 (IQR 6–37) topics. Main reasons for not using healthcare options in Act were that the information in Learn was already sufficient (44%) or no supportive care needs (32%). Discussion: Main reasons for not reaching or using Oncokompas were no symptom burden, no supportive care needs, or lack of time. Users selected many cancer-generic and tumour-specific topics to address, indicating added value of the wide range of available topics

    Acute cholecystitis in high risk surgical patients: percutaneous cholecystostomy versus laparoscopic cholecystectomy (CHOCOLATE trial): Study protocol for a randomized controlled trial

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    <p>Abstract</p> <p>Background</p> <p>Laparoscopic cholecystectomy in acute calculous cholecystitis in high risk patients can lead to significant morbidity and mortality. Percutaneous cholecystostomy may be an alternative treatment option but the current literature does not provide the surgical community with evidence based advice.</p> <p>Methods/Design</p> <p>The CHOCOLATE trial is a randomised controlled, parallel-group, superiority multicenter trial. High risk patients, defined as APACHE-II score 7-14, with acute calculous cholecystitis will be randomised to laparoscopic cholecystectomy or percutaneous cholecystostomy. During a two year period 284 patients will be enrolled from 30 high volume teaching hospitals. The primary endpoint is a composite endpoint of major complications within three months following randomization and need for re-intervention and mortality during the follow-up period of one year. Secondary endpoints include all other complications, duration of hospital admission, difficulty of procedures and total costs.</p> <p>Discussion</p> <p>The CHOCOLATE trial is designed to provide the surgical community with an evidence based guideline in the treatment of acute calculous cholecystitis in high risk patients.</p> <p>Trial Registration</p> <p>Netherlands Trial Register (NTR): <a href="http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2666">NTR2666</a></p

    The evolution of rotating stars

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    First, we review the main physical effects to be considered in the building of evolutionary models of rotating stars on the Upper Main-Sequence (MS). The internal rotation law evolves as a result of contraction and expansion, meridional circulation, diffusion processes and mass loss. In turn, differential rotation and mixing exert a feedback on circulation and diffusion, so that a consistent treatment is necessary. We review recent results on the evolution of internal rotation and the surface rotational velocities for stars on the Upper MS, for red giants, supergiants and W-R stars. A fast rotation is enhancing the mass loss by stellar winds and reciprocally high mass loss is removing a lot of angular momentum. The problem of the ``break-up'' or Ω\Omega-limit is critically examined in connection with the origin of Be and LBV stars. The effects of rotation on the tracks in the HR diagram, the lifetimes, the isochrones, the blue to red supergiant ratios, the formation of W-R stars, the chemical abundances in massive stars as well as in red giants and AGB stars, are reviewed in relation to recent observations for stars in the Galaxy and Magellanic Clouds. The effects of rotation on the final stages and on the chemical yields are examined, as well as the constraints placed by the periods of pulsars. On the whole, this review points out that stellar evolution is not only a function of mass M and metallicity Z, but of angular velocity Ω\Omega as well.Comment: 78 pages, 7 figures, review for Annual Review of Astronomy and Astrophysics, vol. 38 (2000
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