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An application of the KNND method for detecting nearby open clusters based on Gaia-DR1

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Research in Astronomy and Astrophysics 2017年第6期17卷 89-94页

作者： xin-hua gao School of Information Science and Engineering Changzhou University Changzhou 213164 China

This paper presents a preliminary test of the k-th nearest neighbor distance （KNND） method for detecting nearby open clusters based on Gaia-DR1. We select 38 386 nearby stars （〈 100 pc） from the Gaia-DR1 catalog, and then use the KNND method to detect overdense regions in three-dimensional space. We find two overdense regions （the Hyades and Coma Berenices （Coma Ber） open clusters）, and obtain 57 reliable cluster members. Based on these cluster members, the distances to the Hyades and Coma Ber clusters are determined to be 46.0±0.2 and 83.5±0.3 pc, respectively. Our results demonstrate that the KNND method can be used to detect open clusters based on a large volume of astrometry data.

关键词： open clusters and associations individual (Hyades, Coma Ber) - astrometry- parallaxes- stars distances

An application of the k-th nearest neighbor method to open cluster membership determination

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Research in Astronomy and Astrophysics 2016年第12期16卷 46-50页

作者： xin-hua gao School of Information Science and Engineering Changzhou University

We introduce a non-parametric method for open cluster membership determination in threedimensional（3D） velocity space（proper motion and radial velocity）. Clean 3D cluster members can be obtained by statistically analyzing the Euclidean distance between each star and its k-th nearest neighbor in3 D velocity space. We use 513 sample stars in the direction of open cluster M67 to construct a 3D velocity space and test our method; 291 3D cluster members are obtained. The color-magnitude diagram, proper motions, radial velocities and spatial distribution of these 3D cluster members demonstrate the effectiveness of our method. From the 291 3D cluster members, the mean radial velocity and absolute proper motion of M67 are Vr = ＋33.46 ± 0.05 km s-1and（PMRA, PMDEC） =（-7.64 ± 0.07,-5.98 ± 0.07） mas yr-1,respectively. In addition, we use 640 sample stars with precise proper motions and radial velocities in the direction of open cluster NGC 188 to test our method. The test results also show that our method is effective.

关键词： open clusters and associations: individual (M67)-- Hertzsprung-Russell and C-M diagrams--stars: kinematics and dynamics

Kinematic and chemical properties of five open clusters based on SDSS DR7

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Research in Astronomy and Astrophysics 2010年第8期10卷 761-776页

作者： xin-hua gao Li Chen Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory for Astrophysics Shanghai 200234 China

We present metallicities and radial velocities for five old open clusters （NGC 6791, NGC 2420, NGC 2682, NGC 2158, and NGC 7789） using data from the seventh public data release of the Sloan Digital Sky Survey （SDSS）, which includes the directed stellar program SEGUE： Sloan Extension For Galactic Understanding and Exploration. The radial velocities are used to calculate cluster membership probabilities for stars in each cluster region. NGC 6791, NGC 2420, NGC 2682, NGC 2158 and NGC 7789 are found to have mean metallicities [Fe/H]= ＋0.08 ± 0.09, -0.38± 0.11, -0.08±0.05, -0.41 ±0.13 and -0.19 ± 0.13 dex （s.d.）, respectively. The mean radial velocities for NGC 6791, NGC 2420, NGC 2682, NGC 2158 and NGC 7789 are Vr = -45.9 ± 0.2, ＋76.1 ± 0.2, ＋35.0 ± 0.2, ＋26.9 ± 0.2 and -48.2± 0.2 km s^-1（s.e.m.）, respectively. We have compared our results with the values from literatures, and found that our metallicity of NGC 6791 is significantly underestimated （by about 0.3 dex） and our radial velocities of the open clusters agree well with the values derived using high-resolution spectroscopy.

关键词： open clusters and associations general -- open clusters and associations individual (NGC 6791, NGC 2420, NGC 2682, NGC 2158, NGC 7789)

Attractive natural products with strained cyclopropane and/or cyclobutane ring systems

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Science China Chemistry 2016年第9期59卷 1126-1141页

作者： Yao-Yue Fan xin-hua gao Jian-Min Yue Shanghai Institute of Materia Medica Chinese Academy of Sciences

The strained cyclopropane and/or cyclobutane subunits occurred in many complex natural products including terpenoids, steroids and alkaloids. Natural products with cyclopropane and/or cyclobutane motifs not only furnished fascinating structures, but also exhibited versatile biological activities, such as cytotoxic, anti-HIM antimicrobial, antiviral, and immunosuppressive effects. This review covered a large array of structurally unique natural products with strained cyclopropane and/or cyclobutane motifs and summarized their structural features, distributions, biological activities, as well as biogenetic considerations.

关键词： natural products cyclopropane-containing cyclobutane-containing biological activity biosynthetic pathway

Discovery of high-velocity EHB stars in the globular cluster ωCentauri(NGC 5139)

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Research in Astronomy and Astrophysics 2015年第10期15卷 1639-1646页

作者： xin-hua gao Shou-Kun Xu Li Chen School of Information Science and Engineering Changzhou University Shanghai Astronomical Observatory Chinese Academy of Sciences

Abstract We report the discovery of 45 high-velocity extreme horizontal branch （EHB） stars in the globular cluster Omega Centauri （NGC 5139）. The tangential ve- locities of these EHB stars are determined to be in the range 93-313 km s^-1, with an average uncertainty of -27 km s^-1. The central escape velocity of the cluster is determined to be in the range 60~105 km s^-1. These EHB stars are significantly more concentrated toward the cluster core compared with other cluster members. The formation mechanisms of these EHB stars are discussed. Our conclusions can be sum- marized as follows：（1） A comparison of the tangential velocities of these EHB stars to the central escape velocity of the cluster shows that most if not all of these EHB stars are unbound to the cluster; （2） These EHB stars obtained high velocities in the central cluster region no longer than - 1 Myr ago and may be subsequently ejected from the cluster in the next -1 Myr; （3） If the progenitors of these EHB stars were single stars, then they may have experienced a fast mass-loss process. If the progen- itors were in close binaries, then they may have formed through disruptions by the intermediate-mass black hole in the cluster center.

关键词： Galaxy: globular clusters: individual: ω Cen (NGC 5139) -- stars:Hertzsprung-Russell and C-M diagrams -- stars: kinematics and dynamics -- stars:binaries (including multiple): close

3D cluster members and near-infrared distance of open cluster NGC 6819

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Research in Astronomy and Astrophysics 2015年第12期15卷 2193-2203页

作者： xin-hua gao Shou-Kun Xu Li Chen School of Information Science and Engineering Changzhou University Shanghai Astronomical Observatory Chinese Academy of Sciences

In order to obtain clean members of the open cluster NGC 6819, the proper motions and radial velocities of 1691 stars are used to construct a three-dimensional （3D） velocity space. Based on the DBSCAN clustering algorithm, 537 3D cluster members are obtained. From the 537 3D cluster members, the average radial velocity and absolute proper motion of the cluster are Vr = ＋2.30 ±0.04 km s-1 and （PMRA, PMDec） = （-2.5 ±0.5, -4.3 ± 0.5） mas yr-1, respectively. The proper motions, radial velocities, spatial positions and color-magnitude diagram of the 537 3D members indicate that our membership determination is effective. Among the 537 3D cluster members, 15 red clump giants can be easily identified by eye and are used as reliable standard candles for the distance estimate of the cluster. The distance modulus of the cluster is determined to be （m - M）0 -- 11.86 ± 0.05 mag （2355 ±54 pc）, which is quite consistent with published values. The uncertainty of our distance mod- ulus is dominated by the intrinsic dispersion in the luminosities of red clump giants （--0.04 mag）.

关键词： open clusters and associations: individual (NGC 6819) -- Hertzsprung-Russell and C-M diagrams -- stars: kinematics and dynamics -- stars: distances

Suadimins D—J,Monoterpenoid Indole-Quinoline and Bisindole Alkaloids from Melodinus suaveolens

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Chinese Journal of Chemistry 2023年第18期41卷 2296-2304页

作者： xin-hua gao Pei-Qian Wu Yao-Yue Fan Bin Zhou Jian-Min Yue State Key Laboratory of Drug Research Shanghai Institute of Materia MedicaChinese Academy of Sciences555 Zuchongzhi RoadShanghai201203China shandong Laboratory of Yantai Drug Discovery Bohai Rim Advanced Research Institute for Drug DiscoveryYantaiShandong 264117China Research Units of Discovery of New Drug Lead Molecules Chinese Academy of Medical SciencesShanghai 201203China

Comprehensive Summary,Compounds 1—12,including seven complex monoterpenoid indole-quinoline and bisindole alkaloids,suadimins D—J(1—7)with previously unreported carbon-carbon linkages,were isolated and identified from the twigs and leaves of Melodinus *** structures were elucidated by a combination of diverse methods,especially the extensive spectroscopic data analysis and electric circular dichroism(ECD)*** cytotoxicity of these compounds against three cancer cell lines was evaluated,some of which showed moderate activities with IC50 values ranging from 2.4 to 8.0μM.

关键词： Melodinus suaveolens Alkaloids Dimerization Structure elucidation ECD calculations Cytotoxic activity

Rearranged Dichapetalin-Type Triterpenoids with Cytotoxic Activity from Dichapetalum gelonioides

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Chinese Journal of Chemistry 2022年第21期40卷 2531-2538页

作者： xin-hua gao Xi-Yuan Wang Jun-Su Zhou Yan Zhang Hong-Chun Liu Bin Zhou Jian-Min Yue State Key Laboratory of Drug Research Shanghai lnstitute of Materia MedicaChinese Academy of SciencesShanghai 201203China Research Units of Discovery of New Drug Lead Molecules Chinese Academy of Medical SciencesShanghai 201203china Shandong Laboratory of Yantai Drug Discovery Bohai Rim Advanced Research Institute for Drug DiscoveryYantaiShandong 264117China

Dichagelinoids A—C(1—3),three unusual dichapetalin-type triterpenoids,together with two biogenetically related derivatives dichagelinoids D and E(4 and 5)were isolated and characterized by solid data from Dichapetalum *** 1—3 possess a common rearranged C ring and different C6—C2 modified motifs at the A *** evaluation revealed that compounds 1—3 showed distinct cytotoxic activity against the tested human cancer cell lines.

关键词： Dichapetalum gelonioides Natural products Dichapetalin-type triterpenoids Structural elucidation Cytotoxic activity

Correlation of continuous electroencephalogram with clinical assessment scores in acute stroke patients

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Neuroscience Bulletin 2012年第5期28卷 611-617页

作者： Xiyan xin Ying gao hua Zhang Kegang Cao Yongmei Shi Department of Neurology Dongzhimen Hospital Beijing University of Chinese Medicine Beijing 100700 China

Objective To compare electroencephalogram （EEG） symmetry values between stroke patients with different 28-day outcomes, and to assess correlations between clinical characteristics and 28-day outcomes. Methods Twenty-two patients presenting with acute ischemic stroke and persistent neurological deficits at EEG recording were incrementally included. At 28 days after admission, the modified Rankin scale （mRS） was used to evaluate the outcomes, based on which the patients were divided into two a posteriori groups, mRS = 6 and mRS 〈6. Student＇s t-test was used to compare these two groups in terms of brain symmetry index （BSI）, National Institutes of Health stroke scale （NIHSS）, Glasgow coma scale （GCS） and acute physiology and chronic health evaluation II （APACHE II） assessed at admission. Then EEG parameters, NIHSS, GCS and APACHE II were correlated with the mRS. Results There were significant differences in BSI, NIHSS, GCS, and APACHE II between the two groups. Survivors had lower BSI, NIHSS and APACHE II, and higher GCS values, compared with patients who died within 28 days after admission. Besides, BSI at admission had a positive correlation with mRS at 28 days （r = 0.441, P = 0.040）. NIHSS and APACHE II were also correlated with mRS （r = 0.736, P 〈0.000 1; r = 0.667, P = 0.001, respectively）. GCS at admission had a negative correlation with mRS （r = 0.656, P = 0.001）. Conclusion A higher BSI predicts a poorer short-term prognosis for stroke patients. Acute EEG monitoring may be of prognostic value for 28-day outcomes. The early prediction of functional outcomes after stroke may enhance clinical management and minimize short-term mortality.

关键词： electroencephalography brain symmetry index stroke prognosis