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81.
Ute C. Herzfeld Craig S. Lingle Cecily Freeman Chris A. Higginson Michael P. Lambert Li-Her Lee Vera A. Voronina 《Mathematical Geology》1997,29(6):859-890
The Antarctic Ice Sheet plays a major role in the global system, and the large ice streams discharging into the circumpolar
sea represent its gateways to the world’s oceans. Satellite radar altimeter data provide an opportunity for mapping surface
elevation at kilometerresolution with meteraccuracy. Geostaristical methods have been developed for the analysis of these
data. Applications to Seasat data and data from the Geosat Exact Repeat Mission indicate that the grounding line of Lambert
Glacier/Amery Ice Shelf, the largest ice stream in East Antarctica, has advanced 10–12 km between 1978 and 1987–89. The objectives
of this paper are to explore possibilities and limitations of satellite-altimetry-based mapping to capture changes for shorter
time windows and for smaller areas, and to investigate some methodological aspects of the data analysis. We establish that
one season of radar altimeter data is sufficient for constructing a map. This allows study of interannual variation and is
the key for a limeseries analysis approach to study changes in ice streams. Maps of the lower Lambert Glacier and the entire
Amery Ice Shelf are presented for austral winters 1978, 1987, 1988, and 1989. As a first step toward understanding the dynamics
of the ice-stream/iceshelf system, elevation changes are calculated for grounded ice, the grounding zone, and floating ice.
In the absence of (sufficient) surface gravity control for the Lambert Glacier/Amery Ice Shelf area, altimetry-based maps
may facilitate improvement of geoid models as they provide constraints on the terrain correction in the inverse gravimetric
problem. 相似文献
82.
A laboratory study was conducted to determine the efficiency of different aqueous concentrations of an alcohol ethoxylate surfactant in washing residual levels of an oil [automatic transmission fluid (ATF)] from sandy soil. Five glass columns packed with the soil were prepared in a manner that simulated conditions leading to residual saturation in an actual oil leak. Each of four columns was washed continuously with 28 pore volumes of solution by pumping either 0.0 percent (water), 0.5 percent, 1.0 percent, or 2.0 percent aqueous surfactant solutions through the columns. The fifth column was washed intermittently with 28 pore volumes of a 1.0 percent surfactant solution. Water washed only 25.5 percent of the ATF from the column soil, while the 0.5 percent, 1 percent, and 2 percent surfactant solutions washed 55 percent, 60 percent, and 72.8 percent of the ATF, respectively. The distribution of the ATF remaining in the column after washing showed that the ATF removed by water was mainly from the outlet side of the column, while the ATF removed by the 2.0 percent surfactant solution was mainly from the inlet side of the column. This observation indicated that different mechanisms were involved; namely, the displacement of oil through the soil-pore space, the dispersion of oil due to reduced surface tension, and the solubilization of oil by surfactant micelles. In the case of water, the displacement of oil was the main washing mechanism, while all three mechanisms were operative during surfactant washing. ATF dispersion and solubilization were improved at higher surfactant concentrations. The column that was washed intermittently to pulse ATF from dead end pores did not show a significant improvement over the column that was continuously washed with the same 1.0 percent surfactant solution. The results show promising potential for application in the field and will be further investigated in a two-dimensional model aquifer. 相似文献
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88.
Andrés Folguera Emilio Rojas Vera Germán Bottesi Gonzalo Zamora Valcarce Victor A. Ramos 《Journal of Geodynamics》2010,49(5):287-295
The Loncopué Trough is located in the hinterland Andean zone between 36°30′ and 39°S. It constitutes a topographic low bounded by normal faults and filled by lavas and sediments less than 5 Ma old. Reprocessed seismic lines show wedge-like depocenters up to 1700 m deep associated with high-angle faults, correlated with the 27–17 Ma Cura Mallín basin deposits, and buried beneath Pliocene to Quaternary successions and Late Miocene foreland sequences. The southern Central Andes seem to have been under extension in the hinterland zone some 27 Ma ago and again at approximately 5 Ma ago. This last extensional period could have been the product of slab steepening after a shallow subduction cycle in the area, although other alternatives are discussed. Orogenic wedge topography, altered by the first extensional stage in the area, was recovered through Late Miocene inversion, and was associated with foreland sequences. However, since the last extension (<5 Ma) the Andes have not recovered their characteristic contractional behavior that controlled past orogenic growth. 相似文献
89.
Oliveira MM Silva Filho MV Cunha Bastos VL Fernandes FC Cunha Bastos J 《Marine environmental research》2007,63(4):303-312
Brain acetylcholinesterase (AChE) of some fishes from the coast of Rio de Janeiro State was studied as a possible pesticide biomarker in marine environmental monitoring. AChE specific activity in brain varied from 145 to 530 U/g of proteins and the Michaelis-Menten constant (K(M)) for acetylthiocholine varied from 104 to 291 microM among the 20 species studied. The enzyme sensitivity to methyl paraoxon, evaluated by the inhibition kinetic constants, shows that some species (Paralonchurus brasiliensis and Genidens genidens) are more sensitive (IC50-30 min=455 and 468 nM, respectively). The less sensitive Merluccius hubbsi and Percophis brasiliensis (IC50-30 min=3339 and 3259 nM, respectively) belong to the super-order Paracanthopterygii, which includes the more ancient species. On the other hand, more susceptible species belong to the super-order Acanthopterygii, which includes more recent species. These results suggest a possible evolutionary linkage for AChE sensitivity to methyl paraoxon. The application of inhibition kinetic constants for fish brain AChE in phylogenetic studies is still being investigated. The results have shown that a fish sentinel species should have the highest brain AChE level among the more sensitive ones. 相似文献
90.
Vera Pawlowsky Glahn 《Mathematical Geology》1999,31(1):139-142