期刊文献+
共找到21,042篇文章
< 1 2 250 >
每页显示 20 50 100
骨科机器人联合Starr骨盆复位架治疗Tile C型骨盆环骨折 被引量:1
1
作者 姜刚强 焦福德 +3 位作者 应霁翀 虞天明 刘建磊 庄云强 《中国骨伤》 CAS CSCD 2024年第5期445-450,共6页
目的:探讨骨科机器人联合Starr骨盆复位架治疗Tile C型骨盆环骨折的临床疗效。方法:2019年10月至2021年5月采用机器人联合Starr骨盆复位架治疗14例Tile C型骨盆环骨折患者,男9例,女5例;年龄33~69岁。14例患者均为新鲜闭合骨折且不合并... 目的:探讨骨科机器人联合Starr骨盆复位架治疗Tile C型骨盆环骨折的临床疗效。方法:2019年10月至2021年5月采用机器人联合Starr骨盆复位架治疗14例Tile C型骨盆环骨折患者,男9例,女5例;年龄33~69岁。14例患者均为新鲜闭合骨折且不合并股骨、胫腓骨骨折等损伤。入院后4~7 d完成手术,术中在可透视碳素床,通过Starr骨盆复位架牵引复位骨盆环,联合骨科机器人治疗C型骨盆环骨折。观察手术时间、出血量、单枚螺钉置入透视次数、骨折复位质量、患肢功能及并发症等。采用Matta评分标准进行放射学复位评价,末次随访采用Majeed骨盆功能评分系统进行临床疗效评价。结果:14例患者均顺利完成手术,手术时间84~141 min,手术出血量20~50 ml,单枚螺钉置入透视次数4~9次。14例患者均获得随访,随访时间12~24个月。术后所有骨折获得骨性愈合,愈合时间3~7个月,未发现内固定断裂、螺钉松动、感染、神经损伤等并发症。依据Matta影像学复位评估标准:优9例,良4例,可1例。末次随访采用Majeed骨盆功能评分系统:优10例,良4例。结论:机器人联合Starr骨盆复位架治疗C型骨盆环新鲜骨折操作简单、缩短了手术和麻醉时间、并发症少,降低了手术风险,实现了骨盆骨折的微创治疗。但对于陈旧性骨折,因骨折复位困难,该技术并不适用。对于螺钉进钉点区域粉碎的骨折,通道螺钉置入困难,建议采用其他方式固定。对于伴有骨盆外伤史或骨盆发育异常者,术前需仔细评估有无经皮螺钉通道,避免损伤神经、血管。 展开更多
关键词 骨科机器人 starr骨盆复位架 骨盆骨折 螺钉 内固定
下载PDF
基于Hotelling T2-BiLSTM的同步调相机故障诊断方法
2
作者 李俊卿 张承志 +3 位作者 韩小平 黄涛 何玉灵 孔凡春 《智慧电力》 北大核心 2024年第7期96-102,127,共8页
同步调相机故障会严重影响特高压直流输电工程的稳定性。针对特高压电网中不对称电压条件下同步调相机励磁绕组匝间短路故障难以识别问题,提出基于霍特林T2-双向长短期记忆网络(Hotelling T2-BiLSTM)的同步调相机故障诊断方法。首先,从... 同步调相机故障会严重影响特高压直流输电工程的稳定性。针对特高压电网中不对称电压条件下同步调相机励磁绕组匝间短路故障难以识别问题,提出基于霍特林T2-双向长短期记忆网络(Hotelling T2-BiLSTM)的同步调相机故障诊断方法。首先,从三相电压、三相电流、励磁电流、转子振动和无功功率中提取故障特征,计算Hotelling T2统计量以构建故障检测指标;然后,采用BiLSTM模型对特征进行分类,并利用逻辑回归层进行故障诊断;最后,在动模实验室中进行实验验证其有效性。实验结果表明,所提方法具有较高的故障诊断精度。 展开更多
关键词 同步调相机 不对称电压 励磁绕组匝间短路 hotelling T2 BiLSTM 故障诊断
下载PDF
日本沼虾StAR基因克隆及其低氧胁迫下表达分析 被引量:1
3
作者 郑诚 薛程 +1 位作者 赵倩倩 孙盛明 《水产学报》 CAS CSCD 北大核心 2024年第3期64-75,共12页
为了研究类固醇激素合成急性调节蛋白(steroidogenic acute regulatory protein, StAR)在日本沼虾应答低氧胁迫过程中所发挥的作用,实验应用c DNA末端快速扩增(RACE)PCR技术克隆了日本沼虾StAR全长cDNA序列,并利用在线软件对其序列特征... 为了研究类固醇激素合成急性调节蛋白(steroidogenic acute regulatory protein, StAR)在日本沼虾应答低氧胁迫过程中所发挥的作用,实验应用c DNA末端快速扩增(RACE)PCR技术克隆了日本沼虾StAR全长cDNA序列,并利用在线软件对其序列特征进行生物信息学分析,采用半定量RT-PCR方法分析StAR在日本沼虾不同组织的分布情况,采用实时荧光定量PCR(qRT-PCR)与免疫印迹(Western blot)技术对其在不同低氧胁迫阶段中的表达规律进行检测,观察低氧胁迫下精巢组织中StAR蛋白免疫组化定位。结果显示,日本沼虾StAR其cDNA全长3 361 bp (NCBI登录号:MW263908),包括5′-UTR 323 bp,3′-UTR 2 129 bp,开放阅读框909 bp,编码302个氨基酸。氨基酸序列比对及系统进化分析结果显示,日本沼虾StAR基因与三疣梭子蟹等甲壳动物StAR聚类一支,具有最近的亲缘关系。半定量RT-PCR检测结果显示,StAR在日本沼虾不同组织中均有表达,其表达量在肝胰腺和心脏组织中最低,在精巢组织中表达处于较高水平。使用qRT-PCR技术检测日本沼虾精巢中StAR在低氧胁迫下时空表达情况,结果表明,与对照组相比,低氧处理组精巢中StAR基因表达量在1~48 h均显著上调,而在低氧处理组96 h显著降低。此外,本实验对StAR进行了原核表达及抗血清制备,采用Western blot检测StAR蛋白表达丰度基本与基因表达模式相似,免疫组化结果显示,StAR蛋白在精细胞与间质细胞中均有表达。综上所述,长期低氧胁迫显著降低了StAR基因的转录表达水平,并且该基因可能在类固醇合成路径及精子发生过程中均发挥重要作用。本研究结果为进一步解析日本沼虾类固醇激素合成分子机制奠定基础。 展开更多
关键词 日本沼虾 star 克隆 低氧 表达分析
下载PDF
STAR基因与东湖杂交奶绵羊繁殖性状的关联分析 被引量:1
4
作者 李桂丽 李丹妮 +6 位作者 王丽 吴卓芯 王钰晨 郭磊 张希云 张磊 宋宇轩 《中国畜牧杂志》 CAS CSCD 北大核心 2024年第1期137-142,共6页
本实验旨在探究类固醇激素合成急性调节蛋白(Steroidogenic Acute Regulatory Protein,STAR)基因多态性与东湖杂一代奶绵羊发情鉴定评分、产羔数的相关性,鉴定出影响绵羊繁殖性能的关键性位点。本研究以339只东湖杂一代奶绵羊为研究对象... 本实验旨在探究类固醇激素合成急性调节蛋白(Steroidogenic Acute Regulatory Protein,STAR)基因多态性与东湖杂一代奶绵羊发情鉴定评分、产羔数的相关性,鉴定出影响绵羊繁殖性能的关键性位点。本研究以339只东湖杂一代奶绵羊为研究对象,采用竞争性等位基因特异性PCR(KASP)技术对STAR基因的g.31959747T>C、g.31959875A>C2个位点进行基因分型,并利用GLM模型对SNP位点与发情鉴定评分和产羔数进行关联分析。结果表明,g.31959747T>C与奶绵羊发情鉴定评分呈极显著相关,TT型的发情表现更优,但与产羔数差异不显著;g.31959875A>C与发情评分和产羔数均无显著关系;聚合基因型与繁殖性状的关联分析结果表明,TCAC型个体在发情评分、平均产羔数方面均较低。综上,STAR基因g.31959747T>C位点是影响奶绵羊发情评分的关键性位点,可根据育种目标将g.31959747T>C位点作为提高奶绵羊同期发情效果的分子标记,同时将TCAC聚合基因型及时淘汰。本研究结果可为奶绵羊繁殖性状的选育提供参考。 展开更多
关键词 star 东湖杂交奶绵羊 关联分析 发情鉴定评分 产羔数
下载PDF
STAR基因在不同发育期绵羊睾丸和附睾中的表达与组织分布
5
作者 蒋雨婷 王霞 +5 位作者 宋娟娟 李晨硕 王彩丽 陈浩林 李讨讨 马友记 《中国畜禽种业》 2024年第4期77-84,1,共9页
为探讨STAR基因在发育的绵羊睾丸和附睾中的表达模式及潜在功能,该研究采集3月龄、 1周岁和3周岁藏绵羊睾丸和附睾(头、体和尾)组织样本,利用实时荧光定量PCR、蛋白免疫印迹和免疫组织荧光染色法检测STAR基因的表达及其编码蛋白的细胞... 为探讨STAR基因在发育的绵羊睾丸和附睾中的表达模式及潜在功能,该研究采集3月龄、 1周岁和3周岁藏绵羊睾丸和附睾(头、体和尾)组织样本,利用实时荧光定量PCR、蛋白免疫印迹和免疫组织荧光染色法检测STAR基因的表达及其编码蛋白的细胞定位。结果发现,随着年龄的增加,在藏绵羊睾丸和附睾(附睾头除外)中STAR基因在转录水平的表达总体呈下降趋势,而在蛋白质水平的表达呈上调趋势。STAR蛋白主要存在于藏绵羊睾丸间质细胞和附睾假复层纤毛上皮主细胞。鉴于间质细胞和主细胞的主要生物学功能是分泌睾酮和分泌促进精子成熟所需的蛋白质,由此推测,STAR基因可能主要在睾丸间质细胞和附睾主细胞的发育和功能维持中发挥作用,进而促进雄激素的合成和精子的成熟。 展开更多
关键词 绵羊 star基因 睾丸 附睾
下载PDF
Assessment of the Implementation of Energy Conservation Opportunities Arising from Energy Audits;A Study of Four-Star and Five-Star Hotels in Nairobi Kenya
6
作者 Nicholas Ogola Peter Musau Cyrus Wekesa 《Journal of Power and Energy Engineering》 2023年第9期15-44,共30页
This study assesses the implementation of energy conservation opportunities in four-star and five-star hotels in Nairobi. The Covid-19 pandemic had a significant impact on the Hospitality Industry. Currently, there is... This study assesses the implementation of energy conservation opportunities in four-star and five-star hotels in Nairobi. The Covid-19 pandemic had a significant impact on the Hospitality Industry. Currently, there is a growing inclination to furnish guests with superior and sustainable services in an energy-efficient and eco-friendly way. Comprehensive research was conducted from energy audits gathered from the establishments and contracted auditing companies, on top of this, hotel staff were given digital questionnaires. To add to the data, the researcher surveyed the hotels with engineering managers. The Energy Audits found that all 10 hotels had adopted Energy Conservation Opportunities (ECOs). After further analysis, the mean adoption rate of Energy Conservation Opportunities (ECOs) during the past three years was 55.83%, which was below the aim of 100%. According to studies, hotel staff manages energy to cut costs. The researcher found that hotels use up a lot of energy. However, they have conservation potential, depending on government policies, costs, ease of implementation, and management commitment to sustainable practices. Essentially, Energy Conservation Opportunities (ECOs) reduce energy expenditures and boost reliable revenues, especially during high energy prices and uncertainty. 展开更多
关键词 Energy Conservation Opportunities (ECOs) Energy Regulation 2012 Energy Audit 4-star hotel 5-star hotel Energy Management Environmental Sustainability Energy Efficiency
下载PDF
Free Energy of Anisotropic Strangeon Stars 被引量:1
7
作者 Shichuan Chen Yong Gao +1 位作者 Enping Zhou Renxin Xu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第2期50-57,共8页
Can pulsar-like compact objects release further huge free energy besides the kinematic energy of rotation?This is actually relevant to the equation of state of cold supra-nuclear matter,which is still under hot debate... Can pulsar-like compact objects release further huge free energy besides the kinematic energy of rotation?This is actually relevant to the equation of state of cold supra-nuclear matter,which is still under hot debate.Enormous energy is surely needed to understand various observations,such asγ-ray bursts,fast radio bursts and softγ-ray repeaters.In this paper,the elastic/gravitational free energy of solid strangeon stars is revisited for strangeon stars,with two anisotropic models to calculate in general relativity.It is found that huge free energy(>10^(46)erg)could be released via starquakes,given an extremely small anisotropy((p_(t)-p_(r))/p_(r)~10^(-4),with pt/pr the tangential/radial pressure),implying that pulsar-like stars could have great potential of free energy release without extremely strong magnetic fields in the solid strangeon star model. 展开更多
关键词 (stars:)pulsars general-methods numerical-(stars:)gamma-ray bursts general
下载PDF
Spectroscopic Observations of Ten Galactic Wolf-Rayet Stars at Bosscha Observatory:Determination of Stellar Parameters and Mass-loss Rates
8
作者 Hakim Luthfi Malasan Bakuh Danang Setyo Budi 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第9期7-27,共21页
We present optical spectra of 10 Galactic Wolf-Rayet(WR)stars that consist of five WN and five WC stars.The optical observation was conducted using a low-resolution spectrograph NEO-R1000(λ/Δλ~1000)at GAO-ITB RTS(2... We present optical spectra of 10 Galactic Wolf-Rayet(WR)stars that consist of five WN and five WC stars.The optical observation was conducted using a low-resolution spectrograph NEO-R1000(λ/Δλ~1000)at GAO-ITB RTS(27.94 cm,F/10.0),Bosscha Observatory,Lembang.We implemented stellar atmosphere Postdam Wolf-Rayet(PoWR)grid modeling to derive stellar parameters.The normalized optical spectrum can be used to find the best model from the available PoWR grid,then we could derive stellar temperature and transformation radius.To derive luminosity,stellar radius and color excess,we conducted a Spectral Energy Distribution(SED)analysis with additional data on the near-ultraviolet spectrum from the International Ultraviolet Explorer(IUE)database,and UBV and 2MASS JHK broadband filter data.Additional analysis to derive asymptotic terminal wind velocity was conducted from the P-Cygni profile analysis of the high-resolution IUE ultraviolet spectrum.With previously derived parameters,we could determine the mass loss rate of the WR stars.Furthermore,we compared our results with previous work that used PoWR code and the differences are not more than 20%.We conclude that the PoWR spectral grid is sufficient to derive WR stellar parameters quickly and could provide more accurate initial parameter input to the PoWR program code. 展开更多
关键词 stars:massive stars:mass-loss stars:Wolf-Rayet stars:atmospheres stars:winds OUTFLOWS
下载PDF
Formation of a Rapidly Rotating Classical Be-star in a Massive Close Binary System
9
作者 Evgeny Staritsin 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第1期44-50,共7页
This paper investigates the spin-up of a mass-accreting star in a close binary system passing through the first stage of mass exchange in the Hertzsprung gap. Inside an accreting star, angular momentum is carried by m... This paper investigates the spin-up of a mass-accreting star in a close binary system passing through the first stage of mass exchange in the Hertzsprung gap. Inside an accreting star, angular momentum is carried by meridional circulation and shear turbulence. The circulation carries part of the angular momentum of the accreted layers to the accretor's surface. The greater the rate of arrival of angular momentum in the accretor is, the greater this part. It is assumed that this part of the angular momentum can be removed by the disk further from the accretor. If the angular momentum in the matter entering the accretor is more than half the Keplerian value, then the angular momentum obtained by the accretor during mass exchange stage does not depend on the rate of arrival of angular momentum. The accretor may have the characteristics of a Be-star immediately after the end of mass exchange. 展开更多
关键词 (stars:)binaries(including multiple):close stars:emission-line BE stars:early-type stars:rotation
下载PDF
Rotating Massive Strangeon Stars and X-Ray Plateau of Short GRBs
10
作者 Xi-Yan Yang Xiao-Yu Lai +1 位作者 Wei-Wei Tan Ren-Xin Xu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第3期47-57,共11页
Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the rem... Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the remnants of binary strangeon star mergers could even be long-lived massive strangeon stars.We study rigidly rotating strangeon stars in the slowly rotating approximation,using the Lennard-Jones model for the equation of state.Rotation can significantly increase the maximum mass of strangeon stars with unchanged baryon numbers,enlarging the mass-range of long-lived strangeon stars.During spin-down after merger,the decrease of radius of the remnant will lead to the release of gravitational energy.Taking into account the efficiency of converting the gravitational energy luminosity to the observed X-ray luminosity,we find that the gravitational energy could provide an alternative energy source for the plateau emission of X-ray afterglow.The fitting results of X-ray plateau emission of some short gamma-ray bursts suggest that the magnetic dipole field strength of the remnants can be much smaller than that of expected when the plateau emission is powered only by spin-down luminosity of magnetars. 展开更多
关键词 dense matter-(stars) PULSARS general-(stars) gamma-ray burst GENERAL
下载PDF
On the Energy Budget of Starquake-induced Repeating Fast Radio Bursts
11
作者 Wei-Yang Wang Chen Zhang +7 位作者 Enping Zhou Xiaohui Liu Jiarui Niu Zixuan Zhou He Gao Jifeng Liu Renxin Xu Bing Zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第10期180-188,共9页
With a growing sample of fast radio bursts(FRBs),we investigate the energy budget of different power sources within the framework of magnetar starquake triggering mechanism.During a starquake,the energy can be release... With a growing sample of fast radio bursts(FRBs),we investigate the energy budget of different power sources within the framework of magnetar starquake triggering mechanism.During a starquake,the energy can be released in any form through strain,magnetic,rotational,and gravitational energies.The strain energy can be converted from three other kinds of energy during starquakes.The following findings are revealed:(1)The crust can store free magnetic energy of~10^(46)erg by existing toroidal fields,sustaining 10^(6)bursts with frequent starquakes occurring due to crustal instability.(2)The strain energy develops as a rigid object spins down,which can be released during a global starquake accompanied by a glitch.However,it takes a long time to accumulate enough strain energy via spindown.(3)The rotational energy of a magnetar with P■0.1 s can match the energy and luminosity budget of FRBs.(4)The budget of the total gravitational energy is high,but the mechanism and efficiency of converting this energy to radiation deserve further exploration. 展开更多
关键词 stars:magnetars stars:neutron radiation mechanisms:non-thermal
下载PDF
An Asymmetric Galactic Stellar Disk Traced by OB-type Stars from LAMOST DR7
12
作者 Xiaopeng Liu Hao Tian +4 位作者 Wenyuan Cui Linlin Li Jiaming Liu Zhenyan Huo Yawei Gao 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第6期38-51,共14页
Using 9943 OB-type stars from LAMOST DR7 in the solar neighborhood,we fit the vertical stellar density profile with the model including a single exponential distribution at different positions(R,Φ).The distributions ... Using 9943 OB-type stars from LAMOST DR7 in the solar neighborhood,we fit the vertical stellar density profile with the model including a single exponential distribution at different positions(R,Φ).The distributions of the scale heights and scale length show that the young disk traced by the OB-type stars is not axisymmetric.The scale length decreases versus the azimuthal angleΦ,i.e.,from.■kpc withΦ=-3°to■kpc withΦ=9°.Meanwhile we find signal of non-symmetry in the distribution of the scale height of the north and south of the disk plane.The scale height in the north side shows signal of flaring of the disk,while that of the south disk stays almost constant around h_(s)=130 pc.The distribution of the displaceeent of the disk plane Z_(0)also shows variance versus the azimuthal angleΦ,which displays significant differences with the warp model constrained by the Cepheid stars.We also test different values for the position of the Sun,and the distance between the Sun and the Galactic center affects the scale heights and the displacement of the disk significantly,but that does not change our conclusion that the disk is not axisymmetric. 展开更多
关键词 Galaxy:disk galaxies:spiral stars:early-type stars:massive
下载PDF
The Structure and the Density of a Bare Quark Star in a Cold Genesis Theory of Particles
13
作者 Marius Arghirescu 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第4期1933-1980,共48页
Based on the preonic structure of quarks obtained in a Cold genesis theory of particles (CGT), it was obtained a semi-empiric relation for the current mass of quarks specific to CGT but with the constants obtained wit... Based on the preonic structure of quarks obtained in a Cold genesis theory of particles (CGT), it was obtained a semi-empiric relation for the current mass of quarks specific to CGT but with the constants obtained with the aid of the Gell-Mann-Oakes-Renner formula, giving values close to those obtained by the Standard Model, the current quark’s volume at ordinary nuclear temperature being obtained as sum of theoretic apparent volumes of preonic kerneloids. The maximal densities of the current quarks: strange (s), charm (c), bottom (b), and top (t) resulted in the range (0.8 - 4.2) × 1018 kg/m3, as values which could be specific to possible quark stars, in concordance with previous results. By the preonic quark model of CGT, the possible structure of a quark star resulted from the intermediary transforming: Ne(2d+u)→s−¯+λ−and the forming of composite quarks with the structure: C−(λ−-s−¯-λ−) and C+(s−¯-λ−-s−¯), and of Sq-layers: C+C−C+ and C−C+C− which can form composite quarks: Hq±=(SqS¯qSq);(S¯qSqS¯q), corresponding to a constituent mass: M(Hq) = (12,642;12,711) MeV/c2, the forming of heavier quarks inside a quark star resulting as possible in the form: Dq = n3Cq, (n ≥ 3). The Tolman-Oppenheimer limit: MT=0.7M⊙for neutron stars can also be explained by the CGT’s quark model. 展开更多
关键词 Quark star Cold Genesis Current Quark Density Preons Model Preon star Black Hole
下载PDF
Analysis of the Impact of the Blazhko Effect Both on the Van Hoof Effect and Radial Velocity Amplitude in the Star RR Lyr
14
作者 Y.El jariri F.L.Sefyani +5 位作者 A.Benhida Z.Benkhaldoun K.Kolenberg K.Chafouai A.Habib M.Sabil 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第6期253-272,共20页
The Van Hoof effect is a phase shift existing between the radial velocity curves of hydrogen and metallic lines within the atmosphere of pulsating stars.In this article,we present a study of this phenomenon through th... The Van Hoof effect is a phase shift existing between the radial velocity curves of hydrogen and metallic lines within the atmosphere of pulsating stars.In this article,we present a study of this phenomenon through the spectra of the brightest pulsating star RR Lyr of RR Lyrae stars recorded for 22 yr.We based ourselves,on the one hand,on 1268 spectra(41 nights of observation)recorded between the years 1994 and 1997 at the Observatory of Haute Provence(OHP,France)previously observed by Chadid and Gillet,and on the other hand on 1569 spectra(46nights of observation)recorded at our Oukaimeden Observatory(Morocco)between 2015 and 2016.Through this study,we have detected information on atmospheric dynamics that had not previously been detected.Indeed,the Van Hoof effect which results in a clear correlation between the radial velocities of hydrogen and those of the metallic lines has been observed and analyzed at different Blazhko phases.A correlation between the radial velocities of different metallic lines located in the lower atmosphere has been observed as well.For the first time,we were able to show that the amplitude of the radial velocity curves deduced from the lines of hydrogen and that of FeⅡ(λ4923.921?)increases toward the minimum of the Blazhko cycle and decreases toward the maximum of the same Blazhko cycle.Furthermore,we found that the Van Hoof effect is also modulated by the Blazhko effect.Thus,toward the minimum of the Blazhko cycle the Van Hoof effect is more visible and at the maximum of the Blazhko cycle,this effect is minimal.We also observed the temporal evolution of the amplitudes of the radial velocities of the lower and upper atmosphere.When observed over a long time,we can interpret it as a function of the Blazhko phases. 展开更多
关键词 stars:atmospheres stars:variables:RR Lyrae shock waves techniques:spectroscopic techniques:radial velocities stars:individual(RR Lyr)
下载PDF
Enrichment of Chemical Element ^(7)Li in the Rotating Red Clump Star
15
作者 Fang-Wen Wu Han-Feng Song +3 位作者 Qing-Li Li Yun He Xin-Yue Qu Zhuo Han 《Chinese Physics Letters》 SCIE EI CAS CSCD 2024年第8期121-125,共5页
About 2 percent of red clump stars are found to be the lithium-rich and thus the surface lithium increases obviously in some red clump stars.The physical mechanism of the lithium enrichment in these stars has not yet ... About 2 percent of red clump stars are found to be the lithium-rich and thus the surface lithium increases obviously in some red clump stars.The physical mechanism of the lithium enrichment in these stars has not yet been explained satisfactorily by the evolutionary models of single stars.The flash induced internal gravity wave mixing(i.e.,IGW)could play a primary role in explaining the red clump star with lithium enrichment and it has a very significant impact on the internal structure and surface compositions of a star.Rotation can significantly increase the mixing efficiency of the internal gravity wave because the timescale for the enrichment event has been enlarged.Thermohaline mixing can explain the observed behavior of lithium on red giant stars that are more luminosity than the RGB bump.However,it has a very small effect on the diffusion of elements because its diffusion coefficient is much smaller than the one of IGW induced mixing after the core helium flash. 展开更多
关键词 flash starS LITHIUM
下载PDF
On the Identification of N-rich Metal-poor Field Stars with Future Chinese Space Station Telescope
16
作者 Jiajun Zhang Baitian Tang +6 位作者 Jiang Chang Xiangxiang Xue JoséGFernández-Trincado Chengyuan Li Long Wang Hao Tian Yang Huang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第1期151-164,共14页
During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N... During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N enhancement is the fingerprint of chemically enhanced populations in GCs. In this work, we discuss the possibility of identifying N-rich metal-poor field stars with the upcoming Chinese Space Station Telescope(CSST). We focus on the main survey camera with NUV, u, g, r, i, z, y filters and slitless spectrograph with a resolution about 200.The combination of UV sensitive equipment and prominent N-related molecular lines in the UV band bodes well for the identification: the color–color diagram of(u-g) versus(g-r) is capable of separating N-rich field stars from normal halo stars, if metallicity can be estimated without using the information on u-band photometry.Besides, the synthetic spectra show that a signal-to-noise ratio of 10 is sufficient to identify N-rich field stars. In the near future, a large sample of N-rich field stars found by CSST, combined with state-of-the-art N-body simulations will be crucial to deciphering GC-Galaxy co-evolution. 展开更多
关键词 stars:chemically peculiar stars:abundances techniques:photometric techniques:spectroscopic
下载PDF
What is the Role of Gravity,Turbulence and Magnetic Fields in High-mass Star Formation Clouds?
17
作者 An-Xu Luo Hong-Li Liu +2 位作者 Guang-Xing Li Sirong Pan Dong-Ting Yang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第6期21-27,共7页
To explore the potential role of gravity,turbulence and magnetic fields in high-mass star formation in molecular clouds,this study revisits the velocity dispersion–size(σ–L)and density–size(ρ–L)scalings and the ... To explore the potential role of gravity,turbulence and magnetic fields in high-mass star formation in molecular clouds,this study revisits the velocity dispersion–size(σ–L)and density–size(ρ–L)scalings and the associated turbulent energy spectrum using an extensive data sample.The sample includes various hierarchical density structures in high-mass star formation clouds,across scales of 0.01–100 pc.We observeσ∝L^(0.26)andρ∝L^(-1.54)scalings,converging toward a virial equilibrium state.A nearly flat virial parameter–mass(α_(vir)-M)distribution is seen across all density scales,withα_(vir)values centered around unity,suggesting a global equilibrium maintained by the interplay between gravity and turbulence across multiple scales.Our turbulent energy spectrum(E(k))analysis,based on theσ–L andρ–L scalings,yields a characteristic E(k)∝k^(-1.52).These findings indicate the potential significance of gravity,turbulence,and possibly magnetic fields in regulating dynamics of molecular clouds and high-mass star formation therein. 展开更多
关键词 ISM:clouds stars:formation stars:kinematics and dynamics
下载PDF
Risk Factors for Cardiovascular Disease among Hotel Workers, Bohicon, Benin
18
作者 Mênonli Adjobimey Rose Mikponhoué +4 位作者 Eméline Gbaguidi Esdras Hountohotegbè Hélène Sacca Paul Ayélo Vikkey Antoine Hinson 《Occupational Diseases and Environmental Medicine》 2024年第2期130-141,共12页
Introduction: Non-communicable diseases (NCDs) are on the increase in several sectors of activity. The aim of the study was to determine the frequencies of cardiovascular risk factors (CVRF) and factors associated wit... Introduction: Non-communicable diseases (NCDs) are on the increase in several sectors of activity. The aim of the study was to determine the frequencies of cardiovascular risk factors (CVRF) and factors associated with hypertension among hotel workers in the city of Bohicon. Methods: This was a descriptive and analytical cross-sectional study conducted in the period from December 2018 to January 2019. The variables studied were sociodemographic, occupational, anthropometric and behavioral. Participant recruitment was exhaustive. A standardized questionnaire inspired by the STEPS-WHO questionnaire was used for data collection. After the descriptive analysis, a bivariate analysis was performed using Pearson’s Chi-square test or Fisher’s test at the 5% threshold. Results: A total of 101 workers, 53 (52.47%) of them male, participated in the study. The mean age was 30.60 ± 8.20 years, with extremes of 18 and 55 years. The frequencies of the main risk factors were: 68.32% sitting position > 6 hours/day;38.61% shift work;21.78% high psychological demand, 82.18% low decision latitude, 24.75% low social support, 21.78% occupational stress;7 (6.93%) harmful alcohol consumption;6.93% tobacco consumption;48.51% insufficient physical activity;98.02% insufficient fruit and vegetable consumption;59.41% overweight;14.85% HTA. Factors associated with hypertension were: sex, age and marital status. Conclusion: Occupational factors need to be taken into account when assessing CVRFs. NCD control programs are needed in all sectors of activity. A larger study is needed in the hotel sector. 展开更多
关键词 FDRCV Occupational Factors HYPERTENSION hotelS BENIN
下载PDF
The ALMA-QUARKS Survey.Ⅱ.The ACA 1.3 mm Continuum Source Catalog and the Assembly of Dense Gas in Massive Star-Forming Clumps
19
作者 许峰玮 Ke Wang +30 位作者 Tie Liu Lei Zhu Guido Garay Xunchuan Liu Paul Goldsmith Qizhou Zhang Patricio Sanhueza Shengli Qin Jinhua He Mika Juvela Anandmayee Tej Hongli Liu Shanghuo Li Kaho Morii Siju Zhang Jianwen Zhou Amelia Stutz Neal JEvans Kee-Tae Kim Shengyuan Liu Diego Mardones Guangxing Li Leonardo Bronfman Ken’ichi Tatematsu Chang Won Lee Xing Lu Xiaofeng Mai Sihan Jiao James O.Chibueze Keyun Su Viktor L.Tóth 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第6期119-139,共21页
Leveraging the high resolution,sensitivity,and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array(ALMA),the QUARKS survey,standing for“Querying Underlying mechanisms of massive star formation... Leveraging the high resolution,sensitivity,and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array(ALMA),the QUARKS survey,standing for“Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures”,is observing 139 massive starforming clumps at ALMA Band 6(λ~1.3 mm).This paper introduces the Atacama Compact Array(ACA)7 m data of the QUARKS survey,describing the ACA observations and data reduction.Combining multiwavelength data,we provide the first edition of QUARKS atlas,offering insights into the multiscale and multiphase interstellar medium in high-mass star formation.The ACA 1.3 mm catalog includes 207 continuum sources that are called ACA sources.Their gas kinetic temperatures are estimated using three formaldehyde transitions with a non-LTE radiation transfer model,and the mass and density are derived from a dust emission model.The ACA sources are massive(16–84 percentile values of 6–160 M_(⊙)),gravity-dominated(M∝R^(1.1))fragments within massive clumps,with supersonic turbulence(M>1)and embedded star-forming protoclusters.We find a linear correlation between the masses of the fragments and the massive clumps,with a ratio of 6%between the two.When considering fragments as representative of dense gas,the ratio indicates a dense gas fraction(DGF)of 6%,although with a wide scatter ranging from 1%to 10%.If we consider the QUARKS massive clumps to be what is observed at various scales,then the size-independent DGF indicates a self-similar fragmentation or collapsing mode in protocluster formation.With the ACA data over four orders of magnitude of luminosity-to-mass ratio(L/M),we find that the DGF increases significantly with L/M,which indicates clump evolutionary stage.We observed a limited fragmentation at the subclump scale,which can be explained by a dynamic global collapse process. 展开更多
关键词 stars:formation ISM:kinematics and dynamics ISM:clouds stars:protostars
下载PDF
Probing the Galactic Halo with RR Lyrae Stars.VI.The Radial Velocity Curve Templates of RRc Stars
20
作者 Yue Huang Min Fang +8 位作者 Gaochao Liu Xianzhong Zheng Sarah Ann Bird Yang Huang Jianrong Shi Jiangtao Wang Huawei Zhang Haijun Tian Haotong Zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第7期118-134,共17页
We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky ... We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)Data Release 9.Additionally,we derive the relation between the stellar RV curve amplitudes and g-band light curve amplitudes from Zwicky Transient Facility(ZTF)public survey.For those RRc stars without ZTF g-band light curves,we provide the conversions from the light curve amplitudes in ZTF r-and i-bands,Gaia G-band,and V-band from the All-Sky Automated Survey for Supernovae to those in ZTF g-band.We validate our RV curve templates using the RRc star SV Scl and find the uncertainties of systemic RV are less than 2.11 km s~(-1)and 6.08 km s~(-1)based on the Mg I b triplet and Hαlines,respectively.We calculate the systemic RVs of 30 RRc stars using the RV curve templates constructed with the Mg I b triplet and Hαlines and find the systemic RVs are comparable with each other.This RV curve template will be particularly useful for obtaining the systemic RV of RRc using the LAMOST spectroscopy. 展开更多
关键词 starS VARIABLES RR Lyrae-stars-techniques radial velocities
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部