Early Norian flora from Partizansk River Basin of Primorye, Russia     

Elena B Volynets Svetlana A Schorokhova Ge Sun 《东北亚地学研究》2006,9(1):1-12

IntroductionThe Late Triassic strata andflora developed andwell outcropped in southern Pri morye,Russia.Thestrata are marine and non-marine alternate for eachother and yield abundant mollusk and plant fossilsinwhich the Late Triassic Mongugai flora is well-known in the world.Kryshtofovich(1910,1921,1924)and Kryshtofovich&Prynada(1932)studiedthis florainthe earlier ti me,and consequently,Sre-brodolyskaja(1958,1961,1968),Schorokhova(1975,1977,1997,2004)and Krassilov&Schorokhova(1970,1975)ma…  相似文献   

3. Solar System Formation and Early Evolution: the First 100 Million Years     

Thierry Montmerle  Jean-Charles Augereau  Marc Chaussidon  Mathieu Gounelle  Bernard Marty  Alessandro Morbidelli 《Earth, Moon, and Planets》2006,98(1-4):39-95

The solar system, as we know it today, is about 4.5 billion years old. It is widely believed that it was essentially completed 100 million years after the formation of the Sun, which itself took less than 1 million years, although the exact chronology remains highly uncertain. For instance: which, of the giant planets or the terrestrial planets, formed first, and how? How did they acquire their mass? What was the early evolution of the “primitive solar nebula” (solar nebula for short)? What is its relation with the circumstellar disks that are ubiquitous around young low-mass stars today? Is it possible to define a “time zero” (t ₀), the epoch of the formation of the solar system? Is the solar system exceptional or common? This astronomical chapter focuses on the early stages, which determine in large part the subsequent evolution of the proto-solar system. This evolution is logarithmic, being very fast initially, then gradually slowing down. The chapter is thus divided in three parts: (1) The first million years: the stellar era. The dominant phase is the formation of the Sun in a stellar cluster, via accretion of material from a circumstellar disk, itself fed by a progressively vanishing circumstellar envelope. (2) The first 10 million years: the disk era. The dominant phase is the evolution and progressive disappearance of circumstellar disks around evolved young stars; planets will start to form at this stage. Important constraints on the solar nebula and on planet formation are drawn from the most primitive objects in the solar system, i.e., meteorites. (3) The first 100 million years: the “telluric” era. This phase is dominated by terrestrial (rocky) planet formation and differentiation, and the appearance of oceans and atmospheres.  相似文献   

MSX mid-infrared imaging of massive star birth environments – II. Giant H ii regions     

Peter S. Conti  Paul A. Crowther 《Monthly notices of the Royal Astronomical Society》2004,355(3):899-917

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Molecular fraction limits in damped Lyman α absorption systems     

S. J. Curran  M. T. Murphy  Y. M. Pihlström  J. K. Webb  A. D. Bolatto  G. C. Bower 《Monthly notices of the Royal Astronomical Society》2004,352(2):563-570

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The fragmentation of condensations of the primordial gas     

D. R. Flower 《Monthly notices of the Royal Astronomical Society》2002,333(4):763-767

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Metal Dispersal and the Number of Population III Stars     

M.S. Oey 《Astrophysics and Space Science》2002,281(1-2):483-486

Two fundamental constraints on the earliest star formation conditions in the Galaxy are an apparent empirical low-metallicity threshold of-4 ? [Fe/H], an and upper limit to the fraction of Population III halo stars of F _III < 4 × 10^-4. How do these observed constraints compare with predictions of simple models? This is investigated within the framework of element dispersal from clustered core-collapse SNe. Simple arguments considering turbulent mixing within multi-phase ISM suggest that the observed low-metallicity threshold is consistent with rough expected values. However, the observed limit on F _III is two orders of magnitude larger than predictions from this simple, one-zone inhomogeneous chemical evolution.  相似文献   

CMB recombination lines of hydrogen: The differential spectrum     

V. K. Dubrovich  S. I. Grachev 《Astronomy Letters》2004,30(10):657-662

We have calculated the distortions of the cosmic microwave background (CMB) spectrum in the wavelength range 2–50 cm due to the superposition of the CMB hydrogen recombination radiation in subordinate lines. The level populations were determined by numerically solving the equation of recombination kinetics together with the statistical equilibrium equations for a 60-level model hydrogen atom. The relative distortions are ≈10^?7–10^?6, with their wavelength dependence having a low-contrast, wavy pattern. However, the contrast increases severalfold and becomes pronounced when passing to the differential distortion spectrum. We study the dependence of the distortions on cosmological parameters.  相似文献   

Early structure formation in quintessence models and its implications for cosmic reionization from first stars     

U. Maio  K. Dolag  M. Meneghetti  L. Moscardini  N. Yoshida  C. Baccigalupi  M. Bartelmann  F. Perrotta 《Monthly notices of the Royal Astronomical Society》2006,373(2):869-878

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Early development of Chondrus ocellatus Holm （Gigartinaceae, Rhodophyta）     

王爱华  王继成  段德麟 《中国海洋湖沼学报》2006,24(2):129-133

1 INTRODUCTION Red algae C. ocellatus lives in temperate zone of coastal area, and inhabits at substrates from high tide to low tide regions. Its life history is composed of three phases: tetrasporophyte, gametophyte and carposporophyte. Chondrus is one o…  相似文献   

贵州晴隆大厂晚二叠世初期河流相沉积特征——兼论与上下地层接触关系     

李明道 《贵州地质》2008,25(3)

晚二叠世初期,在晴隆大厂一带,以"大厂层"为基底的山间盆地中,形成了一条自北东流向南西的规模较大的曲流河。该河流微相发育,其沉积物包括河道砾岩、边滩砂屑岩和洪泛平原泥质岩等。这套沉积地层上与上二叠统峨眉山玄武岩下与"大厂层"或局部与中二叠统茅口组接触。此乃峨眉地幔隆起边缘的沉积效应。  相似文献