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

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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 {2., kunming 650011,china 2.Key Laboratory for the structure and evolution of celestial objects,chinese academy of {2.,{12. 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 {2. 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

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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,{2. 2.ey Laboratory for the structure and evolution of celestial objects, chinese academy of sciences, kunming 650011,{2. 3Graduate University of chinese academy of sciences, Beijing 100049,{2. 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

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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,{2. 650011,china 2.Key Laboratory for the structure and evolution of celestial objects,chinese academy of sciences,{2. 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 {2. 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

Phylogeny of fireflies (Coleoptera: Lampyridae) inferred from mitochondrial 16S ribosomal DNA, with references to morphological and ethological traits

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Progress in Natural Science:Materials International 2006年第8期16卷 817-826页

作者： LI Xueyan, YANG Shuang, XIE Meng and LIANG Xingcai (Laboratory of Entomology, kunming Institute of Zoology, chinese academy of sciences, kunming 6502.3, china Key Laboratory of Cellular and Molecular evolution, kunming Institute of Zoology, chinese academy of sciences, kunming 6502.3, china Graduate School of the chinese academy of sciences, Beijing 100039, china) [a]Laboratory of Entomology Kunming Institute of Zoology Chinese Academy of Sciences Kunming China [b]Graduate School of the chinese academy of sciences Beijing China [c]Key Laboratory of Cellular and Molecular evolution Kunming Institute of Zoology Chinese Academy of Sciences Kunming China

We sequenced partial mitochondrial 16S ribosomal DNA (16S rDNA) of 18 firefly species from Southwest of china. Combined with homologous sequences previously reported, phylogenetic trees including Japanese, Korean and chinese species were reconstructed by neighbor-joining, maximum parsimony and Bayesian methods. All reconstructions agree on most nodes of the trees. Monophyly of Lampyridae is not supported because Rhagophthalmus ohbai in Rhagophthalmidae is included within it. Lamprigera, a genus placed unreliably in Lampyrinae, shows a close relationship to Amydetinae. Monophyly of Luciolinae is not supported because Pristolycus sagulatus (Lampyrinae) is included within it. In the Luciolinae, monophyly of Curtos and Hotaria is well established, respectively, but both morphological and molecular data continue to indicate that Luciola is not monophyletic and its subdivision is indeed necessary. Within the Lampyrinae, both Pyrocoelia and Diaphanes are not monophyletic, but monophyly of Pyrocoelia + Diaphanes is well supported. Phylogeny of Diaphanes is discussed for the first time. Generic placement of a newly discovered species (Diaphanes pectinealis Li et Liang) sharing some characters of Pyrocoelia and Diaphanes challenges the delimitation of these two similar genera. With references to the firefly mating systems, we suggest that more emphases should be placed on those sexually selected characters such as antennal {2. in taxonomy of Lampyridae.

关键词： Lampyridae mitochondrial 16S rDNA morphological and ethological traits phylogeny.

Multi-epoch X-ray observations of the narrow-line Seyfert 1 galaxy SDSS J160508.87+32.92..4 with XMM-Newton

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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 {2.,kunming 650011,china 2.Key Laboratory for the structure and evolution of celestial objects,chinese academy of {2.,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 2.002.,china 5 Joint Institute of Galaxies and Cosmology,SHAO and USTC,Shanghai 2.0030,china 1. National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China 2. Key Laboratory for the structure and evolution of {2. 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-0.2. 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

Pitfalls in the analysis of ancient human mtDNA

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chinese Science Bulletin 2003年第8期48卷 826-830页

作者： YAO Yonggang1,3 & ZHANG Yaping1,2.1. Laboratory of Molecular evolution and Genome Diversity, kunming Institute of Zoology,{2., kunming 6502.3, china 2. Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, kunming 650091, china 3. Graduate School of the{2., Beijing 100039, china Correspondence should be addressed to Zhang Yaping (e-mail: zhang- yp1@***) Laboratory of Molecular evolution and Genome Diversity Kunning Institute of Zoology Chinese Academy of Sciences China Graduate School of the chinese academy of sciences China Laboratory for Conservation and Utilization of Bio-resource Yunnan University China

The retrieval of DNA from ancient human specimens is not always successful owing to DNA deteriora-tion and contamination although it is vital to provide new insights into the genetic structure of ancient people and to reconstruct the past history. Normally, only short DNA fragments can be retrieved from the ancient specimens. How to identify the authenticity of DNA obtained and to uncover the information it contained are difficult. We employed the ancient mtDNAs reported from Central Asia (including Xin-jiang, china) as an example to discern potentially extraneous DNA contamination based on the updated mtDNA phylog-eny derived from mtDNA control region, coding region, as well as complete sequence information. Our results demon-strated that many mtDNAs reported are more or less prob-lematic. Starting from a reliable mtDNA phylogeney and combining the available modern data into analysis, one can ascertain the authenticity of the ancient DNA, distinguish the potential errors in a data set, and efficiently decipher the meager information it harbored. The reappraisal of the mtDNAs with the age of more than 2.00 years from Central Asia gave support to the suggestion of extensively (pre)historical gene admixture in this region.

关键词：古代人类遗传构造 DNA 脱氧核糖核酸

The deep thermal characteristic of continental margin of the northern South china Sea

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chinese Science Bulletin 2000年第18期45卷 1717-1722页

作者： ZHANG Jian & WANG Jiyang1. Graduate School, University of Science and Technology of china, chinese academy of sciences, Beijing 100039, china 2. Institute of Geology, chinese academy of sciences, Beijing 10002., china Graduate School University of Science and Technology of China Chinese Academy of Sciences Beijing China Institute of Geology Chinese Academy of Sciences Beijing China

Heat flow plays an important role in the study ot thermal structure and thermal evolutionof continental margin of the northern South{2. Sea. The analysis of heat flow value shows that margin heat flow in the northern South{2. Sea is relatively high setting, but the percentage of crustal heat flow is lower than 35% in terrestrial heat flow. The terrestrial heat flow exhibited a current of rise from the Northern Continental Margin to the Southern Central Basin. However, the proportion of crustal heat flow in terrestrial heat flow slowly dropped down in the same direction. It is suggested that the main factor causing high heat flow setting is the moving up of hot material from asthenosphere.

关键词： margin of northern South china Sea terrestrial heat flow thermal structures.

Ionization state of cosmic hydrogen by early stars and quasars

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Research in Astronomy and Astrophysics 2009年第6期9卷 665-681页

作者： Xiao-Chun Mao1,2.1 National Astronomical Observatories, chinese academy of sciences, Beijing 100012. china 2.Graduate University of chinese academy of sciences, Beijing 100049, china National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of chinese academy of sciences Beijing 100049 China

Cosmic hydrogen is reionized and maintained in its highly ionized state by the ultraviolet emission attributed to an early generation of stars and quasars. The Lyα opacity observed in absorption spectra of high-redshift quasars permits more stringent constraints on the ionization state of cosmic hydrogen. Based on density perturbation and structure formation theory, we develop an analytic model to trace the evolution of the ionization state in the post-overlap epoch of reionization, in which the bias factor is taken into account. For quasars, we represent an improved luminosity function by utilizing a hybrid approach for the halo formation rate that is in reasonable agreement with the published measurements at 2.≤ z ≤ 6. Comparison with the classic Press-Schechter mass function of dark matter halos, we demonstrate that the biased mass distribution indeed enhances star formation efficiency in the overdense environment by more than 2. per cent following the overlap of ionized bubbles. In addition, an alternative way is introduced to derive robust estimates of the mean free path for ionizing photons. In our model, star-forming galaxies are likely to dominate the ionizing background radiation beyond z = 3, and quasars contribute equally above a redshift of z ～ 2.5. From 5 ≤ z ≤ 6, the lack of evolution in photoionization rate can thus be explained by the relatively flat evolution in star formation efficiency, although the mean free path of ionizing photons increases rapidly. Moreover, in the redshift interval z ～ 2.- 6, the expected mean free path and Gunn-Peterson optical depth obviously evolve by a factor of ～ 500 and ～50 respectively. We find that the relative values of critical overdensities for hydrogen ionization and collapse could be 430% at z ≈2.and 2. at z ≈6, suggesting a rapid overlap process in the overdense regions around instant quasars following reionization. We further illustrate that the absolute estimates of the fraction of neutral hydrogen computed fr

关键词： cosmology theory -- formation galaxies -- quasars general -- diffuse radiation -- intergalactic medium

Pattern phenomena in an rf discharge dusty plasma system

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Science china(Physics,Mechanics & Astronomy) 2006年第5期49卷 588-596页

作者： HUANG Feng1,2. YE Maofu2.& WANG Long2.1. College of Science, china Agricultural University, Beijing 100083, china 2. Institute of Physics,{2., Beijing 100080, china 1. College of Science China Agricultural University Beijing 100083 China 2. Institute of Physics Chinese Academy of Sciences Beijing 100080 China

Various dust patterns are observed in an rf discharge dusty plasma system. According to the dust growth process from small to large in size, the formation of different dust patterns can be divided into two stages: the small-particle stage (or dust cloud stage), and the large-particle stage (or dust crystal stage). The evolution relations between different dust patterns with gas pressure changing are investigated. Dust voids, dust acoustic waves and strong turbulence modes are presented at the small-particle stage. The self-organized dust lattices and dust clusters are investigated at the large-particle stage. The static structure of a dust lattice is characterized by means of the pair correlation function. Dust clusters formed by particles with different numbers and the regular evolution of the clusters with gas pressure are also investigated. The packing sequences of dust clusters are verified through two-dimensional confined molecular dynamics simulations.

关键词： dusty plasma dust patterns