876 research outputs found

    Facing the wind of the pre-FUor V1331 Cyg

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    The mass outflows in T Tauri stars (TTS) are thought to be an effective mechanism to remove angular momentum during the pre-main-sequence contraction of a low-mass star. The most powerful winds are observed at the FUor stage of stellar evolution. V1331 Cyg has been considered as a TTS at the pre-FUor stage. We analyse high-resolution spectra of V1331 Cyg collected in 1998-2007 and 20-d series of spectra taken in 2012. For the first time the photospheric spectrum of the star is detected and stellar parameters are derived: spectral type G7-K0 IV, mass 2.8 Msun, radius 5 Rsun, vsini < 6 km/s. The photospheric spectrum is highly veiled, but the amount of veiling is not the same in different spectral lines, being lower in weak transitions and much higher in strong transitions. The Fe II 5018, Mg I 5183, K I 7699 and some other lines of metals are accompanied by a `shell' absorption at radial velocity of about -240 km/s. We show that these absorptions form in the post-shock gas in the jet, i.e. the star is seen though its jet. The P Cyg profiles of H-alpha and H-beta indicate the terminal wind velocity of about 500 km/s, which vary on time-scales from several days to years. A model of the stellar wind is developed to interpret the observations. The model is based on calculation of hydrogen spectral lines using the radiative transfer code TORUS. The observed H-alpha and H-beta line profiles and their variability can be well reproduced with a stellar wind model, where the mass-loss rate and collimation (opening angle) of the wind are variable. The changes of the opening angle may be induced by small variability in magetization of the inner disc wind. The mass-loss rate is found to vary within (6-11)x10^{-8} Msun/yr, with the accretion rate of 2.0x10^{-6} Msun/yr.Comment: 11 pages, 12 figures; accepted for publication in MNRAS. Typographical errors have been corrected after the proof stag

    Feasibility and acceptability of psychosocial care forunsuccessful fertility treatment

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    Introduction Many people undergo fertility treatment to have biological children, but around four in ten patients complete all treatment cycles without having the children they desire. This triggers intense grief from which patients report taking on average 2 years to recover. Fertility guidelines and regulators stress the need to support patients through this process, but there is a scarcity of evaluated interventions to this end and evidence about when and how to offer care is lacking. This study explored patients' and healthcare professionals' (HCPs) experiences of and views about provision of psychosocial care (to patients facing unsuccessful fertility treatment, i.e., care provided by a mental health professional to address the emotional, cognitive, behavioural, relational and social needs that patients have at this stage of treatment). Methods Five qualitative online focus groups were conducted with Portuguese participants: three with patients waiting to initiate or undergoing their last cycle of in vitro fertilization/intracytoplasmic sperm injection or having completed it within the last 2 months without achieving a pregnancy and two with HCPs working at fertility clinics. Focus groups were recorded and transcribed verbatim, and data were analysed with Framework Analysis. Results Thirteen patients and nine HCPs participated. Analysis resulted in 1293 codes, systematically organized into 13 categories, 4 themes and 1 metatheme. The latter showed high consensus about the need for psychosocial care for unsuccessful treatment, but perceived challenges in its implementation. Themes reflected (1) consensual demand for psychosocial care at all stages of treatment but particularly at the end, (2) high perceived acceptability of integrating preventive care initiated during treatment with early psychosocial care only for those patients who experience unsuccessful treatment, (3) perceived challenges of implementing psychosocial care for unsuccessful treatment at clinics and (4) suggestions to promote its acceptability and feasibility. Conclusion Patients and HCPs perceive that clinics should improve care provision across the whole treatment pathway and in particular for unsuccessful fertility treatment. Suggestions were made to inform future research focusing on the development and evaluation of psychosocial interventions to this end. Patient or Public Contribution Patients and HCPs participated in the focus groups. Two HCPs also revised the manuscript.Thanks are due to nurse Cláudia Coelho for supporting this project and to patients and healthcare professionals who participated in the focus groups. The authors are also grateful to the European Social Fund and Portuguese Foundation for Science and Technology, I.P. (FCT; Fundação para a Ciência e a Tecnologia) for supporting the present study, through the Portuguese State Budget. Mariana Sousa-Leite has a doctoral fellowship (SFRH/BD/144429/2019), Raquel Costa has a postdoctoral fellowship (SFRH/BPD/117597/2016), and the EPI Unit, ITR and CIPsi (PSI/01662) are also funded by FTC, in the scope of the projects UIDB/04750/2020, LA/P/0064/2020 and UIDB/PSI/01662/2020, respectively

    Integration of Single Cell Traps, Chemical Gradient Generator and Photosensors in a Microfluidic Platform for the Study of Alpha-Synuclein Toxicity in Yeast

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    AbstractAlpha-synuclein (aSyn) is a key player in Parkinson's disease. Genetically engineered yeast cells producing aSyn fused with GFP (aSyn-GFP) have been used to study this protein. In this work, we present a microfluidic platform with integrated photosensors that captures single yeast cells in arrays of hydrodynamic traps and exposes them to a chemical gradient of precise composition. This platform enables the study of the effects of aSyn expression level and aggregation in genetically modified yeast cells by chemical stimulation. The photosensors allow the detection of cells in the traps by measuring the variations in light transmission or of the fluorescence produced by aSyn-GFP for real-time signal acquisition

    Evaluation of Antipsychotic Drugs’ Stability in Oral Fluid Samples

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    Antipsychotics have narrow therapeutic windows, and their monitoring in biological fluids is therefore important; consequently, stability in those fluids must be investigated during method development and validation. This work evaluates the stability of chlorpromazine, levomepromazine, cyamemazine, clozapine, haloperidol, and quetiapine in oral fluid (OF) samples, using the dried saliva spots (DSS) sampling approach and gas chromatography coupled to tandem mass spectrometry. Since many parameters can influence the stability of the target analytes, design of experiments was adopted to check the crucial factors that affect that stability in a multivariate fashion. The studied parameters were the presence of preservatives at different concentrations, temperature, light, and time. It was possible to observe that antipsychotic stability improved when OF samples in DSS were stored at 4 °C, with a low ascorbic acid concentration, and in the absence of light. With these conditions, chlorpromazine and quetiapine were stable for 14 days, clozapine and haloperidol were stable for 28 days, levomepromazine remained stable for 44 days, and cyamemazine was stable for the entire monitored period (146 days). This is the first study that evaluates the stability of these antipsychotics in OF samples after application to DSS cards.info:eu-repo/semantics/publishedVersio

    Acute kidney injury, long-term renal function and mortality in patients undergoing major abdominal surgery: a cohort analysis

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    BACKGROUND: Acute kidney injury (AKI) is frequent during hospitalization and may contribute to adverse consequences. We aimed to evaluate long-term adverse renal function and mortality after postoperative AKI in a cohort of patients undergoing major abdominal surgery. METHODS: We performed a retrospective analysis of adult patients who underwent major non-vascular abdominal surgery between January 2010 and February 2011 at the Department of Surgery II of Hospital de Santa Maria-Centro Hospitalar Lisboa Norte, Portugal. Exclusion criteria were as follows: chronic kidney disease on renal replacement therapy, undergoing renal replacement therapy the week before surgery, death before discharge and loss to follow-up through January 2014. Patients were categorized according to the development of postoperative AKI in the first 48 h after surgery using the Kidney Disease: Improving Global Outcomes classification. AKI was defined by an increase in absolute serum creatinine (SCr) ≥0.3 mg/dL or by a percentage increase in SCr ≥50% and/or by a decrease in urine output to 6 h. Adverse renal outcomes (need for long-term dialysis and/or a 25% decrease in estimated glomerular filtration rate after hospital discharge) and mortality after discharge were evaluated. Cumulative mortality was analysed with the Kaplan-Meier method and log-rank test and outcome predictive factors with the Cox regression. Significance was set at P < 0.05. RESULTS: Of 390 selected patients, 72 (18.5%) developed postoperative AKI. The median follow-up was 38 months. Adverse renal outcomes and death after hospital discharge were more frequent among AKI patients (47.2 versus 22.0%, P < 0.0001; and 47.2 versus 20.5%, P < 0.0001, respectively). The 4 year cumulative probability of death was 44.4% for AKI patients, while it was 19.8% for patients with no AKI (log-rank test, P < 0.0001). In multivariate analysis, AKI was a risk factor for adverse renal outcomes (adjusted hazard ratio 1.6, P = 0.046) and mortality (adjusted hazard ratio 1.4, P = 0.043). CONCLUSIONS: AKI after major abdominal surgery was independently associated with the risk of long-term need for dialysis and/or renal function decline and with the risk of death after hospital discharge

    Coordinated Multiwavelength Observations of V410Tau

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    In November 2001 we undertook a coordinated observing campaign to study the connection between X-ray and optical variability in the weak-line T Tauri star V410Tau. The observing plan included three 15 ksec observations with Chandra using the Advanced CCD Imaging Spectrometer for Spectroscopy scheduled for different phases of the known 1.87 d starspot cycle. Photometric and spectroscopic monitoring of V410Tau involving telescopes on three different continents was scheduled simultaneously with the Chandra exposures.Comment: 3 pages, Poster Proceedings of "1st Potsdam Thinkshop on Sunspots and Starspots", Potsdam, Germany, May 200

    An Infrared Coronagraphic Survey for Substellar Companions

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    We have used the F160W filter (1.4-1.8 um) and the coronagraph on the Near-InfraRed Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope (HST) to survey 45 single stars with a median age of 0.15 Gyr, an average distance of 30 pc, and an average H-magnitude of 7 mag. For the median age we were capable of detecting a 30 M_Jup companion at separations between 15 and 200 AU. A 5 M_Jup object could have been detected at 30 AU around 36% of our primaries. For several of our targets that were less than 30 Myr old, the lower mass limit was as low as a Jupiter mass, well into the high mass planet region. Results of the entire survey include the proper motion verification of five low-mass stellar companions, two brown dwarfs (HR7329B and TWA5B) and one possible brown dwarf binary (Gl 577B/C).Comment: 11 figures, accepted by A

    The Gaia-ESO Survey: Chromospheric Emission, Accretion Properties, and Rotation in γ\gamma Velorum and Chamaeleon I

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    We use the fundamental parameters delivered by the GES consortium in the first internal data release to select the members of γ\gamma Vel and Cha I among the UVES and GIRAFFE spectroscopic observations. A total of 140 γ\gamma Vel members and 74 Cha I members were studied. We calculated stellar luminosities through spectral energy distributions, while stellar masses were derived by comparison with evolutionary tracks. The spectral subtraction of low-activity and slowly rotating templates, which are rotationally broadened to match the vsiniv\sin i of the targets, enabled us to measure the equivalent widths (EWs) and the fluxes in the Hα\alpha and Hβ\beta lines. The Hα\alpha line was also used for identifying accreting objects and for evaluating the mass accretion rate (M˙acc\dot M_{\rm acc}). The distribution of vsiniv\sin i for the members of γ\gamma Vel displays a peak at about 10 km s1^{-1} with a tail toward faster rotators. There is also some indication of a different vsiniv\sin i distribution for the members of its two kinematical populations. Only a handful of stars in γ\gamma Vel display signatures of accretion, while many more accretors were detected in the younger Cha~I. Accreting and active stars occupy two different regions in a TeffT_{\rm eff}-flux diagram and we propose a criterion for distinguishing them. We derive M˙acc\dot M_{\rm acc} in the ranges 101110^{-11}-109M10^{-9} M_\odotyr1^{-1} and 101010^{-10}-107M10^{-7} M_\odotyr1^{-1} for γ\gamma Vel and Cha I accretors, respectively. We find less scatter in the M˙accM\dot M_{\rm acc}-M_\star relation derived through the Hα\alpha EWs, when compared to the Hα\alpha 10%W10\%W diagnostics, in agreement with other authors

    Interpretation of the Veiling of the Photospheric Spectrum for T Tauri Stars in Terms of an Accretion Model

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    The problem on heating the atmospheres of T Tauri stars by radiation from an accretion shock has been solved. The structure and radiation spectrum of the emerging so-called hot spot have been calculated in the LTE approximation. The emission not only in continuum but also in lines has been taken into account for the first time when calculating the spot spectrum. Comparison with observations has shown that the strongest of these lines manifest themselves as narrow components of helium and metal emission lines, while the weaker ones decrease significantly the depth of photospheric absorption lines, although until now, this effect has been thought to be due to the emission continuum alone. The veiling by lines changes the depth of different photospheric lines to a very different degree even within a narrow spectral range. Therefore, the nonmonotonic wavelength dependence of the degree of veiling r found for some CTTS does not suggest a nontrivial spectral energy distribution of the veiling continuum. In general, it makes sense to specify the degree of veiling r only by providing the set of photospheric lines from which this quantity was determined. We show that taking into account the contribution of lines to the veiling of the photospheric spectrum can cause the existing estimates of the accretion rate onto T Tauri stars to decrease by several times, with this being also true for stars with a comparatively weakly veiled spectrum. Neglecting the contribution of lines to the veiling can also lead to appreciable errors in determining the effective temperature, interstellar extinction, radial velocity, and vsin(i)
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