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The Eurybates family is a compact core inside the Menelaus clan, located in the L4 swarm of Jupiter Trojans. Fornasier et al. (Fornasier, S., Dotto, E., Hainaut, O., Marzari, F., Boehnhardt, H., De Luise, F., Barucci, M.A. [2007]. Icarus 190, 622-642) found that this family exhibits a peculiar abundance of spectrally flat objects, similar to Chiron-like Centaurs and C-type main belt asteroids. On the basis of the visible spectra available in literature, Eurybates family’s members seemed to be good candidates for having on their surfaces water/water ice or aqueous altered materials.To improve our knowledge of the surface composition of this peculiar family, we carried out an observational campaign at the Telescopio Nazionale Galileo (TNG), obtaining near-infrared spectra of 7 members. Our data show a surprisingly absence of any spectral feature referable to the presence of water, ices or aqueous altered materials on the surface of the observed objects. Models of the surface composition are attempted, evidencing that amorphous carbon seems to dominate the surface composition of the observed bodies and some amount of silicates (olivine) could be present. 相似文献
323.
B. Gertsch G. Keller T. Adatte Z. Berner A. S. Kassab A. A. A. Tantawy A. M. El-Sabbagh D. Stueben 《International Journal of Earth Sciences》2010,99(1):165-182
Environmental and depositional changes across the Late Cenomanian oceanic anoxic event (OAE2) in the Sinai, Egypt, are examined
based on biostratigraphy, mineralogy, δ13C values and phosphorus analyses. Comparison with the Pueblo, Colorado, stratotype section reveals the Whadi El Ghaib section
as stratigraphically complete across the late Cenomanian–early Turonian. Foraminifera are dominated by high-stress planktic
and benthic assemblages characterized by low diversity, low-oxygen and low-salinity tolerant species, which mark shallow-water
oceanic dysoxic conditions during OAE2. Oyster biostromes suggest deposition occurred in less than 50 m depths in low-oxygen,
brackish, and nutrient-rich waters. Their demise prior to the peak δ13C excursion is likely due to a rising sea-level. Characteristic OAE2 anoxic conditions reached this coastal region only at
the end of the δ13C plateau in deeper waters near the end of the Cenomanian. Increased phosphorus accumulations before and after the δ13C excursion suggest higher oxic conditions and increased detrital input. Bulk-rock and clay mineralogy indicate humid climate
conditions, increased continental runoff and a rising sea up to the first δ13C peak. Above this interval, a dryer and seasonally well-contrasted climate with intermittently dry conditions prevailed.
These results reveal the globally synchronous δ13C shift, but delayed effects of OAE2 dependent on water depth. 相似文献
324.
We use an integrated assessment model of climate change to analyze how alternative decision-making criteria affect preferred investments into greenhouse gas mitigation, the distribution of outcomes, the robustness of the strategies, and the economic value of information. We define robustness as trading a small decrease in a strategy’s expected performance for a significant increase in a strategy’s performance in the worst cases. Specifically, we modify the Dynamic Integrated model of Climate and the Economy (DICE-07) to include a simple representation of a climate threshold response, parametric uncertainty, structural uncertainty, learning, and different decision-making criteria. Economic analyses of climate change strategies typically adopt the expected utility maximization (EUM) framework. We compare EUM with two decision criteria adopted from the finance literature, namely Limited Degree of Confidence (LDC) and Safety First (SF). Both criteria increase the relative weight of the performance under the worst-case scenarios compared to EUM. We show that the LDC and SF criteria provide a computationally feasible foundation for identifying greenhouse gas mitigation strategies that may prove more robust than those identified by the EUM criterion. More robust strategies show higher near-term investments in emissions abatement. Reducing uncertainty has a higher economic value of information for the LDC and SF decision criteria than for EUM. 相似文献
325.
Jane's Ocean Technology 1974–75 by Robert L. Trillo (Editor). Jane's Yearbooks, London, England (in North America, Franklin Watts, Inc., New York), 1974. 344 pp. £12.50 ($55.00). The Ocean Basins and Margins—Volume 2: The North Atlantic by A. E. M. Nairn and F. G. Stehli (Editors). Plenum Publishing, New York, 1974. 598 pp. $38.00. 相似文献
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James M. Dohm Victor R. Baker William V. Boynton Alberto G. Fairén Justin C. Ferris Michael Finch Roberto Furfaro Trent M. Hare Daniel M. Janes Jeffrey S. Kargel Suniti Karunatillake John Keller Kris Kerry Kyeong J. Kim Goro Komatsu William C. Mahaney Dirk Schulze-Makuch Lucia Marinangeli Gian G. Ori Javier Ruiz Shawn J. Wheelock 《Planetary and Space Science》2009,57(5-6):664-684
The Gamma Ray Spectrometer (Mars Odyssey spacecraft) has revealed elemental distributions of potassium (K), thorium (Th), and iron (Fe) on Mars that require fractionation of K (and possibly Th and Fe) consistent with aqueous activity. This includes weathering, evolution of soils, and transport, sorting, and deposition, as well as with the location of first-order geomorphological demarcations identified as possible paleoocean boundaries. The element abundances occur in patterns consistent with weathering in situ and possible presence of relict or exhumed paleosols, deposition of weathered materials (salts and clastic minerals), and weathering/transport under neutral to acidic brines. The abundances are explained by hydrogeology consistent with the possibly overlapping alternatives of paleooceans and/or heterogeneous rock compositions from diverse provenances (e.g., differing igneous compositions). 相似文献
328.
Mark L. Kram Arturo A. Keller Joseph Rossabi Lorne G. Everett 《Ground Water Monitoring & Remediation》2001,21(4):109-123
Contamination from the use of chlorinated solvents, often classified as dense nonaqueous phase liquids (DNAPLs) when in an undissolved state, represents an environmental challenge with global implications. Mass-transfer limitations due to rate-limited dissolution can lead to long-term aquifer persistence for even small volumetric fractions. The identification of DNAPL source zones located beneath the water table is critical to ultimately achieve site remediation and aquifer restoration. This paper provides a comparison of the advantages and disadvantages of many of the methods being used for detecting and delineating DNAPL contaminant source zones. The objective is to determine which options are best to pursue based on site characteristics, method performance, and method costs. DNAPL characterization methods are grouped into approaches, which include site preparation, characterization, and data-processing activities necessary to design an effective remediation system. We compare the different approaches based on the level of chemical and hydrogeologic resolution, and the need for additional data requirements. Our findings can be used to assist with selection of appropriate site remediation management options. 相似文献
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330.