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651.
Catherine Prigent Dennis P. Lettenmaier Filipe Aires Fabrice Papa 《Surveys in Geophysics》2016,37(2):339-355
Up to now, high-resolution mapping of surface water extent from satellites has only been available for a few regions, over limited time periods. The extension of the temporal and spatial coverage was difficult, due to the limitation of the remote sensing technique [e.g., the interaction of the radiation with vegetation or cloud for visible observations or the temporal sampling with the synthetic aperture radar (SAR)]. The advantages and the limitations of the various satellite techniques are reviewed. The need to have a global and consistent estimate of the water surfaces over long time periods triggered the development of a multi-satellite methodology to obtain consistent surface water all over the globe, regardless of the environments. The Global Inundation Extent from Multi-satellites (GIEMS) combines the complementary strengths of satellite observations from the visible to the microwave, to produce a low-resolution monthly dataset (\(0.25^\circ \,\times \,0.25^\circ\)) of surface water extent and dynamics. Downscaling algorithms are now developed and applied to GIEMS, using high-spatial-resolution information from visible, near-infrared, and synthetic aperture radar (SAR) satellite images, or from digital elevation models. Preliminary products are available down to 500-m spatial resolution. This work bridges the gaps and prepares for the future NASA/CNES Surface Water Ocean Topography (SWOT) mission to be launched in 2020. SWOT will delineate surface water extent estimates and their water storage with an unprecedented spatial resolution and accuracy, thanks to a SAR in an interferometry mode. When available, the SWOT data will be adopted to downscale GIEMS, to produce a long time series of water surfaces at global scale, consistent with the SWOT observations. 相似文献
652.
Agriculture represents less than 2 per cent of the GDP of New Caledonia where the economy (and wage-earning activities) is dominated by the service sector and the nickel industry. However, family farming remains strong, especially for the Indigenous Melanesian tribes of the east coast of New Caledonia. Yams (Dioscorea spp.) are still one of the pillars of traditional Kanak society despite the social and economic changes that followed colonisation by France. This study of Kanak yam cultivation on the north-eastern coast of New Caledonia underscores the fact that yam cultivation systems have greatly changed since the 1950s, when they were last described. In addition to customary gift exchanges and subsistence consumption, yams are increasingly being grown for market sales. Five cropping systems, three yam production systems, and three Kanak social activity systems are described and their linkages to each other are explained. There are three levels of Kanak market participation: none, transitional, and fully engaged, and the extent of market participation and associated technical choices defines farmers’ levels of cultural activity and the nature and characteristics of yam cultivation. 相似文献
653.
Jennifer Romon-MartinMaria A. Barucci Catherine de BerghAlain Doressoundiram Nuno Peixinho François Poulet 《Icarus》2002,160(1):59-65
Near-infrared spectra of Centaur 8405 Asbolus have been obtained, covering the whole rotational period. Complementary photometry and visible spectroscopy have also been performed. The aim of this project was to confirm or refute the water ice detection on one side of Asbolus reported by Kern et al. (2000 Astrophys. J.542, L155-L159). We found no absorption feature at any rotational phase of Asbolus. Our study is the first in-depth investigation of a centaur over a complete rotational period. Our results seem also to indicate that a change in the slope from 0.8 to 1.0 μm may occur in Asbolus spectrum. 相似文献
654.
Hugh?St. C.?O'NeillEmail author Mark?I.?Pownceby Catherine?A.?McCammon 《Contributions to Mineralogy and Petrology》2003,146(3):308-325
The chemical potential of oxygen (µO2) in equilibrium with magnesiowüstite solid solution (Mg, Fe)O and metallic Fe has been determined by gas-mixing experiments at 1,473 K supplemented by solid-cell EMF experiments at lower temperatures. The results give:
where IW refers to the Fe-"FeO" equilibrium. The previous work of Srecec et al. (1987) and Wiser and Wood (1991) agree well with this equation, as does that of Hahn and Muan (1962) when their reported compositions are corrected to a new calibration curve for lattice parameter vs. composition. The amount of Fe3+ in the magnesiowüstite solid solution in equilibrium with Fe metal was determined by Mössbauer spectroscopy on selected samples. These data were combined with literature data from gravimetric studies and fitted to a semi-empirical equation:
These results were then used to reassess the activity-composition relations in (Mg, Fe)2SiO4 olivine solid solutions at 1,400 K, from the partitioning of Mg and Fe2+ between olivine and magnesiowüstite in equilibrium with metallic Fe experimentally determined by Wiser and Wood (1991). The olivine solid solution is constrained to be nearly symmetric with
, with a probable uncertainty of less than ±0.5 kJ/mol (one standard deviation). The results also provide a useful constraint on the free energy of formation of Mg2SiO4.Editorial responsibility: B. Collins 相似文献
655.
Catherine M. CORRIGAN Michael E. ZOLENSKY Jason DAHL Michael LONG Joseph WEIR Clyde SAPP Patti Jo BURKETT 《Meteoritics & planetary science》1997,32(4):509-515
Abstract— We have investigated the porosity of a large number of chondritic interplanetary dust particles (IDPs) and meteorites by three techniques: standard liquid/gas flow techniques, a new, noninvasive ultrasonic technique, and image processing of backscattered images. The latter technique is obviously best-suited to sub-kilogram sized samples. We have also measured the gas and liquid permeabilities of some chondrites by two techniques: standard liquid/gas flow techniques, and a new, nondestructive pressure release technique. We find that chondritic IDPs have a somewhat bimodal porosity distribution. Peaks are present at 0 and 4% porosity; a tail then extends to 53%. Type 1–3 chondrite matrix porosities range up to 30%, with a peak at 2%. The bulk porosities for type 1–3 chondrites have the same approximate range as exhibited by the matrix, which indicates that other components of the bulk meteorites (including chondrules and aggregates) have the same average porosity as the matrix. These results reveal that the porosities of primitive materials at scales ranging from nanogram to kilogram are similar, which implies that similar accretion dynamics operated through 12 orders of size magnitude. Permeabilities of the investigated chondrites vary by several orders of magnitude, and there appears to be no simple dependence of permeability with degree of aqueous alteration, chondrite type or porosity. 相似文献
656.
Jean-Marie Auzende Mathilde Cannat Pascal Gente Jean-Pierre Henriet Thierry Juteau Jeffrey Karson Yves Lagabrielle Catherine Mével Maurice Tivey 《地学学报》1994,6(2):143-148
The objective of the 20 Nautile dives of the recent Kanaut cruise was to study the southern wall of the Kane Fracture Zone from its eastern intersection with the Mid-Atlantic Ridge (MAR) to 5 Myr in age. The geological mapping shows four successive massifs, wrench faulted and slightly tilted. The transform-facing walls of these massifs exhibit outcrops of fresh and serpentinized peridotites, gabbros and basalts. The entire crustal exposure is cataclased and metamorphosed to greenschist facies. 相似文献
657.
Tara Sharma Jeff Carmichael Brian Klinkenberg 《Journal of the Indian Society of Remote Sensing》2005,33(2):353-363
The transition to agricultural sustainability involves difficult choices and an understanding of the complex trade-offs associated
with agricultural activities. Decision support tools and techniques assist in making the informed decisions for a transition
to sustainable agriculture. Georgia Basin — Quite Useful Ecosystem Scenario Tool (GB-QUEST) is a computer-based, user-friendly
tool that has been developed to look at the future sustainability scenarios of the Georgia Basin in British Columbia. The
objective of this paper is to describe the agricultural model that has been developed for implementation in GB-QUEST. We present
its framework, spatial methodology for land-use simulation, and the initial results of its application.
The agriculture model is a spatial model that examines the social, economic and environmental consequences of user-defined
agricultural development strategies. The model simulates changes in the Georgia Basin from the year 2000 to 2040 in decadal
steps. User choices of local and global development factors, along with their "worldview" choices, are important inputs in
the model that determine the effects on environmental and socio-economic systems. The model has two components — Generation
of land-use scenarios, and Development of Indicator models. The first component uses cell-based spatial algorithms to simulate
likely changes/conversions in land-use up to the year 2040. The approach used here integrates the functionality of Multi-Criteria
Evaluation (MCE) and Cellular Automata (CA) techniques in order to simulate the land-use conversions. It uses Geographic Information
Systems (GIS) and remote sensing techniques for creating, storing and deriving the data sets required for the model. The second
component develops the indicator models for relating scenario variables to socio-economic and environmental variables such
as physical and economic yields, economic operation costs and nutrient surplus per unit area. These indicator models are used
to evaluate land-use scenarios generated by the users. The model encourages understanding of sustainability, by allowing one
to explore different possible scenarios of the future for their environmental and socio-economic consequences. 相似文献
658.
Sebastien Leblond Sandrine Gombert Jean Louis Colin Remi Losno Catherine Rausch De Traubenberg 《Journal of Atmospheric Chemistry》2004,49(1-3):95-110
Over a period of one year, the moss Scleropodium purum was sampled every two weeks in a French rural area to determine the levels of Li, Na, Al, Si, P, Ca, V, Mn, Fe, Zn, Ba, Hg, and Pb. The element distribution in the moss shoot was studied throughout the year. An apical bioconcentration was discovered for Na, P, Ca, Mn, and Zn, whereas higher levels were found in the basal fraction for Li, Al, Si, V, Fe, Ba, Hg, and Pb. A significant variation of element concentrations was observed during the sampling period. In the apical part Li, Al, Si, V, Fe, Ba, and Hg show maximum levels in the summer and minimum in the autumn. The same pattern was found with Ca and Mn in the whole plant, whereas Na showed opposite fluctuations. 相似文献
659.
Spatial survey of trace metal contaminants in the sediments of the Elizabeth River, Virginia 总被引:5,自引:0,他引:5
The Elizabeth River is a sub-estuary of the James River, the most southern tributary of the Chesapeake Bay. It is a highly industrialized area, and has been designated a "toxic hot spot" due to the heavy loads of contaminant metals and organic compounds in its bed sediments. Fifty surface sediment samples were taken along the channels and shoals of the Mainstem and the Southern Branch portions of the river. The samples were analyzed for trace metals (Cd, Cr, Cu, Pb and Zn), Fe and particle properties (% sand, % silt, % clay and specific surface area) to discern the spatial distribution of contaminant metals in this system. Enrichment factors were calculated to assess the overall level of contamination relative to other surrounding waterways as well as historic contamination levels within the river itself. The highest levels of metals were found to be in close proximity to industrial sources of contamination. The overall level of contamination was 3-10 times higher than baseline levels within the river, and 2-3 times higher than contaminant levels in other area waters. 相似文献
660.
Periodic explosions in the nucleus of a galaxy generate strong shock waves. The shock waves, in moving outwards, produce highly compressed thin layers of gas at distances much larger than the thickness of the layer. When the gas in this layer undergoes fragmentation, the Jeans mass is found to be much less than that if the fragmentation proceeded under normal gravitational pull. It is, therefore, concluded that the explosive events in the galactic centres make the process of star formation highly efficient in the central region of galaxies. 相似文献