727 research outputs found
Low temperature mean opacities for the carbon-rich regime
Asymptotic Giant Branch (AGB) stars undergo a change in their chemical
composition during their evolution. This in turn leads to an alteration of the
radiative opacities, especially in the cool layers of the envelope and the
atmosphere, where molecules are the dominant opacity sources. A key parameter
in this respect is the number ratio of carbon to oxygen atoms (C/O). In terms
of low temperature mean opacities, a variation of this parameter usually cannot
be followed in stellar evolution models, because up to now tabulated values
were only available for scaled solar metal mixtures (with C/O ~ 0.5). We thus
present a set of newly generated tables containing Rosseland mean opacity
coefficients covering both the oxygen-rich (C/O
1) regime. We compare our values to existing tabular data and investigate the
relevant molecular opacity contributors.Comment: 8 pages, 5 figures. To appear in the AIP Proceedings of the IXth
Torino Workshop on AGB Nucleosynthesi
Low-mass lithium-rich AGB stars in the Galactic bulge: evidence for Cool Bottom Processing?
Context: The stellar production of the light element lithium is still a
matter of debate.
Aims: We report the detection of low-mass, Li-rich Asymptotic Giant Branch
(AGB) stars located in the Galactic bulge.
Methods: A homogeneous and well-selected sample of low mass, oxygen-rich AGB
stars in the Galactic bulge has been searched for the absorption lines of Li.
Using spectral synthesis techniques, we determine from high resolution UVES/VLT
spectra the Li abundance in four out of 27 sample stars, and an upper limit for
the remaining stars.
Results: Two stars in our sample have a solar Li abundance or above; these
stars seem to be a novelty, since they do not show any s-element enhancement.
Two more stars have a Li abundance slightly below solar; these stars do show
s-element enhancement in their spectra. Different scenarios which lead to an
increased Li surface abundance in AGB stars are discussed.
Conclusions: Of the different enrichment scenarios presented, Cool Bottom
Processing (CBP) is the most likely one for the Li-rich objects identified
here. Self-enrichment by Hot Bottom Burning (HBB) seems very unlikely as all
Li-rich stars are below the HBB mass limit. Also, the ingestion of a low mass
companion into the stars' envelope is unlikely because the associated
additional effects are lacking. Mass transfer from a former massive binary
companion is a possible scenario, if the companion produced little s-process
elements. A simple theoretical estimation for the Li abundance due to CBP is
presented and compared to the observed values.Comment: 5 pages, 3 figures, accepted by A&A Letter
Lithium abundances along the RGB: FLAMES-GIRAFFE spectra of a large sample of low-mass Bulge stars
Context: A small number of K-type giants on the red giant branch (RGB) is
known to be very rich in lithium (Li). This fact is not accounted for by
standard stellar evolution theory. The exact phase and mechanism of Li
enrichment is still a matter of debate. Aims: Our goal is to probe the
abundance of Li along the RGB, from its base to the tip, to confine Li-rich
phases that are supposed to occur on the RGB. Methods: For this end, we
obtained medium-resolution spectra with the FLAMES spectrograph at the VLT in
GIRAFFE mode for a large sample of 401 low-mass RGB stars located in the
Galactic bulge. The Li abundance was measured in the stars with a detectable Li
670.8 nm line by means of spectral synthesis with COMARCS model atmospheres. A
new 2MASS (J-K) - Teff calibration from COMARCS models is presented in the
Appendix. Results: Thirty-one stars with a detectable Li line were identified,
three of which are Li-rich according to the usual criterion (). The stars are distributed all along the RGB, not concentrated in
any particular phase of the red giant evolution (e.g. the luminosity bump or
the red clump). The three Li-rich stars are clearly brighter than the
luminosity bump and red clump, and do not show any signs of enhanced mass loss.
Conclusions: We conclude that the Li enrichment mechanism cannot be restricted
to a clearly defined phase of the RGB evolution of low-mass stars
(M\sim1M_{\sun}), contrary to earlier suggestions from disk field stars.Comment: 6 pages (14 with appendix), 5 figures (1 in appendix), accepted for
publication in A&
Serum Scavenging Capacity and Folliculogenesis Impact following Flaxseed Consumption in the First-Generation Mice Pups
Flaxseed is a source of antioxidants utilized for female infertility treatment in traditional medicine. This study investigated the effects of flax hydroalcoholic extract and flaxseeds during prenatal and postnatal (PND) periods on folliculogenesis and serum total antioxidant capacity (TAC). Pregnant NMRI mice received 500 and 1000 mg/kg of flax extract (LE) and the same doses of flaxseed (LS). Female pups received the same regimen for 56 days. The body, ovarian morphometry, follicle development, and TAC levels were evaluated. The ovarian weight significantly increased in the LE1000 group compared to the LS500 group. The LE500 group had a considerably lower number of primary and antral follicles compared to the CTL and LS1000 groups. The number of antral follicles significantly increased in the LE1000 group compared to the LS500 and LE500 groups. The number of preovulatory follicles was higher in the LE1000 group. A significant increase in the TAC levels was detected in the LS500, LS1000, and LE1000 groups. LE showed a dose-dependent protective effect on the folliculogenesis in F1, which is more evident with the dosage of 1000 mg/kg. This could be related to the strongest antioxidant property of LE1000, as shown by the highest levels of TAC
Early invasive strategy (< 24 hours) in patients with acute coronary syndromes: Weighing the evidence
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High sensitive TROponin levels In Patients with Chest pain and kidney disease:a multicenter registry: The TROPIC study
Background: Accuracy of high sensitive troponin (hs-cTn) to detect coronary artery disease (CAD) in patients with renal insufficiency is not established. The aim of this study was to evaluate the prognostic role of hs-cTn T and I in patients with chronic kidney disease (CKD).
Methods: All consecutive patients with chest pain, renal insufficiency (eGFR < 60 mL/min/1.73 m2) and high sensitive troponin level were included. The predictive value of baseline and interval troponin (hs-cTnT and hs-cTnI) for the presence of CAD was assessed.
Results: One hundred and thirteen patients with troponin I and 534 with troponin T were included, with 95 (84%) and 463 (87%) diagnosis of CAD respectively. There were no differences in clinical, procedural and outcomes between the two assays. For both, baseline hs-cTn values did not differ between patients with/without CAD showing low area under the curve (AUC). For interval levels, hs-cTnI was significantly higher for patients with CAD (0.2 ± 0.8 vs. 8.9 ± 4.6 ng/mL; p = 0.04) and AUC was more accurate for troponin I than hs-cTnT (AUC 0.85 vs. 0.69). Peak level was greater for hs-cTnI in patients with CAD or thrombus (0.4 ± 0.6 vs. 15 ± 20 ng/mL; p = 0.02; AUC 0.87: 0.79–0.93); no differences were found for troponin T assays (0.8 ± 1.5 vs. 2.2 ± 3.6 ng/mL; p = 1.7), with lower AUC (0.73: 0.69–0.77). Peak troponin levels (both T and I) independently predicted all cause death at 30 days.
Conclusions: Patients with CKD presenting with altered troponin are at high risk of coronary disease. Peak level of both troponin assays predicts events at 30 days, with troponin I being more accurate than troponin T. (Cardiol J 2017; 24, 2: 139–150
Commissioning of the BRIKEN beta-delayed neutron detector for the study of exotic neutron-rich nuclei
published_or_final_versio
Transcatheter Aortic Valve Replacement in Patients at High Risk of Coronary Obstruction
Background: Coronary obstruction following transcatheter aortic valve replacement (TAVR) is a life-threatening complication. For patients at elevated risk, it is not known how valve choice is influenced by clinical and anatomic factors and how outcomes differ between valve platforms. For patients at high risk of coronary obstruction, we sought to describe the anatomical and clinical characteristics of patients treated with both balloon-expandable (BE) and self-expanding (SE) valves. Methods: This was a multicenter international registry of patients undergoing TAVR who are considered to be at high risk of coronary obstruction and receiving pre-emptive coronary protection. Results: A total of 236 patients were included. Patients receiving SE valves were more likely to undergo valve-in-valve procedures and also had smaller sinuses of Valsalva and valve-to-coronary distance. Three-year cardiac mortality was 21.6% with SE vs 3.7% with BE valves. This was primarily driven by increased rates of definite or probable coronary occlusion, which occurred in 12.1% of patients with SE valves vs 2.1% in patients with BE valves. Conclusions: In patients undergoing TAVR with coronary protection, those treated with SE valves had increased rates of clinical and anatomic features that increase the risk of coronary obstruction. These include an increased frequency of valve-in-valve procedures, smaller sinuses of Valsalva, and smaller valve-to-coronary distances. These patients were observed to have increased cardiac mortality compared with patients treated with BE valves, but this is likely due to their higher risk clinical and anatomic phenotypes rather than as a function of the valve type itself
The Nuclear Astrophysics program at n-TOF (CERN)
An important experimental program on Nuclear Astrophysics is being carried out at the n-TOF since several years, in order to address the still open issues in stellar and primordial nucleosynthesis. Several neutron capture reactions relevant to s-process nucleosynthesis have been measured so far, some of which on important branching point radioisotopes. Furthermore, the construction of a second experimental area has recently opened the way to challenging measurements of (n, charged particle) reactions on isotopes of short half-life. The Nuclear Astrophysics program of the n-TOF Collaboration is here described, with emphasis on recent results relevant for stellar nucleosynthesis, stellar neutron sources and primordial nucleosynthesis
Mobility recorded by wearable devices and gold standards: the Mobilise-D procedure for data standardization
Wearable devices are used in movement analysis and physical activity research to extract clinically relevant information about an individual’s mobility. Still, heterogeneity in protocols, sensor characteristics, data formats, and gold standards represent a barrier for data sharing, reproducibility, and external validation. In this study, we aim at providing an example of how movement data (from the real-world and the laboratory) recorded from different wearables and gold standard technologies can be organized, integrated, and stored. We leveraged on our experience from a large multi-centric study (Mobilise-D) to provide guidelines that can prove useful to access, understand, and re-use the data that will be made available from the study. These guidelines highlight the encountered challenges and the adopted solutions with the final aim of supporting standardization and integration of data in other studies and, in turn, to increase and facilitate comparison of data recorded in the scientific community. We also provide samples of standardized data, so that both the structure of the data and the procedure can be easily understood and reproduced
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