检索结果-南通市图书馆

Avoided crossings between non-radial modes in low mass RGB stars

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2012年第12期12卷 1655-1665页

作者： Jun-Jun Guo1,2,3,Yan Li1,2 and Xiang-Jun Lai1,2 1 National Astronomical Observatories/Yunnan Observatory,chinese academy of sciences, kunming 650011,china 2.key laboratory for the structure and evolution of celestial objects,chinese academy of sciences,kunming 650011,china 3 graduate university of chinese academy of sciences,beijing 100049,china National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China key laboratory for the structure and evolution of celestial objects Chinese Academy of Sciences Kunming 650011 China graduate university of chinese academy of sciences Beijing 100049 China

Non-radial p modes and g modes appear simultaneously in red giant stars. Their frequencies have different variation rates,causing their frequencies to become close during stellar evolution so that avoided crossings *** separation between regions where acoustic waves and gravity waves propagate for l=1,2 and 3 is different,which results in the coupling efficiency also being *** present the results of numerical computations of the models we *** find that the two kinds of modes for l=2 and 3 need to be closer in frequency in order for a complete exchange to occur,compared to the case for modes with l=*** scaled oscillation frequencies also present better regularity with evolution than modes with l=1. In order to study the effect of the avoided crossings in detail,we set the mode which has the smallest mode inertia to be the p *** plot the two kinds of modes for l =1,2 and 3 in frequency and periodéchelle diagrams and find modes of l=2 and 3 fit the two relations better;they are more equally spaced in frequency and period than modes with l=*** careful observation of the two kinds oféchelle diagrams for l=2 and 3,we still find that some p modes shift a little from being equally spaced in frequency and some g modes,which are close to those p modes in period,shift a little from being equally spaced in ***,we study the relation between the deviation from period being equally spaced and the mode inertia of g modes for different *** g modes of l=1 with a period closer to the p mode have less inertia and the deviation is bigger in the periodéchelle *** deviation is also obvious. However g modes of l=2 and 3 shift a little or have almost no deviation from being equally spaced in period,even though some of them may have strong coupling and close mode inertia like in the p ***,we suggest a possible method for measuring period spacing of g modes precisely using mixed g modes with l=2 and 3 that have fewer observed mixed g m

关键词： stars:oscillations-stars:red giants

Birthrates and delay times of Type Ia supernovae

在线全文

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 586-590页

作者： WANG Bo1,2,3, LIU ZhengWei1,2,3, HAN YunKun1,2,3, LEI ZhenXin1,2,3, LUO YangPing1,2,3 & HAN ZhanWen1,2 1National Astronomical Observatories/Yunnan Observatory, chinese academy of sciences, kunming 650011, china 2key laboratory for the structure and evolution of celestial objects, chinese academy of sciences, kunming 650011, china 3graduate university of chinese academy of sciences, beijing 100049, china 1. National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China2. Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China

Type Ia supernovae (sNe Ia) play an important role in diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology. However, the nature of the progenitors of sNe Ia is still unclear. In this paper, according to a detailed binary population synthesis study, we obtained sN Ia birthrates and delay times from different progenitor models, and compared them with observations. We find that the Galactic sN Ia birthrate from the double-degenerate (DD) model is close to those inferred from observations, while the birthrate from the single-degenerate (sD) model accounts for only about 1/2-2/3 of the observations. If a single starburst is assumed, the distribution of the delay times of sNe Ia from the sD model is a weak bimodality, where the WD + He channel contributes to the sNe Ia with delay times shorter than 100 Myr, and the WD + Ms and WD + RG channels to those with age longer than 1 Gyr.

关键词： binaries: close stars: evolution supernovae: general white dwarfs

A statistical study of the relation between soft X-ray excess and accretion disk

在线全文

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 102-105页

作者： LIU JieYing1,2,3 & QIAO ErLin1,2 1 National Astronomical Observatories/Yunnan Observatory,chinese academy of science,kunming 650011,china 2.key laboratory for the structure and evolution of celestial objects,chinese academy of sciences,kunming 650011,china 3 graduate university of chinese academy of sciences,beijing 100049,china 1. National Astronomical Observatories/Yunnan Observatory Chinese Academy of Science Kunming 650011 China 2. key laboratory for the structure and evolution of celestial objects Chinese Academy of Sciences Kunming 650011 China 3. graduate university of chinese academy of sciences Beijing 100049 China

To study the origin of the soft X-ray excess,we compile a sample of 94 unobscured,radio-quiet QsOs and seyfert galaxies with available data from GALEX and *** find that 50 sources show strong soft X-ray excess and the other 44 show weak/no soft X-ray *** analyses of the data indicate that the difference in soft X-rays is mainly but not only resulting from different accretion rates(in units of Eddington rate).The statistical study of the sources with soft X-ray excess shows that the strength of soft X-ray excess weakly and positively correlates with the Eddington ratio and increases with the increase of the strength of UV radiations relative to the *** that the UV emissions are from the thin disk,the correlations imply that the origin of soft X-ray excess is associated with the thin disk,either by means of Comptonization of the disk photons or in some other ways.

关键词： accretion:accretion disks ultraviolet:galaxies X-rays:galaxies

Multi-epoch X-ray observations of the narrow-line seyfert 1 galaxy sDss J160508.87+323921.4 with XMM-Newton

在线全文

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 207-211页

作者： AI YanLi1,2,3,YUAN WeiMin1,2,ZHOU HongYan4,5 & WANG JianGuo1,2,3 1 National Astronomical Observatories/Yunnan Observatory,chinese academy of sciences,kunming 650011,china 2.key laboratory for the structure and evolution of celestial objects,chinese academy of sciences,kunming 650011,china 3 graduate university of the chinese academy of sciences,beijing 100049,china 4 Center for Astrophysics,university of science and Technology of china,Hefei 230026,china 5 Joint Institute of Galaxies and Cosmology,sHAO and UsTC,shanghai 200030,china 1. National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China 2. key laboratory for the structure and evolution of celestial objects Chinese Academy of Sciences Kunming 650011 China 3. graduate university of the chinese academy of sciences Beijing 100049 China 4. Center for Astrophysics University of Science and Technology of China Hefei 230026 China 5. Joint Institute of Galaxies and Cosmology SHAO and USTC Shanghai 200030 China

We present results of multi-epoch XMM-Newton observations separated by several years of the narrow-line seyfert 1(NLs1) galaxy,sDss J160508.87+*** NLs1 showed X-ray flux variations on timescales of years as well as low amplitude variations on timescales as short as hours,while the X-ray spectral shape remained essentially *** spectrum shows a significant soft X-ray *** model of reflection from an ionized disc,that is dominant in the whole XMM-Newton bandpass,provides the best description of the observed spectra for all the observations,though alternatives such as Compton scattering(T-0.25 keV) cannot be ruled out in a statistical *** the disc reflection model,the observed variations may originate either from the change in the reflection fraction,or from the variability of the intrinsic X-ray luminosity.

关键词： galaxies:active seyfert X-rays individual

evolutionary pattern of the regulatory network for flower development:Insights gained from a comparison of two Arabidopsis species

在线全文

学校读者我要写书评

暂无评论

Journal of systematics and evolution 2011年第6期49卷 528-538页

作者： 1,2 Yang LIU 1,2Chun-Ce GUO 1Gui-Xia XU 1Hong-Yan sHAN 1Hong-Zhi KONG 1(state key laboratory of systematic and evolutionary Botany,Institute of Botany,chinese academy of sciences,beijing 100093,china) 2(graduate university of chinese academy of sciences,beijing 100049,china) (state key laboratory of systematic and evolutionary Botany Institute of Botany Chinese Academy of Sciences Beijing 100093 China) (graduate university of chinese academy of sciences Beijing 100049 China) *Correspondence: Hong-Zhi KONG *Correspondence: E-mail: hzkong@*** Tel.: 86-10-62836489 Fax: 86-10-62590843.

Previous studies on Arabidopsis thaliana and other model plants have indicated that the development of a flower is controlled by a regulatory network composed of genes and the interactions among *** on the evolution of this network will therefore help understand the genetic basis that underlies flower *** this study,by reviewing the most recent published work,we added 31 genes into the previously proposed regulatory network for flower ***,the number of genes reached *** then compared the composition,structure,and evolutionary rate of these genes between *** and one of its allies,*** found that two genes(FLC and MAF2.show 1:2 and 2:2 relationships between the two species,suggesting that they have experienced independent,post-speciation *** the remaining 58 genes,35(60.3%)have diverged in exon-intron structure and,consequently,code for proteins with different sequence features and *** evolutionary analyses further revealed that,although most floral genes have evolved under strong purifying selection,some have evolved under relaxed or changed constraints,as evidenced by the elevation of nonsynonymous substitution rates and/or the presence of positively selected *** together,these results suggest that the regulatory network for flower development has evolved rather rapidly,with changes in the composition,structure,and functional constraint of genes,as well as the interactions among them,being the most important contributors.

关键词： Arabidopsis evolution flower development regulatory network.

Genetic differentiation of Wolffia globosa in china

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of systematics and evolution 2011年第6期49卷 509-517页

作者： 1,2Jun-Xia YUAN 1Jin PAN 1Bao-sheng WANG 1Da-Ming ZHANG 1(state key laboratory of systematic and evolutionary Botany,Institute of Botany,chinese academy of sciences,beijing 100093,china) 2(graduate university of chinese academy of sciences,beijing 100049,china) (state key laboratory of systematic and evolutionary Botany Institute of Botany Chinese Academy of Sciences Beijing 100093 China) (graduate university of chinese academy of sciences Beijing 100049 China) *Correspondence: Da-Ming ZHANG *Correspondence: E-mail: zhangdm@*** Tel.: 86-10-62836492 Fax: 86-10-62590843.

Wolffia Horkel ex schleid.(Lemnaceae) includes the world’s smallest ***,their bodies are extremely simplified,making classification difficult and *** reports about the genetic structure of these clonal-dominant aquatic plants have been published until *** this study,of 247 samples from 42 populations spanning representative locations in china,two chloroplast haplotypes(glo-cp and un-cp) and 66 amplified fragment length polymorphism genotypes were *** on wide sampling,cpDNA haplotypes,and amplified fragment length polymorphism profiles,we found that there are two genetic lineages(glo-and unlineages) of Wolffia species in *** and genetic diversity of Wolffia species are high compared with other clonal plants(simpson’s index,D = 0.97;Nei’s diversity,H = 0.1835).Different spatial structure patterns were detected between glo-and *** autocorrelation at short distances(slightly negative autocorrelations at larger distances(>1500 km) were detected within the glo-lineage,but no significant spatial genetic structure was detected beyond 100 km within the ***,spatial genetic analysis of *** revealed significant autocorrelation within short distances,indicating that restricted gene flow might be one of the most important factors in shaping genetic structure.

关键词： AFLP chloroplast DNA genetic differentiation spatial genetic structure Wolffia.

sequencing,annotation and comparative analysis of nine BACs of the giant panda(Ailuropoda melanoleuca)

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Life sciences) 2010年第1期53卷 107-111页

作者： ZHENG Yang1,2,3,CAI Jing4,LI JianWen3,6,LI Bo3,LIN RunMao3,TIAN Feng3,WANG XiaoLing3 & WANG Jun3,5 1beijing Institute of Genomics,chinese academy of sciences(CAs),beijing 100029,china 2College of Life science,graduate university of chinese academy of sciences,beijing 100049,china 3beijing Genomics Institute at shenzhen,shenzhen 518083,china 4CAs-Max Planck Junior Research Group on evolutionary Genomics,state key laboratory of Genetic Resources and evolution,kunming Institute of Zoology,chinese academy of sciences(CAs),kunming 650223,china 5Department of Biology,university of Copenhagen,Copenhagen DK-2200,Denmark 6school of Biological science and Engineering,south china university of Technology,Guangzhou 510006,china beijing Institute of Genomics Chinese Academy of Sciences (CAS) Beijing China College of Life science Graduate University of Chinese Academy of Sciences Beijing China beijing Genomics Institute at shenzhen Shenzhen China CAs-Max Planck Junior Research Group on evolutionary Genomics State Key Laboratory of Genetic Resources and Evolution Kunming Institute of Zoology Chinese Academy of Sciences (CAS) Kunming China school of Biological science and Engineering South China University of Technology Guangzhou China Department of Biology University of Copenhagen Copenhagen Denmark

A 10-fold BAC library for the giant panda was constructed and nine BACs were selected to generate finish *** BACs could be used as a validation resource for the de novo assembly accuracy of the whole genome shotgun sequencing reads of the giant panda newly generated by Illumina GA sequencing *** sanger sequencing,assembly,annotation and comparative analysis were carried out on the selected BACs of a joint length 878 *** search and de novo prediction methods were used to annotate genes and *** protein coding genes were predicted,seven of which could be functionally *** seven genes have an average gene size of about 41 kb,an average coding size of about 1.2 kb and an average exon number of 6 per ***,seven tRNA genes were *** 27 percent of the BAC sequence is composed of repeats.A phylogenetic tree was constructed using a neighbor-join algorithm across five species,including the giant panda,human,dog,cat and mouse,which reconfirms dog as the most closely related species to the giant *** results provide detailed sequence and structure information for new genes and repeats of the giant panda,which will be helpful for further studies about the giant panda.

关键词： giant panda BAC sequencing assembly annotation evolution

Early agricultural development and environmental effects in the Neolithic Longdong basin(eastern Gansu)

在线全文

学校读者我要写书评

暂无评论

chinese science Bulletin 2011年第8期56卷 762-771页

作者： ZHOU XinYing LI XiaoQiang ZHAO KeLiang DODsON John sUN Nan YANG Qing state key laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi'an 710075 China laboratory of Human evolution and Archeological science Institute of Vertebrate Paleontology and Paleoanthropology Chinese Academy of Sciences Beijing 100044 China graduate university of chinese academy of sciences Beifing 100049 China Institute for Environmental Research the Australian Nuclear Science and Technology Organization Sydney NSW 1001 Australia

Neolithic agricultural development and environmental effects in the Longdong area were reconstructed using a synthetic approach,investigating pollen,charcoal,and seed remains for two cultural layer sections and five flotation *** show that Neolithic agriculture in the Longdong area had a simple organization and was dominated by the production of common millet,especially in the early and middle Yangshao *** the late Yangshao age,Neolithic agriculture developed into a more complex structure,dominated by both common and foxtail millet and the cultivation of rice and *** production of foxtail millet gradually increased through the Neolithic period,reaching its highest point during the Qijia *** were first cultivated during the late Yangshao culture,approximately 5000 cal a *** production began no later than 4800 cal a BP,and continued to exist in the Qijia culture,approximately 4000 cal a *** production in Neolithic Longdong,specifically in the "Yuan" area of the loess plateau,developed as a shrub and grass dominated *** in the river valleys was partly covered with Picea,Tusga,and Quercus coniferous and broadleaf mixed *** activity during the Neolithic period caused an increase in farmland on the loess tableland and a decrease in the abundance of shrub and grassland in the Longdong *** farmlands were abandoned,vegetation recovered with Hippophae-,Rosaceae-,Ephedra-,and Leguminosae-dominated shrublands and Artemisia-dominated grasslands.

关键词：新石器时代农业发展陇东地区环境影响甘肃东部早期新石器时期盆地

Identification and Categorization of Horizontally Transferred Genes in Prokaryotic Genomes

在线全文

学校读者我要写书评

暂无评论

Acta Biochimica et Biophysica sinica 2005年第8期37卷 561-566页

作者： shuo-Yong sHI~1 Xiao-Hui CAI~1 and Da-fu DING~(1,2*) key laboratory of Proteomics.Institute of Biochemistry and Cell Biology.shanghai Institutes for Biological sciences,chinese academy of sciences,graduate school of the chinese academy of sciences.shanghai 200031,china ~2.school of Life science & Technology.shanghai Jiaotong university.shanghai 200030.china keylaboratoryofProteomics InstituteofBiochemistryandCellBiologyShanghaiInstitutesforBiologicalSciencesChin

Horizontal gene transfer(HGT),a process through which genomes acquire genetic materialsfrom distantly related organisms,is believed to be one of the major forces in prokaryotic genome ***,systematic investigation is still scarce to clarify two basic issues about HGT:(1) what types ofgenes are transferred:and(2)what influence HGT events over the organization and evolution of ***-scale investigations of these two issues will advance the systematical understanding ofHGT in the context of prokaryotic genome *** investigated 82 genomes,we constructed anHGT database across broad evolutionary *** identified four function categories containing a highproportion of horizontally transferred genes:cell envelope,energy metabolism,regulatory functions,andtransport/binding *** biased function distribution indicates that HGT is not completely random;instead,it is under high selective pressure,required by function restraints in ***,wemapped the transferred genes onto the connectivity structure map of organism-specific pathways listed inKyoto Encyclopedia of Genes and Genomes(KEGG).Our results suggest that recruitment of transferredgenes into pathways is also selectively constrained because of the tuned interaction between original *** organization {2.s still conserve well through evolution even with the recruitment ofhorizontally transferred ***,in pathways whose organization were significantly affected byHGT events,the operon-like arrangement of transferred genes was found to be *** resultssuggest that operon plays an essential and directional role in the integration of alien genes into pathways.

关键词： genome evolution horizontal gene transfer function and pathway analysis