LAMOST views δ Scuti pulsating stars Qian, S-B; Li, L-J; He, J-J ...
Monthly Notices of the Royal Astronomical Society,
03/2018, Volume:
475, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
About 766 δ Scuti stars were observed by LAMOST by 2017 June 16. Stellar atmospheric parameters of 525 variables were determined, while spectral types were obtained for all samples. In the ...paper, those spectroscopic data are catalogued. We detect a group of 131 unusual and cool variable stars (UCVs) that are distinguished from the normal δ Scuti stars (NDSTs). On the H–R diagram and the log g–T diagram, the UCVs are far beyond the red edge of pulsational instability trip. Their effective temperatures are lower than 6700 K with periods in the range from 0.09 to 0.22 d. NDSTs have metallicity close to that of the Sun as expected, while UCVs are slightly metal poor than NDSTs. The two peaks on the distributions of the period and stellar atmospheric parameters are all caused by the existence of UCVs. When those UCVs are excluded, it is discovered that the effective temperature, the gravitational acceleration, and the metallicity all are correlated with the pulsating period for NDSTs and their physical properties and evolutionary states are discussed. Detection of those UCVs indicates that about 25 per cent of the known δ Scuti stars may be misclassified. However, if some of them are confirmed to be pulsating stars, they will be a new-type pulsator and their investigations will shed light on theoretical instability domains and on the theories of interacting between the pulsation and the convection of solar-type stars. Meanwhile, 88 δ Scuti stars are detected to be the candidates of binary or multiple systems.
Using spectroscopy from the Sloan Digital Sky Survey Data Release Seven, we systematically determine the electron density n
e and electron temperature T
e of active galaxies and star-forming ...galaxies, while mainly focusing on the narrow-line regions (NLRs). Herein, active galaxies refer to composites, low-ionization narrow emission-line regions (LINERs) and Seyfert galaxies, following the Baldwin-Phillips-Terlevich diagram classifications afforded by the SDSS data. The plasma diagnostics of n
e and T
e are determined through the IS ii λ6716/λ6731 and IO iii λ5007/λ4363 ratios, respectively. By simultaneously determining n
e from S ii and T
e from O iii in our O iii λ4363 emission sample of 15 019 galaxies, we find two clear sequences: T
LINER
T
composite > T
Seyfert > T
star-forming and n
LINER
n
Seyfert > n
composite > n
star-forming. The typical range of n
e in the NLRs of active galactic nuclei (AGNs) is 102 − 3 cm−3. The temperatures in the NLRs range from 1.0 to 2.0 × 104 K for Seyferts, and the ranges are even higher and wider for LINERs and composites. The transitions of n
e and T
e from the NLRs to the discs are revealed.
We also present a comparative study, including stellar mass (M
), specific star formation rate (SFR/M
) and plasma diagnostic results. We propose that YL
Y
SY > Y
C > Y
SF, where Y is the characteristic present-day star-formation time-scale. One remarkable feature of the Seyferts shown on an M
-SFR/M
diagram, which we call the evolutionary pattern of AGNs with high ionization potential, is that the strong O iii λ4363 Seyferts distribute uniformly with the weak Seyferts, definitely a reverse of the situation for star-forming galaxies. It is a natural and well-known consensus that strong O iii λ4363 emissions in star-forming galaxies imply young stellar populations and thus low stellar masses. However, in the AGN case, several strong lines of evidence suggest that some supplementary energy source(s) should be responsible for high ionization potential.
We have realized optical excitation, trapping, and detection of the radioisotope 81Kr with an isotopic abundance of 0.9 ppt. The 124 nm light needed for the production of metastable atoms is ...generated by a resonant discharge lamp. Photon transport through the optically thick krypton gas inside the lamp is simulated and optimized to enhance both brightness and resonance. We achieve a state-of-the-art 81Kr loading rate of 1800 atoms/h, which can be further scaled up by adding more lamps. The all-optical approach overcomes the limitations on precision and sample size of radiokrypton dating, enabling new applications in the earth sciences, particularly for dating of polar ice cores.
The sheared-flow stabilized Z pinch has demonstrated long-lived plasmas with fusion-relevant parameters. We present the first experimental results demonstrating sustained, quasi-steady-state neutron ...production from the fusion Z-pinch experiment, operated with a mixture of 20% deuterium/80% hydrogen by pressure. Neutron emissions lasting approximately 5 μs are reproducibly observed with pinch currents of approximately 200 kA during an approximately 16 μs period of plasma quiescence. The average neutron yield is estimated to be (1.25±0.45)×10^{5} neutrons/pulse and scales with the square of the deuterium concentration. Coincident with the neutron signal, plasma temperatures of 1-2 keV and densities of approximately 10^{17} cm^{-3} with 0.3 cm pinch radii are measured with fully integrated diagnostics.
Aim To investigate the diagnostic accuracy of dual-source computed tomography (DSCT) coronary angiography with and without the application of a β-blocker. Materials and methods An exact binomial ...rendition of the bivariate mixed-effects regression model was used to synthesize diagnostic test data. Results The pooled sensitivity at the patient level was 0.98 95% confidence intervals (CI): 0.97–0.99, and specificity 0.88 (95% CI: 0.84–0.91). The results showed that without heart rate control, the sensitivity and specificity at the patient level did not decrease ( p = 0.27 and 0.56, respectively). At the artery level, no significant differences in sensitivity and specificity for studies with and without heart rate control were detected ( p = 0.04 and 0.05, respectively). At the segment level, the specificity decreased without heart rate control ( p = 0.03), whereas the sensitivity was not influenced ( p = 0.63). The median radiation exposure was 2.6 mSv, with 1.6 mSv and 8 mSv for heart rate-controlled studies and uncontrolled studies, respectively. Conclusions DSCT coronary angiography without heart rate control has a similar excellent diagnostic performance at the patient level as that of heart rate control groups. However, controlling for heart rate to decrease radiation and to provide effective information for selecting the therapeutic strategy and risk stratification is recommended.
Organic spintronic devices have been appealing because of the long spin lifetime of the charge carriers in the organic materials and their low cost, flexibility and chemical diversity. In previous ...studies, the control of resistance of organic spin valves is generally achieved by the alignment of the magnetization directions of the two ferromagnetic electrodes, generating magnetoresistance. Here we employ a new knob to tune the resistance of organic spin valves by adding a thin ferroelectric interfacial layer between the ferromagnetic electrode and the organic spacer: the magnetoresistance of the spin valve depends strongly on the history of the bias voltage, which is correlated with the polarization of the ferroelectric layer; the magnetoresistance even changes sign when the electric polarization of the ferroelectric layer is reversed. These findings enable active control of resistance using both electric and magnetic fields, opening up possibility for multi-state organic spin valves.
We studied the correlations between egg geometrical parameters (i.e., egg shape index, sphericity, geometric mean diameter, surface area, and volume) and eggshell qualities, or the organic matrix in ...eggshell. Eggs were collected from 5 poultry breeds belonging to 3 species (commercial Hy-line Brown Chicken, Shaoxing Duck, Jinding Duck, Taihu Goose, and Zhedong White Goose). The geometrical parameters showed high variation among 3 species of poultry, and even between breeds in the same species. The five geometrical parameters were grouped into 2 sets, one contained shape index and sphericity, the other comprised geometric mean diameter, surface area, and volume. The parameters in the same set can be perfectly fitted to one another. Egg weight, shell membrane weight, and calcified shell weight were significantly correlated with geometric mean diameter, surface area, and volume. In accordance with false discovery rate–adjusted P value, both shell membrane relative weight and calcified shell thickness showed no significant correlations with any of the geometrical parameters. However, the correlations between geometrical parameters and other shell variables (calcified shell weight, shell relative weight, calcified shell thickness uniformity, and eggshell breaking strength) depend on breed. Both constitutive proportions and percentage contents of 3 eggshell matrix components (acid-insoluble, water-insoluble, and both acid and water facultative-soluble matrix) had no effects on egg shape and size. The correlations between the amounts of various shell matrix, egg shape and size depend on breed or species. This study provides a methodology and the correlation between geometrical parameters and eggshell qualities, and between geometrical parameters and organic matrix components in calcified shells.
The GhMYB9 encodes a R2R3 MYB transcription factor in the upland cotton (Gossypium hirsutum L.) genome. Our studies show that GhMYB9 predominantly expressed in flowers and fibers. To gain a better ...understanding of its regulatory mechanism, we isolated the 5′-flanking region of GhMYB9 which was 1 487 bp in length. The cis-acting element prediction shows that this region contained the basic structure of the core promoter elements (TATA-box, CAAT-box) and the transcription start site (TSS). Other motifs, such as defense and stress responsiveness (TC-rich repeats), anaerobic induction (ARE), and MYB binding sites involved in drought-inducibility (MBS), were also found. Histochemical assay shows that the GhMYB9 promoter governed β-glucuronidase (GUS) expression mainly in seeds, fibers, and flowers of transgenic cotton. Also, the activity of the promoter was induced by auxin in fibers of transgenic cotton. This is consistent with its transcript abundance in different tissues. A further deletion analysis confirms that a promoter region from -1 231 to -860 was required for auxin response. Our findings provide a useful reference for the understanding of the transcriptional regulation mechanism of the GhMYB9 gene.
Power production with thermal conversion has met new challenges due the global pressure to use CO2 neutral and renewable fuels, e.g. recycled fuel and biomass. Many of these fuels contain high ...concentrations of elements, such as alkali metals and chlorine, that together are harmful for boiler structures and may cause operational problems. Therefore, detailed quantitative information on release behaviour of the problematic elements, potassium and sodium, is required. For this, a new burner, which allows linear calibration of laser induced breakdown spectroscopy (LIBS) measurement towards higher concentrations relevant for the release studies during thermal conversion of biomass, was designed. The analytical performance of conventional LIBS measurement is significantly improved by introducing microwave radiation to the laser-induced plasma. An enhancement of linearity and up to 60-fold improvement of limit of detection (LOD) was observed with microwave-assisted LIBS (MW-LIBS) in comparison to conventional LIBS. The LOD of Na, K and Ca were 10 ppb, 19 ppb and 16 ppb, respectively. In-flame MW-LIBS measurement was applied to record time-traces of K, Na and Ca during thermal conversion of a poplar pellet. This is the first demonstration of Microwave near-field applicator injected MW-LIBS for gas phase measurement. With broad dynamic measurement range, the proposed method can be applied to extensive research of elemental release behaviour of different fuels. In addition to combustion studies, the MW-LIBS method can be extended to study trace-elements in gas phase in different fields of industry and science.
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•A new burner design, suitable for accurate in-flame LIBS calibration, has been developed.•Applying microwave-assisted LIBS for quantitative elemental detection in gas-phase has demonstrated for the first time.•A record limit of detection (LOD) of sodium, potassium, and calcium at 10 ppb, 19 ppb and 16 ppb, respectively, were recorded.
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