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Food web interactions and the response of Pacific salmon to physical processes in the North Pacific Ocean over interannual and interdecadal timescales are explored using naturally occurring stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N). Stable isotope analyses of five species of sexually mature North Pacific salmon from Alaska (Oncorhynchus spp.) cluster into three groups: chinook salmon (O. tshawytscha) have the highest values, followed by coho (O. kisutch), with chum (O. keta), sockeye (O. nerka), and pink (O. gorbuscha) together having the lowest values. Although detailed isotopic data on salmon prey are lacking, there are limited data on relevant prey items from areas in which they are found in high abundance. These data suggest that the characteristics of the sockeye, pink and chum we have analyzed are compatible with their diets including open ocean squid and zooplankton, which are in general agreement with stomach content analyses. Isotope relationships between muscle and scale show consistent relationships for both δ13C (R2=0.98) and δ15N (R2=0.90). Thus, scales, which have been routinely archived for many systems, can be used for retrospective analyses. Archived sockeye salmon scales spanning 1966–1999 from Red Lake, Kodiak Island, Alaska were analyzed for their stable isotope ratios of carbon and nitrogen. The δ15N record displays a decreasing trend of ˜3‰ from 1969–1982 and an increasing trend of ˜3‰ from 1982–1992, while the variations in δ13C are relatively minor. These trends may result from factors such as shifts in trophic level of feeding and/or feeding location, or may originate at the base of the food web via changes in processes such as nutrient cycling or primary productivity. Detailed studies on prey isotopic variability and its controls are needed to distinguish between these factors, and thus to improve the use of stable isotope analysis as a tool to learn more about present and past ecosystem change in the North Pacific and its relation to climatic change. 相似文献
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Nathaniel D. McClure IV 《Environmental Geology》1985,7(1-2):15-24
The recently completed Tennessee-Tombigbee Waterway (Tenn-Tom) survived many challenges from all three branches of the federal
government A brief overview of these challenges over the past 40 years is presented Central among the challenges was the litigation
involving allegations under the National Environmental Policy Act (NEPA) The response of the U S Army Corps of Engineers to
NEPA and its influence on the Tenn-Tom are presented A summarization of the principal environmental issues related to the
Tenn-Tom is provided to describe the wide spectrum of concerns and controversies associated with the development of this major
waterway The Tenn-Tom met the test in all forums The measures taken to respond in a meaningful way to NEPA and other environmental
statutes are a model that could well be followed in the development of other major projects 相似文献
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Golubev Yu. F. Grushevskii A. V. Koryanov V. V. Lavrenov S. M. Tuchin A. G. Tuchin D. A. 《Solar System Research》2020,54(4):318-328
Solar System Research - We consider space expeditions with a long-term spacecraft stay near the studied celestial body (artificial satellites of small bodies of the Solar System), or expeditions... 相似文献
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The Tennessee–Tombigbee Waterway (Tenn–Tom) was one of the first and largest water resources projects constructed after the
enactment of the National Environmental Policy Act of 1969. This highly controversial project was in litigation for 9 of the
13 years it was under construction. Substantial and innovative measures were incorporated into the project design to minimize
environmental damage and to promote environmental protection. Additionally, a wide variety of environmental mitigation measures,
including the acquisition and management of 35,614 ha of wildlife habitat to compensate for unavoidable impacts. This paper,
which updates a paper published by the American Society of Civil Engineers in 1996, presents an update of the environmental
and restorative measures incorporated into the design, construction, operation, and management of the Tenn–Tom some 15 years
after it was opened for navigation. The paper examines the accuracy of selected predicted impacts, waterway utilization, and
the effectiveness of environmental measures.
Received: 13 March 2000 · Accepted: 12 June 2000 相似文献
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Hydrated mineral surfaces play an important role in many processes in biological, geological, and industrial applications. An energy force field was developed for molecular mechanics and molecular dynamics simulations of hydrated carbonate minerals and was applied to investigate the behavior of water on the calcite surface. The force field is a significant development for large-scale molecular simulations of these systems, and provides good agreement with experimental and previous modeling results. Simulations indicate that water molecules are significantly ordered near the calcite surface. The predominant surface configuration (75-80%) results from coordination of a water molecule with a single calcium cation-carbonate anion pair, while the less common situation involves water coordination with two ion pairs. Surface restructuring and variation in coordination in the water layers results in distinct distances for water oxygens above the calcite surface—a two-component first monolayer (2.3 and 3.0 Å) and a secondary monolayer (5.0 Å). The different coordinations also alter lateral displacement, hydrogen bonding, and surface-normal orientation of the water molecules. The ordering of water molecules and the formation of a unique hydrogen bonding network at the calcite surface influence the physical properties of the interfacial water. Surface exchange of water molecules is observed by molecular dynamics simulation to occur at a rate of one exchange per 10 ps. Diffusion coefficients derived from mean square displacement analysis of atomic trajectories indicate a dependence of water transport based on the distance of the water molecules from the calcite surface. 相似文献
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S. V. Komovkin S. M. Lavrenov A. G. Tuchin D. A. Tuchin V. S. Yaroshevsky 《Solar System Research》2016,50(7):593-596
The article describes a model of the two-way measurements of radial velocity based on the Doppler effect. The relations are presented for the instantaneous value of the increment range at the time of measurement and the radial velocity of the mid-dimensional interval. The compensation of methodological errors of interpretation of the two-way Doppler measurements is considered. 相似文献
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Alberto M. V��squez Zhenguang Huang Ward B. Manchester IV Richard A. Frazin 《Solar physics》2011,274(1-2):259-284
A three-dimensional (3D) tomographic reconstruction of the local differential emission measure (LDEM) of the global solar corona during the whole heliosphere interval (WHI, Carrington rotation CR 2068) is presented, based on STEREO/EUVI images. We determine the 3D distribution of the electron density, mean temperature, and temperature spread, in the range of heliocentric heights 1.03 to 1.23 R ??. The reconstruction is complemented with a potential-field source-surface (PFSS) magnetic-field model. The streamer-core, streamer-leg, and subpolar regions are analyzed and compared to a similar analysis previously performed for CR 2077, very near the absolute minimum of Solar Cycle 23. In each region, the typical values of density and temperature are similar in both periods. The WHI corona exhibits a streamer structure of relatively smaller volume and latitudinal extension than during CR 2077, with a global closed-to-open density contrast about 6% lower, and a somewhat more complex morphology. The average basal electron density is found to be about 2.23 and 1.08×108 cm?3, in the streamer core and subpolar regions, respectively. The electron temperature is quite uniform over the analyzed height range, with average values of about 1.13 and 0.93 MK, in the streamer core and subpolar regions, respectively. Within the streamer closed region, both periods show higher temperatures at mid-latitudes and lower temperatures near the Equator. Both periods show ??>1 in the streamer core and ??<1 in the surrounding open regions, with CR 2077 exhibiting a stronger contrast. Hydrostatic fits to the electron density are performed, and the scale height is compared to the LDEM mean electron temperature. Within the streamer core, the results are consistent with an isothermal hydrostatic plasma regime, with the temperatures of ions and electrons differing by up to about 10%. In the subpolar open regions, the results are consistent with departures from thermal equilibrium with T ions>T e (and values of T ions/T e up to about 1.5), and/or the presence of wave-pressure mechanisms linear in the density. 相似文献