Improvement of in-field critical current (I-c) remains a significant issue for the power applications of REBa2Cu3O7-x (REBCO, RE = Rare earth) coated conductors (CCs). It is extremely difficult to produce costeffectively batched CCs with strong flux pinning behaviors due to the special processing requirements of nano defects, although the batch production of pure CCs has been realized for many years. In this work, a prospective and convenient approach was proposed to enhance the current carrying capability of REBCO CCs by producing mesoscopic holes in CCs via laser drilling. The effect of micro-hole structure such as diameter (d) and spacings (l) between two neighboring holes along longitudinal and transverse directions on I-c, superconducting transition temperature (T-c) and diamagnetism of YGdBCO CCs was comprehensively investigated. With d <= 20 mu m and l >= 0.6 x 0.6 mm, the I-c values of drilled samples are nearly identical with those of original one. However, a considerable decrease of I-c was found in the drilled samples with d > 20 mu m and l < 0.6 x 0.6 mm, displaying a nonlinear I-c change. The T-c values of samples with various micro-hole structures remain the same as that of the virgin one, but the maximum diamagnetic signals reduce gradually with decreasing l. Based on the optimal micro-hole structure (20 mu m diameter, 0.6 x 0.6 mm spacing), the I-c anisotropy at low magnetic fields was studied. Compared to the original sample, the optimally drilled sample has not only obviously higher I-c values at different angles and magnetic fields as a whole, but also maximumly improved I-c about 24% at 160 mT, showing strong flux pinning properties. The possible reasons were discussed in the article. (C) 2021 Elsevier B.V. All rights reserved.

ABSTRACT We present a large, homogeneous catalogue of molecular clouds within 4 kpc from the Sun at low Galactic latitudes (|b| < 10°) with unprecedented accurate distance determinations. Based on the 3D dust reddening map and estimates of colour excesses and distances of over 32 million stars presented in Chen et al., we have identified 567 dust/molecular clouds with a hierarchical structure identification method and obtained their distance estimates by a dust model fitting algorithm. The typical distance uncertainty is less than 5 per cent. As far as we know, this is the first large catalogue of molecular clouds in the Galactic plane with distances derived in a direct manner. The clouds are seen to lie along the Sagittarius, Local and Perseus Arms. In addition to the known structures, we propose the existence of a possible spur, with a pitch angle of about 34°, connecting the Local and the Sagittarius Arms in the fourth quadrant. We have also derived the physical properties of those molecular clouds. The distribution of cloud properties in different parameter spaces agrees grossly with the previous results. Our cloud sample is an ideal starting point to study the concentration of dust and gas in the solar vicinity and their star formation activities.

We present a catalog of 5,290 RR Lyrae stars (RRLs) with metallicities estimated from spectra of the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) and the Sloan Extension for Galactic Understanding and Exploration (SEGUE) surveys. Nearly 70 per cent of them (3,642 objects) also have systemic radial velocities measured. Given the pulsating nature of RRLs, metallicity estimates are based on spectra of individual exposures, by matching them with the synthetic templates. The systemic radial velocities are measured by fitting the observed velocity as a function of phase assuming an empirical pulsating velocity template curve. Various tests show that our analyses yield metallicities with a typical precision of 0.20\,dex and systemic radial velocities with uncertainties ranging from 5 to 21\,km\,s$^{-1}$ (depending on the number of radial velocity measurements available for a given star). Based on the well calibrated near-infrared $PM_{W1}Z$ or $PM_{K_{\rm s}}Z$, and $M_{V}$-[Fe/H] relations, precise distances are derived for these RRLs. Finally, we include Gaia DR2 proper motions in our catalog. The catalog should be very useful for various Galactic studies, especially of the Galactic halo.

According to Wind observations between 2004 June and 2019 May, this Letter investigates the proton and alpha particle temperatures in the space of (θd, Vd/VA) for the first time, where θd and Vd are the radial angle and magnitude of alpha−proton differential flow vector , respectively, VA is the local Alfvén speed. Results show that the temperatures significantly depend on θd as well as Vd/VA. In case of low proton parallel beta (βp∥ < 1), it is found that the proton perpendicular temperature is clearly enhanced when θd is small (≲45°) and Vd/VA ≳ 0.5. On the contrary, the perpendicular temperature of alpha particles is considerably enhanced when θd is large (≳90°) or Vd/VA is sufficiently small. The maximum of proton parallel temperature takes place at θd ∼ 90° accompanied by higher βp∥ and by larger turbulence amplitude of magnetic fluctuations in inertial range. This study should present strong evidence for cyclotron resonance heating of protons and alpha particles in the solar wind. Other mechanisms including Landau resonance and stochastic heating are also proposed, which tend to have different (θd, Vd/VA) spaces than cyclotron resonance heating.

Abstract Objective To provide a theoretical basis for building a Y chromosome database in specific regions by analyzing the pedigree specific core haplogroup and region specific genetic structure in Changshu. Methods One thousand seven hundred and two samples from unrelated Han male individuals in Changshu were collected. Then 27 Y-STR were genotyped through YfilerTM Plus PCR Amplification Kit, Y-SNP haplogroup of each sample was speculated using Y-Predictor software and some samples were verified by amplification refractory mutation system-polymerase chain reaction （ARMS-PCR）. Results A total of 1 556 haplotypes were found on the 27 Y-STR genetic markers of the 1 702 samples. The haplotype diversity （HD） value was 0.999 827. DYS385 （0.933） had the highest gene diversity （GD） value while DYS438 （0.409） had the lowest. By the Y-Predictor software, all samples were confirmed to be from 162 sub-haplogroups of C, D, N, O, Q and R. Samples were randomly selected to verify the prediction results by the software and the prediction accuracy of Y-Predictor software was as high as 95.74%. Conclusion This study found that 27 Y-STR genetic markers have relatively high polymorphisms in the Changshu population, and have good forensic individual identification and paternity testing ability.

The hot massive luminous blue variables (LBVs) represent an important evolutionary phase of massive stars. Here, we report the discovery of a new LBV—LAMOST J0037+4016 in the distant outskirt of the Andromeda galaxy. It is located in the southwestern corner (a possible faint spiral arm) of M31 with an unexpectedly large projection distance of ∼22 kpc from the center. The optical light curve shows a 1.2 mag variation in V band and its outburst and quiescence phases both last over several years. The observed spectra indicate an A-type supergiant at an epoch close to the outburst phase and a hot B-type supergiant with weak [Fe ii ] emission lines at an epoch of much dimmer brightness. The near-infrared color–color diagram further shows that it follows the distribution of Galactic and M31 LBVs rather than B[e] supergiants. All the existing data strongly show that LAMOST J0037+4016 is an LBV. By spectral energy distribution fitting, we find it has a luminosity (4.42 ± 1.64) × 10 5 L ⊙ and an initial mass ∼30 M ⊙ , indicating its nature of a less luminosity class of LBV.

In this paper, we report a detailed analysis of recurrent jets originated from a location with emerging, canceling, and converging negative magnetic field at the east edge of NOAA active region AR11166 from 2011 March 9 to 10. The event presented several interesting features. First, a satellite sunspot appeared and collided with a pre-existing opposite polarity magnetic field and caused a recurrent solar jet event. Second, the evolution of the jets showed blowout-like nature and standard characteristics. Third, the satellite sunspot exhibited a motion toward the southeast of AR11166 and merged with the emerging flux near the opposite polarity sunspot penumbra, which afterward, due to flux convergence and cancellation episodes, caused recurrent jets. Fourth, three of the blowout jets associated with coronal mass ejections (CMEs), were observed from the field of view of the Solar Terrestrial Relations Observatory. Fifth, almost all the blowout jet eruptions were accompanied with flares or with more intense brightening in the jet base region, while almost standard jets did not manifest such obvious features during eruptions. The most important feature, the blowout jets, were inclined to faster and larger scales than the standard jets. The standard jets instead were inclined to be relatively longer-lasting. The obvious shearing and twisting motions of the magnetic field may be interpreted as due to the shearing and twisting motions for a blowout jet eruption. The statistical results show that ~30% of the blowout jets directly developed into CMEs. This suggests that the blowout jets and CMEs should have a close relationship.

Previous studies indicate that interplanetary small magnetic flux ropes (SMFRs) are manifestations of microflare-associated small coronal mass ejections (CMEs), and the hot material with high-charge states heated by related microflares are found in SMFRs. Ordinary CMEs are frequently associated with prominence eruptions, and cool prominence materials are found within some magnetic clouds (MCs). Therefore, the predicted small CMEs may also be frequently associated with small prominence eruptions. In this work, we aim to search for cool prominence materials within SMFRs. We examined all the O5+ and Fe6+ fraction data obtained by the Advanced Composition Explorer (ACE) spacecraft during 1998–2008 and found that 13 SMFRs might exhibit low-charge-state signatures of unusual O5+ and/or Fe6+ abundances. One of the 13 SMFRs also exhibited signatures of high ionic charge states. We also reported a SMFR with high Fe6+ fraction, but the values of Fe6+ is a little lower than the threshold defining unusual Fe6+. However, the Solar Dynamics Observatory/ Atmospheric Imaging Assembly observations confirmed that the progenitor CME of this SMFR is associated with a small eruptive prominence, and the observations also supported the prominence materials were embedded in the CME. These observations are at the edge of the capabilities of ACE/Solar Wind Ion Composition Spectrometer and it cannot be ruled out that they are solely caused by instrumental effects. If these observations are real, they provide new evidence for the conjecture that SMFRs are small-scale MCs but also imply that the connected small CMEs could be associated with flares and prominence eruptions.

We investigate the morphology and kinematics of the Galactic spiral structure based on a new sample of O- and early B-type stars. We select 6858 highly confident OB star candidates from the combined data of the VST Photometric H alpha Survey Data Release 2 (VPHAS+ DR2) and the Gaia Data Release 2 (Gaia DR2). Together with the O-B2 stars from the literature, we build a sample consisting of 14 880 O- and early B-type stars, all with Gaia parallax uncertainties smaller than 20 per cent. The new sample, hitherto the largest one of O- and early B-type stars with robust distance and proper motion estimates, covers the Galactic plane of distances up to 6 kpc from the Sun. The sample allows us to examine the morphology of the Scutum, Sagittarius, Local, and Perseus Arms in great detail. The spiral structure of the Milky Way as traced by O- and early B-type stars shows flocculent patterns. Accurate structure parameters, as well as the means and dispersions of the vertical velocity distributions of the individual spiral arms are presented.

With the photometric data from the SDSS survey, the spectroscopic data from the SDSS/SEGUE and the LAMOST surveys, and the astrometric data from the Gaia DR2, we have identified 67 highly probable member stars of the GD-1 cold stellar stream spread along almost its entire length (i.e., from 126 degrees to 203 degrees in R.A.). With the accurate spectroscopic (i.e., metallicity and line-of-sight velocity) and astrometric (i.e., proper motions) information, the position-velocity diagrams, i.e., phi(1)-mu(proportional to), phi(1)-mu(delta), and phi(1)-v(gsr), of the GD-1 stream are well mapped. The stream has an average metallicity [Fe/H] = -1.96. The rich information of member stars of the stream now available allow one not only to model its origin, but also to place strong constraints on the mass distribution and the gravitational potential of the Milky Way.

We have investigated the metallicity distributions of mono-age stellar populations across the disc of $6 \lesssim R \lesssim 12$\,kpc and $|Z| \lesssim 2$\,kpc using samples selected from the main-sequence turn-off and sub-giant (MSTO-SG) stars targeted by the LAMOST Galactic Spectroscopic surveys. Both the mean values and the profiles of the distributions exhibit significant variations with age and position. We confirm that the oldest ($>11$\,Gyr) stars have nearly flat radial [Fe/H] gradients at all heights above the disc but show negative vertical [Fe/H] gradients. For stars younger than 11\,Gyr, the radial [Fe/H] gradients flatten with $|Z|$, while the vertical [Fe/H] gradients flatten with $R$. Stars of 4--6\,Gyr exhibit steeper negative radial [Fe/H] gradients than those of either younger or older ages. Values of [$\alpha$/Fe] of mono-age stellar populations also show significant radial and vertical gradients, with patterns varying with age. The [Fe/H] distribution profiles of old ($>8$\,Gyr) stars vary little with $R$, while those of younger stars exhibit strong radial variations, probably a consequence of significant radial migration. The [$\alpha$/Fe] radial distribution profiles show opposite patterns of variations with age compared to those of [Fe/H]. We have also explored the impacts of stellar mixing by epicycle motions (blurring) on the [Fe/H] and [$\alpha$/Fe] distributions, and found that blurring mainly change the widths of the distribution profiles. Our results suggest that the disc may have experienced a complex assemblage history, in which both the "inside-out" and "upside-down" formation processes may have played an important role.

We have investigated the distributions of stellar azimuthal and radial velocity components V-Phi and V-R in the vertical position-velocity plane Z-V-Z across the Galactic disk of 6.34 less than or similar to R less than or similar to 12.34 kpc and vertical bar Phi vertical bar less than or similar to 7 degrees.5 using a Gaia and Gaia-LAMOST sample of stars. As found in previous works, the distributions exhibit significant spiral patterns. The V-R distributions also show clear quadrupole patterns, which are the consequence of the well-known tilt of the velocity ellipsoid. The observed spiral and quadrupole patterns in the phase space plane vary strongly with radial and azimuthal positions. The phase spirals of V-Phi become more and more relaxed as R increases. The spiral patterns of V-Phi and V-R and the quadrupole patterns of V-R are strongest at -2 degrees < Phi < 2 degrees but negligible at 4 degrees < Phi < 6 degrees and -6 degrees < Phi < -4 degrees. Our results suggest an external origin of the phase spirals. In this scenario, the intruder, most likely the previously well-known Sagittarius dwarf galaxy, passed through the Galactic plane in the direction toward either Galactic center or anti-center. The azimuthal variations of the phase spirals also help us constrain the passage duration of the intruder. A detailed model is required to reproduce the observed radial and azimuthal variations of the phase spirals of V-Phi and V-R.

We present new three-dimensional (3D) interstellar dust reddening maps of the Galactic plane in three colours, E(G-Ks), E(Bp-Rp) and E(H-Ks). The maps have a spatial angular resolution of 6 arcmin and covers over 7000 deg$^2$ of the Galactic plane for Galactic longitude 0 deg $<$ $l$ $<$ 360 deg and latitude $|b|$ $<$ $10$ deg. The maps are constructed from robust parallax estimates from the Gaia Data Release 2 (Gaia DR2) combined with the high-quality optical photometry from the Gaia DR2 and the infrared photometry from the 2MASS and WISE surveys. We estimate the colour excesses, E(G-Ks), E(Bp-Rp) and E(H-Ks), of over 56 million stars with the machine learning algorithm Random Forest regression, using a training data set constructed from the large-scale spectroscopic surveys LAMOST, SEGUE and APOGEE. The results reveal the large-scale dust distribution in the Galactic disk, showing a number of features consistent with the earlier studies. The Galactic dust disk is clearly warped and show complex structures possibly spatially associated with the Sagittarius, Local and Perseus arms. We also provide the empirical extinction coefficients for the Gaia photometry that can be used to convert the colour excesses presented here to the line-of-sight extinction values in the Gaia photometric bands.

A rapid pyrolysis heat treatment was proposed to prepare YBa2Cu3O7-δ (YBCO) films by a self-developed fluorine-free polymer-assisted chemical solution deposition (PA-CSD) approach. Metal acetates and polyvinyl butyral (PVB) in YBCO wet films were pyrolyzed within 30 min, which is less than one-twentieth the pyrolysis time for conventional fluorine–free CSD methods. The influence of the rapid decomposition on the microstructures of YBCO precursor films was investigated compared to conventionally pyrolyzed films. Based on the rapidly pyrolyzed films, high-temperature firing process was further optimized to fabricate epitaxially grown YBCO films. The results demonstrate that most of the defects generated in the rapid pyrolysis process can nearly be eliminated by extending firing time to 2 h, and thus the textured YBCO films with denser and smoother morphologies were obtained with superconducting transition temperature Tc of 93.3 K and critical current density Jc of 3.1 MA/cm2 at 77 K and self-field. This is almost three times of the Jc of the conventionally pyrolyzed film.

We present a new catalog of 18080 radial velocity (RV) standard stars selected from the APOGEE data. These RV standard stars are observed at least three times and have a median stability (3σRV) around 240 m s−1 over a time baseline longer than 200 days. They are largely distributed in the northern sky and could be extended to the southern sky by the future APOGEE-2 survey. Most of the stars are red giants (J − Ks ≥ 0.5) owing to the APOGEE target selection criteria. Only about 10 per cent of them are main-sequence stars. The H-band magnitude range of the stars is 7–12.5 mag with the faint limit much fainter than the magnitudes of previous RV standard stars. As an application, we show the new set of standard stars to determine the RV zero points of the RAVE, the LAMOST, and the Gaia-RVS Galactic spectroscopic surveys.

Abstract Using the spectroscopic distances of over 0.12 million A-type stars selected from the LAMOST Spectroscopic Survey of the Galactic Anti-center (LSS-GAC), we map their three-dimensional number density distributions in the Galaxy. These stellar number density maps allow an investigation of the Galactic young age thin disk structure with no a priori assumptions about the functional form of its components. The data show strong evidence for a significant flaring young disk. A more detail analysis show that the stellar flaring have different behaviours between the Northern and the Southern Galactic disks. The maps also reveal spatially coherent, kpc-scale stellar substructure in the thin disk. Finally, we detect the Perseus arm stellar overdensity at R ~ 10 kpc.

In this study, we expand the coverage and improve the homogeneity of the distribution of MILES template stars in the parameter space, as well as extend the wavelength coverage of the template spectra to the far red beyond the Can triplet. To achieve this, we have carried out a major observational campaign using two long-slit spectrographs: the OMR mounted on the National Astronomy Observatory of China (NAOC) 2.16-m telescope and the Yunnan Faint Object Spectrograph and Camera (YFOSC) mounted on the Yunnan Astronomical Observatory (YNAO) 2.4-m telescope. The original sample is based on the MILES library, supplemented by 918 stars selected from the PASTEL data base. In total, 822 OMR and 1324 YFOSC spectra have been collected and reduced, covering the wavelength ranges lambda lambda 3800-5180 and lambda lambda 5150-9000, respectively. The spectra have a mean resolution full width at halfmaximum of similar to 3.3 angstrom and are wavelength- and flux-calibrated to an accuracy of similar to 20 km s(-1) and similar to 5 per cent, respectively. The spectra are further corrected for systematic errors in the wavelength calibration to an accuracy of similar to 4 km s(-1) by cross-correlating with the theoretical spectra. Almost all the spectra have an average signal-to-noise ratio better than 100 per pixel. Combined with the MILES spectra, there are now 1731, 1542, 1324 and 1273 stars with spectra covering lambda lambda 3800-5180, lambda lambda 3800-7500, lambda lambda 5150-9000 and lambda lambda 3800-9000, respectively. In this paper, we describe our template star selection, the observation and data reduction, and we present the reduced spectra collected hitherto.

The sky brightness is a critical parameter for estimating the coronal observation conditions for a solar observatory. As part of a site-survey project in Western China, we measured the sky brightness continuously at the Lijiang Observatory in Yunnan province in 2011. A sky brightness monitor (SBM) was adopted to measure the sky brightness in a region extending from 4.5 to 7.0 apparent solar radii based on the experience of the Daniel K. Inouye Solar Telescope (DKIST) site survey. Every month, the data were collected manually for at least one week. We collected statistics of the sky brightness at four bandpasses located at 450, 530, 890, and 940 nm. The results indicate that aerosol scattering is of great importance for the diurnal variation of the sky brightness. For most of the year, the sky brightness remains under 20 millionths per airmass before local Noon. On average, the sky brightness is less than 20 millionths, which accounts for 40.41% of the total observing time on a clear day. The best observation time is from 9:00 to 13:00 (Beijing time). The Lijiang Observatory is therefore suitable for coronagraphs investigating the structures and dynamics of the corona.

Using a sample of about 123,000 stars with accurate 3D velocity measurements from the LAMOST-TGAS data, we confirm the kinematic signature of the Galactic warp recently found by Schönrich & Dehnen. The data reveal a clear trend of increasing mean vertical velocity as a function of absolute vertical angular momentum Lz and azimuthal velocity Vϕ for guiding center radius Rg between 6.0 and 10.5 kpc. The trend is consistent with a large-scale Galactic warp. Similar to Schönrich & Dehnen, we also find a wave-like pattern of versus Lz with an amplitude of ∼0.9 km s−1 on a scale of ∼2.0 kpc, which could arise from bending waves or a winding warp. Finally, we confirm a prominent, localized peak in near Lz ∼ 2150 kpc km s−1 (corresponding to Rg ∼ 9 kpc and Vϕ ∼ 255 km s−1). The additional line-of-sight velocity information from LAMOST reveals that stars in this feature have a large, inward radial velocity of VR ∼ −13.33 ± 0.59 km s−1 and a small radial velocity dispersion of σR ∼ 25.27 ± 0.89 km s−1, suggesting that a stellar stream gives rise to this feature.

We report the discovery of two new unbound hypervelocity stars (HVSs) from the LAMOST spectroscopic surveys. They are, respectively, a B2V-type star of similar to 7M(circle dot) with a Galactic rest-frame radial velocity of 502 km s(-1) at a Galactocentric radius of similar to 21 kpc and a B7V-type star of similar to 4M(circle dot) with a Galactic rest-frame radial velocity of 408 km s-1 at a Galactocentric radius of similar to 30 kpc. The origins of the two HVSs are not clear given their currently poorly measured proper motions. However, the future data releases of Gaia should provide proper motion measurements accurate enough to solve this problem. The ongoing LAMOST spectroscopic surveys are expected to yield more HVSs to form a statistical sample, providing vital constraints on understanding the nature of HVSs and their ejection mechanisms.