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  总被引:3,自引:0,他引:3  
Abstract: The remnant wild population of California Condors ( Gymnogyps californianus ) of the 1980s exhibited a rapid population decline caused by high mortality rates among adult and immature birds. The most prominent mortality factor was lead poisoning resulting from ingestion of bullet fragments in carcasses. Successful captive breeding has allowed many birds to be released to the wild since 1992, based originally on an assumption that exposure to lead could be prevented by food subsidy. The mortality of released birds, however, has generally exceeded levels needed for population stability calculated from simple population models. Collision with overhead wires was the most frequent cause of death in releases before 1994. Lead poisoning again surfaced as a problem starting in 1997 as older birds began feeding on carcasses outside the subsidy program. Although poisonings have been treated successfully by chelation therapy in recaptured birds, food subsidy is proving an ineffective solution to lead exposure. The best long-term solution appears to be either the creation of large reserves where hunting is prohibited or the restriction of hunting to nontoxic ammunition in release areas. Until sources of lead contamination are effectively countered, releases cannot be expected to result in viable populations. In addition, problems involving human-oriented behavior have resulted in the permanent removal of many released birds from the wild. The most promising reduction in human-oriented behavior has been achieved in one release of aversively conditioned, parent-reared birds. Rigorous evaluation of the factors reducing attraction to humans and human structures has been hampered by confounding of techniques in releases. Behavioral problems could be more quickly overcome by adoption of a comprehensive experimental approach.  相似文献   
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We determined the concentrations of organochlorine pesticides and total PCBs in plasma of nestling Wood Storks (Mycteria americana) from two colonies in Georgia in 2000. Of 20 compounds analyzed for, only p,p'-DDE was quantified in reportable concentrations, ranging from <2.0-174.0 ng/g wet weight (ww). Concentrations of p,p'-DDE were significantly greater (P<0.0001) in plasma of nestlings from an inland colony, Chew Mill (x 16.9 ng/g,ww) than a coastal colony, Harris Neck (x 1.2 ng/g,ww). Concentrations from nestlings from Chew Mill were significantly different among sampling weeks (P=0.01), with week 8 being significantly greater than weeks 1, 2, and 5. While the Chew Mill colony had much greater concentrations of p,p'-DDE in plasma of nestlings than the Harris Neck colony, reproduction was greater there (1.8+/-1.0 SD fledged young per nesting attempt) than Harris Neck (1.4+/-1.0 SD fledged young per nesting attempt). While concentrations of p,p'-DDE determined in plasma of nestling Wood Storks are an indirect measure of adult exposure to environmental toxicants, concentrations reported would not be considered detrimental to reproduction in these colonies.  相似文献   
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ABSTRACT: :The model described herein was used to assess effects of the Suwannee River sill (a low earthen dam constructed to impound the Suwannee River within the Okefenokee National Wildlife Refuge to eliminate wildfires) on the hydrologic environment of Okefenokee Swamp, Georgia. Developed with Arc/Info Macro Language routines in the GRID environment, the model distributes water in the swamp landscape using precipitation, inflow, evapotranspiration, outflow, and standing water. Water movement direction and rate are determined by the neighborhood topographic gradient, determined using survey grade Global Positioning Systems technology. Model data include flow rates from USGS monitored gauges, precipitation volumes and water levels measured within the swamp, and estimated evapotranspiration volumes spatially modified by vegetation type. Model output in semi‐monthly time steps includes water depth, water surface elevation above mean sea level, and movement direction and volume. Model simulations indicate the sill impoundment affects 18 percent of the swamp during high water conditions when wildfires are scarce and has minimal spatial effect (increasing hydroperiods in less than 5 percent of the swamp) during low water and drought conditions when fire occurrence is high but precipitation and inflow volumes are limited.  相似文献   
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The influence of carbon, nitrogen, and phosphate source, along with concentration, was determined for effect on the weight average molecular weight, molecular weight distribution, and yield of pullulan produced byAureobasidium pullulans NRRL-Y 6220. Batch systems, scale-up batch, and continuous fermentations of 1 L and 10 L were also evaluated as were processing variables, including solvents, and extraction conditions. Products with weight average molecular weight from 1.0 × 105 to 4.0 × 106 were produced in 100-g quantities by varying fermentation conditions such as constituents of the culture medium, pH, and length of incubation. Three sets of culture conditions were defined for the formation of low (<5.0×105), medium (1.0–2.0×106), and high (>2.0×106) weight average molecular weight polymer. These defined molecular weight fractions of pullulan were used in further studies in producing films and fibers.  相似文献   
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In 2006, we used the U.S. Coast Guard’s Automatic Identification System (AIS) to describe patterns of large commercial ship traffic within a U.S. National Marine Sanctuary located off the coast of Massachusetts. We found that 541 large commercial vessels transited the greater sanctuary 3413 times during the year. Cargo ships, tankers, and tug/tows constituted 78% of the vessels and 82% of the total transits. Cargo ships, tankers, and cruise ships predominantly used the designated Boston Traffic Separation Scheme, while tug/tow traffic was concentrated in the western and northern portions of the sanctuary. We combined AIS data with low-frequency acoustic data from an array of nine autonomous recording units analyzed for 2 months in 2006. Analysis of received sound levels (10–1000 Hz, root-mean-square pressure re 1 μPa ± SE) averaged 119.5 ± 0.3 dB at high-traffic locations. High-traffic locations experienced double the acoustic power of less trafficked locations for the majority of the time period analyzed. Average source level estimates (71–141 Hz, root-mean-square pressure re 1 μPa ± SE) for individual vessels ranged from 158 ± 2 dB (research vessel) to 186 ± 2 dB (oil tanker). Tankers were estimated to contribute 2 times more acoustic power to the region than cargo ships, and more than 100 times more than research vessels. Our results indicate that noise produced by large commercial vessels was at levels and within frequencies that warrant concern among managers regarding the ability of endangered whales to maintain acoustic contact within greater sanctuary waters. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
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The vast darkness of the deep sea is an environment with few obvious genetic isolating barriers, and little is known regarding the macroevolutionary processes that have shaped present-day biodiversity in this habitat. Bioluminescence, the production and emission of light from a living organism through a chemical reaction, is thought to occur in approximately 80 % of the eukaryotic life that inhabits the deep sea (water depth greater than 200 m). In this study, we show, for the first time, that deep-sea fishes that possess species-specific bioluminescent structures (e.g., lanternfishes, dragonfishes) are diversifying into new species at a more rapid rate than deep-sea fishes that utilize bioluminescence in ways that would not promote isolation of populations (e.g., camouflage, predation). This work adds to our understanding of how life thrives and evolution shaped present-day biodiversity in the deep sea, the largest and arguably least explored habitat on earth.  相似文献   
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The modern cast of disaster relief actors includes host nations, non-governmental organisations, private volunteer organisations, military organisations and others. Each group, civilian or military, has valuable skills and experiences critical to disaster relief work. The goal of this paper is to supplement the study of civil–military relief efforts with contemporary anecdotal experience. The paper examines the interaction between US military forces and other disaster relief actors during the 2005 Kashmir earthquake relief effort. The author uses direct observations made while working in Pakistan to contrast the relationships and activities from that effort with other accounts in prevailing scholarly disaster literature and military doctrine. Finally, this paper suggests that the Kashmir model of integration, coordination and transparency of intent creates a framework in which future humanitarian assistance operations could be successfully executed. Recommendations to improve civil–military interaction in future relief efforts will also be addressed.  相似文献   
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Potassium carbonate (K2CO3) solvents offer a lower cost and environmentally benign alternative to the traditional amine‐based solvents for post‐combustion capture of carbon dioxide (CO2) from power station flue gases. The CO2CRC is developing a precipitating K2CO3 process, termed UNO MK 3, which has the potential for significant cost reductions. The costs have been calculated based on capturing 90% of the CO2 emissions from a new build black coal (Illinois No. 6) power station with a net output of 550 MW. With the UNO MK 3 process for CO2 capture, the cost of electricity is predicted to be as low as $73/MWh and the cost of capture as low as $21/tonne of CO2 avoided. The cost of electricity with the UNO MK 3 process represents as low as a 24% increase in the cost of electricity, which meets the target set by the US Department of Energy for capture technologies of adding less than 35% to the cost of electricity.  相似文献   
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