A concordance model of the Lyman α forest at z= 1.95     

Tridivesh Jena  Michael L. Norman  David Tytler  David Kirkman  Nao Suzuki  Angela Chapman  Carl Melis  Pascal Paschos  Brian O'Shea  Geoffrey So  Dan Lubin  Wen-Ching Lin  Dieter Reimers  Eckardt Janknecht  Cora Fechner 《Monthly notices of the Royal Astronomical Society》2005,361(1):70-96

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The “Shiva Hypothesis”: Impacts, mass extinctions, and the galaxy     

Michael R. Rampino  Bruce M. Haggerty 《Earth, Moon, and Planets》1996,72(1-3):441-460

The “Shiva Hypothesis”, in which recurrent, cyclical mass extinctions of life on Earth result from impacts of comets or asteroids, provides a possible unification of important processes in astrophysics, planetary geology, and the history of life. Collisions with Earth-crossing asteroids and comets ≥ a few km in diameter are calculated to produce widespread environmental disasters (dust clouds, wildfires), and occur with the proper frequency to account for the record of five major mass extinctions (from ≥ 10⁸ Mt TNT impacts) and ~ 20 minor mass extinctions (from 10⁷–10⁸ Mt impacts) recorded in the past 540 million years. Recent studies of a number of extinctions show evidence of severe environmental disturbances and mass mortality consistent with the expected after-effects (dust clouds, wildfires) of catastrophic impacts. At least six cases of features generally considered diagnostic of large impacts (e.g., large impact craters, layers with high platinum-group elements, shock-related minerals, and/or microtektites) are known at or close to extinction-event boundaries. Six additional cases of elevated iridium levels at or near extinction boundaries are of the amplitude that might be expected from collision of relatively low-Ir objects such as comets. The records of cratering and mass extinction show a correlation, and might be explained by a combination of periodic and stochastic impactors. The mass extinction record shows evidence for a periodic component of about 26 to 30 Myr, and an ~ 30 Myr periodic component has been detected in impact craters by some workers, with recent pulses of impacts in the last 2–3 million years, and at ~ 35, 65, and 95 million years ago. A cyclical astronomical pacemaker for such pulses of impacts may involve the motions of the Earth through the Milky Way Galaxy. As the Solar System revolves around the galactic center, it also oscillates up and down through the plane of the disk-shaped galaxy with a half-cycle ~ 30±3 Myr. This cycle should lead to quasi-periodic encounters with interstellar clouds, and periodic variations in the galactic tidal force with maxima at times of plane crossing. This “galactic carrousel” effect may provide a viable perturber of the Oort Cloud comets, producing periodic showers of comets in the inner Solar System. These impact pulses, along with stochastic impactors, may represent the major punctuations in earth history.  相似文献   

The spectral variability of Triton from 1997-2000     

Michael D Hicks  Bonnie J Buratti 《Icarus》2004,171(1):210-218

We present the results of a three-year observational program of long-slit spectroscopy and UBVRI photometry of Triton. We find evidence for short-lived albedo variations at wavelengths less than 0.5 μm with the most notable reddening event measured in October 1997 and “normal” colors returning by May 1998. We report a possible variation in the relative 0.73/0.89 μm methane absorption band strengths, suggesting that the transport or denudation of this species may play a major role in the reddening events.  相似文献   

REMOTE SENSING FOREST BIOMASS: AN EVALUATION USING HIGH RESOLUTION REMOTE SENSOR DATA AND LOBLOLLY PINE PLOTS     

John R. Jensen  Michael E. Hodgson 《The Professional geographer》1985,37(1):46-56

Eight-year-old Loblolly pine (Pinus taeda) plots located in South Carolina were evaluated using high resolution aircraft multispectral scanner data to determine if biomass could be accurately measured. Sixteen pine plots located on both sandy and clay soils were treated with 0, 180, or 360 kg. (approximately 0, 400, or 800 lb.) of nitrogen per plot. Indices of biomass from remote sensing data were significantly correlated with in situ biomass measurements made in each plot. A ratio of infrared (.9–1.1 μm) and red (.65–.70 μm) channels yielded the best correlation. The indices were not sensitive to differences in soil type (sandy or clay).  相似文献   

Prediction of lateral variability in fracture intensity using multicomponent shear-wave surface seismic as a precursor to horizontal drilling in the Austin Chalk   总被引：1，自引：0，他引：1  

Michael C. Mueller 《Geophysical Journal International》1991,107(3):409-415

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EARTHWORKS     

Michael M. Kimberley 《地学学报》1993,5(5):511-513

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Stellar masses and star formation histories for 10⁵ galaxies from the Sloan Digital Sky Survey     

Guinevere Kauffmann  Timothy M. Heckman  Simon D. M. White  Stéphane Charlot  Christy Tremonti  Jarle Brinchmann  Gustavo Bruzual  Eric W. Peng  Mark Seibert  Mariangela Bernardi  Michael Blanton  Jon Brinkmann  Francisco Castander  Istvan Csábai  Masataka Fukugita  Zeljko Ivezic  Jeffrey A. Munn  Robert C. Nichol  Nikhil Padmanabhan  Aniruddha R. Thakar  David H. Weinberg  Donald York 《Monthly notices of the Royal Astronomical Society》2003,341(1):33-53

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A close one-term approximation to the highest Stokes wave on deep water     

R.C.T. Rainey  Michael S. Longuet-Higgins   《Ocean Engineering》2006,33(14-15):2012-2024

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The Kaidun meteorite: Clasts of alkaline‐rich fractionated materials     

Andrei V. Ivanov  Nataliya N. Kononkova  S. Vincent Yang  Michael E. Zolensky 《Meteoritics & planetary science》2003,38(5):725-737

Abstract— Clasts of alkaline (the second find in meteorites) and subalkaline rocks were found in the Kaidun meteorite. One of them (#d4A) is a large crystal of albite with inclusions of fluorapatite, arfvedsonite, aenigmatite, and wilkinsonite. The two latter minerals were previously unknown in meteorites. Another clast (#d[3–5]D) has a melt crystallization texture of mainly feldspar (oligoclase) composition and contains relict grains of both high‐Ca and low‐Ca pyroxene and fluorapatite. The mineralogical characteristics of these clasts suggest a genetic relationship and an origin from the same parent body. The textural and mineralogical characteristics of the clasts indicate origin by extensive igneous differentiation. Such processes most likely took place in a rather large differentiated body. The material of clast #d(3–5)D is similar in some mineralogical respects to basaltic shergottites.  相似文献   

Galaxy voids in cold dark matter universes     

A. J. Benson  Fiona Hoyle  Fernando Torres  Michael S. Vogeley 《Monthly notices of the Royal Astronomical Society》2003,340(1):160-174

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