Abstract
We present the second release of value-added catalogues of the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC DR2). The catalogues present values of radial velocity Vr, ...atmospheric parameters – effective temperature Teff, surface gravity log g, metallicity Fe/H, α-element to iron (metal) abundance ratio α/Fe (α/M), elemental abundances C/H and N/H and absolute magnitudes MV and $M_{K_{\rm s}}$ deduced from 1.8 million spectra of 1.4 million unique stars targeted by the LSS-GAC since 2011 September until 2014 June. The catalogues also give values of interstellar reddening, distance and orbital parameters determined with a variety of techniques, as well as proper motions and multiband photometry from the far-UV to the mid-IR collected from the literature and various surveys. Accuracies of radial velocities reach 5 km s−1 for the late-type stars, and those of distance estimates range between 10 and 30 per cent, depending on the spectral signal-to-noise ratios. Precisions of Fe/H, C/H and N/H estimates reach 0.1 dex, and those of α/Fe and α/M reach 0.05 dex. The large number of stars, the contiguous sky coverage, the simple yet non-trivial target selection function and the robust estimates of stellar radial velocities and atmospheric parameters, distances and elemental abundances make the catalogues a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disc.
We re-estimate the peculiar velocity of the Sun with respect to the local standard of rest (LSR) using a sample of local stars within 600 pc of the Sun, selected from the Large Sky Area Multi-Object ...Fiber Spectroscopic Telescope (LAMOST, also named the Guoshoujing Telescope) Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC). The sample consists of 94 332 FGK main-sequence stars with well-determined radial velocities and atmospheric parameters. To derive the LSR, two independent analyses are applied to the data. First, we determine the solar motion by comparing the observed velocity distribution to that generated with the analytic formulism of Schönrich & Binney that has been demonstrated to show excellent agreement with rigorous torus-based dynamics modelling by Binney & McMillan. Secondly, we propose that cold populations of thin disc stars, selected by applying an orbital eccentricity cut, can be directly used to determine the LSR without the need of asymmetric drift corrections. Both approaches yield consistent results of solar motion in the direction of Galactic rotation, V
⊙, that are much higher than the standard value adopted hitherto, derived from Strömgren's equation. The newly deduced values of V
⊙ are 1–2 km s−1 smaller than the more recent estimates derived from the Geneva–Copenhagen Survey (GCS) sample of stars in the solar neighbourhood (within 100 pc). We attribute the small difference to the presence of several well-known moving groups in the GCS sample that, fortunately, hardly affect the LSS-GAC sample. The newly derived radial (U
⊙) and vertical (W
⊙) components of the solar motion agree well with the previous studies. In addition, for all components of the solar motion, the values yielded by stars of different spectral types in the LSS-GAC sample are consistent with each other, suggesting that the local disc is well relaxed and that the LSR reported in the current work is robust. Our final recommended LSR is, (U⊙, V⊙, W⊙) = (7.01 ± 0.20, 10.13 ± 0.12, 4.95 ± 0.09) km s−1.
As a major component of the LAMOST Galactic surveys, the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC) aims to survey a significant volume of the Galactic thin/thick discs and halo ...for a contiguous sky area of over 3400 deg2 centred on the Galactic anticentre (|b| ≤ 30°, 150 ≤ l ≤ 210°), and obtain λλ3700–9000 low-resolution (R ∼ 1800) spectra for a statistically complete sample of ∼3 M stars of all colours down to a limiting magnitude of r ∼ 17.8 mag (to 18.5 mag for limited fields). Together with Gaia, the LSS-GAC will yield a unique data set to advance our understanding of the structure and assemblage history of the Galaxy, in particular its disc(s). In addition to the main survey, the LSS-GAC will also target hundreds of thousands objects in the vicinity fields of M 31 and M 33 and survey a significant fraction (over a million) of randomly selected very bright stars (r ≤ 14 mag) in the Northern hemisphere. During the Pilot and the first year Regular Surveys of LAMOST, a total of 1042 586 750 867 spectra of a signal-to-noise ratio S/N(7450 Å) ≥ 10 S/N(4650 Å) ≥ 10 have been collected. In this paper, we present a detailed description of the target selection algorithm, survey design, observations and the first data release of value-added catalogues (including radial velocities, effective temperatures, surface gravities, metallicities, values of interstellar extinction, distances, proper motions and orbital parameters) of the LSS-GAC.
To explore the characteristics of Helicobacter pylori resistance in China and the association between antibiotic resistance and several clinical factors.
H. pylori strains were collected from ...patients in 13 provinces or cities in China between 2010 and 2016. Demographic data including type of disease, geographic area, age, gender and isolation year were collected to analyse their association with antibiotic resistance. Antibiotic resistance was detected using the Etest test and the Kirby-Bauer disc diffusion method.
H. pylori were successfully cultured from 1117 patients. The prevalence of metronidazole, clarithromycin (CLA), azithromycin, levofloxacin (LEV), moxifloxacin, amoxicillin (AMO), tetracycline and rifampicin resistance was 78.2, 22.1, 23.3, 19.2, 17.2, 3.4, 1.9 and 1.5%, respectively. No resistance to furazolidone was observed. The resistance rates to LEV and moxifloxacin were higher in strains isolated from patients with gastritis compared to those with duodenal ulcer and among women. Compared to patients ≥40 years old, younger patients exhibited lower resistance rates to CLA, azithromycin, LEV and moxifloxacin. The resistance rates to CLA and AMO were higher in strains isolated more recently, and we also found that the prevalence of resistance to metronidazole, CLA, azithromycin and AMO were significantly different among different regions of China.
The resistance rates to metronidazole, CLA and LEV were high in China. Patient age, gender, disease and location were associated with the resistance of H. pylori to some antibiotics. Furazolidone, AMO and tetracycline are better choices for H. pylori treatment in China.
Accurate determination of stellar atmospheric parameters and elemental abundances is crucial for Galactic archaeology via large-scale spectroscopic surveys. In this paper, we estimate stellar ...atmospheric parameters -- effective temperature T sub( eff), surface gravity log g and metallicity Fe/H, absolute magnitudes M sub( V) and M sub( Ks), ...-element to metal (and iron) abundance ratio .../M (and .../Fe), as well as carbon and nitrogen abundances C/H and N/H from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) spectra with a multivariate regression method based on kernel-based principal component analysis, using stars in common with other surveys (Hipparcos, Kepler, Apache Point Observatory Galactic Evolution Experiment) as training data sets. Both internal and external examinations indicate that given a spectral signal-to-noise ratio (SNR) better than 50, our method is capable of delivering stellar parameters with a precision of ~100 K for T sub( eff), ~0.1 dex for log g, 0.3-0.4 mag for M sub( V) and M sub( Ks), 0.1 dex for Fe/H, C/H and N/H, and better than 0.05 dex for .../M (.../Fe). The results are satisfactory even for a spectral SNR of 20. The work presents first determinations of C/H and N/H abundances from a vast data set of LAMOST, and, to our knowledge, the first reported implementation of absolute magnitude estimation directly based on a vast data set of observed spectra. The derived stellar parameters for millions of stars from the LAMOST surveys will be publicly available in the form of value-added catalogues. (ProQuest: ... denotes formulae/symbols omitted.)
We introduce the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) stellar parameter pipeline at Peking University – lsp3, developed and implemented for the determinations of radial ...velocity V
r and stellar atmospheric parameters (effective temperature T
eff, surface gravity log g, metallicity Fe/H) for the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC). We describe the algorithms of lsp3 and examine the accuracy of parameters yielded by it. The precision and accuracy of parameters yielded are investigated by comparing results of multi-epoch observations and of candidate members of open and globular clusters, with photometric calibration, as well as with independent determinations available from a number of external data bases, including the PASTEL archive, the APOGEE, SDSS and RAVE surveys, as well as those released in the LAMOST DR1. The uncertainties of lsp3 parameters are characterized and quantified as a function of the spectral signal-to-noise ratio (SNR) and stellar atmospheric parameters. We conclude that the current implementation of lsp3 has achieved an accuracy of 5.0 km s−1, 150 K, 0.25 dex, 0.15 dex for the radial velocity, effective temperature, surface gravity and metallicity, respectively, for LSS-GAC spectra of FGK stars of SNRs per pixel higher than 10. The lsp3 has been applied to over a million LSS-GAC spectra collected hitherto. Stellar parameters yielded by the lsp3 will be released to the general public following the data policy of LAMOST, together with estimates of the interstellar extinction E(B − V) and stellar distances, deduced by combining spectroscopic and multiband photometric measurements using a variety of techniques.
Aims
Diseases caused by pathogenic fungi was a major constrain in increasing productivity and improving quality of Panax notoginseng. The aim of this research was to evaluate the inhibitory activity ...of essential oils (EOs) from Asteraceae family, Chrysanthemum indicum and Laggera pterodonta, against pathogenic fungi of P. notoginseng.
Methods and Results
The antifungal activity was investigated using multiple methods, disclosing that the EOs from C. indicum and L. pterodonta are active against hypha growth of different fungi but with different degrees of potency. Checkerboard testing indicated that the combination of EOs with hymexazol had synergistic effect against Pythium aphanidermatum, and exhibited additive effects against bulk of targeted pathogenic fungi. Besides, we found that the baseline sensitivity of Fusarium oxysporum to L. pterodonta EOs was higher than those of C. indicum by means of mycelium growth rate method. Finally, the practicability of those EOs as plant pesticide was confirmed by in vivo model showing that EOs can significantly inhibit the occurrence of root rot of P. notoginseng caused by F. oxysporum.
Conclusion
Those studies suggest that the EOs from C. indicum and L. pterodonta had the potential to develop into new pollution‐free pesticides for the protection of precious Chinese herbal medicines.
Significance and Impact of the Study
This study provided a new way of biological control for overcoming the frequent diseases occurrence of P. notoginseng.
Using spin-polarized low energy electron microscopy, we discovered a new type of domain wall structure in perpendicularly magnetized Fe/Ni bilayers grown epitaxially on Cu(100). Specifically, we ...observed unexpected Néel-type walls with fixed chirality in the magnetic stripe phase. Furthermore, we find that the chirality of the domain walls is determined by the film growth order with the chirality being right handed in Fe/Ni bilayers and left handed in Ni/Fe bilayers, suggesting that the underlying mechanism is the Dzyaloshinskii-Moriya interaction at the film interfaces. Our observations may open a new route to control chiral spin structures using interfacial engineering in transition metal heterostructures.
Field-orthogonal temporal mode analysis of optical fields has recently been developed for a new framework of quantum information science. However, so far, the exact profiles of the temporal modes are ...not known, which makes it difficult to achieve mode selection and demultiplexing. Here, we report a novel method that measures directly the exact form of the temporal modes. This, in turn, enables us to make mode-orthogonal homodyne detection with mode-matched local oscillators. We apply the method to a pulse-pumped, specially engineered fiber parametric amplifier and demonstrate temporally multiplexed multidimensional quantum entanglement of continuous variables in telecom wavelength. The temporal mode characterization technique can be generalized to other pulse-excited systems to find their eigenmodes for multiplexing in the temporal domain.
The outstanding strength-ductility combination has always been a challenging problem in the development of metal materials, high entropy alloys/medium entropy alloys (HEAs/MEAs) are considered to be ...the key material to solve this problem. Here a novel non-equiatomic Ni46Co24Fe24Al3Ti3 MEA with equiaxed grains was prepared by vacuum suspension melting, which consists of FCC matrix and heterogeneous L12 precipitate. In the current work, the different states of the Ni46Co24Fe24Al3Ti3 MEA from as-cast to after thermo-mechanical processing (TMP) were systematically researched. The result shows that the heterogeneous L12 precipitate of the as-cast alloy is composed of cubic precipitates at the grain boundary and spherical precipitates in the grain interior. After TMP, a short-rod L12 precipitated by discontinuous precipitation reaction (DP) at the grain boundary, and a spherical L12 precipitated by continuous precipitation reaction (CP) in the grain interior. Meanwhile, the alloy shows outstanding mechanical properties in the tensile test at room temperature. The ultimate tensile strength of the as-cast alloy is 935 MPa, with an elongation of 32%. The strength of the alloy is further improved after TMP, the yield strength and ultimate tensile strength are respectively 820 MPa and 1236 MPa, with an elongation of 23% retained. Compared with the single-phase NiCoFe MEA, the yield strength and ultimate tensile strength are significantly increased by 310％ and 147％. The excellent mechanical properties of the alloy are attributed to the combination of the soft FCC matrix and the strengthening of the L12 precipitate.
•A non-equimolar ratio Ni46Co24Fe24Al3Ti3 HEA alloy was designed and fabricated by vacuum suspension melting.•Spherical L12 nano-precipitations precipitates in the equiaxed grain of the as-cast alloy.•Precipitation strengthening is the main strengthening mechanism of the alloy after thermo-mechanical processing.
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