Abstract
We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; Fe/H < –2.0) stars, selected as extremely metal-poor (EMP; Fe/H < –3.0) candidates from the Sloan ...Digital Sky Survey and Large sky Area Multi-Object Fiber Spectroscopic Telescope survey. High-resolution spectroscopic observations were performed using GEMINI-N/GRACES. We find 10 EMP stars among our candidates, and we newly identify three carbon-enhanced metal-poor stars with Ba/Fe < 0. Although chemical abundances of our VMP/EMP stars generally follow the overall trend of other Galactic halo stars, there are a few exceptions. One Na-rich star (Na/Fe = +1.14) with low Mg/Fe suggests a possible chemical connection with second-generation stars in a globular cluster. The progenitor of an extremely Na-poor star (Na/Fe = –1.02) with high K- and Ni-abundance ratios may have undergone a distinct nucleosynthesis episode, associated with core-collapse supernovae (SNe) having a high explosion energy. We have also found a Mg-rich star (Mg/Fe = +0.73) with slightly enhanced Na and extremely low Ba/Fe, indicating that its origin is not associated with neutron-capture events. On the other hand, the origin of the lowest Mg abundance (Mg/Fe = –0.61) star could be explained by accretion from a dwarf galaxy, or formation in a gas cloud largely polluted by SNe Ia. We have also explored the progenitor masses of our EMP stars by comparing their chemical-abundance patterns with those predicted by Population III SNe models, and find a mass range of 10–26
M
⊙
, suggesting that such stars were primarily responsible for the chemical enrichment of the early Milky Way.
We report the result of a high-resolution spectroscopic study on seven magnesium (Mg) enhanced stars. The high Mg abundances in these stars imply that they were born in an environment heavily ...affected by the nucleosynthesis products of massive stars. We measure abundances of 16 elements including Mg and they show various abundance patterns implying their diverse origin. Three of our program stars show a very high Mg to Si ratio (Mg/Si ≈ 0.18–0.25), which might be well explained by fall-back supernovae or by supernovae with rapid rotating progenitors having an initial mass higher than about 20 𝑀⊙. Another three of our program stars have high light to heavy s-process element ratios (Y/Ba ≈ 0.30–0.44), which are consistent with the theoretical prediction of the nucleosynthesis in rapidly rotating massive stars with an initial mass of about 𝑀 = 40 𝑀⊙. We also report a star having both high Y (Y/Fe = 0.2) and Ba (Ba/Fe = 0.28) abundance ratios, and it also shows the highest Zn abundance ratio (Zn/Fe = 0.27) among our sample, implying the nucleosynthesis by asymmetric supernova explosion induced by very rapid rotation of a massive progenitor having an initial mass between 20 𝑀⊙ ≲ 𝑀 ≲ 40 𝑀⊙. A relative deficiency of odd-number elements, which would be a signature of the pair-instability nucleosynthesis, is not found in our sample.
We report the result of a high-resolution spectroscopic study on seven magnesium (Mg) enhanced stars. The high Mg abundances in these stars imply that they were born in an environment heavily ...affected by the nucleosynthesis products of massive stars. We measure abundances of 16 elements including Mg and they show various abundance patterns implying their diverse origin. Three of our program stars show a very high Mg to Si ratio (Mg/Si ≈ 0.18-0.25), which might be well explained by fall-back supernovae or by supernovae with rapid rotating progenitors having an initial mass higher than about 20 M⊙. Another three of our program stars have high light to heavy s-process element ratios (Y/Ba ≈ 0.30-0.44), which are consistent with the theoretical prediction of the nucleosynthesis in rapidly rotating massive stars with an initial mass of about M = 40 M⊙. We also report a star having both high Y (Y/Fe = 0.2) and Ba (Ba/Fe = 0.28) abundance ratios, and it also shows the highest Zn abundance ratio (Zn/Fe = 0.27) among our sample, implying the nucleosynthesis by asymmetric supernova explosion induced by very rapid rotation of a massive progenitor having an initial mass between 20 M⊙ ≲ M ≲ 40 M⊙. A relative deficiency of odd-number elements, which would be a signature of the pair-instability nucleosynthesis, is not found in our sample.
We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; Fe/H \(<\) -2.0) stars, selected as extremely metal-poor (EMP; Fe/H \(<\) -3.0) candidates from SDSS and ...LAMOST survey. High-resolution spectroscopic observations were performed using GEMINI-N/GRACES. We find ten EMP stars among our candidates, and we newly identify three carbon-enhanced metal poor (CEMP) stars with Ba/Fe \(<\) 0. Although chemical abundances of our VMP/EMP stars generally follow the overall trend of other Galactic halo stars, there are a few exceptions. One Na-rich star (Na/Fe = +1.14) with low Mg/Fe suggests a possible chemical connection with second-generation stars in a globular cluster. The progenitor of an extremely Na-poor star (Na/Fe = -1.02) with an enhancement of K- and Ni-abundance ratios may have undergone a distinct nucleosynthesis episode, associated with core-collapse supernovae (CCSNe) having a high explosion energy. We have also found a Mg-rich star (Mg/Fe = +0.73) with slightly enhanced Na and extremely low Ba/Fe, indicating that its origin is not associated with neutron-capture events. On the other hand, the origin of the lowest Mg abundance (Mg/Fe = -0.61) star could be explained by accretion from a dwarf galaxy, or formation in a gas cloud largely polluted by SNe Ia. We have also explored the progenitor masses of our EMP stars by comparing their chemical-abundance patterns with those predicted by Population III SNe models, and find a mass range of 10 - 26 \(M_\odot\), suggesting that such stars were primarily responsible for the chemical enrichment of the early Milky Way.
We report on the chemo-dynamical analysis of SPLUS J142445.34-254247.1, an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process. This star was first ...selected as a metal-poor candidate from its narrow-band S-PLUS photometry and followed up spectroscopically in medium-resolution with Gemini South/GMOS, which confirmed its low-metallicity status. High-resolution spectroscopy was gathered with GHOST at Gemini South, allowing for the determination of chemical abundances for 36 elements, from carbon to thorium. At Fe/H=-3.39, SPLUS J1424-2542 is one of the lowest metallicity stars with measured Th and has the highest logeps(Th/Eu) observed to date, making it part of the "actinide-boost" category of r-process enhanced stars. The analysis presented here suggests that the gas cloud from which SPLUS J1424-2542 was formed must have been enriched by at least two progenitor populations. The light-element (Z<=30) abundance pattern is consistent with the yields from a supernova explosion of metal-free stars with 11.3-13.4 Msun, and the heavy-element (Z>=38) abundance pattern can be reproduced by the yields from a neutron star merger (1.66Msun and 1.27Msun) event. A kinematical analysis also reveals that SPLUS J1424-2542 is a low-mass, old halo star with a likely in-situ origin, not associated with any known early merger events in the Milky Way.
Immunoglobulin A vasculitis (IgA vasculitis) is one of the most common forms of vasculitis in children. It rarely occurs in adults. It is a systemic vasculitis with IgA deposition and is ...characterized by the classical tetrad of purpura, arthritis/arthralgia, gastrointestinal and renal involvement. Certain types of infections, and pharmacological agents have been reported to be associated with IgA vasculitis. Here, we describe a case of IgA vasculitis triggered by infective endocarditis in a patient undergoing maintenance hemodialysis.
A 70-year-old man undergoing hemodialysis was admitted because of skin purpura, abdominal pain, diarrhea, and lower back pain. We suspected him as IgA vasculitis based on the clinical features and skin biopsy findings. Transesophageal echocardiography revealed infective endocarditis, which predisposed him to IgA vasculitis. He was treated with antibiotics and low-dose corticosteroids, which led to resolution of vasculitis.
This is the first case of IgA vasculitis triggered by infective endocarditis in a patient undergoing hemodialysis. Patients undergoing hemodialysis are at a high risk of infection because of immune dysfunction and frequent venipuncture. The incidence of infective endocarditis associated with IgA vasculitis is very low, but it has been repeatedly reported. Therefore, it is necessary to consider infective endocarditis in patients with clinical features that indicate IgA vasculitis.
Brain-derived neurotrophic factor (BDNF), an exercise-induced neurotrophin, is an important factor in memory consolidation and cognitive function. This study evaluates the association between plasma ...BDNF levels and frailty in community-dwelling older adults. Plasma BDNF levels were analyzed in a total of 302 individuals aged 70-84 years from the Korean Frailty and Aging Cohort Study. There were 30 (9.9%) participants with frailty. They were older and had a higher prevalence of dementia and depression than those without frailty. There were no differences in the proportion of male sex between the frail and non-frail groups. Plasma BDNF levels were significantly lower in participants with frailty than in those without frailty. The presence of frailty was significantly associated with plasma BDNF levels (odds ratio 0.508, 95% confidence interval 0.304-0.849) as well as age, hemoglobin, and the presence of dementia, and depression. After adjustment for confounding factors, the significant association between plasma BDNF and frailty was maintained (0.495, 0.281-0.874). This association remained consistent after exclusion of individuals with dementia, depression, stroke, diabetes, and osteoporosis. Plasma BDNF levels were significantly associated with frailty in community-dwelling older adults. Our study may suggest the possible role of BDNF as a novel biomarker of frailty.
The rhodium(III)-catalyzed direct functionalization of aniline C-H bonds with α-diazo compounds is described. These transformations provide a facile construction of ortho-alkylated anilines with ...diazo malonates or highly substituted indoles with diazo acetoacetates.
Unlike pigment‐based colors, which are determined by their molecular structure, diverse colors can be expressed by a regular arrangement of nanomaterials. However, existing techniques for ...constructing such nanostructures have struggled to combine high precision and speed, resulting in a narrow gamut, and prolonged color fabrication time. Here, this work reports a phototunable mono ink that can generate a wide range of colors by controlling regularly arranged nanostructure. Core–shell growth controlled by polymerization time precisely regulates the distance between arranged particles at a nanometer‐scale, enabling the generation of various colors. Moreover, the wide and thin arrangement induces constrained out‐of‐plane growth, thus facilitating the intricate color generation at the desired location via photopolymerization. Upon terminating polymerization by oxygen gas, the generated colors are readily fixed and kept stable. Utilizing programmed ultraviolet illumination, large‐scale and high‐resolution (≈1 µm) full‐color printings are demonstrated at high speed (100 mm2 s−1).
Unlike traditional pigment‐based inks, this work introduces a novel mono ink. This innovative formulation facilitates the creation of a broad spectrum of colors by meticulously constructing regularly arranged nanostructures using ultraviolet light. With this ink, one can attain rapid and high‐resolution printing of multicolored images. Notably, the speed of printing is consistent, regardless of the printing area, ensuring high‐throughput capabilities.
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