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881.
Eric Buffetaut 《地学学报》1989,1(1):69-74
The Late Cretaceous (mainly Campanian and Maastrichtian) non-marine vertebrate faunas of Europe contain archosaurian reptiles which belong to groups otherwise known mainly or only from the southern ('Gondwanan') continents. They include titanosaurid sauropods, abelisaurid theropods, and trematochampsid crocodilians. The occurrence of these forms together with others of 'Asiamerican' affinities gives the Late Cretaceous vertebrate faunas of Europe a peculiar composition, which makes them clearly different from the well-known faunas from western North America and Central Asia. The Gondwanan dinosaurs and crocodilians from Europe provide evidence of faunal interchange across the Tethys Sea during the Cretaceous, possibly via the Alboran plate, or the Apulian plate, which may have functioned as 'stepping-stones', especially during periods of low sea level. 相似文献
882.
883.
Wang-Hong Yang R. James Kirkpatrick Norma Vergo John McHone Tryggvi I. Emilsson Eric Oldfield 《Meteoritics & planetary science》1986,21(1):117-124
High-resolution solid-state silicon-29 nuclear magnetic resonance spectroscopy using “magic-angle” sample-spinning can readily detect the presence of the high pressure silica polymorphs coesite and stishovite in whole-rock samples from a Meteor Crater, Arizona, impact sample, and yields accurate coesite/stishovite ratios. Such determinations are being carried out by partially suppressing (saturating) intense quartz signals (which have long spin-lattice relaxation times) by means of short experimental recycle-times. This method enhances the signal-to-noise ratios of coesite and stishovite (which have relatively short spin-lattice relaxation times). For the sample examined, the coesite/stishovite ratio is about 27. 相似文献
884.
885.
Eric A. Crecelius 《Marine Chemistry》1980,8(3):245-250
The elemental solubilities of three coal fly ash samples and two coastal marine-aerosol samples in seawater are different. The coal fly ash samples were collected from the electrostatic precipitators on coal-fired power plants. The air particulates were collected by a high-volume air sampler located near the Washington coast. Samples were neutron-activated then contacted with seawater for several hours. The elements that were partially solubilized from both fly ash and aerosols included As, Sb, Se, Br and Cr. Zinc and Co were more soluble in aerosols then fly ash. 相似文献
886.
Herbert W. Schnopper Eric Silver Stephen Murray Suzanne Romaine Simon Bandler Christine Jones William Forman Norman Madden Jeffery Beeman Eugene Haller Finn Christensen Niels Westergaard Juan Fabregat Victor Reglero Alvaro Gimenez Noah Brosch Elia Liebowitz Hagai Netzer Marco Barbera Alfonso Collura Salvatore Sciortino 《Astrophysics and Space Science》2001,276(1):49-65
The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe K region (1100 cm2). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin2 . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations. 相似文献
887.
Anthony?C.?WithersEmail author Eric?J.?Essene Youxue?Zhang 《Contributions to Mineralogy and Petrology》2003,145(2):199-204
The transition between rutile and α-PbO2 structured TiO2 (TiO2II) has been investigated at 700–1,200 °C and 4.2–9.6 GPa. Hydrothermal phase equilibrium experiments were performed in the multi-anvil apparatus to bracket the phase boundary at 700, 1,000, and 1,200 °C. The equilibrium phase boundary is described by the equation: P (GPa)=1.29+0.0065 T ( °C). In addition, growth of TiO2II was observed in experiments at 500 and 600 °C, although growth of rutile was too slow to bracket unambiguously the equilibrium boundary at these temperatures. Water was not detected in either rutile or TiO2II, and dry synthesis experiments at 1,200 °C were consistent with the phase boundary determined in the fluid-bearing experiments, suggesting that the equilibrium is unaffected by the presence of water. Our bracket of the phase boundary at 700 °C is consistent with the reversed, dry experiments of Akaogi et al. (1992) and the reversals of Olsen et al. (1999). The new data suggest that the phase boundary is linear, in agreement with Akaogi et al. (1992), but in striking contrast to the phase diagram inferred by Olsen et al. (1999). The natural occurrence of TiO2II requires formation pressures considerably higher than the graphite–diamond phase boundary. 相似文献
888.
Rock-magnetic proxies of climate change from loess -paleosol sediments of the Czech Republic 总被引:6,自引:0,他引:6
Summary Rock-magnetic characteristics of late Pleistocene loess-paleosol sequences in the Czech Republic show patterns of variation
that reflect climate-related depositional and diagenetic processes which acted on the sedimentary profiles. Mass-normalized
magnetic susceptibility is high in interglacial and interstadial paleosols, while uniformly low values are measured in unweathered
loess horizons. Normalized ferrimagnetic susceptibility and anhysteretic remanent magnetization show an enhancement of ultrafine
(superparamagnetic, SP) and fine (single-domain, SD, and pseudo-single-domain, PSD) grains in chernozem paleosols correlated
with δ18O substages 5c and 5a as well as in the Holocene soil. The parabraunerde paleosol associated with peak interglacial conditions,
correlated with δ18O substage 5e, shows evidence of diagenetic loss of fine grained magnetic minerals, although coarse (multidomain, MD) grains
appear to be preserved.
Low temperature remanence behavior plus high temperature susceptibility measurements of representative samples from each lithologic
unit indicate that magnetite and maghemite are the dominant magnetic minerals within the sediments. Variations in concentration-independent
rock-magnetic parameters are therefore primarily a function of grain size variations through the profile. It is anticipated
that with additional magnetic and non-magnetic sedimentological and geochemical tests, a quantitative rock-magnetic — paleoclimate
model can be developed for the central European loess region. 相似文献
889.
The land cover and carbon cycle consequences of large-scale utilizations of biomass as an energy source 总被引:1,自引:0,他引:1
Rik Leemans André van Amstel Coos Battjes Eric Kreileman Sander Toet 《Global Environmental Change》1996,6(4):335-357
The use of modern biomass for energy generation has been considered in many studies as a possible measure for reducing or stabilizing global carbon dioxide (CO2) emissions. In this paper we assess the impacts of large-scale global utilization of biomass on regional and grid scale land cover, greenhouse gas emissions, and carbon cycle. We have implemented in the global environmental change model IMAGE the LESS biomass intensive scenario, which was developed for the Second Assessment Report of IPCC. This scenario illustrates the potential for reducing energy related emission by different sets of fuel mixes and a higher energy efficiency. Our analysis especially covers different consequences involved with such modern biomass scenarios. We emphasize influences of CO2 concentrations and climate change on biomass crop yield, land use, competition between food and biomass crops, and the different interregional trade patterns for modern biomass based energy. Our simulations show that the original LESS scenario is rather optimistic on the land requirements for large-scale biomass plantations. Our simulations show that 797 Mha is required while the original LESS scenario is based on 550 Mha. Such expansion of agricultural land will influence deforestation patterns and have significant consequenses for environmental issues, such as biodiversity. Altering modern biomass requirements and the locations where they are grown in the scenario shows that the outcome is sensitive for regional emissions and feedbacks in the C cycle and that competition between food and modern biomass can be significant. We conclude that the cultivation of large quantities of modern biomass is feasible, but that its effectiveness to reduce emissions of greenhouse gases has to be evaluated in combination with many other environmental land use and socio-economic factors. 相似文献
890.
A mesoscale atmospheric numerical model is coupled with a physically based snow-pack model and with a snow-drift model. The snow model is verified for the French Alps by comparing its simulations to observations performed at the Col de Porte in the Chartreuse Massif. The snow erosion threshold depends on snow-pack properties such as density, dendricity, sphericity and particle size. The atmospheric turbulence scheme is modified in order to take into account stabilization effects due to airborne blown snow particles. In particular, vertically integrated stability functions for the stable boundary layer are completed by including the threshold friction velocity for snow erosion. The snow-drift model is calibrated by simulating the conditions observed during the Byrd snow project, held in West Antarctica in 1962. Finally, sensitivity experiments to the snow-surface properties show the importance of their accurate representation when modelling the contribution of deflation to the Antarctic surface mass balance. 相似文献