Dawn; the Vesta–HED connection; and the geologic context for eucrites,diogenites, and howardites     

Harry Y. McSween Jr.  Richard P. Binzel  M. Cristina De Sanctis  Eleonora Ammannito  Thomas H. Prettyman  Andrew W. Beck  Vishnu Reddy  Lucille Le Corre  Michael J. Gaffey  Thomas B. McCord  Carol A. Raymond  Christopher T. Russell  the Dawn Science Team 《Meteoritics & planetary science》2013,48(11):2090-2104

The Dawn mission has provided new evidence strengthening the identification of asteroid Vesta as the parent body of the howardite, eucrite, and diogenite (HED) meteorites. The evidence includes Vesta's petrologic complexity, detailed spectroscopic characteristics, unique space weathering, diagnostic geochemical abundances and neutron absorption characteristics, chronology of surface units and impact history, occurrence of exogenous carbonaceous chondritic materials in the regolith, and dimensions of the core, all of which are consistent with HED observations and constraints. Global mapping of the distributions of HED lithologies by Dawn cameras and spectrometers provides the missing geologic context for these meteorites, thereby allowing tests of petrogenetic models and increasing their scientific value.  相似文献   

Growth and mortality of juvenile winter flounder in two New England estuaries     

Carol Meise  Jeremy S. Collie  J. Widman  P. Howell 《Estuaries and Coasts》1999,22(2):297-303

A length-based model for calculating growth and mortality of juvenile winter flounder (Pseudopleuronectes americanus) populations has been developed. This model is based on work by Sullivan et al. (1990) and incorporates the von Bertalanffy growth equation, including stochasticity in growth, and a mortality rate that decreases exponentially with size. The length-based model was fit to observed size-frequency distributions, and model likelihood profiles were generated to produce 95% confidence intervals about parameter estimates. We analyzed size-frequency distributions of 3 to 15 cm juvenile winter flounder, collected with a 1-m beam trawl, at monthly intervals from June to October during 1993 and 1994. Growth rates were higher at a contaminated site, New Haven Harbor, than at a clean site, the Connecticut River estuary, however, the parameter estimates had overlapping 95% confidence intervals. Mortality rates were similar at the two sites.  相似文献   

Global financial stability,rapid transition to a low-carbon economy and social justice: can climate-related financial risk disclosure do it all?     

Carol Farbotko 《The Australian geographer》2019,50(3):273-278

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Ceres’ spectral link to carbonaceous chondrites—Analysis of the dark background materials          下载免费PDF全文

Michael Schäfer  Tanja Schäfer  Matthew R. M. Izawa  Edward A. Cloutis  Stefan E. Schröder  Thomas Roatsch  Frank Preusker  Katrin Stephan  Klaus‐Dieter Matz  Carol A. Raymond  Christopher T. Russell 《Meteoritics & planetary science》2018,53(9):1925-1945

Ceres’ surface has commonly been linked with carbonaceous chondrites (CCs) by ground‐based telescopic observations, because of its low albedo, flat to red‐sloped spectra in the visible and near‐infrared (VIS/NIR) wavelength region, and the absence of distinct absorption bands, though no currently known meteorites provide complete spectral matches to Ceres. Spatially resolved data of the Dawn Framing Camera (FC) reveal a generally dark surface covered with bright spots exhibiting reflectance values several times higher than Ceres’ background. In this work, we investigated FC data from High Altitude Mapping Orbit (HAMO) and Ceres eXtended Juling (CXJ) orbit (~140 m/pixel) for global spectral variations. We found that the cerean surface mainly differs by spectral slope over the whole FC wavelength region (0.4–1.0 μm). Areas exhibiting slopes ?1 constitute only ~3% of the cerean surface and mainly occur in the bright material in and around young craters, whereas slopes ≥?10% μm^?1 occur on more than 90% of the cerean surface; the latter being denoted as Ceres’ background material in this work. FC and Visible and Infrared Spectrometer (VIR) spectra of this background material were compared to the suite of CCs spectrally investigated so far regarding their VIS/NIR region and 2.7 μm absorption, as well as their reflectance at 0.653 μm. This resulted in a good match to heated CI Ivuna (heated to 200–300 °C) and a better match for CM1 meteorites, especially Moapa Valley. This possibly indicates that the alteration of CM2 to CM1 took place on Ceres.  相似文献   

XFEM formulation with sub-interpolation,and equivalence to zero-thickness interface elements     

Laura Crusat  Ignacio Carol  Daniel Garolera 《国际地质力学数值与分析法杂志》2019,43(1):45-76

This paper describes a particular formulation of the extended finite element method (XFEM) specifically conceived for application to existing discontinuities of fixed location, for instance, in geological media. The formulation is based on two nonstandard assumptions: (1) the use of sub-interpolation functions for each subdomain and (2) the use of fictitious displacement variables on the nodes across the discontinuity (instead of the more traditional jump variables). Thanks to the first of those assumptions, the proposed XFEM formulation may be shown to be equivalent to the standard finite element method with zero-thickness interface elements for the discontinuities (FEM+z). The said equivalence is theoretically proven for the case of quadrangular elements cut in two quadrangles by the discontinuity, and only approximate for other types of intersections of quadrangular or triangular elements, in which the XFEM formulation corresponds to a kinematically restricted version of the corresponding interface plus continuum scheme. The proposed XFEM formulation with sub-interpolation, also helps improving spurious oscillations of the results obtained with natural interpolation functions when the discontinuity runs skew to the mesh. A possible explanation for these oscillations is provided, which also explains the improvement observed with sub-interpolation. The paper also discusses the oscillations observed in the numerical results when some nodes are too close to the discontinuity and proposes the remedy of moving those nodes onto the discontinuity itself. All the aspects discussed are illustrated with some examples of application, the results of which are compared with closed-form analytical solutions or to existing XFEM results from the literature.  相似文献   

In tribute to founding editor,Antony R. Orme, 1932–2020     

Carol P. Harden 《自然地理学》2020,41(4):289-290

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Impacts of multiple stressors on annual recruitment in striped bass (Morone saxatilis) in the Sacramento-San Joaquin estuary     

Howard C. Bailey  Carol Digiorgio  David E. Hinton 《Marine environmental research》1996,42(1-4)

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Great Microwave Bursts and hard X-rays from solar flares     

Herbert J. Wiehl  David A. Batchelor  Carol Jo Crannell  Brian R. Dennis  Phillip N. Price  Andreas Magun 《Solar physics》1985,96(2):339-356

The microwave and hard X-ray characteristics of 13 solar flares that produced microwave fluxes greater than 500 solar flux units have been analyzed. These Great Microwave Bursts were observed in the frequency range from 3 to 35 GHz at Bern, and simultaneous hard X-ray observations were made in the energy range from 30 to 500 keV with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission spacecraft. The principal aim of this analysis is to determine whether or not the same distribution of energetic electrons can explain both emissions. The temporal and spectral behaviors of the microwaves as a function of frequency and the X-rays as a function of energy were tested for correlations, with results suggesting that optically thick microwave emission, at a frequency near the peak frequency, originates in the same electron population that produces the hard X-rays. The microwave emission at lower frequencies, however, is poorly correlated with emission at the frequency which appears to characterize this common source. A single-temperature and a multitemperature model were tested for consistency with the coincident X-ray and microwave spectra at microwave burst maximum. Four events are inconsistent with both of the models tested, and neither of the models attempts to explain the high-frequency part of the microwave spectrum. A source area derived on the basis of the single-temperature model agrees to within the uncertainties with the observed area of the one burst for which spatially resolved X-ray images are available.Swiss National Science Foundation Fellow from the University of Bern.Also Energy/Environmental Research Group, Incorporated, Tucson, Arizona, and Department of Physics and Astronomy, University of North Carolina, Chapel Hill. Present address: Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland.  相似文献   

Alternative representation of planetary perturbations     

Carol Williams 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):35-35

An attempt is made to find a representation of planetary perturbations which does not require a Fourier expansion. For the planetary type three body problem a sequence of canonical transformations is given based on Landen transformations coupled with a rescaling of the time. The expansion is carried out to the order 2 in the Hamiltonian.  相似文献   

Vertical cloud structure of Jupiter's Equitorial Plumes     

Carol R. Stoker  Charles W. Hord 《Icarus》1985,64(3):557-575

A model for the vertical cloud structure of Jupiter's Equitorial Plumes is deduced based on an analysis of Voyager images of the equitorial region in the 6190Å methane band and the 6000-Å continuum, and ground-based 8900-Å methane band images of Jupiter. A computer code that represents scattering and absorption from aerosol and gas layers was applied to a heirarchy of increasingly complex model aerosol structures to match the observations in the three wavelengths. The observations are consistent with a model for the vertical cloud structure of the equitorial region that consists of four aerosol layers. A high-altitude haze layer (HAL) with optical depth τ = 1 uniformly blankets the equitorial region at an altitude between 100 and 250 mbar. Below that, a middle-level cloud layer between 400 and 800 mbar contains the well-known Equatorial Plumes. The Plume clouds are optically thick (τ ≥ 12), bright clouds with single scattering albedo $\text{ω}\text{= 0.997}$. They are probably composed of ammonia ice. The darker ($\text{ω}\text{= 0.990}$) interplume regions contain optically thinner clouds (2 ≤ τ ≤ 5) at the same altitude as the Plumes. An opaque cloud deck between 4000 and 6000 mbar, which is probably composed of water, forms the lowest model layer. In addition to these three layers, a thin forward scattering haze layer above 100 mbar was included in the models for consistency with previous work (Tomasko et al., 1978). We conclude that the vertical structure of the Equatorial Plume clouds is consistent with the hypothesis (Hunt et al., 1981) that the Plumes are caused by upwelling at the ammonia condensation level produced by bouyancy due to latent heat release from the condensation of water clouds nearly three scale heights below the Plumes.  相似文献