We report on the properties of pre-main-sequence objects in the Taurus molecular clouds as observed in seven mid- and far-infrared bands with the Spitzer Space Telescope. There are 215 previously ...identified members of the Taurus star-forming region in our ~44 deg2 map these members exhibit a range of Spitzer colors that we take to define young stars still surrounded by circumstellar dust (noting that ~20% of the bona fide Taurus members exhibit no detectable dust excesses). We looked for new objects in the survey field with similar Spitzer properties, aided by extensive optical, X-ray, and ultraviolet imaging, and found 148 new candidate members of Taurus. We have obtained follow-up spectroscopy for about half the candidate sample, thus far confirming 34 new members, three probable new members, and 10 possible new members, an increase of 15%-20% in Taurus members. Of the objects for which we have spectroscopy, seven are now confirmed extragalactic objects, and one is a background Be star. The remaining 93 candidate objects await additional analysis and/or data to be confirmed or rejected as Taurus members. Most of the new members are Class II M stars and are located along the same cloud filaments as the previously identified Taurus members. Among non-members with Spitzer colors similar to young, dusty stars are evolved Be stars, planetary nebulae, carbon stars, galaxies, and active galactic nuclei.
Context.The Taurus Molecular Cloud (TMC) is the nearest large star-forming region, prototypical for the distributed mode of low-mass star formation. Pre-main sequence stars are luminous X-ray ...sources, probably mostly owing to magnetic energy release. Aims.The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST) presented in this paper surveys the most populated ≈5 square degrees of the TMC, using the XMM-Newton X-ray observatory to study the thermal structure, variability, and long-term evolution of hot plasma, to investigate the magnetic dynamo, and to search for new potential members of the association. Many targets are also studied in the optical, and high-resolution X-ray grating spectroscopy has been obtained for selected bright sources. Methods.The X-ray spectra have been coherently analyzed with two different thermal models (2-component thermal model, and a continuous emission measure distribution model). We present overall correlations with fundamental stellar parameters that were derived from the previous literature. A few detections from Chandra observations have been added. Results.The present overview paper introduces the project and provides the basic results from the X-ray analysis of all sources detected in the XEST survey. Comprehensive tables summarize the stellar properties of all targets surveyed. The survey goes deeper than previous X-ray surveys of Taurus by about an order of magnitude and for the first time systematically accesses very faint and strongly absorbed TMC objects. We find a detection rate of 85% and 98% for classical and weak-line T Tau stars (CTTS resp. WTTS), and identify about half of the surveyed protostars and brown dwarfs. Overall, 136 out of 169 surveyed stellar systems are detected. We describe an X-ray luminosity vs. mass correlation, discuss the distribution of X-ray-to-bolometric luminosity ratios, and show evidence for lower X-ray luminosities in CTTS compared to WTTS. Detailed analysis (e.g., variability, rotation-activity relations, influence of accretion on X-rays) will be discussed in a series of accompanying papers.
Over the past decades, rare earth elements (REE) and their radioactive isotopes have received tremendous attention in sedimentary geochemistry, as tracers for the geological history of the ...continental crust and provenance studies. In this study, we report on elemental concentrations and neodymium (Nd) isotopic compositions for a large number of sediments collected near the mouth of rivers worldwide, including some of the world’s major rivers. Sediments were leached for removal of non-detrital components, and both clay and silt fractions were retained for separate geochemical analyses. Our aim was to re-examine, at the scale of a large systematic survey, whether or not REE and Nd isotopes could be fractionated during Earth surface processes.
Our results confirmed earlier assumptions that river sediments do not generally exhibit any significant grain-size dependent Nd isotopic variability. Most sediments from rivers draining old cratonic areas, sedimentary systems and volcanic provinces displayed similar Nd isotopic signatures in both clay and silt fractions, with ΔεNd(clay–silt)<|1|. A subtle decoupling of Nd isotopes between clays and silts was identified however in a few major river systems (e.g. Nile, Mississippi, Fraser), with clays being systematically shifted towards more radiogenic values. This observation suggests that preferential weathering of volcanic and/or sedimentary rocks relative to more resistant lithologies may occur in river basins, possibly leading locally to Nd isotopic decoupling between different size fractions. Except for volcanogenic sediments, silt fractions generally displayed homogeneous REE concentrations, exhibiting relatively flat shale-normalized patterns. However, clay fractions were almost systematically characterized by a progressive enrichment from the heavy to the light REE and a positive europium (Eu) anomaly. In agreement with results from previous soil investigations, the observed REE fractionation between clays and silts is probably best explained by preferential alteration of feldspars and/or accessory mineral phases. Importantly, this finding clearly indicates that silicate weathering can lead to decoupling of REE between different grain-size fractions, with implications for sediment provenance studies.
Finally, we propose a set of values for a World River Average Clay (WRAC) and Average Silt (WRAS), which provide new estimates for the average composition of the weathered and eroded upper continental crust, respectively, and could be used for future comparison purposes.
Context. PIONIER stands for Precision Integrated-Optics Near-infrared Imaging ExpeRiment. It combines four 1.8m Auxilliary Telescopes or four 8m Unit Telescopes of the Very Large Telescope ...Interferometer (ESO, Chile) using an integrated optics combiner. The instrument was integrated at IPAG in December 2009 and commissioned at the Paranal Observatory in October 2010. It has provided scientific observations since November 2010. Aims. In this paper, we explain the instrumental concept and describe the standard operational modes and the data reduction strategy. We present the typical performance and discuss how to improve them. Methods. This paper is based on laboratory data obtained during the integrations at IPAG, as well as on-sky data gathered during the commissioning at VLTI. We illustrate the imaging capability of PIONIER on the binaries δ Sco and HIP11231. Results. PIONIER provides six visibilities and three independent closure phases in the H band, either in a broadband mode or with a low spectral dispersion (R = 40), using natural light (i.e. unpolarized). The limiting magnitude is Hmag = 7 in dispersed mode under median atmospheric conditions (seeing < 1, τ0 > 3ms) with the 1.8m Auxiliary Telescopes. We demonstrate a precision of 0.5deg on the closure phases. The precision on the calibrated visibilities ranges from 3% to 15% depending on the atmospheric conditions. Conclusions. PIONIER was installed and successfully tested as a visitor instrument for the VLTI. It permits high angular resolution imaging studies at an unprecedented level of sensitivity. The successful combination of the four 8m Unit Telescopes in March 2011 demonstrates that VLTI is ready for four-telescope operation.
The pivotal clinical trials have largely demonstrated the efficacy and safety of ustekinumab in Crohn's disease. Real-life cohorts published so far only include very few bio-naïve patients. This ...study assesses effectiveness and safety of ustekinumab in bio-naïve and bio-failure patients treated with ustekinumab in routine practice and look for predictors of response.
We performed a retrospective monocentric study. Initial response was assessed by maintenance therapy beyond week 16. Sustained response was assessed by the continuation or cessation of therapy over time for another reason than stopping in sustained remission. Treatment persistence was assessed by Kaplan Meier curves and predictors of treatment persistence were studied by univariate and multivariate Cox model.
Out of 156 recorded patients, three patients were still in their induction phase at time of analysis and 5 patients were lost to follow-up, leaving 148 patients for clinical effectiveness analyses, including 35 bio-naïve when starting ustekinumab. A maintenance therapy was initiated in 79.7%. At one year, the probability to be still treated with ustekinumab was 73.8%. Treatment cessation increased with smoking in multivariate analysis. Previous biologic failure (as a whole), CRP and fecal calprotectin baseline levels did not influence initial response and treatment persistence.
A large proportion of CD patients initially respond to ustekinumab and continue this treatment beyond one year. Treatment persistence is as high in bio-failure as in bio-naïve patients.
Friedreich's ataxia (FA) is a rare autosomal recessive mitochondrial disease most commonly due to a triplet repeat expansion guanine-adenine-adenine (GAA) in the FXN gene. Cardiac disease is the ...major cause of death, patients with reduced left ventricular ejection fraction (LVEF) having the worse prognosis. Longitudinal strain (LS) appeared to be a better predictor of outcome than LVEF in different diseases. We compared the prognostic value of LS measured from the 4 chambers view to LVEF.
From 2003 to 2017 consecutive patients with FA were included and LS analysis was retrospectively performed.
We studied 140 patients, with a median age of 34 (26–41) years (Q1–Q3) with age at onset of 14 (11–19) years and GAA repeats on the shorter allele of 600 (467–783) pb. Mean LS was 19.9 ± 5.0% and LVEF 64 ± 8%. After a mean follow-up of 7.4 ± 3.9 years, 14 patients died. In univariate Cox analysis, all-cause mortality was associated with: LS (HR 0.83; 95%CI, 0.75–0.91, p = 0.0002), LVEF (HR 0.30; 95%CI, 0.19–0.49, p < 0.0001), GAA repeats on the shorter allele (HR 1.29; 95%CI, 1.10–1.51, p = 0.002), age at onset (HR 0.87; 95%CI, 0.77–0.98, p = 0.018), LVSystolic Diameter (HR 1.17; 95%CI, 1.09–1.26, p < 0.0001), LVMass index (HR 1.02; 95%CI, 1.00–1.04, p = 0.027), and LVDiastolic Diameter (HR1.12; 95%CI, 1.01–1.23, p = 0.028). In multivariate analysis, LVEF was the only independent predictor of mortality (HR 0.41; 95%CI, 0.23–0.74, p = 0.0029).
In FA, LS was not an independent predictor of mortality, LVEF remained the only independent predictor in the present study.
•Longitudinal strain correlates with the length of both alleles of the FXN gene in Friedreich Ataxia (FA).•Longitudinal strain (LS) is a strong prognostic factor in univariate analysis in FA.•LS is not an independent predictor of mortality when LVEF is included in the analysis in FA patients.•The role of longitudinal strain in the management of FA patients remains to be defined.
Recent studies of the substellar population in the Taurus cloud have revealed a deficit of brown dwarfs compared to the Trapezium cluster population. However, these works have concentrated on the ...highest stellar density regions of the Taurus cloud. We have performed a large scale optical survey of this region, covering a total area of QQQ ?28 deg2, and encompassing the densest parts of the cloud as well as their surroundings, down to a mass detection limit of 15 MJ. We present the optical spectroscopic follow-up observations of 97 photometrically selected potential new low-mass Taurus members, of which 27 are strong late-M spectral type (SpT . M4V) candidates. Our spectroscopic survey is 87% complete down to i' = 20 for spectral types later than M4V, which corresponds to a mass completeness limit of 30 MJ for ages ,10 Myr and Av , 4. We derive spectral types, visual absorption and luminosity class estimates and discuss our criteria to assess Taurus membership. These observations reveal 5 new VLM Taurus members and 12 new BDs. Two of the new VLM sources and four of the new substellar members exhibit accretion/outflow signatures similar to higher mass classical T Tauri stars. From levels of Ha emission we derive a fraction of accreting sources of 42% in the substellar Taurus population. Combining our observations with previously published results, we derive an updated substellar to stellar ratio in Taurus of Rss = 0.23 c 0.05. This ratio now appears consistent with the value previously derived in the Trapezium cluster under similar assumptions of 0.26 c 0.04. We find indications that the relative numbers of BDs with respect to stars is decreased by a factor 2 in the central regions of the aggregates with respect to the more distributed population. Our findings are best explained in the context of the embryo-ejection model where brown dwarfs originate from dynamical interactions in small N unstable multiple systems.
With the PACS instrument on Herschel, 134 low mass members of the Taurus star-forming region spanning the M4-L0 spectral type range and covering the transition from low mass stars to brown dwarfs ...were observed. Combining the new Herschel results with other Herschel programs, a total of 150 of the 154 M4-L0 Taurus members have observations, and we have added an additional 3 targets from Spitzer to form the 153-object TBOSS (Taurus Boundary of Stellar/Substellar) sample, a 99% complete study. Among the 150 targets, 70 μm flux densities were measured for 7 of the 7 Class I objects, 48 of the 67 Class II objects, and 3 of the 76 Class III objects. For the detected Class II objects, the median 70 μm flux density level declines with spectral type; however, the distribution of excess relative to central object flux density does not change across the stellar/substellar boundary in the M4-L0 range. Connecting the 70 μm TBOSS values with the results from K0-M3 Class II members results in the first comprehensive census of far-IR emission across the full mass spectrum of the stellar and substellar population of a star-forming region, and the median flux density declines with spectral type in a trend analogous to the flux density decline expected for the central objects. Spectral energy distributions (SEDs) were constructed for all TBOSS targets covering the optical to far-IR range and extending to the submm/mm for a subset of sources with longer wavelength data. Based on an initial exploration of the impact of different physical parameters on the Herschel flux densities, geometrical factors such as inclination and structural parameters such as scale height and flaring have the largest influence on the flux densities in the PACS bands. From the 24 μm to 70 μm spectral index of the SEDs, 5 new candidate transition disks were identified. Considering the previously known and new candidate transition disks, the spectral indices over longer wavelengths (≥70 μm) are not distinct from those of the full Class II population, suggesting that the outer regions of the transition disks are similar to Class II disks. The steep 24 μm to 70 μm slope for a subset of 8 TBOSS targets may be an indication of truncated disks in these systems, however additional measurements are required to establish the outer radii of these disks conclusively. From existing high angular resolution companion search observations, two examples of mixed pair systems that include secondaries with disks were measured in the Herschel data. Finally, comparing the TBOSS results with a Herschel study of Ophiuchus brown dwarfs reveals a lower fraction of disks around the Taurus substellar population with flux densities comparable to the Ophiuchus disks. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia, and with important participation from NASA.Appendices are available in electronic form at www.aanda.org Tables 1, 2, 4, 5, and A.1-A.4 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/570/A29
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