172 research outputs found
Asteroseismology of KIC 8263801:Is it a member of NGC 6866 and a red clump star?
We present an asteroseismic analysis of the Kepler light curve of KIC
8263801, a red-giant star in the open cluster NGC 6866 that has previously been
reported to be a helium-burning red-clump star. We extracted the frequencies of
the radial and quadrupole modes from its frequency power spectrum and
determined its properties using a grid of evolutionary models constructed with
MESA. The oscillation frequencies were calculated using the GYRE code and the
surface term was corrected using the Ball & Gizon(2014) prescription. We find
that the star has a mass of , age Gyr and radius . By analyzing the internal
structure of the best-fitting model, we infer the evolutionary status of the
star KIC 8263801 as being on the ascending part of the red giant branch, and
not on the red clump. This result is verified using a purely asteroseismic
diagnostic, the diagram which can distinguish red
giant branch stars from red clump stars. Finally, by comparing its age with NGC
6866 ( Gyr) we conclude that KIC 8263801 is not a member of
this open cluster
A Tough Metal‐Coordinated Elastomer: A Fatigue‐Resistant, Notch‐Insensitive Material with an Excellent Self‐Healing Capacity
Self-healing materials can prolong device life, but their relatively weak mechanical strength limits their applications. Introducing tunable metal-ligand interactions into self-healing systems can improve their mechanical strength. However, applying this concept to solid elastomers is a challenge. To address this need, polyurethane-containing metal complexes were fabricated by introduction of a pyridine-containing ligand into polyurethane, and subsequent coordination with Fe2+. The strong reversible coordination bond provides mechanical strength and self-healing ability. By optimizing the monomer ratio and Fe2+ content, the resulting complex possesses a very high tensile strength of 4.6MPa at strain of around 498% and a high Young's modulus (3.2MPa). Importantly, the metal complex exhibits an extremely high self-healing efficiency of approximately 96% of tensile strength at room temperature and around 30% at 5 degrees C. The complex is notch-insensitive and the fracture energy is 76186J/m(2), which is among the highest reported values for self-healing systems
An in-depth study of grid-based asteroseismic analysis
NASA's Kepler mission is providing basic asteroseismic data for hundreds of
stars. One of the more common ways of determining stellar characteristics from
these data is by so-called "grid based" modelling. We have made a detailed
study of grid-based analysis techniques to study the errors (and
error-correlations) involved. As had been reported earlier, we find that it is
relatively easy to get very precise values of stellar radii using grid-based
techniques. However, we find that there are small, but significant, biases that
can result because of the grid of models used. The biases can be minimized if
metallicity is known. Masses cannot be determined as precisely as the radii,
and suffer from larger systematic effects. We also find that the errors in mass
and radius are correlated. A positive consequence of this correlation is that
log g can be determined both precisely and accurately with almost no systematic
biases. Radii and log g can be determined with almost no model dependence to
within 5% for realistic estimates of error in asteroseismic and conventional
observations. Errors in mass can be somewhat higher unless accurate metallicity
estimates are available. Age estimates of individual stars are the most model
dependent. The errors are larger too. However, we find that for star-clusters,
it is possible to get a relatively precise age if one assumes that all stars in
a given cluster have the same age.Comment: ApJ, in pres
Bis(μ-3,5-dinitrobenzoato-κ2 O 1:O 1′)bis(μ-3,5-dinitrobenzoato)-κ3 O 1,O 1′:O 1;κ3 O 1:O 1,O 1′-bis[(3,5-dinitrobenzoato-κ2 O 1,O 1′)(1,10-phenanthroline-κ2 N,N)dysprosium(III)]
In the binuclear title complex, [Dy2(C7H3N2O6)6(C12H8N2)2], the DyIII ions exhibit a distorted monocapped square-antiprismatic geometry and are coordinated by seven O atoms of four 3,5-dinitrobenzoate (DNBA) anions and two N atoms of a phenanthroline ligand. The carboxylate groups of the DNBA anions exhibit three coordination modes: bidentate chelating, bidentate chelating–bridging and tridentate chelating–bridging. The center of the molecule is located on a crystallographic center of inversion
Distinct host immune responses in recurrent vulvovaginal candidiasis and vulvovaginal candidiasis
Recurrent vulvovaginal candidiasis (RVVC) and vulvovaginal candidiasis (RVVC) are one of the most common gynecological infections, primarily caused by Candida species. Although risk factors of RVVC and VVC have been identified in many studies, antifungal immunological mechanisms are still not fully understood. We performed a 1-year prospective study in a local hospital to monitor 98 patients clinically diagnosed with gynecological Candida infection. The results showed that 20.41% (20/98) are with RVVC, and 79.59% (78/98) patients have VVC. C. albicans accounts for 90% and 96.1% of all strains isolated collected from RVVC and VVC patients, respectively. Antifungal susceptibility testing showed no significant difference in Candida species between RVVC and VVC patients. However, the serum levels of IFN-γ, TNF-α, and IL-17F in the RVVC group were significantly lower than those of the VVC group, while IL-4, IL-6, and IL-10 were higher in the RVVC patients than VVC patients. IL-17A and IL-2 levels were comparable between the two groups. Taken together, our results suggest that the host-immune responses, especially Th1/2 immunity, may play important roles in prognosis of RVVC and VVC
Modeling Eridani and asteroseismic tests of element diffusion
Taking into account the helium and metal diffusion, we explore the possible
evolutionary status and perform seismic analysis of MOST target: the star
Eridani. We adopt the different input parameters to construct the
models by fitting the available observational constraints: e.g., ,
, , . From computation, we obtain the average large spacings of
Eridani about Hz. The age of the diffused models has
been found to be about 1 Gyr, which is younger than one determined previously
by models without diffusion. We found that the effect of pure helium diffusion
on the internal structure of the young low-mass star is slight, but the metal
diffusion influence is obvious. The metal diffusion leads the models to have
much higher temperature in the radiation interior, correspondingly the higher
sound speed in the interior of the model, thereby the larger frequency and
spacings.Comment: 16 pages, 4 figures, accepted for publication in ChjA
In situ Carbon Modification of g-C3N4 from Urea Co-crystal with Enhanced Photocatalytic Activity Towards Degradation of Organic Dyes Under Visible Light
An in situ strategy was introduced for synthesizing carbon modified graphitic carbon nitride(g-C3N4) by using urea/4-aminobenzoic acid(PABA) co-crystal(PABA@Urea) as precursor materials. Via co-calcination of the PABA co-former and the urea in PABA@Urea co-crystals, C guest species were generated and compounded into g-C3N4 matrix in situ by replacing the lattice N of the carbon nitride and forming carbon dots onto its layer surface. The carbon modification dramatically enhanced visible-light harvesting and charge carrier separation. Therefore, visible light photo-catalytic oxidation of methylene blue(MB) pollution in water over the carbon modified g-C3N4 (C/g-C3N4) was notably improved. Up to 99% of methylene blue(MB) was eliminated within 60 min by the optimal sample prepared from the PABA@Urea co-crystal with a PABA content of 0.1%(mass ratio), faster than the degradation rate over bare g-C3N4. The present study demonstrates a new way to boost up the photocatalysis performance of g-C3N4, which holds great potential concerning the degradation of organic dyes from water
Detection of solar-like oscillations from Kepler photometry of the open cluster NGC 6819
Asteroseismology of stars in clusters has been a long-sought goal because the
assumption of a common age, distance and initial chemical composition allows
strong tests of the theory of stellar evolution. We report results from the
first 34 days of science data from the Kepler Mission for the open cluster NGC
6819 -- one of four clusters in the field of view. We obtain the first clear
detections of solar-like oscillations in the cluster red giants and are able to
measure the large frequency separation and the frequency of maximum oscillation
power. We find that the asteroseismic parameters allow us to test
cluster-membership of the stars, and even with the limited seismic data in
hand, we can already identify four possible non-members despite their having a
better than 80% membership probability from radial velocity measurements. We
are also able to determine the oscillation amplitudes for stars that span about
two orders of magnitude in luminosity and find good agreement with the
prediction that oscillation amplitudes scale as the luminosity to the power of
0.7. These early results demonstrate the unique potential of asteroseismology
of the stellar clusters observed by Kepler.Comment: 5 pages, 4 figures, accepted by ApJ (Lett.
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